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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..6833f05 --- /dev/null +++ b/.gitattributes @@ -0,0 +1,3 @@ +* text=auto +*.txt text +*.md text diff --git a/1708-h.zip b/1708-h.zip Binary files differnew file mode 100644 index 0000000..acc70b4 --- /dev/null +++ b/1708-h.zip diff --git a/1708-h/1708-h.htm b/1708-h/1708-h.htm new file mode 100644 index 0000000..7aa5a1b --- /dev/null +++ b/1708-h/1708-h.htm @@ -0,0 +1,9358 @@ +<?xml version="1.0" encoding="us-ascii"?> + +<!DOCTYPE html + PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" > + +<html xmlns="http://www.w3.org/1999/xhtml" lang="en"> + <head> + <title> + A History of Science, Vol. IV by Henry Smith Williams + </title> + <style type="text/css" xml:space="preserve"> + + body { margin:5%; background:#faebd0; text-align:justify} + P { text-indent: 1em; margin-top: .25em; margin-bottom: .25em; } + H1,H2,H3,H4,H5,H6 { text-align: center; margin-left: 15%; margin-right: 15%; } + hr { width: 50%; text-align: center;} + .foot { margin-left: 20%; margin-right: 20%; text-align: justify; text-indent: -3em; font-size: 90%; } + blockquote {font-size: 97%; font-style: italic; margin-left: 10%; margin-right: 10%;} + .mynote {background-color: #DDE; color: #000; padding: .5em; margin-left: 10%; margin-right: 10%; font-family: sans-serif; font-size: 95%;} + .toc { margin-left: 10%; margin-bottom: .75em;} + .toc2 { margin-left: 20%;} + div.fig { display:block; margin:0 auto; text-align:center; } + div.middle { margin-left: 20%; margin-right: 20%; text-align: justify; } + .figleft {float: left; margin-left: 0%; margin-right: 1%;} + .figright {float: right; margin-right: 0%; margin-left: 1%;} + .pagenum {display:inline; font-size: 70%; font-style:normal; + margin: 0; padding: 0; position: absolute; right: 1%; + text-align: right;} + pre { font-style: italic; font-size: 90%; margin-left: 10%;} + +</style> + </head> + <body> +<pre xml:space="preserve"> + +The Project Gutenberg EBook of A History of Science, Volume 4(of 5), by +Henry Smith Williams + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: A History of Science, Volume 4(of 5) + +Author: Henry Smith Williams + +Release Date: November 18, 2009 [EBook #1708] +Last Updated: January 26, 2013 + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK HISTORY OF SCIENCE, V4 *** + + + + +Produced by Charles Keller, and David Widger + + + + + + +</pre> + <p> + <br /><br /> + </p> + <h1> + A HISTORY OF SCIENCE + </h1> + <h2> + BY HENRY SMITH WILLIAMS, M.D., LL.D. <br /> <br /> <br /> ASSISTED BY EDWARD + H. WILLIAMS, M.D. <br /> <br /> <br /> IN FIVE VOLUMES <br /> <br /> VOLUME IV. + </h2> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> + </p> + <blockquote> + <p class="toc"> + <big><b>CONTENTS</b></big> + </p> + <p> + <br /> <a href="#link2H_4_0001"> <b>BOOK IV. MODERN DEVELOPMENT OF THE + CHEMICAL AND BIOLOGICAL SCIENCES</b> </a><br /> <br /> <br /> + </p> + <p class="toc"> + <a href="#link2H_4_0002"> I. THE PHLOGISTON THEORY IN CHEMISTRY </a> + </p> + <p class="toc"> + <a href="#link2H_4_0003"> II. THE BEGINNINGS OF MODERN CHEMISTRY </a> + </p> + <p class="toc"> + <a href="#link2H_4_0004"> III. CHEMISTRY SINCE THE TIME OF DALTON </a> + </p> + <p class="toc"> + <a href="#link2H_4_0005"> IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH + CENTURY </a> + </p> + <p class="toc"> + <a href="#link2H_4_0006"> V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH + CENTURY </a> + </p> + <p class="toc"> + <a href="#link2H_4_0007"> VI. THEORIES OF ORGANIC EVOLUTION </a> + </p> + <p class="toc"> + <a href="#link2H_4_0008"> VII. EIGHTEENTH-CENTURY MEDICINE </a> + </p> + <p class="toc"> + <a href="#link2H_4_0009"> VIII. NINETEENTH-CENTURY MEDICINE </a> + </p> + <p class="toc"> + <a href="#link2H_4_0010"> IX. THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY + </a> + </p> + <p class="toc"> + <a href="#link2H_4_0011"> X. THE NEW SCIENCE OF ORIENTAL ARCHAEOLOGY + </a> + </p> + <p class="toc"> + <a href="#link2H_APPE"> APPENDIX </a> + </p> + </blockquote> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a name="link2H_4_0001" id="link2H_4_0001"> + <!-- H2 anchor --> </a> + </p> + <h2> + BOOK IV. MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES + </h2> + <p> + AS regards chronology, the epoch covered in the present volume is + identical with that viewed in the preceding one. But now as regards + subject matter we pass on to those diverse phases of the physical world + which are the field of the chemist, and to those yet more intricate + processes which have to do with living organisms. So radical are the + changes here that we seem to be entering new worlds; and yet, here as + before, there are intimations of the new discoveries away back in the + Greek days. The solution of the problem of respiration will remind us that + Anaxagoras half guessed the secret; and in those diversified studies which + tell us of the Daltonian atom in its wonderful transmutations, we shall be + reminded again of the Clazomenian philosopher and his successor + Democritus. + </p> + <p> + Yet we should press the analogy much too far were we to intimate that the + Greek of the elder day or any thinker of a more recent period had + penetrated, even in the vaguest way, all of the mysteries that the + nineteenth century has revealed in the fields of chemistry and biology. At + the very most the insight of those great Greeks and of the wonderful + seventeenth-century philosophers who so often seemed on the verge of our + later discoveries did no more than vaguely anticipate their successors of + this later century. To gain an accurate, really specific knowledge of the + properties of elementary bodies was reserved for the chemists of a recent + epoch. The vague Greek questionings as to organic evolution were + world-wide from the precise inductions of a Darwin. If the mediaeval + Arabian endeavored to dull the knife of the surgeon with the use of drugs, + his results hardly merit to be termed even an anticipation of modern + anaesthesia. And when we speak of preventive medicine—of + bacteriology in all its phases—we have to do with a marvellous field + of which no previous generation of men had even the slightest inkling. + </p> + <p> + All in all, then, those that lie before us are perhaps the most wonderful + and the most fascinating of all the fields of science. As the chapters of + the preceding book carried us out into a macrocosm of inconceivable + magnitude, our present studies are to reveal a microcosm of equally + inconceivable smallness. As the studies of the physicist attempted to + reveal the very nature of matter and of energy, we have now to seek the + solution of the yet more inscrutable problems of life and of mind. + </p> + <p> + <a name="link2H_4_0002" id="link2H_4_0002"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + I. THE PHLOGISTON THEORY IN CHEMISTRY + </h2> + <p> + The development of the science of chemistry from the "science" of alchemy + is a striking example of the complete revolution in the attitude of + observers in the field of science. As has been pointed out in a preceding + chapter, the alchemist, having a preconceived idea of how things should + be, made all his experiments to prove his preconceived theory; while the + chemist reverses this attitude of mind and bases his conceptions on the + results of his laboratory experiments. In short, chemistry is what alchemy + never could be, an inductive science. But this transition from one point + of view to an exactly opposite one was necessarily a very slow process. + Ideas that have held undisputed sway over the minds of succeeding + generations for hundreds of years cannot be overthrown in a moment, unless + the agent of such an overthrow be so obvious that it cannot be challenged. + The rudimentary chemistry that overthrew alchemy had nothing so obvious + and palpable. + </p> + <p> + The great first step was the substitution of the one principle, + phlogiston, for the three principles, salt, sulphur, and mercury. We have + seen how the experiment of burning or calcining such a metal as lead + "destroyed" the lead as such, leaving an entirely different substance in + its place, and how the original metal could be restored by the addition of + wheat to the calcined product. To the alchemist this was "mortification" + and "revivification" of the metal. For, as pointed out by Paracelsus, + "anything that could be killed by man could also be revivified by him, + although this was not possible to the things killed by God." The burning + of such substances as wood, wax, oil, etc., was also looked upon as the + same "killing" process, and the fact that the alchemist was unable to + revivify them was regarded as simply the lack of skill on his part, and in + no wise affecting the theory itself. + </p> + <p> + But the iconoclastic spirit, if not the acceptance of all the teachings, + of the great Paracelsus had been gradually taking root among the better + class of alchemists, and about the middle of the seventeenth century + Robert Boyle (1626-1691) called attention to the possibility of making a + wrong deduction from the phenomenon of the calcination of the metals, + because of a very important factor, the action of the air, which was + generally overlooked. And he urged his colleagues of the laboratories to + give greater heed to certain other phenomena that might pass unnoticed in + the ordinary calcinating process. In his work, The Sceptical Chemist, he + showed the reasons for doubting the threefold constitution of matter; and + in his General History of the Air advanced some novel and carefully + studied theories as to the composition of the atmosphere. This was an + important step, and although Boyle is not directly responsible for the + phlogiston theory, it is probable that his experiments on the atmosphere + influenced considerably the real founders, Becker and Stahl. + </p> + <p> + Boyle gave very definitely his idea of how he thought air might be + composed. "I conjecture that the atmospherical air consists of three + different kinds of corpuscles," he says; "the first, those numberless + particles which, in the form of vapors or dry exhalations, ascend from the + earth, water, minerals, vegetables, animals, etc.; in a word, whatever + substances are elevated by the celestial or subterraneal heat, and thence + diffused into the atmosphere. The second may be yet more subtle, and + consist of those exceedingly minute atoms, the magnetical effluvia of the + earth, with other innumerable particles sent out from the bodies of the + celestial luminaries, and causing, by their influence, the idea of light + in us. The third sort is its characteristic and essential property, I mean + permanently elastic parts. Various hypotheses may be framed relating to + the structure of these later particles of the air. They might be resembled + to the springs of watches, coiled up and endeavoring to restore + themselves; to wool, which, being compressed, has an elastic force; to + slender wires of different substances, consistencies, lengths, and + thickness; in greater curls or less, near to, or remote from each other, + etc., yet all continuing springy, expansible, and compressible. Lastly, + they may also be compared to the thin shavings of different kinds of wood, + various in their lengths, breadth, and thickness. And this, perhaps, will + seem the most eligible hypothesis, because it, in some measure, + illustrates the production of the elastic particles we are considering. + For no art or curious instruments are required to make these shavings + whose curls are in no wise uniform, but seemingly casual; and what is more + remarkable, bodies that before seemed unelastic, as beams and blocks, will + afford them."(1) + </p> + <p> + Although this explanation of the composition of the air is most crude, it + had the effect of directing attention to the fact that the atmosphere is + not "mere nothingness," but a "something" with a definite composition, and + this served as a good foundation for future investigations. To be sure, + Boyle was neither the first nor the only chemist who had suspected that + the air was a mixture of gases, and not a simple one, and that only + certain of these gases take part in the process of calcination. Jean Rey, + a French physician, and John Mayow, an Englishman, had preformed + experiments which showed conclusively that the air was not a simple + substance; but Boyle's work was better known, and in its effect probably + more important. But with all Boyle's explanations of the composition of + air, he still believed that there was an inexplicable something, a "vital + substance," which he was unable to fathom, and which later became the + basis of Stahl's phlogiston theory. Commenting on this mysterious + substance, Boyle says: "The difficulty we find in keeping flame and fire + alive, though but for a little time, without air, renders it suspicious + that there be dispersed through the rest of the atmosphere some odd + substance, either of a solar, astral, or other foreign nature; on account + of which the air is so necessary to the substance of flame!" It was this + idea that attracted the attention of George Ernst Stahl (1660-1734), a + professor of medicine in the University of Halle, who later founded his + new theory upon it. Stahl's theory was a development of an earlier + chemist, Johann Joachim Becker (1635-1682), in whose footsteps he followed + and whose experiments he carried further. + </p> + <p> + In many experiments Stahl had been struck with the fact that certain + substances, while differing widely, from one another in many respects, + were alike in combustibility. From this he argued that all combustible + substances must contain a common principle, and this principle he named + phlogiston. This phlogiston he believed to be intimately associated in + combination with other substances in nature, and in that condition not + perceivable by the senses; but it was supposed to escape as a substance + burned, and become apparent to the senses as fire or flame. In other + words, phlogiston was something imprisoned in a combustible structure + (itself forming part of the structure), and only liberated when this + structure was destroyed. Fire, or flame, was FREE phlogiston, while the + imprisoned phlogiston was called COMBINED PHLOGISTON, or combined fire. + The peculiar quality of this strange substance was that it disliked + freedom and was always striving to conceal itself in some combustible + substance. Boyle's tentative suggestion that heat was simply motion was + apparently not accepted by Stahl, or perhaps it was unknown to him. + </p> + <p> + According to the phlogistic theory, the part remaining after a substance + was burned was simply the original substance deprived of phlogiston. To + restore the original combustible substance, it was necessary to heat the + residue of the combustion with something that burned easily, so that the + freed phlogiston might again combine with the ashes. This was explained by + the supposition that the more combustible a substance was the more + phlogiston it contained, and since free phlogiston sought always to + combine with some suitable substance, it was only necessary to mix the + phlogisticating agents, such as charcoal, phosphorus, oils, fats, etc., + with the ashes of the original substance, and heat the mixture, the + phlogiston thus freed uniting at once with the ashes. This theory fitted + very nicely as applied to the calcined lead revivified by the grains of + wheat, although with some other products of calcination it did not seem to + apply at all. + </p> + <p> + It will be seen from this that the phlogistic theory was a step towards + chemistry and away from alchemy. It led away from the idea of a "spirit" + in metals that could not be seen, felt, or appreciated by any of the + senses, and substituted for it a principle which, although a falsely + conceived one, was still much more tangible than the "spirit," since it + could be seen and felt as free phlogiston and weighed and measured as + combined phlogiston. The definiteness of the statement that a metal, for + example, was composed of phlogiston and an element was much less + enigmatic, even if wrong, than the statement of the alchemist that "metals + are produced by the spiritual action of the three principles, salt, + mercury, sulphur"—particularly when it is explained that salt, + mercury, and sulphur were really not what their names implied, and that + there was no universally accepted belief as to what they really were. + </p> + <p> + The metals, which are now regarded as elementary bodies, were considered + compounds by the phlogistians, and they believed that the calcining of a + metal was a process of simplification. They noted, however, that the + remains of calcination weighed more than the original product, and the + natural inference from this would be that the metal must have taken in + some substance rather than have given off anything. But the phlogistians + had not learned the all-important significance of weights, and their + explanation of variation in weight was either that such gain or loss was + an unimportant "accident" at best, or that phlogiston, being light, tended + to lighten any substance containing it, so that driving it out of the + metal by calcination naturally left the residue heavier. + </p> + <p> + At first the phlogiston theory seemed to explain in an indisputable way + all the known chemical phenomena. Gradually, however, as experiments + multiplied, it became evident that the plain theory as stated by Stahl and + his followers failed to explain satisfactorily certain laboratory + reactions. To meet these new conditions, certain modifications were + introduced from time to time, giving the theory a flexibility that would + allow it to cover all cases. But as the number of inexplicable experiments + continued to increase, and new modifications to the theory became + necessary, it was found that some of these modifications were directly + contradictory to others, and thus the simple theory became too cumbersome + from the number of its modifications. Its supporters disagreed among + themselves, first as to the explanation of certain phenomena that did not + seem to accord with the phlogistic theory, and a little later as to the + theory itself. But as yet there was no satisfactory substitute for this + theory, which, even if unsatisfactory, seemed better than anything that + had gone before or could be suggested. + </p> + <p> + But the good effects of the era of experimental research, to which the + theory of Stahl had given such an impetus, were showing in the attitude of + the experimenters. The works of some of the older writers, such as Boyle + and Hooke, were again sought out in their dusty corners and consulted, and + their surmises as to the possible mixture of various gases in the air were + more carefully considered. Still the phlogiston theory was firmly grounded + in the minds of the philosophers, who can hardly be censured for adhering + to it, at least until some satisfactory substitute was offered. The + foundation for such a theory was finally laid, as we shall see presently, + by the work of Black, Priestley, Cavendish, and Lavoisier, in the + eighteenth century, but the phlogiston theory cannot be said to have + finally succumbed until the opening years of the nineteenth century. + </p> + <p> + <a name="link2H_4_0003" id="link2H_4_0003"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + II. THE BEGINNINGS OF MODERN CHEMISTRY + </h2> + <h3> + THE "PNEUMATIC" CHEMISTS + </h3> + <p> + Modern chemistry may be said to have its beginning with the work of + Stephen Hales (1677-1761), who early in the eighteenth century began his + important study of the elasticity of air. Departing from the point of view + of most of the scientists of the time, he considered air to be "a fine + elastic fluid, with particles of very different nature floating in it"; + and he showed that these "particles" could be separated. He pointed out, + also, that various gases, or "airs," as he called them, were contained in + many solid substances. The importance of his work, however, lies in the + fact that his general studies were along lines leading away from the + accepted doctrines of the time, and that they gave the impetus to the + investigation of the properties of gases by such chemists as Black, + Priestley, Cavendish, and Lavoisier, whose specific discoveries are the + foundation-stones of modern chemistry. + </p> + <p> + JOSEPH BLACK + </p> + <p> + The careful studies of Hales were continued by his younger confrere, Dr. + Joseph Black (1728-1799), whose experiments in the weights of gases and + other chemicals were first steps in quantitative chemistry. But even more + important than his discoveries of chemical properties in general was his + discovery of the properties of carbonic-acid gas. + </p> + <p> + Black had been educated for the medical profession in the University of + Glasgow, being a friend and pupil of the famous Dr. William Cullen. But + his liking was for the chemical laboratory rather than for the practice of + medicine. Within three years after completing his medical course, and when + only twenty-three years of age, he made the discovery of the properties of + carbonic acid, which he called by the name of "fixed air." After + discovering this gas, Black made a long series of experiments, by which he + was able to show how widely it was distributed throughout nature. Thus, in + 1757, he discovered that the bubbles given off in the process of brewing, + where there was vegetable fermentation, were composed of it. To prove + this, he collected the contents of these bubbles in a bottle containing + lime-water. When this bottle was shaken violently, so that the lime-water + and the carbonic acid became thoroughly mixed, an insoluble white powder + was precipitated from the solution, the carbonic acid having combined + chemically with the lime to form the insoluble calcium carbonate, or + chalk. This experiment suggested another. Fixing a piece of burning + charcoal in the end of a bellows, he arranged a tube so that the gas + coming from the charcoal would pass through the lime-water, and, as in the + case of the bubbles from the brewer's vat, he found that the white + precipitate was thrown down; in short, that carbonic acid was given off in + combustion. Shortly after, Black discovered that by blowing through a + glass tube inserted into lime-water, chalk was precipitated, thus proving + that carbonic acid was being constantly thrown off in respiration. + </p> + <p> + The effect of Black's discoveries was revolutionary, and the attitude of + mind of the chemists towards gases, or "airs," was changed from that time + forward. Most of the chemists, however, attempted to harmonize the new + facts with the older theories—to explain all the phenomena on the + basis of the phlogiston theory, which was still dominant. But while many + of Black's discoveries could not be made to harmonize with that theory, + they did not directly overthrow it. It required the additional discoveries + of some of Black's fellow-scientists to complete its downfall, as we shall + see. + </p> + <p> + HENRY CAVENDISH + </p> + <p> + This work of Black's was followed by the equally important work of his + former pupil, Henry Cavendish (1731-1810), whose discovery of the + composition of many substances, notably of nitric acid and of water, was + of great importance, adding another link to the important chain of + evidence against the phlogiston theory. Cavendish is one of the most + eccentric figures in the history of science, being widely known in his own + time for his immense wealth and brilliant intellect, and also for his + peculiarities and his morbid sensibility, which made him dread society, + and probably did much in determining his career. Fortunately for him, and + incidentally for the cause of science, he was able to pursue laboratory + investigations without being obliged to mingle with his dreaded + fellow-mortals, his every want being provided for by the immense fortune + inherited from his father and an uncle. + </p> + <p> + When a young man, as a pupil of Dr. Black, he had become imbued with the + enthusiasm of his teacher, continuing Black's investigations as to the + properties of carbonic-acid gas when free and in combination. One of his + first investigations was reported in 1766, when he communicated to the + Royal Society his experiments for ascertaining the properties of + carbonic-acid and hydrogen gas, in which he first showed the possibility + of weighing permanently elastic fluids, although Torricelli had before + this shown the relative weights of a column of air and a column of + mercury. Other important experiments were continued by Cavendish, and in + 1784 he announced his discovery of the composition of water, thus robbing + it of its time-honored position as an "element." But his claim to priority + in this discovery was at once disputed by his fellow-countryman James Watt + and by the Frenchman Lavoisier. Lavoisier's claim was soon disallowed even + by his own countrymen, but for many years a bitter controversy was carried + on by the partisans of Watt and Cavendish. The two principals, however, + seem never to have entered into this controversy with anything like the + same ardor as some of their successors, as they remained on the best of + terms.(1) It is certain, at any rate, that Cavendish announced his + discovery officially before Watt claimed that the announcement had been + previously made by him, "and, whether right or wrong, the honor of + scientific discoveries seems to be accorded naturally to the man who first + publishes a demonstration of his discovery." Englishmen very generally + admit the justness of Cavendish's claim, although the French scientist + Arago, after reviewing the evidence carefully in 1833, decided in favor of + Watt. + </p> + <p> + It appears that something like a year before Cavendish made known his + complete demonstration of the composition of water, Watt communicated to + the Royal Society a suggestion that water was composed of + "dephlogisticated air (oxygen) and phlogiston (hydrogen) deprived of part + of its latent heat." Cavendish knew of the suggestion, but in his + experiments refuted the idea that the hydrogen lost any of its latent + heat. Furthermore, Watt merely suggested the possible composition without + proving it, although his idea was practically correct, if we can rightly + interpret the vagaries of the nomenclature then in use. But had Watt taken + the steps to demonstrate his theory, the great "Water Controversy" would + have been avoided. Cavendish's report of his discovery to the Royal + Society covers something like forty pages of printed matter. In this he + shows how, by passing an electric spark through a closed jar containing a + mixture of hydrogen gas and oxygen, water is invariably formed, apparently + by the union of the two gases. The experiment was first tried with + hydrogen and common air, the oxygen of the air uniting with the hydrogen + to form water, leaving the nitrogen of the air still to be accounted for. + With pure oxygen and hydrogen, however, Cavendish found that pure water + was formed, leaving slight traces of any other, substance which might not + be interpreted as being Chemical impurities. There was only one possible + explanation of this phenomenon—that hydrogen and oxygen, when + combined, form water. + </p> + <p> + "By experiments with the globe it appeared," wrote Cavendish, "that when + inflammable and common air are exploded in a proper proportion, almost all + the inflammable air, and near one-fifth the common air, lose their + elasticity and are condensed into dew. And by this experiment it appears + that this dew is plain water, and consequently that almost all the + inflammable air is turned into pure water. + </p> + <p> + "In order to examine the nature of the matter condensed on firing a + mixture of dephlogisticated and inflammable air, I took a glass globe, + holding 8800 grain measures, furnished with a brass cock and an apparatus + for firing by electricity. This globe was well exhausted by an air-pump, + and then filled with a mixture of inflammable and dephlogisticated air by + shutting the cock, fastening the bent glass tube into its mouth, and + letting up the end of it into a glass jar inverted into water and + containing a mixture of 19,500 grain measures of dephlogisticated air, and + 37,000 of inflammable air; so that, upon opening the cock, some of this + mixed air rushed through the bent tube and filled the globe. The cock was + then shut and the included air fired by electricity, by means of which + almost all of it lost its elasticity (was condensed into water vapors). + The cock was then again opened so as to let in more of the same air to + supply the place of that destroyed by the explosion, which was again + fired, and the operation continued till almost the whole of the mixture + was let into the globe and exploded. By this means, though the globe held + not more than a sixth part of the mixture, almost the whole of it was + exploded therein without any fresh exhaustion of the globe." + </p> + <p> + At first this condensed matter was "acid to the taste and contained two + grains of nitre," but Cavendish, suspecting that this was due to + impurities, tried another experiment that proved conclusively that his + opinions were correct. "I therefore made another experiment," he says, + "with some more of the same air from plants in which the proportion of + inflammable air was greater, so that the burnt air was almost completely + phlogisticated, its standard being one-tenth. The condensed liquor was + then not at all acid, but seemed pure water." + </p> + <p> + From these experiments he concludes "that when a mixture of inflammable + and dephlogisticated air is exploded, in such proportions that the burnt + air is not much phlogisticated, the condensed liquor contains a little + acid which is always of the nitrous kind, whatever substance the + dephlogisticated air is procured from; but if the proportion be such that + the burnt air is almost entirely phlogisticated, the condensed liquor is + not at all acid, but seems pure water, without any addition whatever."(2) + </p> + <p> + These same experiments, which were undertaken to discover the composition + of water, led him to discover also the composition of nitric acid. He had + observed that, in the combustion of hydrogen gas with common air, the + water was slightly tinged with acid, but that this was not the case when + pure oxygen gas was used. Acting upon this observation, he devised an + experiment to determine the nature of this acid. He constructed an + apparatus whereby an electric spark was passed through a vessel containing + common air. After this process had been carried on for several weeks a + small amount of liquid was formed. This liquid combined with a solution of + potash to form common nitre, which "detonated with charcoal, sparkled when + paper impregnated with it was burned, and gave out nitrous fumes when + sulphuric acid was poured on it." In other words, the liquid was shown to + be nitric acid. Now, since nothing but pure air had been used in the + initial experiment, and since air is composed of nitrogen and oxygen, + there seemed no room to doubt that nitric acid is a combination of + nitrogen and oxygen. + </p> + <p> + This discovery of the nature of nitric acid seems to have been about the + last work of importance that Cavendish did in the field of chemistry, + although almost to the hour of his death he was constantly occupied with + scientific observations. Even in the last moments of his life this habit + asserted itself, according to Lord Brougham. "He died on March 10, 1810, + after a short illness, probably the first, as well as the last, which he + ever suffered. His habit of curious observation continued to the end. He + was desirous of marking the progress of the disease and the gradual + extinction of the vital powers. With these ends in view, that he might not + be disturbed, he desired to be left alone. His servant, returning sooner + than he had wished, was ordered again to leave the chamber of death, and + when he came back a second time he found his master had expired."(3) + </p> + <p> + JOSEPH PRIESTLEY + </p> + <p> + While the opulent but diffident Cavendish was making his important + discoveries, another Englishman, a poor country preacher named Joseph + Priestley (1733-1804) was not only rivalling him, but, if anything, + outstripping him in the pursuit of chemical discoveries. In 1761 this + young minister was given a position as tutor in a nonconformist academy at + Warrington, and here, for six years, he was able to pursue his studies in + chemistry and electricity. In 1766, while on a visit to London, he met + Benjamin Franklin, at whose suggestion he published his History of + Electricity. From this time on he made steady progress in scientific + investigations, keeping up his ecclesiastical duties at the same time. In + 1780 he removed to Birmingham, having there for associates such scientists + as James Watt, Boulton, and Erasmus Darwin. + </p> + <p> + Eleven years later, on the anniversary of the fall of the Bastile in + Paris, a fanatical mob, knowing Priestley's sympathies with the French + revolutionists, attacked his house and chapel, burning both and destroying + a great number of valuable papers and scientific instruments. Priestley + and his family escaped violence by flight, but his most cherished + possessions were destroyed; and three years later he quitted England + forever, removing to the United States, whose struggle for liberty he had + championed. The last ten years of his life were spent at Northumberland, + Pennsylvania, where he continued his scientific researches. + </p> + <p> + Early in his scientific career Priestley began investigations upon the + "fixed air" of Dr. Black, and, oddly enough, he was stimulated to this by + the same thing that had influenced Black—that is, his residence in + the immediate neighborhood of a brewery. It was during the course of a + series of experiments on this and other gases that he made his greatest + discovery, that of oxygen, or "dephlogisticated air," as he called it. The + story of this important discovery is probably best told in Priestley's own + words: + </p> + <p> + "There are, I believe, very few maxims in philosophy that have laid firmer + hold upon the mind than that air, meaning atmospheric air, is a simple + elementary substance, indestructible and unalterable, at least as much so + as water is supposed to be. In the course of my inquiries I was, however, + soon satisfied that atmospheric air is not an unalterable thing; for that, + according to my first hypothesis, the phlogiston with which it becomes + loaded from bodies burning in it, and the animals breathing it, and + various other chemical processes, so far alters and depraves it as to + render it altogether unfit for inflammation, respiration, and other + purposes to which it is subservient; and I had discovered that agitation + in the water, the process of vegetation, and probably other natural + processes, restore it to its original purity.... + </p> + <p> + "Having procured a lens of twelve inches diameter and twenty inches local + distance, I proceeded with the greatest alacrity, by the help of it, to + discover what kind of air a great variety of substances would yield, + putting them into the vessel, which I filled with quicksilver, and kept + inverted in a basin of the same .... With this apparatus, after a variety + of experiments.... on the 1st of August, 1774, I endeavored to extract air + from mercurius calcinatus per se; and I presently found that, by means of + this lens, air was expelled from it very readily. Having got about three + or four times as much as the bulk of my materials, I admitted water to it, + and found that it was not imbibed by it. But what surprised me more than I + can express was that a candle burned in this air with a remarkably + vigorous flame, very much like that enlarged flame with which a candle + burns in nitrous oxide, exposed to iron or liver of sulphur; but as I had + got nothing like this remarkable appearance from any kind of air besides + this particular modification of vitrous air, and I knew no vitrous acid + was used in the preparation of mercurius calcinatus, I was utterly at a + loss to account for it."(4) + </p> + <p> + The "new air" was, of course, oxygen. Priestley at once proceeded to + examine it by a long series of careful experiments, in which, as will be + seen, he discovered most of the remarkable qualities of this gas. + Continuing his description of these experiments, he says: + </p> + <p> + "The flame of the candle, besides being larger, burned with more splendor + and heat than in that species of nitrous air; and a piece of red-hot wood + sparkled in it, exactly like paper dipped in a solution of nitre, and it + consumed very fast; an experiment that I had never thought of trying with + dephlogisticated nitrous air. + </p> + <p> + "... I had so little suspicion of the air from the mercurius calcinatus, + etc., being wholesome, that I had not even thought of applying it to the + test of nitrous air; but thinking (as my reader must imagine I frequently + must have done) on the candle burning in it after long agitation in water, + it occurred to me at last to make the experiment; and, putting one measure + of nitrous air to two measures of this air, I found not only that it was + diminished, but that it was diminished quite as much as common air, and + that the redness of the mixture was likewise equal to a similar mixture of + nitrous and common air.... The next day I was more surprised than ever I + had been before with finding that, after the above-mentioned mixture of + nitrous air and the air from mercurius calcinatus had stood all night,... + a candle burned in it, even better than in common air." + </p> + <p> + A little later Priestley discovered that "dephlogisticated air... is a + principal element in the composition of acids, and may be extracted by + means of heat from many substances which contain them.... It is likewise + produced by the action of light upon green vegetables; and this seems to + be the chief means employed to preserve the purity of the atmosphere." + </p> + <p> + This recognition of the important part played by oxygen in the atmosphere + led Priestley to make some experiments upon mice and insects, and finally + upon himself, by inhalations of the pure gas. "The feeling in my lungs," + he said, "was not sensibly different from that of common air, but I + fancied that my breathing felt peculiarly light and easy for some time + afterwards. Who can tell but that in time this pure air may become a + fashionable article in luxury?... Perhaps we may from these experiments + see that though pure dephlogisticated air might be useful as a medicine, + it might not be so proper for us in the usual healthy state of the body." + </p> + <p> + This suggestion as to the possible usefulness of oxygen as a medicine was + prophetic. A century later the use of oxygen had become a matter of + routine practice with many physicians. Even in Priestley's own time such + men as Dr. John Hunter expressed their belief in its efficacy in certain + conditions, as we shall see, but its value in medicine was not fully + appreciated until several generations later. + </p> + <p> + Several years after discovering oxygen Priestley thus summarized its + properties: "It is this ingredient in the atmospheric air that enables it + to support combustion and animal life. By means of it most intense heat + may be produced, and in the purest of it animals will live nearly five + times as long as in an equal quantity of atmospheric air. In respiration, + part of this air, passing the membranes of the lungs, unites with the + blood and imparts to it its florid color, while the remainder, uniting + with phlogiston exhaled from venous blood, forms mixed air. It is + dephlogisticated air combined with water that enables fishes to live in + it."(5) + </p> + <p> + KARL WILHELM SCHEELE + </p> + <p> + The discovery of oxygen was the last but most important blow to the + tottering phlogiston theory, though Priestley himself would not admit it. + But before considering the final steps in the overthrow of Stahl's famous + theory and the establishment of modern chemistry, we must review the work + of another great chemist, Karl Wilhelm Scheele (1742-1786), of Sweden, who + discovered oxygen quite independently, although later than Priestley. In + the matter of brilliant discoveries in a brief space of time Scheele + probably eclipsed all his great contemporaries. He had a veritable genius + for interpreting chemical reactions and discovering new substances, in + this respect rivalling Priestley himself. Unlike Priestley, however, he + planned all his experiments along the lines of definite theories from the + beginning, the results obtained being the logical outcome of a + predetermined plan. + </p> + <p> + Scheele was the son of a merchant of Stralsund, Pomerania, which then + belonged to Sweden. As a boy in school he showed so little aptitude for + the study of languages that he was apprenticed to an apothecary at the age + of fourteen. In this work he became at once greatly interested, and, when + not attending to his duties in the dispensary, he was busy day and night + making experiments or studying books on chemistry. In 1775, still employed + as an apothecary, he moved to Stockholm, and soon after he sent to + Bergman, the leading chemist of Sweden, his first discovery—that of + tartaric acid, which he had isolated from cream of tartar. This was the + beginning of his career of discovery, and from that time on until his + death he sent forth accounts of new discoveries almost uninterruptedly. + Meanwhile he was performing the duties of an ordinary apothecary, and + struggling against poverty. His treatise upon Air and Fire appeared in + 1777. In this remarkable book he tells of his discovery of oxygen—"empyreal" + or "fire-air," as he calls it—which he seems to have made + independently and without ever having heard of the previous discovery by + Priestley. In this book, also, he shows that air is composed chiefly of + oxygen and nitrogen gas. + </p> + <p> + Early in his experimental career Scheele undertook the solution of the + composition of black oxide of manganese, a substance that had long puzzled + the chemists. He not only succeeded in this, but incidentally in the + course of this series of experiments he discovered oxygen, baryta, and + chlorine, the last of far greater importance, at least commercially, than + the real object of his search. In speaking of the experiment in which the + discovery was made he says: + </p> + <p> + "When marine (hydrochloric) acid stood over manganese in the cold it + acquired a dark reddish-brown color. As manganese does not give any + colorless solution without uniting with phlogiston (probably meaning + hydrogen), it follows that marine acid can dissolve it without this + principle. But such a solution has a blue or red color. The color is here + more brown than red, the reason being that the very finest portions of the + manganese, which do not sink so easily, swim in the red solution; for + without these fine particles the solution is red, and red mixed with black + is brown. The manganese has here attached itself so loosely to acidum + salis that the water can precipitate it, and this precipitate behaves like + ordinary manganese. When, now, the mixture of manganese and spiritus salis + was set to digest, there arose an effervescence and smell of aqua + regis."(6) + </p> + <p> + The "effervescence" he refers to was chlorine, which he proceeded to + confine in a suitable vessel and examine more fully. He described it as + having a "quite characteristically suffocating smell," which was very + offensive. He very soon noted the decolorizing or bleaching effects of + this now product, finding that it decolorized flowers, vegetables, and + many other substances. + </p> + <p> + Commercially this discovery of chlorine was of enormous importance and the + practical application of this new chemical in bleaching cloth soon + supplanted the old process of crofting—that is, bleaching by + spreading the cloth upon the grass. But although Scheele first pointed out + the bleaching quality of his newly discovered gas, it was the French + savant, Berthollet, who, acting upon Scheele's discovery that the new gas + would decolorize vegetables and flowers, was led to suspect that this + property might be turned to account in destroying the color of cloth. In + 1785 he read a paper before the Academy of Sciences of Paris, in which he + showed that bleaching by chlorine was entirely satisfactory, the color but + not the substance of the cloth being affected. He had experimented + previously and found that the chlorine gas was soluble in water and could + thus be made practically available for bleaching purposes. In 1786 James + Watt examined specimens of the bleached cloth made by Berthollet, and upon + his return to England first instituted the process of practical bleaching. + His process, however, was not entirely satisfactory, and, after undergoing + various modifications and improvements, it was finally made thoroughly + practicable by Mr. Tennant, who hit upon a compound of chlorine and lime—the + chloride of lime—which was a comparatively cheap chemical product, + and answered the purpose better even than chlorine itself. + </p> + <p> + To appreciate how momentous this discovery was to cloth manufacturers, it + should be remembered that the old process of bleaching consumed an entire + summer for the whitening of a single piece of linen; the new process + reduced the period to a few hours. To be sure, lime had been used with + fair success previous to Tennant's discovery, but successful and practical + bleaching by a solution of chloride of lime was first made possible by him + and through Scheele's discovery of chlorine. + </p> + <p> + Until the time of Scheele the great subject of organic chemistry had + remained practically unexplored, but under the touch of his marvellous + inventive genius new methods of isolating and studying animal and + vegetable products were introduced, and a large number of acids and other + organic compounds prepared that had been hitherto unknown. His + explanations of chemical phenomena were based on the phlogiston theory, in + which, like Priestley, he always, believed. Although in error in this + respect, he was, nevertheless, able to make his discoveries with extremely + accurate interpretations. A brief epitome of the list of some of his more + important discoveries conveys some idea, of his fertility of mind as well + as his industry. In 1780 he discovered lactic acid,(7) and showed that it + was the substance that caused the acidity of sour milk; and in the same + year he discovered mucic acid. Next followed the discovery of tungstic + acid, and in 1783 he added to his list of useful discoveries that of + glycerine. Then in rapid succession came his announcements of the new + vegetable products citric, malic, oxalic, and gallic acids. Scheele not + only made the discoveries, but told the world how he had made them—how + any chemist might have made them if he chose—for he never considered + that he had really discovered any substance until he had made it, + decomposed it, and made it again. + </p> + <p> + His experiments on Prussian blue are most interesting, not only because of + the enormous amount of work involved and the skill he displayed in his + experiments, but because all the time the chemist was handling, smelling, + and even tasting a compound of one of the most deadly poisons, ignorant of + the fact that the substance was a dangerous one to handle. His escape from + injury seems almost miraculous; for his experiments, which were most + elaborate, extended over a considerable period of time, during which he + seems to have handled this chemical with impunity. + </p> + <p> + While only forty years of age and just at the zenith of his fame, Scheele + was stricken by a fatal illness, probably induced by his ceaseless labor + and exposure. It is gratifying to know, however, that during the last + eight or nine years of his life he had been less bound down by pecuniary + difficulties than before, as Bergman had obtained for him an annual grant + from the Academy. But it was characteristic of the man that, while + devoting one-sixth of the amount of this grant to his personal wants, the + remaining five-sixths was devoted to the expense of his experiments. + </p> + <p> + LAVOISIER AND THE FOUNDATION OF MODERN CHEMISTRY + </p> + <p> + The time was ripe for formulating the correct theory of chemical + composition: it needed but the master hand to mould the materials into the + proper shape. The discoveries in chemistry during the eighteenth century + had been far-reaching and revolutionary in character. A brief review of + these discoveries shows how completely they had subverted the old ideas of + chemical elements and chemical compounds. Of the four substances earth, + air, fire, and water, for many centuries believed to be elementary bodies, + not one has stood the test of the eighteenth-century chemists. Earth had + long since ceased to be regarded as an element, and water and air had + suffered the same fate in this century. And now at last fire itself, the + last of the four "elements" and the keystone to the phlogiston arch, was + shown to be nothing more than one of the manifestations of the new + element, oxygen, and not "phlogiston" or any other intangible substance. + </p> + <p> + In this epoch of chemical discoveries England had produced such mental + giants and pioneers in science as Black, Priestley, and Cavendish; Sweden + had given the world Scheele and Bergman, whose work, added to that of + their English confreres, had laid the broad base of chemistry as a + science; but it was for France to produce a man who gave the final touches + to the broad but rough workmanship of its foundation, and establish it as + the science of modern chemistry. It was for Antoine Laurent Lavoisier + (1743-1794) to gather together, interpret correctly, rename, and classify + the wealth of facts that his immediate predecessors and contemporaries had + given to the world. + </p> + <p> + The attitude of the mother-countries towards these illustrious sons is an + interesting piece of history. Sweden honored and rewarded Scheele and + Bergman for their efforts; England received the intellectuality of + Cavendish with less appreciation than the Continent, and a fanatical mob + drove Priestley out of the country; while France, by sending Lavoisier to + the guillotine, demonstrated how dangerous it was, at that time at least, + for an intelligent Frenchman to serve his fellowman and his country well. + </p> + <p> + "The revolution brought about by Lavoisier in science," says Hoefer, + "coincides by a singular act of destiny with another revolution, much + greater indeed, going on then in the political and social world. Both + happened on the same soil, at the same epoch, among the same people; and + both marked the commencement of a new era in their respective spheres."(8) + </p> + <p> + Lavoisier was born in Paris, and being the son of an opulent family, was + educated under the instruction of the best teachers of the day. With + Lacaille he studied mathematics and astronomy; with Jussieu, botany; and, + finally, chemistry under Rouelle. His first work of importance was a paper + on the practical illumination of the streets of Paris, for which a prize + had been offered by M. de Sartine, the chief of police. This prize was not + awarded to Lavoisier, but his suggestions were of such importance that the + king directed that a gold medal be bestowed upon the young author at the + public sitting of the Academy in April, 1776. Two years later, at the age + of thirty-five, Lavoisier was admitted a member of the Academy. + </p> + <p> + In this same year he began to devote himself almost exclusively to + chemical inquiries, and established a laboratory in his home, fitted with + all manner of costly apparatus and chemicals. Here he was in constant + communication with the great men of science of Paris, to all of whom his + doors were thrown open. One of his first undertakings in this laboratory + was to demonstrate that water could not be converted into earth by + repeated distillations, as was generally advocated; and to show also that + there was no foundation to the existing belief that it was possible to + convert water into a gas so "elastic" as to pass through the pores of a + vessel. He demonstrated the fallaciousness of both these theories in + 1768-1769 by elaborate experiments, a single investigation of this series + occupying one hundred and one days. + </p> + <p> + In 1771 he gave the first blow to the phlogiston theory by his experiments + on the calcination of metals. It will be recalled that one basis for the + belief in phlogiston was the fact that when a metal was calcined it was + converted into an ash, giving up its "phlogiston" in the process. To + restore the metal, it was necessary to add some substance such as wheat or + charcoal to the ash. Lavoisier, in examining this process of restoration, + found that there was always evolved a great quantity of "air," which he + supposed to be "fixed air" or carbonic acid—the same that escapes in + effervescence of alkalies and calcareous earths, and in the fermentation + of liquors. He then examined the process of calcination, whereby the + phlogiston of the metal was supposed to have been drawn off. But far from + finding that phlogiston or any other substance had been driven off, he + found that something had been taken on: that the metal "absorbed air," and + that the increased weight of the metal corresponded to the amount of air + "absorbed." Meanwhile he was within grasp of two great discoveries, that + of oxygen and of the composition of the air, which Priestley made some two + years later. + </p> + <p> + The next important inquiry of this great Frenchman was as to the + composition of diamonds. With the great lens of Tschirnhausen belonging to + the Academy he succeeded in burning up several diamonds, regardless of + expense, which, thanks to his inheritance, he could ignore. In this + process he found that a gas was given off which precipitated lime from + water, and proved to be carbonic acid. Observing this, and experimenting + with other substances known to give off carbonic acid in the same manner, + he was evidently impressed with the now well-known fact that diamond and + charcoal are chemically the same. But if he did really believe it, he was + cautious in expressing his belief fully. "We should never have expected," + he says, "to find any relation between charcoal and diamond, and it would + be unreasonable to push this analogy too far; it only exists because both + substances seem to be properly ranged in the class of combustible bodies, + and because they are of all these bodies the most fixed when kept from + contact with air." + </p> + <p> + As we have seen, Priestley, in 1774, had discovered oxygen, or + "dephlogisticated air." Four years later Lavoisier first advanced his + theory that this element discovered by Priestley was the universal + acidifying or oxygenating principle, which, when combined with charcoal or + carbon, formed carbonic acid; when combined with sulphur, formed sulphuric + (or vitriolic) acid; with nitrogen, formed nitric acid, etc., and when + combined with the metals formed oxides, or calcides. Furthermore, he + postulated the theory that combustion was not due to any such illusive + thing as "phlogiston," since this did not exist, and it seemed to him that + the phenomena of combustion heretofore attributed to phlogiston could be + explained by the action of the new element oxygen and heat. This was the + final blow to the phlogiston theory, which, although it had been tottering + for some time, had not been completely overthrown. + </p> + <p> + In 1787 Lavoisier, in conjunction with Guyon de Morveau, Berthollet, and + Fourcroy, introduced the reform in chemical nomenclature which until then + had remained practically unchanged since alchemical days. Such expressions + as "dephlogisticated" and "phlogisticated" would obviously have little + meaning to a generation who were no longer to believe in the existence of + phlogiston. It was appropriate that a revolution in chemical thought + should be accompanied by a corresponding revolution in chemical names, and + to Lavoisier belongs chiefly the credit of bringing about this revolution. + In his Elements of Chemistry he made use of this new nomenclature, and it + seemed so clearly an improvement over the old that the scientific world + hastened to adopt it. In this connection Lavoisier says: "We have, + therefore, laid aside the expression metallic calx altogether, and have + substituted in its place the word oxide. By this it may be seen that the + language we have adopted is both copious and expressive. The first or + lowest degree of oxygenation in bodies converts them into oxides; a second + degree of additional oxygenation constitutes the class of acids of which + the specific names drawn from their particular bases terminate in ous, as + in the nitrous and the sulphurous acids. The third degree of oxygenation + changes these into the species of acids distinguished by the termination + in ic, as the nitric and sulphuric acids; and, lastly, we can express a + fourth or higher degree of oxygenation by adding the word oxygenated to + the name of the acid, as has already been done with oxygenated muriatic + acid."(9) + </p> + <p> + This new work when given to the world was not merely an epoch-making book; + it was revolutionary. It not only discarded phlogiston altogether, but set + forth that metals are simple elements, not compounds of "earth" and + "phlogiston." It upheld Cavendish's demonstration that water itself, like + air, is a compound of oxygen with another element. In short, it was + scientific chemistry, in the modern acceptance of the term. + </p> + <p> + Lavoisier's observations on combustion are at once important and + interesting: "Combustion," he says, "... is the decomposition of oxygen + produced by a combustible body. The oxygen which forms the base of this + gas is absorbed by and enters into combination with the burning body, + while the caloric and light are set free. Every combustion necessarily + supposes oxygenation; whereas, on the contrary, every oxygenation does not + necessarily imply concomitant combustion; because combustion properly so + called cannot take place without disengagement of caloric and light. + Before combustion can take place, it is necessary that the base of oxygen + gas should have greater affinity to the combustible body than it has to + caloric; and this elective attraction, to use Bergman's expression, can + only take place at a certain degree of temperature which is different for + each combustible substance; hence the necessity of giving the first motion + or beginning to every combustion by the approach of a heated body. This + necessity of heating any body we mean to burn depends upon certain + considerations which have not hitherto been attended to by any natural + philosopher, for which reason I shall enlarge a little upon the subject in + this place: + </p> + <p> + "Nature is at present in a state of equilibrium, which cannot have been + attained until all the spontaneous combustions or oxygenations possible in + an ordinary degree of temperature had taken place.... To illustrate this + abstract view of the matter by example: Let us suppose the usual + temperature of the earth a little changed, and it is raised only to the + degree of boiling water; it is evident that in this case phosphorus, which + is combustible in a considerably lower degree of temperature, would no + longer exist in nature in its pure and simple state, but would always be + procured in its acid or oxygenated state, and its radical would become one + of the substances unknown to chemistry. By gradually increasing the + temperature of the earth, the same circumstance would successively happen + to all the bodies capable of combustion; and, at the last, every possible + combustion having taken place, there would no longer exist any combustible + body whatever, and every substance susceptible of the operation would be + oxygenated and consequently incombustible. + </p> + <p> + "There cannot, therefore, exist, as far as relates to us, any combustible + body but such as are non-combustible at the ordinary temperature of the + earth, or, what is the same thing in other words, that it is essential to + the nature of every combustible body not to possess the property of + combustion unless heated, or raised to a degree of temperature at which + its combustion naturally takes place. When this degree is once produced, + combustion commences, and the caloric which is disengaged by the + decomposition of the oxygen gas keeps up the temperature which is + necessary for continuing combustion. When this is not the case—that + is, when the disengaged caloric is not sufficient for keeping up the + necessary temperature—the combustion ceases. This circumstance is + expressed in the common language by saying that a body burns ill or with + difficulty."(10) + </p> + <p> + It needed the genius of such a man as Lavoisier to complete the refutation + of the false but firmly grounded phlogiston theory, and against such a + book as his Elements of Chemistry the feeble weapons of the supporters of + the phlogiston theory were hurled in vain. + </p> + <p> + But while chemists, as a class, had become converts to the new chemistry + before the end of the century, one man, Dr. Priestley, whose work had done + so much to found it, remained unconverted. In this, as in all his + life-work, he showed himself to be a most remarkable man. Davy said of + him, a generation later, that no other person ever discovered so many new + and curious substances as he; yet to the last he was only an amateur in + science, his profession, as we know, being the ministry. There is hardly + another case in history of a man not a specialist in science accomplishing + so much in original research as did this chemist, physiologist, + electrician; the mathematician, logician, and moralist; the theologian, + mental philosopher, and political economist. He took all knowledge for his + field; but how he found time for his numberless researches and + multifarious writings, along with his every-day duties, must ever remain a + mystery to ordinary mortals. + </p> + <p> + That this marvellously receptive, flexible mind should have refused + acceptance to the clearly logical doctrines of the new chemistry seems + equally inexplicable. But so it was. To the very last, after all his + friends had capitulated, Priestley kept up the fight. From America he sent + out his last defy to the enemy, in 1800, in a brochure entitled "The + Doctrine of Phlogiston Upheld," etc. In the mind of its author it was + little less than a paean of victory; but all the world beside knew that it + was the swan-song of the doctrine of phlogiston. Despite the defiance of + this single warrior the battle was really lost and won, and as the century + closed "antiphlogistic" chemistry had practical possession of the field. + </p> + <p> + <a name="link2H_4_0004" id="link2H_4_0004"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + III. CHEMISTRY SINCE THE TIME OF DALTON + </h2> + <h3> + JOHN DALTON AND THE ATOMIC THEORY + </h3> + <p> + Small beginnings as have great endings—sometimes. As a case in + point, note what came of the small, original effort of a self-trained + back-country Quaker youth named John Dalton, who along towards the close + of the eighteenth century became interested in the weather, and was led to + construct and use a crude water-gauge to test the amount of the rainfall. + The simple experiments thus inaugurated led to no fewer than two hundred + thousand recorded observations regarding the weather, which formed the + basis for some of the most epochal discoveries in meteorology, as we have + seen. But this was only a beginning. The simple rain-gauge pointed the way + to the most important generalization of the nineteenth century in a field + of science with which, to the casual observer, it might seem to have no + alliance whatever. The wonderful theory of atoms, on which the whole + gigantic structure of modern chemistry is founded, was the logical + outgrowth, in the mind of John Dalton, of those early studies in + meteorology. + </p> + <p> + The way it happened was this: From studying the rainfall, Dalton turned + naturally to the complementary process of evaporation. He was soon led to + believe that vapor exists, in the atmosphere as an independent gas. But + since two bodies cannot occupy the same space at the same time, this + implies that the various atmospheric gases are really composed of discrete + particles. These ultimate particles are so small that we cannot see them—cannot, + indeed, more than vaguely imagine them—yet each particle of vapor, + for example, is just as much a portion of water as if it were a drop out + of the ocean, or, for that matter, the ocean itself. But, again, water is + a compound substance, for it may be separated, as Cavendish has shown, + into the two elementary substances hydrogen and oxygen. Hence the atom of + water must be composed of two lesser atoms joined together. Imagine an + atom of hydrogen and one of oxygen. Unite them, and we have an atom of + water; sever them, and the water no longer exists; but whether united or + separate the atoms of hydrogen and of oxygen remain hydrogen and oxygen + and nothing else. Differently mixed together or united, atoms produce + different gross substances; but the elementary atoms never change their + chemical nature—their distinct personality. + </p> + <p> + It was about the year 1803 that Dalton first gained a full grasp of the + conception of the chemical atom. At once he saw that the hypothesis, if + true, furnished a marvellous key to secrets of matter hitherto insoluble—questions + relating to the relative proportions of the atoms themselves. It is known, + for example, that a certain bulk of hydrogen gas unites with a certain + bulk of oxygen gas to form water. If it be true that this combination + consists essentially of the union of atoms one with another (each single + atom of hydrogen united to a single atom of oxygen), then the relative + weights of the original masses of hydrogen and of oxygen must be also the + relative weights of each of their respective atoms. If one pound of + hydrogen unites with five and one-half pounds of oxygen (as, according to + Dalton's experiments, it did), then the weight of the oxygen atom must be + five and one-half times that of the hydrogen atom. Other compounds may + plainly be tested in the same way. Dalton made numerous tests before he + published his theory. He found that hydrogen enters into compounds in + smaller proportions than any other element known to him, and so, for + convenience, determined to take the weight of the hydrogen atom as unity. + The atomic weight of oxygen then becomes (as given in Dalton's first table + of 1803) 5.5; that of water (hydrogen plus oxygen) being of course 6.5. + The atomic weights of about a score of substances are given in Dalton's + first paper, which was read before the Literary and Philosophical Society + of Manchester, October 21, 1803. I wonder if Dalton himself, great and + acute intellect though he had, suspected, when he read that paper, that he + was inaugurating one of the most fertile movements ever entered on in the + whole history of science? + </p> + <p> + Be that as it may, it is certain enough that Dalton's contemporaries were + at first little impressed with the novel atomic theory. Just at this time, + as it chanced, a dispute was waging in the field of chemistry regarding a + matter of empirical fact which must necessarily be settled before such a + theory as that of Dalton could even hope for a bearing. This was the + question whether or not chemical elements unite with one another always in + definite proportions. Berthollet, the great co-worker with Lavoisier, and + now the most authoritative of living chemists, contended that substances + combine in almost indefinitely graded proportions between fixed extremes. + He held that solution is really a form of chemical combination—a + position which, if accepted, left no room for argument. + </p> + <p> + But this contention of the master was most actively disputed, in + particular by Louis Joseph Proust, and all chemists of repute were obliged + to take sides with one or the other. For a time the authority of + Berthollet held out against the facts, but at last accumulated evidence + told for Proust and his followers, and towards the close of the first + decade of our century it came to be generally conceded that chemical + elements combine with one another in fixed and definite proportions. + </p> + <p> + More than that. As the analysts were led to weigh carefully the quantities + of combining elements, it was observed that the proportions are not only + definite, but that they bear a very curious relation to one another. If + element A combines with two different proportions of element B to form two + compounds, it appears that the weight of the larger quantity of B is an + exact multiple of that of the smaller quantity. This curious relation was + noticed by Dr. Wollaston, one of the most accurate of observers, and a + little later it was confirmed by Johan Jakob Berzelius, the great Swedish + chemist, who was to be a dominating influence in the chemical world for a + generation to come. But this combination of elements in numerical + proportions was exactly what Dalton had noticed as early as 1802, and what + bad led him directly to the atomic weights. So the confirmation of this + essential point by chemists of such authority gave the strongest + confirmation to the atomic theory. + </p> + <p> + During these same years the rising authority of the French chemical world, + Joseph Louis Gay-Lussac, was conducting experiments with gases, which he + had undertaken at first in conjunction with Humboldt, but which later on + were conducted independently. In 1809, the next year after the publication + of the first volume of Dalton's New System of Chemical Philosophy, + Gay-Lussac published the results of his observations, and among other + things brought out the remarkable fact that gases, under the same + conditions as to temperature and pressure, combine always in definite + numerical proportions as to volume. Exactly two volumes of hydrogen, for + example, combine with one volume of oxygen to form water. Moreover, the + resulting compound gas always bears a simple relation to the combining + volumes. In the case just cited, the union of two volumes of hydrogen and + one of oxygen results in precisely two volumes of water vapor. + </p> + <p> + Naturally enough, the champions of the atomic theory seized upon these + observations of Gay-Lussac as lending strong support to their hypothesis—all + of them, that is, but the curiously self-reliant and self-sufficient + author of the atomic theory himself, who declined to accept the + observations of the French chemist as valid. Yet the observations of + Gay-Lussac were correct, as countless chemists since then have + demonstrated anew, and his theory of combination by volumes became one of + the foundation-stones of the atomic theory, despite the opposition of the + author of that theory. + </p> + <p> + The true explanation of Gay-Lussac's law of combination by volumes was + thought out almost immediately by an Italian savant, Amadeo, Avogadro, and + expressed in terms of the atomic theory. The fact must be, said Avogadro, + that under similar physical conditions every form of gas contains exactly + the same number of ultimate particles in a given volume. Each of these + ultimate physical particles may be composed of two or more atoms (as in + the case of water vapor), but such a compound atom conducts itself as if + it were a simple and indivisible atom, as regards the amount of space that + separates it from its fellows under given conditions of pressure and + temperature. The compound atom, composed of two or more elementary atoms, + Avogadro proposed to distinguish, for purposes of convenience, by the name + molecule. It is to the molecule, considered as the unit of physical + structure, that Avogadro's law applies. + </p> + <p> + This vastly important distinction between atoms and molecules, implied in + the law just expressed, was published in 1811. Four years later, the + famous French physicist Ampere outlined a similar theory, and utilized the + law in his mathematical calculations. And with that the law of Avogadro + dropped out of sight for a full generation. Little suspecting that it was + the very key to the inner mysteries of the atoms for which they were + seeking, the chemists of the time cast it aside, and let it fade from the + memory of their science. + </p> + <p> + This, however, was not strange, for of course the law of Avogadro is based + on the atomic theory, and in 1811 the atomic theory was itself still being + weighed in the balance. The law of multiple proportions found general + acceptance as an empirical fact; but many of the leading lights of + chemistry still looked askance at Dalton's explanation of this law. Thus + Wollaston, though from the first he inclined to acceptance of the + Daltonian view, cautiously suggested that it would be well to use the + non-committal word "equivalent" instead of "atom"; and Davy, for a similar + reason, in his book of 1812, speaks only of "proportions," binding himself + to no theory as to what might be the nature of these proportions. + </p> + <p> + At least two great chemists of the time, however, adopted the atomic view + with less reservation. One of these was Thomas Thomson, professor at + Edinburgh, who, in 1807, had given an outline of Dalton's theory in a + widely circulated book, which first brought the theory to the general + attention of the chemical world. The other and even more noted advocate of + the atomic theory was Johan Jakob Berzelius. This great Swedish chemist at + once set to work to put the atomic theory to such tests as might be + applied in the laboratory. He was an analyst of the utmost skill, and for + years he devoted himself to the determination of the combining weights, + "equivalents" or "proportions," of the different elements. These + determinations, in so far as they were accurately made, were simple + expressions of empirical facts, independent of any theory; but gradually + it became more and more plain that these facts all harmonize with the + atomic theory of Dalton. So by common consent the proportionate combining + weights of the elements came to be known as atomic weights—the name + Dalton had given them from the first—and the tangible conception of + the chemical atom as a body of definite constitution and weight gained + steadily in favor. + </p> + <p> + From the outset the idea had had the utmost tangibility in the mind of + Dalton. He had all along represented the different atoms by geometrical + symbols—as a circle for oxygen, a circle enclosing a dot for + hydrogen, and the like—and had represented compounds by placing + these symbols of the elements in juxtaposition. Berzelius proposed to + improve upon this method by substituting for the geometrical symbol the + initial of the Latin name of the element represented—O for oxygen, H + for hydrogen, and so on—a numerical coefficient to follow the letter + as an indication of the number of atoms present in any given compound. + This simple system soon gained general acceptance, and with slight + modifications it is still universally employed. Every school-boy now is + aware that H2O is the chemical way of expressing the union of two atoms of + hydrogen with one of oxygen to form a molecule of water. But such a + formula would have had no meaning for the wisest chemist before the day of + Berzelius. + </p> + <p> + The universal fame of the great Swedish authority served to give general + currency to his symbols and atomic weights, and the new point of view thus + developed led presently to two important discoveries which removed the + last lingering doubts as to the validity of the atomic theory. In 1819 two + French physicists, Dulong and Petit, while experimenting with heat, + discovered that the specific heats of solids (that is to say, the amount + of heat required to raise the temperature of a given mass to a given + degree) vary inversely as their atomic weights. In the same year Eilhard + Mitscherlich, a German investigator, observed that compounds having the + same number of atoms to the molecule are disposed to form the same angles + of crystallization—a property which he called isomorphism. + </p> + <p> + Here, then, were two utterly novel and independent sets of empirical facts + which harmonize strangely with the supposition that substances are + composed of chemical atoms of a determinate weight. This surely could not + be coincidence—it tells of law. And so as soon as the claims of + Dulong and Petit and of Mitscherlich had been substantiated by other + observers, the laws of the specific heat of atoms, and of isomorphism, + took their place as new levers of chemical science. With the aid of these + new tools an impregnable breastwork of facts was soon piled about the + atomic theory. And John Dalton, the author of that theory, plain, + provincial Quaker, working on to the end in semi-retirement, became known + to all the world and for all time as a master of masters. + </p> + <p> + HUMPHRY DAVY AND ELECTRO-CHEMISTRY + </p> + <p> + During those early years of the nineteenth century, when Dalton was + grinding away at chemical fact and theory in his obscure Manchester + laboratory, another Englishman held the attention of the chemical world + with a series of the most brilliant and widely heralded researches. This + was Humphry Davy, a young man who had conic to London in 1801, at the + instance of Count Rumford, to assume the chair of chemical philosophy in + the Royal Institution, which the famous American had just founded. + </p> + <p> + Here, under Davy's direction, the largest voltaic battery yet constructed + had been put in operation, and with its aid the brilliant young + experimenter was expected almost to perform miracles. And indeed he + scarcely disappointed the expectation, for with the aid of his battery he + transformed so familiar a substance as common potash into a metal which + was not only so light that it floated on water, but possessed the + seemingly miraculous property of bursting into flames as soon as it came + in contact with that fire-quenching liquid. If this were not a miracle, it + had for the popular eye all the appearance of the miraculous. + </p> + <p> + What Davy really had done was to decompose the potash, which hitherto had + been supposed to be elementary, liberating its oxygen, and thus isolating + its metallic base, which he named potassium. The same thing was done with + soda, and the closely similar metal sodium was discovered—metals of + a unique type, possessed of a strange avidity for oxygen, and capable of + seizing on it even when it is bound up in the molecules of water. + Considered as mere curiosities, these discoveries were interesting, but + aside from that they were of great theoretical importance, because they + showed the compound nature of some familiar chemicals that had been + regarded as elements. Several other elementary earths met the same fate + when subjected to the electrical influence; the metals barium, calcium, + and strontium being thus discovered. Thereafter Davy always referred to + the supposed elementary substances (including oxygen, hydrogen, and the + rest) as "unde-compounded" bodies. These resist all present efforts to + decompose them, but how can one know what might not happen were they + subjected to an influence, perhaps some day to be discovered, which + exceeds the battery in power as the battery exceeds the blowpipe? + </p> + <p> + Another and even more important theoretical result that flowed from Davy's + experiments during this first decade of the century was the proof that no + elementary substances other than hydrogen and oxygen are produced when + pure water is decomposed by the electric current. It was early noticed by + Davy and others that when a strong current is passed through water, + alkalies appear at one pole of the battery and acids at the other, and + this though the water used were absolutely pure. This seemingly told of + the creation of elements—a transmutation but one step removed from + the creation of matter itself—under the influence of the new + "force." It was one of Davy's greatest triumphs to prove, in the series of + experiments recorded in his famous Bakerian lecture of 1806, that the + alleged creation of elements did not take place, the substances found at + the poles of the battery having been dissolved from the walls of the + vessels in which the water experimented upon had been placed. Thus the + same implement which had served to give a certain philosophical warrant to + the fading dreams of alchemy banished those dreams peremptorily from the + domain of present science. + </p> + <p> + "As early as 1800," writes Davy, "I had found that when separate portions + of distilled water, filling two glass tubes, connected by moist bladders, + or any moist animal or vegetable substances, were submitted to the + electrical action of the pile of Volta by means of gold wires, a + nitro-muriatic solution of gold appeared in the tube containing the + positive wire, or the wire transmitting the electricity, and a solution of + soda in the opposite tube; but I soon ascertained that the muriatic acid + owed its existence to the animal or vegetable matters employed; for when + the same fibres of cotton were made use of in successive experiments, and + washed after every process in a weak solution of nitric acid, the water in + the apparatus containing them, though acted on for a great length of time + with a very strong power, at last produced no effects upon nitrate of + silver. + </p> + <p> + "In cases when I had procured much soda, the glass at its point of contact + with the wire seemed considerably corroded; and I was confirmed in my idea + of referring the production of the alkali principally to this source, by + finding that no fixed saline matter could be obtained by electrifying + distilled water in a single agate cup from two points of platina with the + Voltaic battery. + </p> + <p> + "Mr. Sylvester, however, in a paper published in Mr. Nicholson's journal + for last August, states that though no fixed alkali or muriatic acid + appears when a single vessel is employed, yet that they are both formed + when two vessels are used. And to do away with all objections with regard + to vegetable substances or glass, he conducted his process in a vessel + made of baked tobacco-pipe clay inserted in a crucible of platina. I have + no doubt of the correctness of his results; but the conclusion appears + objectionable. He conceives, that he obtained fixed alkali, because the + fluid after being heated and evaporated left a matter that tinged turmeric + brown, which would have happened had it been lime, a substance that exists + in considerable quantities in all pipe-clay; and even allowing the + presence of fixed alkali, the materials employed for the manufacture of + tobacco-pipes are not at all such as to exclude the combinations of this + substance. + </p> + <p> + "I resumed the inquiry; I procured small cylindrical cups of agate of the + capacity of about one-quarter of a cubic inch each. They were boiled for + some hours in distilled water, and a piece of very white and transparent + amianthus that had been treated in the same way was made then to connect + together; they were filled with distilled water and exposed by means of + two platina wires to a current of electricity, from one hundred and fifty + pairs of plates of copper and zinc four inches square, made active by + means of solution of alum. After forty-eight hours the process was + examined: Paper tinged with litmus plunged into the tube containing the + transmitting or positive wire was immediately strongly reddened. Paper + colored by turmeric introduced into the other tube had its color much + deepened; the acid matter gave a very slight degree of turgidness to + solution of nitrate of soda. The fluid that affected turmeric retained + this property after being strongly boiled; and it appeared more vivid as + the quantity became reduced by evaporation; carbonate of ammonia was mixed + with it, and the whole dried and exposed to a strong heat; a minute + quantity of white matter remained, which, as far as my examinations could + go, had the properties of carbonate of soda. I compared it with similar + minute portions of the pure carbonates of potash, and similar minute + portions of the pure carbonates of potash and soda. It was not so + deliquescent as the former of these bodies, and it formed a salt with + nitric acid, which, like nitrate of soda, soon attracted moisture from a + damp atmosphere and became fluid. + </p> + <p> + "This result was unexpected, but it was far from convincing me that the + substances which were obtained were generated. In a similar process with + glass tubes, carried on under exactly the same circumstances and for the + same time, I obtained a quantity of alkali which must have been more than + twenty times greater, but no traces of muriatic acid. There was much + probability that the agate contained some minute portion of saline matter, + not easily detected by chemical analysis, either in combination or + intimate cohesion in its pores. To determine this, I repeated this a + second, a third, and a fourth time. In the second experiment turbidness + was still produced by a solution of nitrate of silver in the tube + containing the acid, but it was less distinct; in the third process it was + barely perceptible; and in the fourth process the two fluids remained + perfectly clear after the mixture. The quantity of alkaline matter + diminished in every operation; and in the last process, though the battery + had been kept in great activity for three days, the fluid possessed, in a + very slight degree, only the power of acting on paper tinged with + turmeric; but its alkaline property was very sensible to litmus paper + slightly reddened, which is a much more delicate test; and after + evaporation and the process by carbonate of ammonia, a barely perceptible + quantity of fixed alkali was still left. The acid matter in the other tube + was abundant; its taste was sour; it smelled like water over which large + quantities of nitrous gas have been long kept; it did not effect solution + of muriate of barytes; and a drop of it placed upon a polished plate of + silver left, after evaporation, a black stain, precisely similar to that + produced by extremely diluted nitrous acid. + </p> + <p> + "After these results I could no longer doubt that some saline matter + existing in the agate tubes had been the source of the acid matter capable + of precipitating nitrate of silver and much of the alkali. Four additional + repetitions of the process, however, convinced me that there was likewise + some other cause for the presence of this last substance; for it continued + to appear to the last in quantities sufficiently distinguishable, and + apparently equal in every case. I had used every precaution, I had + included the tube in glass vessels out of the reach of the circulating + air; all the acting materials had been repeatedly washed with distilled + water; and no part of them in contact with the fluid had been touched by + the fingers. + </p> + <p> + "The only substance that I could now conceive as furnishing the fixed + alkali was the water itself. This water appeared pure by the tests of + nitrate of silver and muriate of barytes; but potash of soda, as is well + known, rises in small quantities in rapid distillation; and the New River + water which I made use of contains animal and vegetable impurities, which + it was easy to conceive might furnish neutral salts capable of being + carried over in vivid ebullition."(1) Further experiment proved the + correctness of this inference, and the last doubt as to the origin of the + puzzling chemical was dispelled. + </p> + <p> + Though the presence of the alkalies and acids in the water was explained, + however, their respective migrations to the negative and positive poles of + the battery remained to be accounted for. Davy's classical explanation + assumed that different elements differ among themselves as to their + electrical properties, some being positively, others negatively, + electrified. Electricity and "chemical affinity," he said, apparently are + manifestations of the same force, acting in the one case on masses, in the + other on particles. Electro-positive particles unite with electro-negative + particles to form chemical compounds, in virtue of the familiar principle + that opposite electricities attract one another. When compounds are + decomposed by the battery, this mutual attraction is overcome by the + stronger attraction of the poles of the battery itself. + </p> + <p> + This theory of binary composition of all chemical compounds, through the + union of electro-positive and electro-negative atoms or molecules, was + extended by Berzelius, and made the basis of his famous system of + theoretical chemistry. This theory held that all inorganic compounds, + however complex their composition, are essentially composed of such binary + combinations. For many years this view enjoyed almost undisputed sway. It + received what seemed strong confirmation when Faraday showed the definite + connection between the amount of electricity employed and the amount of + decomposition produced in the so-called electrolyte. But its claims were + really much too comprehensive, as subsequent discoveries proved. + </p> + <p> + ORGANIC CHEMISTRY AND THE IDEA OF THE MOLECULE + </p> + <p> + When Berzelius first promulgated his binary theory he was careful to + restrict its unmodified application to the compounds of the inorganic + world. At that time, and for a long time thereafter, it was supposed that + substances of organic nature had some properties that kept them aloof from + the domain of inorganic chemistry. It was little doubted that a so-called + "vital force" operated here, replacing or modifying the action of ordinary + "chemical affinity." It was, indeed, admitted that organic compounds are + composed of familiar elements—chiefly carbon, oxygen, hydrogen, and + nitrogen; but these elements were supposed to be united in ways that could + not be imitated in the domain of the non-living. It was regarded almost as + an axiom of chemistry that no organic compound whatever could be put + together from its elements—synthesized—in the laboratory. To + effect the synthesis of even the simplest organic compound, it was thought + that the "vital force" must be in operation. + </p> + <p> + Therefore a veritable sensation was created in the chemical world when, in + the year 1828, it was announced that the young German chemist, Friedrich + Wohler, formerly pupil of Berzelius, and already known as a coming master, + had actually synthesized the well-known organic product urea in his + laboratory at Sacrow. The "exception which proves the rule" is something + never heard of in the domain of logical science. Natural law knows no + exceptions. So the synthesis of a single organic compound sufficed at a + blow to break down the chemical barrier which the imagination of the + fathers of the science had erected between animate and inanimate nature. + Thenceforth the philosophical chemist would regard the plant and animal + organisms as chemical laboratories in which conditions are peculiarly + favorable for building up complex compounds of a few familiar elements, + under the operation of universal chemical laws. The chimera "vital force" + could no longer gain recognition in the domain of chemistry. + </p> + <p> + Now a wave of interest in organic chemistry swept over the chemical world, + and soon the study of carbon compounds became as much the fashion as + electrochemistry had been in the, preceding generation. + </p> + <p> + Foremost among the workers who rendered this epoch of organic chemistry + memorable were Justus Liebig in Germany and Jean Baptiste Andre Dumas in + France, and their respective pupils, Charles Frederic Gerhardt and + Augustus Laurent. Wohler, too, must be named in the same breath, as also + must Louis Pasteur, who, though somewhat younger than the others, came + upon the scene in time to take chief part in the most important of the + controversies that grew out of their labors. + </p> + <p> + Several years earlier than this the way had been paved for the study of + organic substances by Gay-Lussac's discovery, made in 1815, that a certain + compound of carbon and nitrogen, which he named cyanogen, has a peculiar + degree of stability which enables it to retain its identity and enter into + chemical relations after the manner of a simple body. A year later Ampere + discovered that nitrogen and hydrogen, when combined in certain + proportions to form what he called ammonium, have the same property. + Berzelius had seized upon this discovery of the compound radical, as it + was called, because it seemed to lend aid to his dualistic theory. He + conceived the idea that all organic compounds are binary unions of various + compound radicals with an atom of oxygen, announcing this theory in 1818. + Ten years later, Liebig and Wohler undertook a joint investigation which + resulted in proving that compound radicals are indeed very abundant among + organic substances. Thus the theory of Berzelius seemed to be + substantiated, and organic chemistry came to be defined as the chemistry + of compound radicals. + </p> + <p> + But even in the day of its seeming triumph the dualistic theory was + destined to receive a rude shock. This came about through the + investigations of Dumas, who proved that in a certain organic substance an + atom of hydrogen may be removed and an atom of chlorine substituted in its + place without destroying the integrity of the original compound—much + as a child might substitute one block for another in its play-house. Such + a substitution would be quite consistent with the dualistic theory, were + it not for the very essential fact that hydrogen is a powerfully + electro-positive element, while chlorine is as strongly electro-negative. + Hence the compound radical which united successively with these two + elements must itself be at one time electro-positive, at another + electro-negative—a seeming inconsistency which threw the entire + Berzelian theory into disfavor. + </p> + <p> + In its place there was elaborated, chiefly through the efforts of Laurent + and Gerhardt, a conception of the molecule as a unitary structure, built + up through the aggregation of various atoms, in accordance with "elective + affinities" whose nature is not yet understood A doctrine of "nuclei" and + a doctrine of "types" of molecular structure were much exploited, and, + like the doctrine of compound radicals, became useful as aids to memory + and guides for the analyst, indicating some of the plans of molecular + construction, though by no means penetrating the mysteries of chemical + affinity. They are classifications rather than explanations of chemical + unions. But at least they served an important purpose in giving + definiteness to the idea of a molecular structure built of atoms as the + basis of all substances. Now at last the word molecule came to have a + distinct meaning, as distinct from "atom," in the minds of the generality + of chemists, as it had had for Avogadro a third of a century before. + Avogadro's hypothesis that there are equal numbers of these molecules in + equal volumes of gases, under fixed conditions, was revived by Gerhardt, + and a little later, under the championship of Cannizzaro, was exalted to + the plane of a fixed law. Thenceforth the conception of the molecule was + to be as dominant a thought in chemistry as the idea of the atom had + become in a previous epoch. + </p> + <p> + CHEMICAL AFFINITY + </p> + <p> + Of course the atom itself was in no sense displaced, but Avogadro's law + soon made it plain that the atom had often usurped territory that did not + really belong to it. In many cases the chemists had supposed themselves + dealing with atoms as units where the true unit was the molecule. In the + case of elementary gases, such as hydrogen and oxygen, for example, the + law of equal numbers of molecules in equal spaces made it clear that the + atoms do not exist isolated, as had been supposed. Since two volumes of + hydrogen unite with one volume of oxygen to form two volumes of water + vapor, the simplest mathematics show, in the light of Avogadro's law, not + only that each molecule of water must contain two hydrogen atoms (a point + previously in dispute), but that the original molecules of hydrogen and + oxygen must have been composed in each case of two atoms—-else how + could one volume of oxygen supply an atom for every molecule of two + volumes of water? + </p> + <p> + What, then, does this imply? Why, that the elementary atom has an avidity + for other atoms, a longing for companionship, an "affinity"—call it + what you will—which is bound to be satisfied if other atoms are in + the neighborhood. Placed solely among atoms of its own kind, the oxygen + atom seizes on a fellow oxygen atom, and in all their mad dancings these + two mates cling together—possibly revolving about each other in + miniature planetary orbits. Precisely the same thing occurs among the + hydrogen atoms. But now suppose the various pairs of oxygen atoms come + near other pairs of hydrogen atoms (under proper conditions which need not + detain us here), then each oxygen atom loses its attachment for its + fellow, and flings itself madly into the circuit of one of the hydrogen + couplets, and—presto!—there are only two molecules for every + three there were before, and free oxygen and hydrogen have become water. + The whole process, stated in chemical phraseology, is summed up in the + statement that under the given conditions the oxygen atoms had a greater + affinity for the hydrogen atoms than for one another. + </p> + <p> + As chemists studied the actions of various kinds of atoms, in regard to + their unions with one another to form molecules, it gradually dawned upon + them that not all elements are satisfied with the same number of + companions. Some elements ask only one, and refuse to take more; while + others link themselves, when occasion offers, with two, three, four, or + more. Thus we saw that oxygen forsook a single atom of its own kind and + linked itself with two atoms of hydrogen. Clearly, then, the oxygen atom, + like a creature with two hands, is able to clutch two other atoms. But we + have no proof that under any circumstances it could hold more than two. + Its affinities seem satisfied when it has two bonds. But, on the other + hand, the atom of nitrogen is able to hold three atoms of hydrogen, and + does so in the molecule of ammonium (NH3); while the carbon atom can hold + four atoms of hydrogen or two atoms of oxygen. + </p> + <p> + Evidently, then, one atom is not always equivalent to another atom of a + different kind in combining powers. A recognition of this fact by + Frankland about 1852, and its further investigation by others (notably A. + Kekule and A. S. Couper), led to the introduction of the word equivalent + into chemical terminology in a new sense, and in particular to an + understanding of the affinities or "valency" of different elements, which + proved of the most fundamental importance. Thus it was shown that, of the + four elements that enter most prominently into organic compounds, hydrogen + can link itself with only a single bond to any other element—it has, + so to speak, but a single hand with which to grasp—while oxygen has + capacity for two bonds, nitrogen for three (possibly for five), and carbon + for four. The words monovalent, divalent, trivalent, tretrava-lent, etc., + were coined to express this most important fact, and the various elements + came to be known as monads, diads, triads, etc. Just why different + elements should differ thus in valency no one as yet knows; it is an + empirical fact that they do. And once the nature of any element has been + determined as regards its valency, a most important insight into the + possible behavior of that element has been secured. Thus a consideration + of the fact that hydrogen is monovalent, while oxygen is divalent, makes + it plain that we must expect to find no more than three compounds of these + two elements—namely, H—O—(written HO by the chemist, and + called hydroxyl); H—O—H (H2O, or water), and H—O—O—H + (H2O2, or hydrogen peroxide). It will be observed that in the first of + these compounds the atom of oxygen stands, so to speak, with one of its + hands free, eagerly reaching out, therefore, for another companion, and + hence, in the language of chemistry, forming an unstable compound. Again, + in the third compound, though all hands are clasped, yet one pair links + oxygen with oxygen; and this also must be an unstable union, since the + avidity of an atom for its own kind is relatively weak. Thus the + well-known properties of hydrogen peroxide are explained, its easy + decomposition, and the eagerness with which it seizes upon the elements of + other compounds. + </p> + <p> + But the molecule of water, on the other hand, has its atoms arranged in a + state of stable equilibrium, all their affinities being satisfied. Each + hydrogen atom has satisfied its own affinity by clutching the oxygen atom; + and the oxygen atom has both its bonds satisfied by clutching back at the + two hydrogen atoms. Therefore the trio, linked in this close bond, have no + tendency to reach out for any other companion, nor, indeed, any power to + hold another should it thrust itself upon them. They form a "stable" + compound, which under all ordinary circumstances will retain its identity + as a molecule of water, even though the physical mass of which it is a + part changes its condition from a solid to a gas from ice to vapor. + </p> + <p> + But a consideration of this condition of stable equilibrium in the + molecule at once suggests a new question: How can an aggregation of atoms, + having all their affinities satisfied, take any further part in chemical + reactions? Seemingly such a molecule, whatever its physical properties, + must be chemically inert, incapable of any atomic readjustments. And so in + point of fact it is, so long as its component atoms cling to one another + unremittingly. But this, it appears, is precisely what the atoms are + little prone to do. It seems that they are fickle to the last degree in + their individual attachments, and are as prone to break away from bondage + as they are to enter into it. Thus the oxygen atom which has just flung + itself into the circuit of two hydrogen atoms, the next moment flings + itself free again and seeks new companions. It is for all the world like + the incessant change of partners in a rollicking dance. This incessant + dissolution and reformation of molecules in a substance which as a whole + remains apparently unchanged was first fully appreciated by Ste.-Claire + Deville, and by him named dissociation. It is a process which goes on much + more actively in some compounds than in others, and very much more + actively under some physical conditions (such as increase of temperature) + than under others. But apparently no substances at ordinary temperatures, + and no temperature above the absolute zero, are absolutely free from its + disturbing influence. Hence it is that molecules having all the valency of + their atoms fully satisfied do not lose their chemical activity—since + each atom is momentarily free in the exchange of partners, and may seize + upon different atoms from its former partners, if those it prefers are at + hand. + </p> + <p> + While, however, an appreciation of this ceaseless activity of the atom is + essential to a proper understanding of its chemical efficiency, yet from + another point of view the "saturated" molecule—that is, the molecule + whose atoms have their valency all satisfied—may be thought of as a + relatively fixed or stable organism. Even though it may presently be torn + down, it is for the time being a completed structure; and a consideration + of the valency of its atoms gives the best clew that has hitherto been + obtainable as to the character of its architecture. How important this + matter of architecture of the molecule—of space relations of the + atoms—may be—was demonstrated as long ago as 1823, when Liebig + and Wohler proved, to the utter bewilderment of the chemical world, that + two substances may have precisely the same chemical constitution—the + same number and kind of atoms—and yet differ utterly in physical + properties. The word isomerism was coined by Berzelius to express this + anomalous condition of things, which seemed to negative the most + fundamental truths of chemistry. Naming the condition by no means + explained it, but the fact was made clear that something besides the mere + number and kind of atoms is important in the architecture of a molecule. + It became certain that atoms are not thrown together haphazard to build a + molecule, any more than bricks are thrown together at random to form a + house. + </p> + <p> + How delicate may be the gradations of architectural design in building a + molecule was well illustrated about 1850, when Pasteur discovered that + some carbon compounds—as certain sugars—can only be + distinguished from one another, when in solution, by the fact of their + twisting or polarizing a ray of light to the left or to the right, + respectively. But no inkling of an explanation of these strange variations + of molecular structure came until the discovery of the law of valency. + Then much of the mystery was cleared away; for it was plain that since + each atom in a molecule can hold to itself only a fixed number of other + atoms, complex molecules must have their atoms linked in definite chains + or groups. And it is equally plain that where the atoms are numerous, the + exact plan of grouping may sometimes be susceptible of change without + doing violence to the law of valency. It is in such cases that isomerism + is observed to occur. + </p> + <p> + By paying constant heed to this matter of the affinities, chemists are + able to make diagrammatic pictures of the plan of architecture of any + molecule whose composition is known. In the simple molecule of water + (H2O), for example, the two hydrogen atoms must have released each other + before they could join the oxygen, and the manner of linking must + apparently be that represented in the graphic formula H—O—H. + With molecules composed of a large number of atoms, such graphic + representation of the scheme of linking is of course increasingly + difficult, yet, with the affinities for a guide, it is always possible. Of + course no one supposes that such a formula, written in a single plane, can + possibly represent the true architecture of the molecule: it is at best + suggestive or diagrammatic rather than pictorial. Nevertheless, it affords + hints as to the structure of the molecule such as the fathers of chemistry + would not have thought it possible ever to attain. + </p> + <p> + PERIODICITY OF ATOMIC WEIGHTS + </p> + <p> + These utterly novel studies of molecular architecture may seem at first + sight to take from the atom much of its former prestige as the + all-important personage of the chemical world. Since so much depends upon + the mere position of the atoms, it may appear that comparatively little + depends upon the nature of the atoms themselves. But such a view is + incorrect, for on closer consideration it will appear that at no time has + the atom been seen to renounce its peculiar personality. Within certain + limits the character of a molecule may be altered by changing the + positions of its atoms (just as different buildings may be constructed of + the same bricks), but these limits are sharply defined, and it would be as + impossible to exceed them as it would be to build a stone building with + bricks. From first to last the brick remains a brick, whatever the style + of architecture it helps to construct; it never becomes a stone. And just + as closely does each atom retain its own peculiar properties, regardless + of its surroundings. + </p> + <p> + Thus, for example, the carbon atom may take part in the formation at one + time of a diamond, again of a piece of coal, and yet again of a particle + of sugar, of wood fibre, of animal tissue, or of a gas in the atmosphere; + but from first to last—from glass-cutting gem to intangible gas—there + is no demonstrable change whatever in any single property of the atom + itself. So far as we know, its size, its weight, its capacity for + vibration or rotation, and its inherent affinities, remain absolutely + unchanged throughout all these varying fortunes of position and + association. And the same thing is true of every atom of all of the + seventy-odd elementary substances with which the modern chemist is + acquainted. Every one appears always to maintain its unique integrity, + gaining nothing and losing nothing. + </p> + <p> + All this being true, it would seem as if the position of the Daltonian + atom as a primordial bit of matter, indestructible and non-transmutable, + had been put to the test by the chemistry of our century, and not found + wanting. Since those early days of the century when the electric battery + performed its miracles and seemingly reached its limitations in the hands + of Davy, many new elementary substances have been discovered, but no + single element has been displaced from its position as an undecomposable + body. Rather have the analyses of the chemist seemed to make it more and + more certain that all elementary atoms are in truth what John Herschel + called them, "manufactured articles"—primordial, changeless, + indestructible. + </p> + <p> + And yet, oddly enough, it has chanced that hand in hand with the + experiments leading to such a goal have gone other experiments arid + speculations of exactly the opposite tenor. In each generation there have + been chemists among the leaders of their science who have refused to admit + that the so-called elements are really elements at all in any final sense, + and who have sought eagerly for proof which might warrant their + scepticism. The first bit of evidence tending to support this view was + furnished by an English physician, Dr. William Prout, who in 1815 called + attention to a curious relation to be observed between the atomic weight + of the various elements. Accepting the figures given by the authorities of + the time (notably Thomson and Berzelius), it appeared that a strikingly + large proportion of the atomic weights were exact multiples of the weight + of hydrogen, and that others differed so slightly that errors of + observation might explain the discrepancy. Prout felt that it could not be + accidental, and he could think of no tenable explanation, unless it be + that the atoms of the various alleged elements are made up of different + fixed numbers of hydrogen atoms. Could it be that the one true element—the + one primal matter—is hydrogen, and that all other forms of matter + are but compounds of this original substance? + </p> + <p> + Prout advanced this startling idea at first tentatively, in an anonymous + publication; but afterwards he espoused it openly and urged its + tenability. Coming just after Davy's dissociation of some supposed + elements, the idea proved alluring, and for a time gained such popularity + that chemists were disposed to round out the observed atomic weights of + all elements into whole numbers. But presently renewed determinations of + the atomic weights seemed to discountenance this practice, and Prout's + alleged law fell into disrepute. It was revived, however, about 1840, by + Dumas, whose great authority secured it a respectful hearing, and whose + careful redetermination of the weight of carbon, making it exactly twelve + times that of hydrogen, aided the cause. + </p> + <p> + Subsequently Stas, the pupil of Dumas, undertook a long series of + determinations of atomic weights, with the expectation of confirming the + Proutian hypothesis. But his results seemed to disprove the hypothesis, + for the atomic weights of many elements differed from whole numbers by + more, it was thought, than the limits of error of the experiments. It was + noteworthy, however, that the confidence of Dumas was not shaken, though + he was led to modify the hypothesis, and, in accordance with previous + suggestions of Clark and of Marignac, to recognize as the primordial + element, not hydrogen itself, but an atom half the weight, or even + one-fourth the weight, of that of hydrogen, of which primordial atom the + hydrogen atom itself is compounded. But even in this modified form the + hypothesis found great opposition from experimental observers. + </p> + <p> + In 1864, however, a novel relation between the weights of the elements and + their other characteristics was called to the attention of chemists by + Professor John A. R. Newlands, of London, who had noticed that if the + elements are arranged serially in the numerical order of their atomic + weights, there is a curious recurrence of similar properties at intervals + of eight elements This so-called "law of octaves" attracted little + immediate attention, but the facts it connotes soon came under the + observation of other chemists, notably of Professors Gustav Hinrichs in + America, Dmitri Mendeleeff in Russia, and Lothar Meyer in Germany. + Mendeleeff gave the discovery fullest expression, explicating it in 1869, + under the title of "the periodic law." + </p> + <p> + Though this early exposition of what has since been admitted to be a most + important discovery was very fully outlined, the generality of chemists + gave it little heed till a decade or so later, when three new elements, + gallium, scandium, and germanium, were discovered, which, on being + analyzed, were quite unexpectedly found to fit into three gaps which + Mendeleeff had left in his periodic scale. In effect the periodic law had + enabled Mendeleeff to predicate the existence of the new elements years + before they were discovered. Surely a system that leads to such results is + no mere vagary. So very soon the periodic law took its place as one of the + most important generalizations of chemical science. + </p> + <p> + This law of periodicity was put forward as an expression of observed + relations independent of hypothesis; but of course the theoretical + bearings of these facts could not be overlooked. As Professor J. H. + Gladstone has said, it forces upon us "the conviction that the elements + are not separate bodies created without reference to one another, but that + they have been originally fashioned, or have been built up, from one + another, according to some general plan." It is but a short step from that + proposition to the Proutian hypothesis. + </p> + <p> + NEW WEAPONS—SPECTROSCOPE AND CAMERA + </p> + <p> + But the atomic weights are not alone in suggesting the compound nature of + the alleged elements. Evidence of a totally different kind has contributed + to the same end, from a source that could hardly have been imagined when + the Proutian hypothesis, was formulated, through the tradition of a novel + weapon to the armamentarium of the chemist—the spectroscope. The + perfection of this instrument, in the hands of two German scientists, + Gustav Robert Kirchhoff and Robert Wilhelm Bunsen, came about through the + investigation, towards the middle of the century, of the meaning of the + dark lines which had been observed in the solar spectrum by Fraunhofer as + early as 1815, and by Wollaston a decade earlier. It was suspected by + Stokes and by Fox Talbot in England, but first brought to demonstration by + Kirchhoff and Bunsen, that these lines, which were known to occupy + definite positions in the spectrum, are really indicative of particular + elementary substances. By means of the spectroscope, which is essentially + a magnifying lens attached to a prism of glass, it is possible to locate + the lines with great accuracy, and it was soon shown that here was a new + means of chemical analysis of the most exquisite delicacy. It was found, + for example, that the spectroscope could detect the presence of a quantity + of sodium so infinitesimal as the one two-hundred-thousandth of a grain. + But what was even more important, the spectroscope put no limit upon the + distance of location of the substance it tested, provided only that + sufficient light came from it. The experiments it recorded might be + performed in the sun, or in the most distant stars or nebulae; indeed, one + of the earliest feats of the instrument was to wrench from the sun the + secret of his chemical constitution. + </p> + <p> + To render the utility of the spectroscope complete, however, it was + necessary to link with it another new chemical agency—namely, + photography. This now familiar process is based on the property of light + to decompose certain unstable compounds of silver, and thus alter their + chemical composition. Davy and Wedgwood barely escaped the discovery of + the value of the photographic method early in the nineteenth century. + Their successors quite overlooked it until about 1826, when Louis J. M. + Daguerre, the French chemist, took the matter in hand, and after many + years of experimentation brought it to relative perfection in 1839, in + which year the famous daguerreotype first brought the matter to popular + attention. In the same year Mr. Fox Talbot read a paper on the subject + before the Royal Society, and soon afterwards the efforts of Herschel and + numerous other natural philosophers contributed to the advancement of the + new method. + </p> + <p> + In 1843 Dr. John W. Draper, the famous English-American chemist and + physiologist, showed that by photography the Fraunhofer lines in the solar + spectrum might be mapped with absolute accuracy; also proving that the + silvered film revealed many lines invisible to the unaided eye. The value + of this method of observation was recognized at once, and, as soon as the + spectroscope was perfected, the photographic method, in conjunction with + its use, became invaluable to the chemist. By this means comparisons of + spectra may be made with a degree of accuracy not otherwise obtainable; + and, in case of the stars, whole clusters of spectra may be placed on + record at a single observation. + </p> + <p> + As the examination of the sun and stars proceeded, chemists were amazed or + delighted, according to their various preconceptions, to witness the proof + that many familiar terrestrial elements are to be found in the celestial + bodies. But what perhaps surprised them most was to observe the enormous + preponderance in the sidereal bodies of the element hydrogen. Not only are + there vast quantities of this element in the sun's atmosphere, but some + other suns appeared to show hydrogen lines almost exclusively in their + spectra. Presently it appeared that the stars of which this is true are + those white stars, such as Sirius, which had been conjectured to be the + hottest; whereas stars that are only red-hot, like our sun, show also the + vapors of many other elements, including iron and other metals. + </p> + <p> + In 1878 Professor J. Norman Lockyer, in a paper before the Royal Society, + called attention to the possible significance of this series of + observations. He urged that the fact of the sun showing fewer elements + than are observed here on the cool earth, while stars much hotter than the + sun show chiefly one element, and that one hydrogen, the lightest of known + elements, seemed to give color to the possibility that our alleged + elements are really compounds, which at the temperature of the hottest + stars may be decomposed into hydrogen, the latter "element" itself being + also doubtless a compound, which might be resolved under yet more trying + conditions. + </p> + <p> + Here, then, was what might be termed direct experimental evidence for the + hypothesis of Prout. Unfortunately, however, it is evidence of a kind + which only a few experts are competent to discuss—so very delicate a + matter is the spectral analysis of the stars. What is still more + unfortunate, the experts do not agree among themselves as to the validity + of Professor Lockyer's conclusions. Some, like Professor Crookes, have + accepted them with acclaim, hailing Lockyer as "the Darwin of the + inorganic world," while others have sought a different explanation of the + facts he brings forward. As yet it cannot be said that the controversy has + been brought to final settlement. Still, it is hardly to be doubted that + now, since the periodic law has seemed to join hands with the + spectroscope, a belief in the compound nature of the so-called elements is + rapidly gaining ground among chemists. More and more general becomes the + belief that the Daltonian atom is really a compound radical, and that back + of the seeming diversity of the alleged elements is a single form of + primordial matter. Indeed, in very recent months, direct experimental + evidence for this view has at last come to hand, through the study of + radio-active substances. In a later chapter we shall have occasion to + inquire how this came about. + </p> + <p> + <a name="link2H_4_0005" id="link2H_4_0005"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH CENTURY + </h2> + <h3> + ALBRECHT VON HALLER + </h3> + <p> + An epoch in physiology was made in the eighteenth century by the genius + and efforts of Albrecht von Haller (1708-1777), of Berne, who is perhaps + as worthy of the title "The Great" as any philosopher who has been so + christened by his contemporaries since the time of Hippocrates. Celebrated + as a physician, he was proficient in various fields, being equally famed + in his own time as poet, botanist, and statesman, and dividing his + attention between art and science. + </p> + <p> + As a child Haller was so sickly that he was unable to amuse himself with + the sports and games common to boys of his age, and so passed most of his + time poring over books. When ten years of age he began writing poems in + Latin and German, and at fifteen entered the University of Tubingen. At + seventeen he wrote learned articles in opposition to certain accepted + doctrines, and at nineteen he received his degree of doctor. Soon after + this he visited England, where his zeal in dissecting brought him under + suspicion of grave-robbery, which suspicion made it expedient for him to + return to the Continent. After studying botany in Basel for some time he + made an extended botanical journey through Switzerland, finally settling + in his native city, Berne, as a practising physician. During this time he + did not neglect either poetry or botany, publishing anonymously a + collection of poems. + </p> + <p> + In 1736 he was called to Gottingen as professor of anatomy, surgery, + chemistry, and botany. During his labors in the university he never + neglected his literary work, sometimes living and sleeping for days and + nights together in his library, eating his meals while delving in his + books, and sleeping only when actually compelled to do so by fatigue. + During all this time he was in correspondence with savants from all over + the world, and it is said of him that he never left a letter of any kind + unanswered. + </p> + <p> + Haller's greatest contribution to medical science was his famous doctrine + of irritability, which has given him the name of "father of modern nervous + physiology," just as Harvey is called "the father of the modern physiology + of the blood." It has been said of this famous doctrine of irritability + that "it moved all the minds of the century—and not in the + departments of medicine alone—in a way of which we of the present + day have no satisfactory conception, unless we compare it with our modern + Darwinism."(1) + </p> + <p> + The principle of general irritability had been laid down by Francis + Glisson (1597-1677) from deductive studies, but Haller proved by + experiments along the line of inductive methods that this irritability was + not common to all "fibre as well as to the fluids of the body," but + something entirely special, and peculiar only to muscular substance. He + distinguished between irritability of muscles and sensibility of nerves. + In 1747 he gave as the three forces that produce muscular movements: + elasticity, or "dead nervous force"; irritability, or "innate nervous + force"; and nervous force in itself. And in 1752 he described one hundred + and ninety experiments for determining what parts of the body possess + "irritability"—that is, the property of contracting when stimulated. + His conclusion that this irritability exists in muscular substance alone + and is quite independent of the nerves proceeding to it aroused a + controversy that was never definitely settled until late in the nineteenth + century, when Haller's theory was found to be entirely correct. + </p> + <p> + It was in pursuit of experiments to establish his theory of irritability + that Haller made his chief discoveries in embryology and development. He + proved that in the process of incubation of the egg the first trace of the + heart of the chick shows itself in the thirty-eighth hour, and that the + first trace of red blood showed in the forty-first hour. By his + investigations upon the lower animals he attempted to confirm the theory + that since the creation of genus every individual is derived from a + preceding individual—the existing theory of preformation, in which + he believed, and which taught that "every individual is fully and + completely preformed in the germ, simply growing from microscopic to + visible proportions, without developing any new parts." + </p> + <p> + In physiology, besides his studies of the nervous system, Haller studied + the mechanism of respiration, refuting the teachings of Hamberger + (1697-1755), who maintained that the lungs contract independently. Haller, + however, in common with his contemporaries, failed utterly to understand + the true function of the lungs. The great physiologist's influence upon + practical medicine, while most profound, was largely indirect. He was a + theoretical rather than a practical physician, yet he is credited with + being the first physician to use the watch in counting the pulse. + </p> + <p> + BATTISTA MORGAGNI AND MORBID ANATOMY + </p> + <p> + A great contemporary of Haller was Giovanni Battista Morgagni (1682-1771), + who pursued what Sydenham had neglected, the investigation in anatomy, + thus supplying a necessary counterpart to the great Englishman's work. + Morgagni's investigations were directed chiefly to the study of morbid + anatomy—the study of the structure of diseased tissue, both during + life and post mortem, in contrast to the normal anatomical structures. + This work cannot be said to have originated with him; for as early as 1679 + Bonnet had made similar, although less extensive, studies; and later many + investigators, such as Lancisi and Haller, had made post-mortem studies. + But Morgagni's De sedibus et causis morborum per anatomen indagatis was + the largest, most accurate, and best-illustrated collection of cases that + had ever been brought together, and marks an epoch in medical science. + From the time of the publication of Morgagni's researches, morbid anatomy + became a recognized branch of the medical science, and the effect of the + impetus thus given it has been steadily increasing since that time. + </p> + <p> + WILLIAM HUNTER + </p> + <p> + William Hunter (1718-1783) must always be remembered as one of the + greatest physicians and anatomists of the eighteenth century, and + particularly as the first great teacher of anatomy in England; but his + fame has been somewhat overshadowed by that of his younger brother John. + </p> + <p> + Hunter had been intended and educated for the Church, but on the advice of + the surgeon William Cullen he turned his attention to the study of + medicine. His first attempt at teaching was in 1746, when he delivered a + series of lectures on surgery for the Society of Naval Practitioners. + These lectures proved so interesting and instructive that he was at once + invited to give others, and his reputation as a lecturer was soon + established. He was a natural orator and story-teller, and he combined + with these attractive qualities that of thoroughness and clearness in + demonstrations, and although his lectures were two hours long he made them + so full of interest that his pupils seldom tired of listening. He believed + that he could do greater good to the world by "publicly teaching his art + than by practising it," and even during the last few days of his life, + when he was so weak that his friends remonstrated against it, he continued + his teaching, fainting from exhaustion at the end of his last lecture, + which preceded his death by only a few days. + </p> + <p> + For many years it was Hunter's ambition to establish a museum where the + study of anatomy, surgery, and medicine might be advanced, and in 1765 he + asked for a grant of a plot of ground for this purpose, offering to spend + seven thousand pounds on its erection besides endowing it with a + professorship of anatomy. Not being able to obtain this grant, however, he + built a house, in which were lecture and dissecting rooms, and his museum. + In this museum were anatomical preparations, coins, minerals, and + natural-history specimens. + </p> + <p> + Hunter's weakness was his love of controversy and his resentment of + contradiction. This brought him into strained relations with many of the + leading physicians of his time, notably his own brother John, who himself + was probably not entirely free from blame in the matter. Hunter is said to + have excused his own irritability on the grounds that being an anatomist, + and accustomed to "the passive submission of dead bodies," contradictions + became the more unbearable. Many of the physiological researches begun by + him were carried on and perfected by his more famous brother, particularly + his investigations of the capillaries, but he added much to the anatomical + knowledge of several structures of the body, notably as to the structure + of cartilages and joints. + </p> + <p> + JOHN HUNTER + </p> + <p> + In Abbot Islip's chapel in Westminster Abbey, close to the resting-place + of Ben Jonson, rest the remains of John Hunter (1728-1793), famous in the + annals of medicine as among the greatest physiologists and surgeons that + the world has ever produced: a man whose discoveries and inventions are + counted by scores, and whose field of research was only limited by the + outermost boundaries of eighteenth-century science, although his efforts + were directed chiefly along the lines of his profession. + </p> + <p> + Until about twenty years of age young Hunter had shown little aptitude for + study, being unusually fond of out-door sports and amusements; but about + that time, realizing that some occupation must be selected, he asked + permission of his brother William to attempt some dissections in his + anatomical school in London. To the surprise of his brother he made this + dissection unusually well; and being given a second, he acquitted himself + with such skill that his brother at once predicted that he would become a + great anatomist. Up to this time he had had no training of any kind to + prepare him for his professional career, and knew little of Greek or Latin—languages + entirely unnecessary for him, as he proved in all of his life work. Ottley + tells the story that, when twitted with this lack of knowledge of the + "dead languages" in after life, he said of his opponent, "I could teach + him that on the dead body which he never knew in any language, dead or + living." + </p> + <p> + By his second year in dissection he had become so skilful that he was + given charge of some of the classes in his brother's school; in 1754 he + became a surgeon's pupil in St. George's Hospital, and two years later + house-surgeon. Having by overwork brought on symptoms that seemed to + threaten consumption, he accepted the position of staff-surgeon to an + expedition to Belleisle in 1760, and two years later was serving with the + English army at Portugal. During all this time he was constantly engaged + in scientific researches, many of which, such as his observations of + gun-shot wounds, he put to excellent use in later life. On returning to + England much improved in health in 1763, he entered at once upon his + career as a London surgeon, and from that time forward his progress was a + practically uninterrupted series of successes in his profession. + </p> + <p> + Hunter's work on the study of the lymphatics was of great service to the + medical profession. This important net-work of minute vessels distributed + throughout the body had recently been made the object of much study, and + various students, including Haller, had made extensive investigations + since their discovery by Asellius. But Hunter, in 1758, was the first to + discover the lymphatics in the neck of birds, although it was his brother + William who advanced the theory that the function of these vessels was + that of absorbents. One of John Hunter's pupils, William Hewson + (1739-1774), first gave an account, in 1768, of the lymphatics in reptiles + and fishes, and added to his teacher's investigations of the lymphatics in + birds. These studies of the lymphatics have been regarded, perhaps with + justice, as Hunter's most valuable contributions to practical medicine. + </p> + <p> + In 1767 he met with an accident by which he suffered a rupture of the + tendo Achillis—the large tendon that forms the attachment of the + muscles of the calf to the heel. From observations of this accident, and + subsequent experiments upon dogs, he laid the foundation for the now + simple and effective operation for the cure of club feet and other + deformities involving the tendons. In 1772 he moved into his residence at + Earlscourt, Brompton, where he gathered about him a great menagerie of + animals, birds, reptiles, insects, and fishes, which he used in his + physiological and surgical experiments. Here he performed a countless + number of experiments—more, probably, than "any man engaged in + professional practice has ever conducted." These experiments varied in + nature from observations of the habits of bees and wasps to major surgical + operations performed upon hedgehogs, dogs, leopards, etc. It is said that + for fifteen years he kept a flock of geese for the sole purpose of + studying the process of development in eggs. + </p> + <p> + Hunter began his first course of lectures in 1772, being forced to do this + because he had been so repeatedly misquoted, and because he felt that he + could better gauge his own knowledge in this way. Lecturing was a sore + trial to him, as he was extremely diffident, and without writing out his + lectures in advance he was scarcely able to speak at all. In this he + presented a marked contrast to his brother William, who was a fluent and + brilliant speaker. Hunter's lectures were at best simple readings of the + facts as he had written them, the diffident teacher seldom raising his + eyes from his manuscript and rarely stopping until his complete lecture + had been read through. His lectures were, therefore, instructive rather + than interesting, as he used infinite care in preparing them; but + appearing before his classes was so dreaded by him that he is said to have + been in the habit of taking a half-drachm of laudanum before each lecture + to nerve him for the ordeal. One is led to wonder by what name he shall + designate that quality of mind that renders a bold and fearless surgeon + like Hunter, who is undaunted in the face of hazardous and dangerous + operations, a stumbling, halting, and "frightened" speaker before a little + band of, at most, thirty young medical students. And yet this same thing + is not unfrequently seen among the boldest surgeons. + </p> + <p> + Hunter's Operation for the Cure of Aneurisms + </p> + <p> + It should be an object-lesson to those who, ignorantly or otherwise, + preach against the painless vivisection as practised to-day, that by the + sacrifice of a single deer in the cause of science Hunter discovered a + fact in physiology that has been the means of saving thousands of human + lives and thousands of human bodies from needless mutilation. We refer to + the discovery of the "collateral circulation" of the blood, which led, + among other things, to Hunter's successful operation upon aneurisms. + </p> + <p> + Simply stated, every organ or muscle of the body is supplied by one large + artery, whose main trunk distributes the blood into its lesser branches, + and thence through the capillaries. Cutting off this main artery, it would + seem, should cut off entirely the blood-supply to the particular organ + which is supplied by this vessel; and until the time of Hunter's + demonstration this belief was held by most physiologists. But nature has + made a provision for this possible stoppage of blood-supply from a single + source, and has so arranged that some of the small arterial branches + coming from the main supply-trunk are connected with other arterial + branches coming from some other supply-trunk. Under normal conditions the + main arterial trunks supply their respective organs, the little connecting + arterioles playing an insignificant part. But let the main supply-trunk be + cut off or stopped for whatever reason, and a remarkable thing takes + place. The little connecting branches begin at once to enlarge and draw + blood from the neighboring uninjured supply-trunk, This enlargement + continues until at last a new route for the circulation has been + established, the organ no longer depending on the now defunct original + arterial trunk, but getting on as well as before by this "collateral" + circulation that has been established. + </p> + <p> + The thorough understanding of this collateral circulation is one of the + most important steps in surgery, for until it was discovered amputations + were thought necessary in such cases as those involving the artery + supplying a leg or arm, since it was supposed that, the artery being + stopped, death of the limb and the subsequent necessity for amputation + were sure to follow. Hunter solved this problem by a single operation upon + a deer, and his practicality as a surgeon led him soon after to apply this + knowledge to a certain class of surgical cases in a most revolutionary and + satisfactory manner. + </p> + <p> + What led to Hunter's far-reaching discovery was his investigation as to + the cause of the growth of the antlers of the deer. Wishing to ascertain + just what part the blood-supply on the opposite sides of the neck played + in the process of development, or, perhaps more correctly, to see what + effect cutting off the main blood-supply would have, Hunter had one of the + deer of Richmond Park caught and tied, while he placed a ligature around + one of the carotid arteries—one of the two principal arteries that + supply the head with blood. He observed that shortly after this the antler + (which was only half grown and consequently very vascular) on the side of + the obliterated artery became cold to the touch—from the lack of + warmth-giving blood. There was nothing unexpected in this, and Hunter + thought nothing of it until a few days later, when he found, to his + surprise, that the antler had become as warm as its fellow, and was + apparently increasing in size. Puzzled as to how this could be, and + suspecting that in some way his ligature around the artery had not been + effective, he ordered the deer killed, and on examination was astonished + to find that while his ligature had completely shut off the blood-supply + from the source of that carotid artery, the smaller arteries had become + enlarged so as to supply the antler with blood as well as ever, only by a + different route. + </p> + <p> + Hunter soon had a chance to make a practical application of the knowledge + thus acquired. This was a case of popliteal aneurism, operations for which + had heretofore proved pretty uniformly fatal. An aneurism, as is generally + understood, is an enlargement of a certain part of an artery, this + enlargement sometimes becoming of enormous size, full of palpitating + blood, and likely to rupture with fatal results at any time. If by any + means the blood can be allowed to remain quiet for even a few hours in + this aneurism it will form a clot, contract, and finally be absorbed and + disappear without any evil results. The problem of keeping the blood + quiet, with the heart continually driving it through the vessel, is not a + simple one, and in Hunter's time was considered so insurmountable that + some surgeons advocated amputation of any member having an aneurism, while + others cut down upon the tumor itself and attempted to tie off the artery + above and below. The first of these operations maimed the patient for + life, while the second was likely to prove fatal. + </p> + <p> + In pondering over what he had learned about collateral circulation and the + time required for it to become fully established, Hunter conceived the + idea that if the blood-supply was cut off from above the aneurism, thus + temporarily preventing the ceaseless pulsations from the heart, this blood + would coagulate and form a clot before the collateral circulation could + become established or could affect it. The patient upon whom he performed + his now celebrated operation was afflicted with a popliteal aneurism—that + is, the aneurism was located on the large popliteal artery just behind the + knee-joint. Hunter, therefore, tied off the femoral, or main supplying + artery in the thigh, a little distance above the aneurism. The operation + was entirely successful, and in six weeks' time the patient was able to + leave the hospital, and with two sound limbs. Naturally the simplicity and + success of this operation aroused the attention of Europe, and, alone, + would have made the name of Hunter immortal in the annals of surgery. The + operation has ever since been called the "Hunterian" operation for + aneurism, but there is reason to believe that Dominique Anel (born about + 1679) performed a somewhat similar operation several years earlier. It is + probable, however, that Hunter had never heard of this work of Anel, and + that his operation was the outcome of his own independent reasoning from + the facts he had learned about collateral circulation. Furthermore, + Hunter's mode of operation was a much better one than Anel's, and, while + Anel's must claim priority, the credit of making it widely known will + always be Hunter's. + </p> + <p> + The great services of Hunter were recognized both at home and abroad, and + honors and positions of honor and responsibility were given him. In 1776 + he was appointed surgeon-extraordinary to the king; in 1783 he was elected + a member of the Royal Society of Medicine and of the Royal Academy of + Surgery at Paris; in 1786 he became deputy surgeon-general of the army; + and in 1790 he was appointed surgeon-general and inspector-general of + hospitals. All these positions he filled with credit, and he was actively + engaged in his tireless pursuit of knowledge and in discharging his many + duties when in October, 1793, he was stricken while addressing some + colleagues, and fell dead in the arms of a fellow-physician. + </p> + <p> + LAZZARO SPALLANZANI + </p> + <p> + Hunter's great rival among contemporary physiologists was the Italian + Lazzaro Spallanzani (1729-1799), one of the most picturesque figures in + the history of science. He was not educated either as a scientist or + physician, devoting, himself at first to philosophy and the languages, + afterwards studying law, and later taking orders. But he was a keen + observer of nature and of a questioning and investigating mind, so that he + is remembered now chiefly for his discoveries and investigations in the + biological sciences. One important demonstration was his controversion of + the theory of abiogenesis, or "spontaneous generation," as propounded by + Needham and Buffon. At the time of Needham's experiments it had long been + observed that when animal or vegetable matter had lain in water for a + little time—long enough for it to begin to undergo decomposition—the + water became filled with microscopic creatures, the "infusoria + animalculis." This would tend to show, either that the water or the animal + or vegetable substance contained the "germs" of these minute organisms, or + else that they were generated spontaneously. It was known that boiling + killed these animalcules, and Needham agreed, therefore, that if he first + heated the meat or vegetables, and also the water containing them, and + then placed them in hermetically scaled jars—if he did this, and + still the animalcules made their appearance, it would be proof-positive + that they had been generated spontaneously. Accordingly he made numerous + experiments, always with the same results—that after a few days the + water was found to swarm with the microscopic creatures. The thing seemed + proven beyond question—providing, of course, that there had been no + slips in the experiments. + </p> + <p> + But Abbe Spallanzani thought that he detected such slips in Needham's + experiment. The possibility of such slips might come in several ways: the + contents of the jar might not have been boiled for a sufficient length of + time to kill all the germs, or the air might not have been excluded + completely by the sealing process. To cover both these contingencies, + Spallanzani first hermetically sealed the glass vessels and then boiled + them for three-quarters of an hour. Under these circumstances no + animalcules ever made their appearance—a conclusive demonstration + that rendered Needham's grounds for his theory at once untenable.(2) + </p> + <p> + Allied to these studies of spontaneous generation were Spallanzani's + experiments and observations on the physiological processes of generation + among higher animals. He experimented with frogs, tortoises, and dogs; and + settled beyond question the function of the ovum and spermatozoon. + Unfortunately he misinterpreted the part played by the spermatozoa in + believing that their surrounding fluid was equally active in the + fertilizing process, and it was not until some forty years later (1824) + that Dumas corrected this error. + </p> + <p> + THE CHEMICAL THEORY OF DIGESTION + </p> + <p> + Among the most interesting researches of Spallanzani were his experiments + to prove that digestion, as carried on in the stomach, is a chemical + process. In this he demonstrated, as Rene Reaumur had attempted to + demonstrate, that digestion could be carried on outside the walls of the + stomach as an ordinary chemical reaction, using the gastric juice as the + reagent for performing the experiment. The question as to whether the + stomach acted as a grinding or triturating organ, rather than as a + receptacle for chemical action, had been settled by Reaumur and was no + longer a question of general dispute. Reaumur had demonstrated + conclusively that digestion would take place in the stomach in the same + manner and the same time if the substance to be digested was protected + from the peristalic movements of the stomach and subjected to the action + of the gastric juice only. He did this by introducing the substances to be + digested into the stomach in tubes, and thus protected so that while the + juices of the stomach could act upon them freely they would not be + affected by any movements of the organ. + </p> + <p> + Following up these experiments, he attempted to show that digestion could + take place outside the body as well as in it, as it certainly should if it + were a purely chemical process. He collected quantities of gastric juice, + and placing it in suitable vessels containing crushed grain or flesh, kept + the mixture at about the temperature of the body for several hours. After + repeated experiments of this kind, apparently conducted with great care, + Reaumur reached the conclusion that "the gastric juice has no more effect + out of the living body in dissolving or digesting the food than water, + mucilage, milk, or any other bland fluid."(3) Just why all of these + experiments failed to demonstrate a fact so simple does not appear; but to + Spallanzani, at least, they were by no means conclusive, and he proceeded + to elaborate upon the experiments of Reaumur. He made his experiments in + scaled tubes exposed to a certain degree of heat, and showed conclusively + that the chemical process does go on, even when the food and gastric juice + are removed from their natural environment in the stomach. In this he was + opposed by many physiologists, among them John Hunter, but the truth of + his demonstrations could not be shaken, and in later years we find Hunter + himself completing Spallanzani's experiments by his studies of the + post-mortem action of the gastric juice upon the stomach walls. + </p> + <p> + That Spallanzani's and Hunter's theories of the action of the gastric + juice were not at once universally accepted is shown by an essay written + by a learned physician in 1834. In speaking of some of Spallanzani's + demonstrations, he writes: "In some of the experiments, in order to give + the flesh or grains steeped in the gastric juice the same temperature with + the body, the phials were introduced under the armpits. But this is not a + fair mode of ascertaining the effects of the gastric juice out of the + body; for the influence which life may be supposed to have on the solution + of the food would be secured in this case. The affinities connected with + life would extend to substances in contact with any part of the system: + substances placed under the armpits are not placed at least in the same + circumstances with those unconnected with a living animal." But just how + this writer reaches the conclusion that "the experiments of Reaumur and + Spallanzani give no evidence that the gastric juice has any peculiar + influence more than water or any other bland fluid in digesting the + food"(4) is difficult to understand. + </p> + <p> + The concluding touches were given to the new theory of digestion by John + Hunter, who, as we have seen, at first opposed Spallanzani, but who + finally became an ardent champion of the chemical theory. Hunter now + carried Spallanzani's experiments further and proved the action of the + digestive fluids after death. For many years anatomists had been puzzled + by pathological lesion of the stomach, found post mortem, when no symptoms + of any disorder of the stomach had been evinced during life. Hunter + rightly conceived that these lesions were caused by the action of the + gastric juice, which, while unable to act upon the living tissue, + continued its action chemically after death, thus digesting the walls of + the stomach in which it had been formed. And, as usual with his + observations, he turned this discovery to practical use in accounting for + certain phenomena of digestion. The following account of the stomach being + digested after death was written by Hunter at the desire of Sir John + Pringle, when he was president of the Royal Society, and the circumstance + which led to this is as follows: "I was opening, in his presence, the body + of a patient of his own, where the stomach was in part dissolved, which + appeared to him very unaccountable, as there had been no previous symptom + that could have led him to suspect any disease in the stomach. I took that + opportunity of giving him my ideas respecting it, and told him that I had + long been making experiments on digestion, and considered this as one of + the facts which proved a converting power in the gastric juice.... There + are a great many powers in nature which the living principle does not + enable the animal matter, with which it is combined, to resist—viz., + the mechanical and most of the strongest chemical solvents. It renders it, + however, capable of resisting the powers of fermentation, digestion, and + perhaps several others, which are well known to act on the same matter + when deprived of the living principle and entirely to decompose it." + </p> + <p> + Hunter concludes his paper with the following paragraph: "These + appearances throw considerable light on the principle of digestion, and + show that it is neither a mechanical power, nor contractions of the + stomach, nor heat, but something secreted in the coats of the stomach, and + thrown into its cavity, which there animalizes the food or assimilates it + to the nature of the blood. The power of this juice is confined or limited + to certain substances, especially of the vegetable and animal kingdoms; + and although this menstruum is capable of acting independently of the + stomach, yet it is indebted to that viscus for its continuance."(5) + </p> + <p> + THE FUNCTION OF RESPIRATION + </p> + <p> + It is a curious commentary on the crude notions of mechanics of previous + generations that it should have been necessary to prove by experiment that + the thin, almost membranous stomach of a mammal has not the power to + pulverize, by mere attrition, the foods that are taken into it. However, + the proof was now for the first time forthcoming, and the question of the + general character of the function of digestion was forever set at rest. + Almost simultaneously with this great advance, corresponding progress was + made in an allied field: the mysteries of respiration were at last cleared + up, thanks to the new knowledge of chemistry. The solution of the problem + followed almost as a matter of course upon the advances of that science in + the latter part of the century. Hitherto no one since Mayow, of the + previous century, whose flash of insight had been strangely overlooked and + forgotten, had even vaguely surmised the true function of the lungs. The + great Boerhaave had supposed that respiration is chiefly important as an + aid to the circulation of the blood; his great pupil, Haller, had believed + to the day of his death in 1777 that the main purpose of the function is + to form the voice. No genius could hope to fathom the mystery of the lungs + so long as air was supposed to be a simple element, serving a mere + mechanical purpose in the economy of the earth. + </p> + <p> + But the discovery of oxygen gave the clew, and very soon all the chemists + were testing the air that came from the lungs—Dr. Priestley, as + usual, being in the van. His initial experiments were made in 1777, and + from the outset the problem was as good as solved. Other experimenters + confirmed his results in all their essentials—notably Scheele and + Lavoisier and Spallanzani and Davy. It was clearly established that there + is chemical action in the contact of the air with the tissue of the lungs; + that some of the oxygen of the air disappears, and that carbonic-acid gas + is added to the inspired air. It was shown, too, that the blood, having + come in contact with the air, is changed from black to red in color. These + essentials were not in dispute from the first. But as to just what + chemical changes caused these results was the subject of controversy. + Whether, for example, oxygen is actually absorbed into the blood, or + whether it merely unites with carbon given off from the blood, was long in + dispute. + </p> + <p> + Each of the main disputants was biased by his own particular views as to + the moot points of chemistry. Lavoisier, for example, believed oxygen gas + to be composed of a metal oxygen combined with the alleged element heat; + Dr. Priestley thought it a compound of positive electricity and + phlogiston; and Humphry Davy, when he entered the lists a little later, + supposed it to be a compound of oxygen and light. Such mistaken notions + naturally complicated matters and delayed a complete understanding of the + chemical processes of respiration. It was some time, too, before the idea + gained acceptance that the most important chemical changes do not occur in + the lungs themselves, but in the ultimate tissues. Indeed, the matter was + not clearly settled at the close of the century. Nevertheless, the problem + of respiration had been solved in its essentials. Moreover, the vastly + important fact had been established that a process essentially identical + with respiration is necessary to the existence not only of all creatures + supplied with lungs, but to fishes, insects, and even vegetables—in + short, to every kind of living organism. + </p> + <p> + ERASMUS DARWIN AND VEGETABLE PHYSIOLOGY + </p> + <p> + Some interesting experiments regarding vegetable respiration were made + just at the close of the century by Erasmus Darwin, and recorded in his + Botanic Garden as a foot-note to the verse: + </p> + <p> + "While spread in air the leaves respiring play." + </p> + <p> + These notes are worth quoting at some length, as they give a clear idea of + the physiological doctrines of the time (1799), while taking advance + ground as to the specific matter in question: + </p> + <p> + "There have been various opinions," Darwin says, "concerning the use of + the leaves of plants in the vegetable economy. Some have contended that + they are perspiratory organs. This does not seem probable from an + experiment of Dr. Hales, Vegetable Statics, p. 30. He, found, by cutting + off branches of trees with apples on them and taking off the leaves, that + an apple exhaled about as much as two leaves the surfaces of which were + nearly equal to the apple; whence it would appear that apples have as good + a claim to be termed perspiratory organs as leaves. Others have believed + them excretory organs of excrementitious juices, but as the vapor exhaled + from vegetables has no taste, this idea is no more probable than the + other; add to this that in most weathers they do not appear to perspire or + exhale at all. + </p> + <p> + "The internal surface of the lungs or air-vessels in men is said to be + equal to the external surface of the whole body, or almost fifteen square + feet; on this surface the blood is exposed to the influence of the + respired air through the medium, however, of a thin pellicle; by this + exposure to the air it has its color changed from deep red to bright + scarlet, and acquires something so necessary to the existence of life that + we can live scarcely a minute without this wonderful process. + </p> + <p> + "The analogy between the leaves of plants and the lungs or gills of + animals seems to embrace so many circumstances that we can scarcely + withhold our consent to their performing similar offices. + </p> + <p> + "1. The great surface of leaves compared to that of the trunk and branches + of trees is such that it would seem to be an organ well adapted for the + purpose of exposing the vegetable juices to the influence of the air; + this, however, we shall see afterwards is probably performed only by their + upper surfaces, yet even in this case the surface of the leaves in general + bear a greater proportion to the surface of the tree than the lungs of + animals to their external surfaces. + </p> + <p> + "2. In the lung of animals the blood, after having been exposed to the air + in the extremities of the pulmonary artery, is changed in color from deep + red to bright scarlet, and certainly in some of its essential properties + it is then collected by the pulmonary vein and returned to the heart. To + show a similarity of circumstances in the leaves of plants, the following + experiment was made, June 24, 1781. A stalk with leaves and seed-vessels + of large spurge (Euphorbia helioscopia) had been several days placed in a + decoction of madder (Rubia tinctorum) so that the lower part of the stem + and two of the undermost leaves were immersed in it. After having washed + the immersed leaves in clear water I could readily discover the color of + the madder passing along the middle rib of each leaf. The red artery was + beautifully visible on the under and on the upper surface of the leaf; but + on the upper side many red branches were seen going from it to the + extremities of the leaf, which on the other side were not visible except + by looking through it against the light. On this under side a system of + branching vessels carrying a pale milky fluid were seen coming from the + extremities of the leaf, and covering the whole under side of it, and + joining two large veins, one on each side of the red artery in the middle + rib of the leaf, and along with it descending to the foot-stalk or + petiole. On slitting one of these leaves with scissors, and having a + magnifying-glass ready, the milky blood was seen oozing out of the + returning veins on each side of the red artery in the middle rib, but none + of the red fluid from the artery. + </p> + <p> + "All these appearances were more easily seen in a leaf of Picris treated + in the same manner; for in this milky plant the stems and middle rib of + the leaves are sometimes naturally colored reddish, and hence the color of + the madder seemed to pass farther into the ramifications of their + leaf-arteries, and was there beautifully visible with the returning + branches of milky veins on each side." + </p> + <p> + Darwin now goes on to draw an incorrect inference from his observations: + </p> + <p> + "3. From these experiments," he says, "the upper surface of the leaf + appeared to be the immediate organ of respiration, because the colored + fluid was carried to the extremities of the leaf by vessels most + conspicuous on the upper surface, and there changed into a milky fluid, + which is the blood of the plant, and then returned by concomitant veins on + the under surface, which were seen to ooze when divided with scissors, and + which, in Picris, particularly, render the under surface of the leaves + greatly whiter than the upper one." + </p> + <p> + But in point of fact, as studies of a later generation were to show, it is + the under surface of the leaf that is most abundantly provided with + stomata, or "breathing-pores." From the stand-point of this later + knowledge, it is of interest to follow our author a little farther, to + illustrate yet more fully the possibility of combining correct + observations with a faulty inference. + </p> + <p> + "4. As the upper surface of leaves constitutes the organ of respiration, + on which the sap is exposed in the termination of arteries beneath a thin + pellicle to the action of the atmosphere, these surfaces in many plants + strongly repel moisture, as cabbage leaves, whence the particles of rain + lying over their surfaces without touching them, as observed by Mr. + Melville (Essays Literary and Philosophical: Edinburgh), have the + appearance of globules of quicksilver. And hence leaves with the upper + surfaces on water wither as soon as in the dry air, but continue green for + many days if placed with the under surface on water, as appears in the + experiments of Monsieur Bonnet (Usage des Feuilles). Hence some aquatic + plants, as the water-lily (Nymphoea), have the lower sides floating on the + water, while the upper surfaces remain dry in the air. + </p> + <p> + "5. As those insects which have many spiracula, or breathing apertures, as + wasps and flies, are immediately suffocated by pouring oil upon them, I + carefully covered with oil the surfaces of several leaves of phlomis, of + Portugal laurel, and balsams, and though it would not regularly adhere, I + found them all die in a day or two. + </p> + <p> + "It must be added that many leaves are furnished with muscles about their + foot-stalks, to turn their surfaces to the air or light, as mimosa or + Hedysarum gyrans. From all these analogies I think there can be no doubt + but that leaves of trees are their lungs, giving out a phlogistic material + to the atmosphere, and absorbing oxygen, or vital air. + </p> + <p> + "6. The great use of light to vegetation would appear from this theory to + be by disengaging vital air from the water which they perspire, and thence + to facilitate its union with their blood exposed beneath the thin surface + of their leaves; since when pure air is thus applied it is probable that + it can be more readily absorbed. Hence, in the curious experiments of Dr. + Priestley and Mr. Ingenhouz, some plants purified less air than others—that + is, they perspired less in the sunshine; and Mr. Scheele found that by + putting peas into water which about half covered them they converted the + vital air into fixed air, or carbonic-acid gas, in the same manner as in + animal respiration. + </p> + <p> + "7. The circulation in the lungs or leaves of plants is very similar to + that of fish. In fish the blood, after having passed through their gills, + does not return to the heart as from the lungs of air-breathing animals, + but the pulmonary vein taking the structure of an artery after having + received the blood from the gills, which there gains a more florid color, + distributes it to the other parts of their bodies. The same structure + occurs in the livers of fish, whence we see in those animals two + circulations independent of the power of the heart—viz., that + beginning at the termination of the veins of the gills and branching + through the muscles, and that which passes through the liver; both which + are carried on by the action of those respective arteries and veins."(6) + </p> + <p> + Darwin is here a trifle fanciful in forcing the analogy between plants and + animals. The circulatory system of plants is really not quite so + elaborately comparable to that of fishes as he supposed. But the + all-important idea of the uniformity underlying the seeming diversity of + Nature is here exemplified, as elsewhere in the writings of Erasmus + Darwin; and, more specifically, a clear grasp of the essentials of the + function of respiration is fully demonstrated. + </p> + <p> + ZOOLOGY AT THE CLOSE OF THE EIGHTEENTH CENTURY + </p> + <p> + Several causes conspired to make exploration all the fashion during the + closing epoch of the eighteenth century. New aid to the navigator had been + furnished by the perfected compass and quadrant, and by the invention of + the chronometer; medical science had banished scurvy, which hitherto had + been a perpetual menace to the voyager; and, above all, the restless + spirit of the age impelled the venturesome to seek novelty in fields + altogether new. Some started for the pole, others tried for a northeast or + northwest passage to India, yet others sought the great fictitious + antarctic continent told of by tradition. All these of course failed of + their immediate purpose, but they added much to the world's store of + knowledge and its fund of travellers' tales. + </p> + <p> + Among all these tales none was more remarkable than those which told of + strange living creatures found in antipodal lands. And here, as did not + happen in every field, the narratives were often substantiated by the + exhibition of specimens that admitted no question. Many a company of + explorers returned more or less laden with such trophies from the animal + and vegetable kingdoms, to the mingled astonishment, delight, and + bewilderment of the closet naturalists. The followers of Linnaeus in the + "golden age of natural history," a few decades before, had increased the + number of known species of fishes to about four hundred, of birds to one + thousand, of insects to three thousand, and of plants to ten thousand. But + now these sudden accessions from new territories doubled the figure for + plants, tripled it for fish and birds, and brought the number of described + insects above twenty thousand. Naturally enough, this wealth of new + material was sorely puzzling to the classifiers. The more discerning began + to see that the artificial system of Linnaeus, wonderful and useful as it + had been, must be advanced upon before the new material could be + satisfactorily disposed of. The way to a more natural system, based on + less arbitrary signs, had been pointed out by Jussieu in botany, but the + zoologists were not prepared to make headway towards such a system until + they should gain a wider understanding of the organisms with which they + had to deal through comprehensive studies of anatomy. Such studies of + individual forms in their relations to the entire scale of organic beings + were pursued in these last decades of the century, but though two or three + most important generalizations were achieved (notably Kaspar Wolff's + conception of the cell as the basis of organic life, and Goethe's + all-important doctrine of metamorphosis of parts), yet, as a whole, the + work of the anatomists of the period was germinative rather than + fruit-bearing. Bichat's volumes, telling of the recognition of the + fundamental tissues of the body, did not begin to appear till the last + year of the century. The announcement by Cuvier of the doctrine of + correlation of parts bears the same date, but in general the studies of + this great naturalist, which in due time were to stamp him as the + successor of Linnaeus, were as yet only fairly begun. + </p> + <p> + <a name="link2H_4_0006" id="link2H_4_0006"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH CENTURY + </h2> + <h3> + CUVIER AND THE CORRELATION OF PARTS + </h3> + <p> + We have seen that the focal points of the physiological world towards the + close of the eighteenth century were Italy and England, but when + Spallanzani and Hunter passed away the scene shifted to France. The time + was peculiarly propitious, as the recent advances in many lines of science + had brought fresh data for the student of animal life which were in need + of classification, and, as several minds capable of such a task were in + the field, it was natural that great generalizations should have come to + be quite the fashion. Thus it was that Cuvier came forward with a + brand-new classification of the animal kingdom, establishing four great + types of being, which he called vertebrates, mollusks, articulates, and + radiates. Lamarck had shortly before established the broad distinction + between animals with and those without a backbone; Cuvier's Classification + divided the latter—the invertebrates—into three minor groups. + And this division, familiar ever since to all students of zoology, has + only in very recent years been supplanted, and then not by revolution, but + by a further division, which the elaborate recent studies of lower forms + of life seemed to make desirable. + </p> + <p> + In the course of those studies of comparative anatomy which led to his new + classification, Cuvier's attention was called constantly to the peculiar + co-ordination of parts in each individual organism. Thus an animal with + sharp talons for catching living prey—as a member of the cat tribe—has + also sharp teeth, adapted for tearing up the flesh of its victim, and a + particular type of stomach, quite different from that of herbivorous + creatures. This adaptation of all the parts of the animal to one another + extends to the most diverse parts of the organism, and enables the skilled + anatomist, from the observation of a single typical part, to draw + inferences as to the structure of the entire animal—a fact which was + of vast aid to Cuvier in his studies of paleontology. It did not enable + Cuvier, nor does it enable any one else, to reconstruct fully the extinct + animal from observation of a single bone, as has sometimes been asserted, + but what it really does establish, in the hands of an expert, is + sufficiently astonishing. + </p> + <p> + "While the study of the fossil remains of the greater quadrupeds is more + satisfactory," he writes, "by the clear results which it affords, than + that of the remains of other animals found in a fossil state, it is also + complicated with greater and more numerous difficulties. Fossil shells are + usually found quite entire, and retaining all the characters requisite for + comparing them with the specimens contained in collections of natural + history, or represented in the works of naturalists. Even the skeletons of + fishes are found more or less entire, so that the general forms of their + bodies can, for the most part, be ascertained, and usually, at least, + their generic and specific characters are determinable, as these are + mostly drawn from their solid parts. In quadrupeds, on the contrary, even + when their entire skeletons are found, there is great difficulty in + discovering their distinguishing characters, as these are chiefly founded + upon their hairs and colors and other marks which have disappeared + previous to their incrustation. It is also very rare to find any fossil + skeletons of quadrupeds in any degree approaching to a complete state, as + the strata for the most part only contain separate bones, scattered + confusedly and almost always broken and reduced to fragments, which are + the only means left to naturalists for ascertaining the species or genera + to which they have belonged. + </p> + <p> + "Fortunately comparative anatomy, when thoroughly understood, enables us + to surmount all these difficulties, as a careful application of its + principles instructs us in the correspondences and dissimilarities of the + forms of organized bodies of different kinds, by which each may be + rigorously ascertained from almost every fragment of its various parts and + organs. + </p> + <p> + "Every organized individual forms an entire system of its own, all the + parts of which naturally correspond, and concur to produce a certain + definite purpose, by reciprocal reaction, or by combining towards the same + end. Hence none of these separate parts can change their forms without a + corresponding change in the other parts of the same animal, and + consequently each of these parts, taken separately, indicates all the + other parts to which it has belonged. Thus, as I have elsewhere shown, if + the viscera of an animal are so organized as only to be fitted for the + digestion of recent flesh, it is also requisite that the jaws should be so + constructed as to fit them for devouring prey; the claws must be + constructed for seizing and tearing it to pieces; the teeth for cutting + and dividing its flesh; the entire system of the limbs, or organs of + motion, for pursuing and overtaking it; and the organs of sense for + discovering it at a distance. Nature must also have endowed the brain of + the animal with instincts sufficient for concealing itself and for laying + plans to catch its necessary victims.... + </p> + <p> + "To enable the animal to carry off its prey when seized, a corresponding + force is requisite in the muscles which elevate the head, and this + necessarily gives rise to a determinate form of the vertebrae to which + these muscles are attached and of the occiput into which they are + inserted. In order that the teeth of a carnivorous animal may be able to + cut the flesh, they require to be sharp, more or less so in proportion to + the greater or less quantity of flesh that they have to cut. It is + requisite that their roots should be solid and strong, in proportion to + the quantity and size of the bones which they have to break to pieces. The + whole of these circumstances must necessarily influence the development + and form of all the parts which contribute to move the jaws...." + </p> + <p> + After these observations, it will be easily seen that similar conclusions + may be drawn with respect to the limbs of carnivorous animals, which + require particular conformations to fit them for rapidity of motion in + general; and that similar considerations must influence the forms and + connections of the vertebrae and other bones constituting the trunk of the + body, to fit them for flexibility and readiness of motion in all + directions. The bones also of the nose, of the orbit, and of the ears + require certain forms and structures to fit them for giving perfection to + the senses of smell, sight, and hearing, so necessary to animals of prey. + In short, the shape and structure of the teeth regulate the forms of the + condyle, of the shoulder-blade, and of the claws, in the same manner as + the equation of a curve regulates all its other properties; and as in + regard to any particular curve all its properties may be ascertained by + assuming each separate property as the foundation of a particular + equation, in the same manner a claw, a shoulder-blade, a condyle, a leg or + arm bone, or any other bone separately considered, enables us to discover + the description of teeth to which they have belonged; and so also + reciprocally we may determine the forms of the other bones from the teeth. + Thus commencing our investigations by a careful survey of any one bone by + itself, a person who is sufficiently master of the laws of organic + structure may, as it were, reconstruct the whole animal to which that bone + belonged."(1) + </p> + <p> + We have already pointed out that no one is quite able to perform the + necromantic feat suggested in the last sentence; but the exaggeration is + pardonable in the enthusiast to whom the principle meant so much and in + whose hands it extended so far. + </p> + <p> + Of course this entire principle, in its broad outlines, is something with + which every student of anatomy had been familiar from the time when + anatomy was first studied, but the full expression of the "law of + co-ordination," as Cuvier called it, had never been explicitly made + before; and, notwithstanding its seeming obviousness, the exposition which + Cuvier made of it in the introduction to his classical work on comparative + anatomy, which was published during the first decade of the nineteenth + century, ranks as a great discovery. It is one of those generalizations + which serve as guideposts to other discoveries. + </p> + <p> + BICHAT AND THE BODILY TISSUES + </p> + <p> + Much the same thing may be said of another generalization regarding the + animal body, which the brilliant young French physician Marie Francois + Bichat made in calling attention to the fact that each vertebrate + organism, including man, has really two quite different sets of organs—one + set under volitional control, and serving the end of locomotion, the other + removed from volitional control, and serving the ends of the "vital + processes" of digestion, assimilation, and the like. He called these sets + of organs the animal system and the organic system, respectively. The + division thus pointed out was not quite new, for Grimaud, professor of + physiology in the University of Montpellier, had earlier made what was + substantially the same classification of the functions into "internal or + digestive and external or locomotive"; but it was Bichat's exposition that + gave currency to the idea. + </p> + <p> + Far more important, however, was another classification which Bichat put + forward in his work on anatomy, published just at the beginning of the + last century. This was the division of all animal structures into what + Bichat called tissues, and the pointing out that there are really only a + few kinds of these in the body, making up all the diverse organs. Thus + muscular organs form one system; membranous organs another; glandular + organs a third; the vascular mechanism a fourth, and so on. The + distinction is so obvious that it seems rather difficult to conceive that + it could have been overlooked by the earliest anatomists; but, in point of + fact, it is only obvious because now it has been familiarly taught for + almost a century. It had never been given explicit expression before the + time of Bichat, though it is said that Bichat himself was somewhat + indebted for it to his master, Desault, and to the famous alienist Pinel. + </p> + <p> + However that may be, it is certain that all subsequent anatomists have + found Bichat's classification of the tissues of the utmost value in their + studies of the animal functions. Subsequent advances were to show that the + distinction between the various tissues is not really so fundamental as + Bichat supposed, but that takes nothing from the practical value of the + famous classification. + </p> + <p> + It was but a step from this scientific classification of tissues to a + similar classification of the diseases affecting them, and this was one of + the greatest steps towards placing medicine on the plane of an exact + science. This subject of these branches completely fascinated Bichat, and + he exclaimed, enthusiastically: "Take away some fevers and nervous + trouble, and all else belongs to the kingdom of pathological anatomy." But + out of this enthusiasm came great results. Bichat practised as he + preached, and, believing that it was only possible to understand disease + by observing the symptoms carefully at the bedside, and, if the disease + terminated fatally, by post-mortem examination, he was so arduous in his + pursuit of knowledge that within a period of less than six months he had + made over six hundred autopsies—a record that has seldom, if ever, + been equalled. Nor were his efforts fruitless, as a single example will + suffice to show. By his examinations he was able to prove that diseases of + the chest, which had formerly been classed under the indefinite name + "peripneumonia," might involve three different structures, the pleural sac + covering the lungs, the lung itself, and the bronchial tubes, the diseases + affecting these organs being known respectively as pleuritis, pneumonia, + and bronchitis, each one differing from the others as to prognosis and + treatment. The advantage of such an exact classification needs no + demonstration. + </p> + <p> + LISTER AND THE PERFECTED MICROSCOPE + </p> + <p> + At the same time when these broad macroscopical distinctions were being + drawn there were other workers who were striving to go even deeper into + the intricacies of the animal mechanism with the aid of the microscope. + This undertaking, however, was beset with very great optical difficulties, + and for a long time little advance was made upon the work of preceding + generations. Two great optical barriers, known technically as spherical + and chromatic aberration—the one due to a failure of the rays of + light to fall all in one plane when focalized through a lens, the other + due to the dispersive action of the lens in breaking the white light into + prismatic colors—confronted the makers of microscopic lenses, and + seemed all but insuperable. The making of achromatic lenses for telescopes + had been accomplished, it is true, by Dolland in the previous century, by + the union of lenses of crown glass with those of flint glass, these two + materials having different indices of refraction and dispersion. But, + aside from the mechanical difficulties which arise when the lens is of the + minute dimensions required for use with the microscope, other perplexities + are introduced by the fact that the use of a wide pencil of light is a + desideratum, in order to gain sufficient illumination when large + magnification is to be secured. + </p> + <p> + In the attempt to overcome those difficulties, the foremost physical + philosophers of the time came to the aid of the best opticians. Very early + in the century, Dr. (afterwards Sir David) Brewster, the renowned Scotch + physicist, suggested that certain advantages might accrue from the use of + such gems as have high refractive and low dispersive indices, in place of + lenses made of glass. Accordingly lenses were made of diamond, of + sapphire, and so on, and with some measure of success. But in 1812 a much + more important innovation was introduced by Dr. William Hyde Wollaston, + one of the greatest and most versatile, and, since the death of Cavendish, + by far the most eccentric of English natural philosophers. This was the + suggestion to use two plano-convex lenses, placed at a prescribed distance + apart, in lieu of the single double-convex lens generally used. This + combination largely overcame the spherical aberration, and it gained + immediate fame as the "Wollaston doublet." + </p> + <p> + To obviate loss of light in such a doublet from increase of reflecting + surfaces, Dr. Brewster suggested filling the interspace between the two + lenses with a cement having the same index of refraction as the lenses + themselves—an improvement of manifest advantage. An improvement yet + more important was made by Dr. Wollaston himself in the introduction of + the diaphragm to limit the field of vision between the lenses, instead of + in front of the anterior lens. A pair of lenses thus equipped Dr. + Wollaston called the periscopic microscope. Dr. Brewster suggested that in + such a lens the same object might be attained with greater ease by + grinding an equatorial groove about a thick or globular lens and filling + the groove with an opaque cement. This arrangement found much favor, and + came subsequently to be known as a Coddington lens, though Mr. Coddington + laid no claim to being its inventor. + </p> + <p> + Sir John Herschel, another of the very great physicists of the time, also + gave attention to the problem of improving the microscope, and in 1821 he + introduced what was called an aplanatic combination of lenses, in which, + as the name implies, the spherical aberration was largely done away with. + It was thought that the use of this Herschel aplanatic combination as an + eyepiece, combined with the Wollaston doublet for the objective, came as + near perfection as the compound microscope was likely soon to come. But in + reality the instrument thus constructed, though doubtless superior to any + predecessor, was so defective that for practical purposes the simple + microscope, such as the doublet or the Coddington, was preferable to the + more complicated one. + </p> + <p> + Many opticians, indeed, quite despaired of ever being able to make a + satisfactory refracting compound microscope, and some of them had taken up + anew Sir Isaac Newton's suggestion in reference to a reflecting + microscope. In particular, Professor Giovanni Battista Amici, a very + famous mathematician and practical optician of Modena, succeeded in + constructing a reflecting microscope which was said to be superior to any + compound microscope of the time, though the events of the ensuing years + were destined to rob it of all but historical value. For there were + others, fortunately, who did not despair of the possibilities of the + refracting microscope, and their efforts were destined before long to be + crowned with a degree of success not even dreamed of by any preceding + generation. + </p> + <p> + The man to whom chief credit is due for directing those final steps that + made the compound microscope a practical implement instead of a scientific + toy was the English amateur optician Joseph Jackson Lister. Combining + mathematical knowledge with mechanical ingenuity, and having the practical + aid of the celebrated optician Tulley, he devised formulae for the + combination of lenses of crown glass with others of flint glass, so + adjusted that the refractive errors of one were corrected or compensated + by the other, with the result of producing lenses of hitherto unequalled + powers of definition; lenses capable of showing an image highly magnified, + yet relatively free from those distortions and fringes of color that had + heretofore been so disastrous to true interpretation of magnified + structures. + </p> + <p> + Lister had begun his studies of the lens in 1824, but it was not until + 1830 that he contributed to the Royal Society the famous paper detailing + his theories and experiments. Soon after this various continental + opticians who had long been working along similar lines took the matter + up, and their expositions, in particular that of Amici, introduced the + improved compound microscope to the attention of microscopists everywhere. + And it required but the most casual trial to convince the experienced + observers that a new implement of scientific research had been placed in + their hands which carried them a long step nearer the observation of the + intimate physical processes which lie at the foundation of vital + phenomena. For the physiologist this perfection of the compound microscope + had the same significance that the, discovery of America had for the + fifteenth-century geographers—it promised a veritable world of + utterly novel revelations. Nor was the fulfilment of that promise long + delayed. + </p> + <p> + Indeed, so numerous and so important were the discoveries now made in the + realm of minute anatomy that the rise of histology to the rank of an + independent science may be said to date from this period. Hitherto, ever + since the discovery of magnifying-glasses, there had been here and there a + man, such as Leuwenhoek or Malpighi, gifted with exceptional vision, and + perhaps unusually happy in his conjectures, who made important + contributions to the knowledge of the minute structure of organic tissues; + but now of a sudden it became possible for the veriest tyro to confirm or + refute the laborious observations of these pioneers, while the skilled + observer could step easily beyond the barriers of vision that hitherto + were quite impassable. And so, naturally enough, the physiologists of the + fourth decade of the nineteenth century rushed as eagerly into the new + realm of the microscope as, for example, their successors of to-day are + exploring the realm of the X-ray. + </p> + <p> + Lister himself, who had become an eager interrogator of the instrument he + had perfected, made many important discoveries, the most notable being his + final settlement of the long-mooted question as to the true form of the + red corpuscles of the human blood. In reality, as everybody knows + nowadays, these are biconcave disks, but owing to their peculiar figure it + is easily possible to misinterpret the appearances they present when seen + through a poor lens, and though Dr. Thomas Young and various other + observers had come very near the truth regarding them, unanimity of + opinion was possible only after the verdict of the perfected microscope + was given. + </p> + <p> + These blood corpuscles are so infinitesimal in size that something like + five millions of them are found in each cubic millimetre of the blood, yet + they are isolated particles, each having, so to speak, its own + personality. This, of course, had been known to microscopists since the + days of the earliest lenses. It had been noticed, too, by here and there + an observer, that certain of the solid tissues seemed to present something + of a granular texture, as if they, too, in their ultimate constitution, + were made up of particles. And now, as better and better lenses were + constructed, this idea gained ground constantly, though for a time no one + saw its full significance. In the case of vegetable tissues, indeed, the + fact that little particles encased a membranous covering, and called + cells, are the ultimate visible units of structure had long been known. + But it was supposed that animal tissues differed radically from this + construction. The elementary particles of vegetables "were regarded to a + certain extent as individuals which composed the entire plant, while, on + the other hand, no such view was taken of the elementary parts of + animals." + </p> + <p> + ROBERT BROWN AND THE CELL NUCLEUS + </p> + <p> + In the year 1833 a further insight into the nature of the ultimate + particles of plants was gained through the observation of the English + microscopist Robert Brown, who, in the course of his microscopic studies + of the epidermis of orchids, discovered in the cells "an opaque spot," + which he named the nucleus. Doubtless the same "spot" had been seen often + enough before by other observers, but Brown was the first to recognize it + as a component part of the vegetable cell and to give it a name. + </p> + <p> + "I shall conclude my observations on Orchideae," said Brown, "with a + notice of some points of their general structure, which chiefly relate to + the cellular tissue. In each cell of the epidermis of a great part of this + family, especially of those with membranous leaves, a single circular + areola, generally somewhat more opaque than, the membrane of the cell, is + observable. This areola, which is more or less distinctly granular, is + slightly convex, and although it seems to be on the surface is in reality + covered by the outer lamina of the cell. There is no regularity as to its + place in the cell; it is not unfrequently, however, central or nearly so. + </p> + <p> + "As only one areola belongs to each cell, and as in many cases where it + exists in the common cells of the epidermis, it is also visible in the + cutaneous glands or stomata, and in these is always double—one being + on each side of the limb—it is highly probable that the cutaneous + gland is in all cases composed of two cells of peculiar form, the line of + union being the longitudinal axis of the disk or pore. + </p> + <p> + "This areola, or nucleus of the cell as perhaps it might be termed, is not + confined to the epidermis, being also found, not only in the pubescence of + the surface, particularly when jointed, as in cypripedium, but in many + cases in the parenchyma or internal cells of the tissue, especially when + these are free from the deposition of granular matter. + </p> + <p> + "In the compressed cells of the epidermis the nucleus is in a + corresponding degree flattened; but in the internal tissue it is often + nearly spherical, more or less firmly adhering to one of the walls, and + projecting into the cavity of the cell. In this state it may not + unfrequently be found in the substance of the column and in that of the + perianthium. + </p> + <p> + "The nucleus is manifest also in the tissue of the stigma, where in + accordance with the compression of the utriculi, it has an intermediate + form, being neither so much flattened as in the epidermis nor so convex as + it is in the internal tissue of the column. + </p> + <p> + "I may here remark that I am acquainted with one case of apparent + exception to the nucleus being solitary in each utriculus or cell—namely, + in Bletia Tankervilliae. In the utriculi of the stigma of this plant, I + have generally, though not always, found a second areola apparently on the + surface, and composed of much larger granules than the ordinary nucleus, + which is formed of very minute granular matter, and seems to be deep + seated. + </p> + <p> + "Mr. Bauer has represented the tissue of the stigma, in the species of + Bletia, both before and, as he believes, after impregnation; and in the + latter state the utriculi are marked with from one to three areolae of + similar appearance. + </p> + <p> + "The nucleus may even be supposed to exist in the pollen of this family. + In the early stages of its formation, at least a minute areola is of ten + visible in the simple grain, and in each of the constituent parts of cells + of the compound grain. But these areolae may perhaps rather be considered + as merely the points of production of the tubes. + </p> + <p> + "This nucleus of the cell is not confined to orchideae, but is equally + manifest in many other monocotyledonous families; and I have even found + it, hitherto however in very few cases, in the epidermis of dicotyledonous + plants; though in this primary division it may perhaps be said to exist in + the early stages of development of the pollen. Among monocotyledons, the + orders in which it is most remarkable are Liliaceae, Hemerocallideae, + Asphodeleae, Irideae, and Commelineae. + </p> + <p> + "In some plants belonging to this last-mentioned family, especially in + Tradascantia virginica, and several nearly related species, it is + uncommonly distinct, not in the epidermis and in the jointed hairs of the + filaments, but in the tissue of the stigma, in the cells of the ovulum + even before impregnation, and in all the stages of formation of the grains + of pollen, the evolution of which is so remarkable in tradascantia. + </p> + <p> + "The few indications of the presence of this nucleus, or areola, that I + have hitherto met with in the publications of botanists are chiefly in + some figures of epidermis, in the recent works of Meyen and Purkinje, and + in one case, in M. Adolphe Broigniart's memoir on the structure of leaves. + But so little importance seems to be attached to it that the appearance is + not always referred to in the explanations of the figures in which it is + represented. Mr. Bauer, however, who has also figured it in the utriculi + of the stigma of Bletia Tankervilliae has more particularly noticed it, + and seems to consider it as only visible after impregnation."(2) + </p> + <p> + SCHLEIDEN AND SCHWANN AND THE CELL THEORY + </p> + <p> + That this newly recognized structure must be important in the economy of + the cell was recognized by Brown himself, and by the celebrated German + Meyen, who dealt with it in his work on vegetable physiology, published + not long afterwards; but it remained for another German, the professor of + botany in the University of Jena, Dr. M. J. Schleiden, to bring the + nucleus to popular attention, and to assert its all-importance in the + economy of the cell. + </p> + <p> + Schleiden freely acknowledged his indebtedness to Brown for first + knowledge of the nucleus, but he soon carried his studies of that + structure far beyond those of its discoverer. He came to believe that the + nucleus is really the most important portion of the cell, in that it is + the original structure from which the remainder of the cell is developed. + Hence he named it the cytoblast. He outlined his views in an epochal paper + published in Muller's Archives in 1838, under title of "Beitrage zur + Phytogenesis." This paper is in itself of value, yet the most important + outgrowth of Schleiden's observations of the nucleus did not spring from + his own labors, but from those of a friend to whom he mentioned his + discoveries the year previous to their publication. This friend was Dr. + Theodor Schwann, professor of physiology in the University of Louvain. + </p> + <p> + At the moment when these observations were communicated to him Schwann was + puzzling over certain details of animal histology which he could not + clearly explain. His great teacher, Johannes Muller, had called attention + to the strange resemblance to vegetable cells shown by certain cells of + the chorda dorsalis (the embryonic cord from which the spinal column is + developed), and Schwann himself had discovered a corresponding similarity + in the branchial cartilage of a tadpole. Then, too, the researches of + Friedrich Henle had shown that the particles that make up the epidermis of + animals are very cell-like in appearance. Indeed, the cell-like character + of certain animal tissues had come to be matter of common note among + students of minute anatomy. Schwann felt that this similarity could not be + mere coincidence, but he had gained no clew to further insight until + Schleiden called his attention to the nucleus. Then at once he reasoned + that if there really is the correspondence between vegetable and animal + tissues that he suspected, and if the nucleus is so important in the + vegetable cell as Schleiden believed, the nucleus should also be found in + the ultimate particles of animal tissues. + </p> + <p> + Schwann's researches soon showed the entire correctness of this + assumption. A closer study of animal tissues under the microscope showed, + particularly in the case of embryonic tissues, that "opaque spots" such as + Schleiden described are really to be found there in abundance—forming, + indeed, a most characteristic phase of the structure. The location of + these nuclei at comparatively regular intervals suggested that they are + found in definite compartments of the tissue, as Schleiden had shown to be + the case with vegetables; indeed, the walls that separated such cell-like + compartments one from another were in some cases visible. Particularly was + this found to be the case with embryonic tissues, and the study of these + soon convinced Schwann that his original surmise had been correct, and + that all animal tissues are in their incipiency composed of particles not + unlike the ultimate particles of vegetables in short, of what the + botanists termed cells. Adopting this name, Schwann propounded what soon + became famous as his cell theory, under title of Mikroskopische + Untersuchungen uber die Ubereinstimmung in der Structur und dent Wachsthum + der Thiere und Pflanzen. So expeditious had been his work that this book + was published early in 1839, only a few months after the appearance of + Schleiden's paper. + </p> + <p> + As the title suggests, the main idea that actuated Schwann was to unify + vegetable and animal tissues. Accepting cell-structure as the basis of all + vegetable tissues, he sought to show that the same is true of animal + tissues, all the seeming diversities of fibre being but the alteration and + development of what were originally simple cells. And by cell Schwann + meant, as did Schleiden also, what the word ordinarily implies—a + cavity walled in on all sides. He conceived that the ultimate constituents + of all tissues were really such minute cavities, the most important part + of which was the cell wall, with its associated nucleus. He knew, indeed, + that the cell might be filled with fluid contents, but he regarded these + as relatively subordinate in importance to the wall itself. This, however, + did not apply to the nucleus, which was supposed to lie against the cell + wall and in the beginning to generate it. Subsequently the wall might grow + so rapidly as to dissociate itself from its contents, thus becoming a + hollow bubble or true cell; but the nucleus, as long as it lasted, was + supposed to continue in contact with the cell wall. Schleiden had even + supposed the nucleus to be a constituent part of the wall, sometimes lying + enclosed between two layers of its substance, and Schwann quoted this view + with seeming approval. Schwann believed, however, that in the mature cell + the nucleus ceased to be functional and disappeared. + </p> + <p> + The main thesis as to the similarity of development of vegetable and + animal tissues and the cellular nature of the ultimate constitution of + both was supported by a mass of carefully gathered evidence which a + multitude of microscopists at once confirmed, so Schwann's work became a + classic almost from the moment of its publication. Of course various other + workers at once disputed Schwann's claim to priority of discovery, in + particular the English microscopist Valentin, who asserted, not without + some show of justice, that he was working closely along the same lines. + Put so, for that matter, were numerous others, as Henle, Turpin, + Du-mortier, Purkinje, and Muller, all of whom Schwann himself had quoted. + Moreover, there were various physiologists who earlier than any of these + had foreshadowed the cell theory—notably Kaspar Friedrich Wolff, + towards the close of the previous century, and Treviranus about 1807, But, + as we have seen in so many other departments of science, it is one thing + to foreshadow a discovery, it is quite another to give it full expression + and make it germinal of other discoveries. And when Schwann put forward + the explicit claim that "there is one universal principle of development + for the elementary parts, of organisms, however different, and this + principle is the formation of cells," he enunciated a doctrine which was + for all practical purposes absolutely new and opened up a novel field for + the microscopist to enter. A most important era in physiology dates from + the publication of his book in 1839. + </p> + <p> + THE CELL THEORY ELABORATED + </p> + <p> + That Schwann should have gone to embryonic tissues for the establishment + of his ideas was no doubt due very largely to the influence of the great + Russian Karl Ernst von Baer, who about ten years earlier had published the + first part of his celebrated work on embryology, and whose ideas were + rapidly gaining ground, thanks largely to the advocacy of a few men, + notably Johannes Muller, in Germany, and William B. Carpenter, in England, + and to the fact that the improved microscope had made minute anatomy + popular. Schwann's researches made it plain that the best field for the + study of the animal cell is here, and a host of explorers entered the + field. The result of their observations was, in the main, to confirm the + claims of Schwann as to the universal prevalence of the cell. The + long-current idea that animal tissues grow only as a sort of deposit from + the blood-vessels was now discarded, and the fact of so-called plantlike + growth of animal cells, for which Schwann contended, was universally + accepted. Yet the full measure of the affinity between the two classes of + cells was not for some time generally apprehended. + </p> + <p> + Indeed, since the substance that composes the cell walls of plants is + manifestly very different from the limiting membrane of the animal cell, + it was natural, so long as the wall was considered the most essential part + of the structure, that the divergence between the two classes of cells + should seem very pronounced. And for a time this was the conception of the + matter that was uniformly accepted. But as time went on many observers had + their attention called to the peculiar characteristics of the contents of + the cell, and were led to ask themselves whether these might not be more + important than had been supposed. In particular, Dr. Hugo von Mohl, + professor of botany in the University of Tubingen, in the course of his + exhaustive studies of the vegetable cell, was impressed with the peculiar + and characteristic appearance of the cell contents. He observed + universally within the cell "an opaque, viscid fluid, having granules + intermingled in it," which made up the main substance of the cell, and + which particularly impressed him because under certain conditions it could + be seen to be actively in motion, its parts separated into filamentous + streams. + </p> + <p> + Von Mohl called attention to the fact that this motion of the cell + contents had been observed as long ago as 1774 by Bonaventura Corti, and + rediscovered in 1807 by Treviranus, and that these observers had described + the phenomenon under the "most unsuitable name of 'rotation of the cell + sap.'" Von Mohl recognized that the streaming substance was something + quite different from sap. He asserted that the nucleus of the cell lies + within this substance and not attached to the cell wall as Schleiden had + contended. He saw, too, that the chlorophyl granules, and all other of the + cell contents, are incorporated with the "opaque, viscid fluid," and in + 1846 he had become so impressed with the importance of this universal cell + substance that he gave it the name of protoplasm. Yet in so doing he had + no intention of subordinating the cell wall. The fact that Payen, in 1844, + had demonstrated that the cell walls of all vegetables, high or low, are + composed largely of one substance, cellulose, tended to strengthen the + position of the cell wall as the really essential structure, of which the + protoplasmic contents were only subsidiary products. + </p> + <p> + Meantime, however, the students of animal histology were more and more + impressed with the seeming preponderance of cell contents over cell walls + in the tissues they studied. They, too, found the cell to be filled with a + viscid, slimy fluid capable of motion. To this Dujardin gave the name of + sarcode. Presently it came to be known, through the labors of Kolliker, + Nageli, Bischoff, and various others, that there are numerous lower forms + of animal life which seem to be composed of this sarcode, without any cell + wall whatever. The same thing seemed to be true of certain cells of higher + organisms, as the blood corpuscles. Particularly in the case of cells that + change their shape markedly, moving about in consequence of the streaming + of their sarcode, did it seem certain that no cell wall is present, or + that, if present, its role must be insignificant. + </p> + <p> + And so histologists came to question whether, after all, the cell contents + rather than the enclosing wall must not be the really essential structure, + and the weight of increasing observations finally left no escape from the + conclusion that such is really the case. But attention being thus + focalized on the cell contents, it was at once apparent that there is a + far closer similarity between the ultimate particles of vegetables and + those of animals than had been supposed. Cellulose and animal membrane + being now regarded as more by-products, the way was clear for the + recognition of the fact that vegetable protoplasm and animal sarcode are + marvellously similar in appearance and general properties. The closer the + observation the more striking seemed this similarity; and finally, about + 1860, it was demonstrated by Heinrich de Bary and by Max Schultze that the + two are to all intents and purposes identical. Even earlier Remak had + reached a similar conclusion, and applied Von Mohl's word protoplasm to + animal cell contents, and now this application soon became universal. + Thenceforth this protoplasm was to assume the utmost importance in the + physiological world, being recognized as the universal "physical basis of + life," vegetable and animal alike. This amounted to the logical extension + and culmination of Schwann's doctrine as to the similarity of development + of the two animate kingdoms. Yet at the same time it was in effect the + banishment of the cell that Schwann had defined. The word cell was + retained, it is true, but it no longer signified a minute cavity. It now + implied, as Schultze defined it, "a small mass of protoplasm endowed with + the attributes of life." This definition was destined presently to meet + with yet another modification, as we shall see; but the conception of the + protoplasmic mass as the essential ultimate structure, which might or + might not surround itself with a protective covering, was a permanent + addition to physiological knowledge. The earlier idea had, in effect, + declared the shell the most important part of the egg; this developed view + assigned to the yolk its true position. + </p> + <p> + In one other important regard the theory of Schleiden and Schwann now + became modified. This referred to the origin of the cell. Schwann had + regarded cell growth as a kind of crystallization, beginning with the + deposit of a nucleus about a granule in the intercellular substance—the + cytoblastema, as Schleiden called it. But Von Mohl, as early as 1835, had + called attention to the formation of new vegetable cells through the + division of a pre-existing cell. Ehrenberg, another high authority of the + time, contended that no such division occurs, and the matter was still in + dispute when Schleiden came forward with his discovery of so-called free + cell-formation within the parent cell, and this for a long time diverted + attention from the process of division which Von Mohl had described. All + manner of schemes of cell-formation were put forward during the ensuing + years by a multitude of observers, and gained currency notwithstanding Von + Mohl's reiterated contention that there are really but two ways in which + the formation of new cells takes place—namely, "first, through + division of older cells; secondly, through the formation of secondary + cells lying free in the cavity of a cell." + </p> + <p> + But gradually the researches of such accurate observers as Unger, Nageli, + Kolliker, Reichart, and Remak tended to confirm the opinion of Von Mohl + that cells spring only from cells, and finally Rudolf Virchow brought the + matter to demonstration about 1860. His Omnis cellula e cellula became + from that time one of the accepted data of physiology. This was + supplemented a little later by Fleming's Omnis nucleus e nucleo, when + still more refined methods of observation had shown that the part of the + cell which always first undergoes change preparatory to new cell-formation + is the all-essential nucleus. Thus the nucleus was restored to the + important position which Schwann and Schleiden had given it, but with + greatly altered significance. Instead of being a structure generated de + novo from non-cellular substance, and disappearing as soon as its function + of cell-formation was accomplished, the nucleus was now known as the + central and permanent feature of every cell, indestructible while the cell + lives, itself the division-product of a pre-existing nucleus, and the + parent, by division of its substance, of other generations of nuclei. The + word cell received a final definition as "a small mass of protoplasm + supplied with a nucleus." + </p> + <p> + In this widened and culminating general view of the cell theory it became + clear that every animate organism, animal or vegetable, is but a cluster + of nucleated cells, all of which, in each individual case, are the direct + descendants of a single primordial cell of the ovum. In the developed + individuals of higher organisms the successive generations of cells become + marvellously diversified in form and in specific functions; there is a + wonderful division of labor, special functions being chiefly relegated to + definite groups of cells; but from first to last there is no function + developed that is not present, in a primitive way, in every cell, however + isolated; nor does the developed cell, however specialized, ever forget + altogether any one of its primordial functions or capacities. All + physiology, then, properly interpreted, becomes merely a study of cellular + activities; and the development of the cell theory takes its place as the + great central generalization in physiology of the nineteenth century. + Something of the later developments of this theory we shall see in another + connection. + </p> + <p> + ANIMAL CHEMISTRY + </p> + <p> + Just at the time when the microscope was opening up the paths that were to + lead to the wonderful cell theory, another novel line of interrogation of + the living organism was being put forward by a different set of observers. + Two great schools of physiological chemistry had arisen—one under + guidance of Liebig and Wohler, in Germany, the other dominated by the + great French master Jean Baptiste Dumas. Liebig had at one time + contemplated the study of medicine, and Dumas had achieved distinction in + connection with Prevost, at Geneva, in the field of pure physiology before + he turned his attention especially to chemistry. Both these masters, + therefore, and Wohler as well, found absorbing interest in those phases of + chemistry that have to do with the functions of living tissues; and it was + largely through their efforts and the labors of their followers that the + prevalent idea that vital processes are dominated by unique laws was + discarded and physiology was brought within the recognized province of the + chemist. So at about the time when the microscope had taught that the cell + is the really essential structure of the living organism, the chemists had + come to understand that every function of the organism is really the + expression of a chemical change—that each cell is, in short, a + miniature chemical laboratory. And it was this combined point of view of + anatomist and chemist, this union of hitherto dissociated forces, that + made possible the inroads into the unexplored fields of physiology that + were effected towards the middle of the nineteenth century. + </p> + <p> + One of the first subjects reinvestigated and brought to proximal solution + was the long-mooted question of the digestion of foods. Spallanzani and + Hunter had shown in the previous century that digestion is in some sort a + solution of foods; but little advance was made upon their work until 1824, + when Prout detected the presence of hydrochloric acid in the gastric + juice. A decade later Sprott and Boyd detected the existence of peculiar + glands in the gastric mucous membrane; and Cagniard la Tour and Schwann + independently discovered that the really active principle of the gastric + juice is a substance which was named pepsin, and which was shown by + Schwann to be active in the presence of hydrochloric acid. + </p> + <p> + Almost coincidently, in 1836, it was discovered by Purkinje and Pappenheim + that another organ than the stomach—namely, the pancreas—has a + share in digestion, and in the course of the ensuing decade it came to be + known, through the efforts of Eberle, Valentin, and Claude Bernard, that + this organ is all-important in the digestion of starchy and fatty foods. + It was found, too, that the liver and the intestinal glands have each an + important share in the work of preparing foods for absorption, as also has + the saliva—that, in short, a coalition of forces is necessary for + the digestion of all ordinary foods taken into the stomach. + </p> + <p> + And the chemists soon discovered that in each one of the essential + digestive juices there is at least one substance having certain + resemblances to pepsin, though acting on different kinds of food. The + point of resemblance between all these essential digestive agents is that + each has the remarkable property of acting on relatively enormous + quantities of the substance which it can digest without itself being + destroyed or apparently even altered. In virtue of this strange property, + pepsin and the allied substances were spoken of as ferments, but more + recently it is customary to distinguish them from such organized ferments + as yeast by designating them enzymes. The isolation of these enzymes, and + an appreciation of their mode of action, mark a long step towards the + solution of the riddle of digestion, but it must be added that we are + still quite in the dark as to the real ultimate nature of their strange + activity. + </p> + <p> + In a comprehensive view, the digestive organs, taken as a whole, are a + gateway between the outside world and the more intimate cells of the + organism. Another equally important gateway is furnished by the lungs, and + here also there was much obscurity about the exact method of functioning + at the time of the revival of physiological chemistry. That oxygen is + consumed and carbonic acid given off during respiration the chemists of + the age of Priestley and Lavoisier had indeed made clear, but the mistaken + notion prevailed that it was in the lungs themselves that the important + burning of fuel occurs, of which carbonic acid is a chief product. But now + that attention had been called to the importance of the ultimate cell, + this misconception could not long hold its ground, and as early as 1842 + Liebig, in the course of his studies of animal heat, became convinced that + it is not in the lungs, but in the ultimate tissues to which they are + tributary, that the true consumption of fuel takes place. Reviving + Lavoisier's idea, with modifications and additions, Liebig contended, and + in the face of opposition finally demonstrated, that the source of animal + heat is really the consumption of the fuel taken in through the stomach + and the lungs. He showed that all the activities of life are really the + product of energy liberated solely through destructive processes, + amounting, broadly speaking, to combustion occurring in the ultimate cells + of the organism. Here is his argument: + </p> + <p> + LIEBIG ON ANIMAL HEAT + </p> + <p> + "The oxygen taken into the system is taken out again in the same forms, + whether in summer or in winter; hence we expire more carbon in cold + weather, and when the barometer is high, than we do in warm weather; and + we must consume more or less carbon in our food in the same proportion; in + Sweden more than in Sicily; and in our more temperate climate a full + eighth more in winter than in summer. + </p> + <p> + "Even when we consume equal weights of food in cold and warm countries, + infinite wisdom has so arranged that the articles of food in different + climates are most unequal in the proportion of carbon they contain. The + fruits on which the natives of the South prefer to feed do not in the + fresh state contain more than twelve per cent. of carbon, while the + blubber and train-oil used by the inhabitants of the arctic regions + contain from sixty-six to eighty per cent. of carbon. + </p> + <p> + "It is no difficult matter, in warm climates, to study moderation in + eating, and men can bear hunger for a long time under the equator; but + cold and hunger united very soon exhaust the body. + </p> + <p> + "The mutual action between the elements of the food and the oxygen + conveyed by the circulation of the blood to every part of the body is the + source of animal heat. + </p> + <p> + "All living creatures whose existence depends on the absorption of oxygen + possess within themselves a source of heat independent of surrounding + objects. + </p> + <p> + "This truth applies to all animals, and extends besides to the germination + of seeds, to the flowering of plants, and to the maturation of fruits. It + is only in those parts of the body to which arterial blood, and with it + the oxygen absorbed in respiration, is conveyed that heat is produced. + Hair, wool, or feathers do not possess an elevated temperature. This high + temperature of the animal body, or, as it may be called, disengagement of + heat, is uniformly and under all circumstances the result of the + combination of combustible substance with oxygen. + </p> + <p> + "In whatever way carbon may combine with oxygen, the act of combination + cannot take place without the disengagement of heat. It is a matter of + indifference whether the combination takes place rapidly or slowly, at a + high or at a low temperature; the amount of heat liberated is a constant + quantity. The carbon of the food, which is converted into carbonic acid + within the body, must give out exactly as much heat as if it had been + directly burned in the air or in oxygen gas; the only difference is that + the amount of heat produced is diffused over unequal times. In oxygen the + combustion is more rapid and the heat more intense; in air it is slower, + the temperature is not so high, but it continues longer. + </p> + <p> + "It is obvious that the amount of heat liberated must increase or diminish + with the amount of oxygen introduced in equal times by respiration. Those + animals which respire frequently, and consequently consume much oxygen, + possess a higher temperature than others which, with a body of equal size + to be heated, take into the system less oxygen. The temperature of a child + (102 degrees) is higher than that of an adult (99.5 degrees). That of + birds (104 to 105.4 degrees) is higher than that of quadrupeds (98.5 to + 100.4 degrees), or than that of fishes or amphibia, whose proper + temperature is from 3.7 to 2.6 degrees higher than that of the medium in + which they live. All animals, strictly speaking, are warm-blooded; but in + those only which possess lungs is the temperature of the body independent + of the surrounding medium. + </p> + <p> + "The most trustworthy observations prove that in all climates, in the + temperate zones as well as at the equator or the poles, the temperature of + the body in man, and of what are commonly called warm-blooded animals, is + invariably the same; yet how different are the circumstances in which they + live. + </p> + <p> + "The animal body is a heated mass, which bears the same relation to + surrounding objects as any other heated mass. It receives heat when the + surrounding objects are hotter, it loses heat when they are colder than + itself. We know that the rapidity of cooling increases with the difference + between the heated body and that of the surrounding medium—that is, + the colder the surrounding medium the shorter the time required for the + cooling of the heated body. How unequal, then, must be the loss of heat of + a man at Palermo, where the actual temperature is nearly equal to that of + the body, and in the polar regions, where the external temperature is from + 70 to 90 degrees lower. + </p> + <p> + "Yet notwithstanding this extremely unequal loss of heat, experience has + shown that the blood of an inhabitant of the arctic circle has a + temperature as high as that of the native of the South, who lives in so + different a medium. This fact, when its true significance is perceived, + proves that the heat given off to the surrounding medium is restored + within the body with great rapidity. This compensation takes place more + rapidly in winter than in summer, at the pole than at the equator. + </p> + <p> + "Now in different climates the quantity of oxygen introduced into the + system of respiration, as has been already shown, varies according to the + temperature of the external air; the quantity of inspired oxygen increases + with the loss of heat by external cooling, and the quantity of carbon or + hydrogen necessary to combine with this oxygen must be increased in like + ratio. It is evident that the supply of heat lost by cooling is effected + by the mutual action of the elements of the food and the inspired oxygen, + which combine together. To make use of a familiar, but not on that account + a less just illustration, the animal body acts, in this respect, as a + furnace, which we supply with fuel. It signifies nothing what intermediate + forms food may assume, what changes it may undergo in the body, the last + change is uniformly the conversion of carbon into carbonic acid and of its + hydrogen into water; the unassimilated nitrogen of the food, along with + the unburned or unoxidized carbon, is expelled in the excretions. In order + to keep up in a furnace a constant temperature, we must vary the supply of + fuel according to the external temperature—that is, according to the + supply of oxygen. + </p> + <p> + "In the animal body the food is the fuel; with a proper supply of oxygen + we obtain the heat given out during its oxidation or combustion."(3) + </p> + <p> + BLOOD CORPUSCLES, MUSCLES, AND GLANDS + </p> + <p> + Further researches showed that the carriers of oxygen, from the time of + its absorption in the lungs till its liberation in the ultimate tissues, + are the red corpuscles, whose function had been supposed to be the + mechanical one of mixing of the blood. It transpired that the red + corpuscles are composed chiefly of a substance which Kuhne first isolated + in crystalline form in 1865, and which was named haemoglobin—a + substance which has a marvellous affinity for oxygen, seizing on it + eagerly at the lungs vet giving it up with equal readiness when coursing + among the remote cells of the body. When freighted with oxygen it becomes + oxyhaemoglobin and is red in color; when freed from its oxygen it takes a + purple hue; hence the widely different appearance of arterial and venous + blood, which so puzzled the early physiologists. + </p> + <p> + This proof of the vitally important role played by the red-blood + corpuscles led, naturally, to renewed studies of these infinitesimal + bodies. It was found that they may vary greatly in number at different + periods in the life of the same individual, proving that they may be both + developed and destroyed in the adult organism. Indeed, extended + observations left no reason to doubt that the process of corpuscle + formation and destruction may be a perfectly normal one—that, in + short, every red-blood corpuscle runs its course and dies like any more + elaborate organism. They are formed constantly in the red marrow of bones, + and are destroyed in the liver, where they contribute to the formation of + the coloring matter of the bile. Whether there are other seats of such + manufacture and destruction of the corpuscles is not yet fully determined. + Nor are histologists agreed as to whether the red-blood corpuscles + themselves are to be regarded as true cells, or merely as fragments of + cells budded out from a true cell for a special purpose; but in either + case there is not the slightest doubt that the chief function of the red + corpuscle is to carry oxygen. + </p> + <p> + If the oxygen is taken to the ultimate cells before combining with the + combustibles it is to consume, it goes without saying that these + combustibles themselves must be carried there also. Nor could it be in + doubt that the chiefest of these ultimate tissues, as regards, quantity of + fuel required, are the muscles. A general and comprehensive view of the + organism includes, then, digestive apparatus and lungs as the channels of + fuel-supply; blood and lymph channels as the transportation system; and + muscle cells, united into muscle fibres, as the consumption furnaces, + where fuel is burned and energy transformed and rendered available for the + purposes of the organism, supplemented by a set of excretory organs, + through which the waste products—the ashes—are eliminated from + the system. + </p> + <p> + But there remain, broadly speaking, two other sets of organs whose size + demonstrates their importance in the economy of the organism, yet whose + functions are not accounted for in this synopsis. These are those + glandlike organs, such as the spleen, which have no ducts and produce no + visible secretions, and the nervous mechanism, whose central organs are + the brain and spinal cord. What offices do these sets of organs perform in + the great labor-specializing aggregation of cells which we call a living + organism? + </p> + <p> + As regards the ductless glands, the first clew to their function was given + when the great Frenchman Claude Bernard (the man of whom his admirers + loved to say, "He is not a physiologist merely; he is physiology itself") + discovered what is spoken of as the glycogenic function of the liver. The + liver itself, indeed, is not a ductless organ, but the quantity of its + biliary output seems utterly disproportionate to its enormous size, + particularly when it is considered that in the case of the human species + the liver contains normally about one-fifth of all the blood in the entire + body. Bernard discovered that the blood undergoes a change of composition + in passing through the liver. The liver cells (the peculiar forms of which + had been described by Purkinje, Henle, and Dutrochet about 1838) have the + power to convert certain of the substances that come to them into a + starchlike compound called glycogen, and to store this substance away till + it is needed by the organism. This capacity of the liver cells is quite + independent of the bile-making power of the same cells; hence the + discovery of this glycogenic function showed that an organ may have more + than one pronounced and important specific function. But its chief + importance was in giving a clew to those intermediate processes between + digestion and final assimilation that are now known to be of such vital + significance in the economy of the organism. + </p> + <p> + In the forty odd years that have elapsed since this pioneer observation of + Bernard, numerous facts have come to light showing the extreme importance + of such intermediate alterations of food-supplies in the blood as that + performed by the liver. It has been shown that the pancreas, the spleen, + the thyroid gland, the suprarenal capsules are absolutely essential, each + in its own way, to the health of the organism, through metabolic changes + which they alone seem capable of performing; and it is suspected that + various other tissues, including even the muscles themselves, have + somewhat similar metabolic capacities in addition to their recognized + functions. But so extremely intricate is the chemistry of the substances + involved that in no single case has the exact nature of the metabolisms + wrought by these organs been fully made out. Each is in its way a chemical + laboratory indispensable to the right conduct of the organism, but the + precise nature of its operations remains inscrutable. The vast importance + of the operations of these intermediate organs is unquestioned. + </p> + <p> + A consideration of the functions of that other set of organs known + collectively as the nervous system is reserved for a later chapter. + </p> + <p> + <a name="link2H_4_0007" id="link2H_4_0007"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + VI. THEORIES OF ORGANIC EVOLUTION + </h2> + <h3> + GOETHE AND THE METAMORPHOSIS OF PARTS + </h3> + <p> + When Coleridge said of Humphry Davy that he might have been the greatest + poet of his time had he not chosen rather to be the greatest chemist, it + is possible that the enthusiasm of the friend outweighed the caution of + the critic. But however that may be, it is beyond dispute that the man who + actually was the greatest poet of that time might easily have taken the + very highest rank as a scientist had not the muse distracted his + attention. Indeed, despite these distractions, Johann Wolfgang von Goethe + achieved successes in the field of pure science that would insure + permanent recognition for his name had he never written a stanza of + poetry. Such is the versatility that marks the highest genius. + </p> + <p> + It was in 1790 that Goethe published the work that laid the foundations of + his scientific reputation—the work on the Metamorphoses of Plants, + in which he advanced the novel doctrine that all parts of the flower are + modified or metamorphosed leaves. + </p> + <p> + "Every one who observes the growth of plants, even superficially," wrote + Goethe, "will notice that certain external parts of them become + transformed at times and go over into the forms of the contiguous parts, + now completely, now to a greater or less degree. Thus, for example, the + single flower is transformed into a double one when, instead of stamens, + petals are developed, which are either exactly like the other petals of + the corolla in form, and color or else still bear visible signs of their + origin. + </p> + <p> + "When we observe that it is possible for a plant in this way to take a + step backward, we shall give so much the more heed to the regular course + of nature and learn the laws of transformation according to which she + produces one part through another, and displays the most varying forms + through the modification of one single organ. + </p> + <p> + "Let us first direct our attention to the plant at the moment when it + develops out of the seed-kernel. The first organs of its upward growth are + known by the name of cotyledons; they have also been called seed-leaves. + </p> + <p> + "They often appear shapeless, filled with new matter, and are just as + thick as they are broad. Their vessels are unrecognizable and are hardly + to be distinguished from the mass of the whole; they bear almost no + resemblance to a leaf, and we could easily be misled into regarding them + as special organs. Occasionally, however, they appear as real leaves, + their vessels are capable of the most minute development, their similarity + to the following leaves does not permit us to take them for special + organs, but we recognize them instead to be the first leaves of the stalk. + </p> + <p> + "The cotyledons are mostly double, and there is an observation to be made + here which will appear still more important as we proceed—that is, + that the leaves of the first node are often paired, even when the + following leaves of the stalk stand alternately upon it. Here we see an + approximation and a joining of parts which nature afterwards separates and + places at a distance from one another. It is still more remarkable when + the cotyledons take the form of many little leaves gathered about an axis, + and the stalk which grows gradually from their midst produces the + following leaves arranged around it singly in a whorl. This may be + observed very exactly in the growth of the pinus species. Here a corolla + of needles forms at the same time a calyx, and we shall have occasion to + remember the present case in connection with similar phenomena later. + </p> + <p> + "On the other hand, we observe that even the cotyledons which are most + like a leaf when compared with the following leaves of the stalk are + always more undeveloped or less developed. This is chiefly noticeable in + their margin which is extremely simple and shows few traces of + indentation. + </p> + <p> + "A few or many of the next following leaves are often already present in + the seed, and lie enclosed between the cotyledons; in their folded state + they are known by the name of plumules. Their form, as compared with the + cotyledons and the following leaves, varies in different plants. Their + chief point of variance, however, from the cotyledons is that they are + flat, delicate, and formed like real leaves generally. They are wholly + green, rest on a visible node, and can no longer deny their relationship + to the following leaves of the stalk, to which, however, they are usually + still inferior, in so far as that their margin is not completely + developed. + </p> + <p> + "The further development, however, goes on ceaselessly in the leaf, from + node to node; its midrib is elongated, and more or less additional ribs + stretch out from this towards the sides. The leaves now appear notched, + deeply indented, or composed of several small leaves, in which last case + they seem to form complete little branches. The date-palm furnishes a + striking example of such a successive transformation of the simplest leaf + form. A midrib is elongated through a succession of several leaves, the + single fan-shaped leaf becomes torn and diverted, and a very complicated + leaf is developed, which rivals a branch in form. + </p> + <p> + "The transition to inflorescence takes place more or less rapidly. In the + latter case we usually observe that the leaves of the stalk loose their + different external divisions, and, on the other hand, spread out more or + less in their lower parts where they are attached to the stalk. If the + transition takes place rapidly, the stalk, suddenly become thinner and + more elongated since the node of the last-developed leaf, shoots up and + collects several leaves around an axis at its end. + </p> + <p> + "That the petals of the calyx are precisely the same organs which have + hitherto appeared as leaves on the stalk, but now stand grouped about a + common centre in an often very different form, can, as it seems to me, be + most clearly demonstrated. Already in connection with the cotyledons + above, we noticed a similar working of nature. The first species, while + they are developing out of the seed-kernel, display a radiate crown of + unmistakable needles; and in the first childhood of these plants we see + already indicated that force of nature whereby when they are older their + flowering and fruit-giving state will be produced. + </p> + <p> + "We see this force of nature, which collects several leaves around an + axis, produce a still closer union and make these approximated, modified + leaves still more unrecognizable by joining them together either wholly or + partially. The bell-shaped or so-called one-petalled calices represent + these cloudy connected leaves, which, being more or less indented from + above, or divided, plainly show their origin. + </p> + <p> + "We can observe the transition from the calyx to the corolla in more than + one instance, for, although the color of the calyx is still usually green, + and like the color of the leaves of the stalk, it nevertheless often + varies in one or another of its parts—at the tips, the margins, the + back, or even, the inward side—while the outer still remains on + green. + </p> + <p> + "The relationship of the corolla to the leaves of the stalk is shown in + more than one way, since on the stalks of some plants appear leaves which + are already more or less colored long before they approach inflorescence; + others are fully colored when near inflorescence. Nature also goes over at + once to the corolla, sometimes by skipping over the organs of the calyx, + and in such a case we likewise have an opportunity to observe that leaves + of the stalk become transformed into petals. Thus on the stalk of tulips, + for instance, there sometimes appears an almost completely developed and + colored petal. Even more remarkable is the case when such a leaf, half + green and half of it belonging to the stalk, remains attached to the + latter, while another colored part is raised with the corolla, and the + leaf is thus torn in two. + </p> + <p> + "The relationship between the petals and stamens is very close. In some + instances nature makes the transition regular—e.g., among the Canna + and several plants of the same family. A true, little-modified petal is + drawn together on its upper margin, and produces a pollen sac, while the + rest of the petal takes the place of the stamen. In double flowers we can + observe this transition in all its stages. In several kinds of roses, + within the fully developed and colored petals there appear other ones + which are drawn together in the middle or on the side. This drawing + together is produced by a small weal, which appears as a more or less + complete pollen sac, and in the same proportion the leaf approaches the + simple form of a stamen. + </p> + <p> + "The pistil in many cases looks almost like a stamen without anthers, and + the relationship between the formation of the two is much closer than + between the other parts. In retrograde fashion nature often produces cases + where the style and stigma (Narben) become retransformed into petals—that + is, the Ranunculus Asiaticus becomes double by transforming the stigma and + style of the fruit-receptacle into real petals, while the stamens are + often found unchanged immediately behind the corolla. + </p> + <p> + "In the seed receptacles, in spite of their formation, of their special + object, and of their method of being joined together, we cannot fail to + recognize the leaf form. Thus, for instance, the pod would be a simple + leaf folded and grown together on its margin; the siliqua would consist of + more leaves folded over another; the compound receptacles would be + explained as being several leaves which, being united above one centre, + keep their inward parts separate and are joined on their margins. We can + convince ourselves of this by actual sight when such composite capsules + fall apart after becoming ripe, because then every part displays an opened + pod."(1) + </p> + <p> + The theory thus elaborated of the metamorphosis of parts was presently + given greater generality through extension to the animal kingdom, in the + doctrine which Goethe and Oken advanced independently, that the vertebrate + skull is essentially a modified and developed vertebra. These were + conceptions worthy of a poet—impossible, indeed, for any mind that + had not the poetic faculty of correlation. But in this case the poet's + vision was prophetic of a future view of the most prosaic science. The + doctrine of metamorphosis of parts soon came to be regarded as of + fundamental importance. + </p> + <p> + But the doctrine had implications that few of its early advocates + realized. If all the parts of a flower—sepal, petal, stamen, pistil, + with their countless deviations of contour and color—are but + modifications of the leaf, such modification implies a marvellous + differentiation and development. To assert that a stamen is a + metamorphosed leaf means, if it means anything, that in the long sweep of + time the leaf has by slow or sudden gradations changed its character + through successive generations, until the offspring, so to speak, of a + true leaf has become a stamen. But if such a metamorphosis as this is + possible—if the seemingly wide gap between leaf and stamen may be + spanned by the modification of a line of organisms—where does the + possibility of modification of organic type find its bounds? Why may not + the modification of parts go on along devious lines until the remote + descendants of an organism are utterly unlike that organism? Why may we + not thus account for the development of various species of beings all + sprung from one parent stock? That, too, is a poet's dream; but is it only + a dream? Goethe thought not. Out of his studies of metamorphosis of parts + there grew in his mind the belief that the multitudinous species of plants + and animals about us have been evolved from fewer and fewer earlier parent + types, like twigs of a giant tree drawing their nurture from the same + primal root. It was a bold and revolutionary thought, and the world + regarded it as but the vagary of a poet. + </p> + <p> + ERASMUS DARWIN + </p> + <p> + Just at the time when this thought was taking form in Goethe's brain, the + same idea was germinating in the mind of another philosopher, an + Englishman of international fame, Dr. Erasmus Darwin, who, while he lived, + enjoyed the widest popularity as a poet, the rhymed couplets of his + Botanic Garden being quoted everywhere with admiration. And posterity + repudiating the verse which makes the body of the book, yet grants + permanent value to the book itself, because, forsooth, its copious + explanatory foot-notes furnish an outline of the status of almost every + department of science of the time. + </p> + <p> + But even though he lacked the highest art of the versifier, Darwin had, + beyond peradventure, the imagination of a poet coupled with profound + scientific knowledge; and it was his poetic insight, correlating organisms + seemingly diverse in structure and imbuing the lowliest flower with a + vital personality, which led him to suspect that there are no lines of + demarcation in nature. "Can it be," he queries, "that one form of organism + has developed from another; that different species are really but modified + descendants of one parent stock?" The alluring thought nestled in his mind + and was nurtured there, and grew in a fixed belief, which was given fuller + expression in his Zoonomia and in the posthumous Temple of Nature. + </p> + <p> + Here is his rendering of the idea as versified in the Temple of Nature: + </p> +<pre xml:space="preserve"> + "Organic life beneath the shoreless waves + Was born, and nursed in Ocean's pearly caves; + First forms minute, unseen by spheric glass, + Move on the mud, or pierce the watery mass; + These, as successive generations bloom, + New powers acquire and larger limbs assume; + Whence countless groups of vegetation spring, + And breathing realms of fin, and feet, and wing. + + "Thus the tall Oak, the giant of the wood, + Which bears Britannia's thunders on the flood; + The Whale, unmeasured monster of the main; + The lordly lion, monarch of the plain; + The eagle, soaring in the realms of air, + Whose eye, undazzled, drinks the solar glare; + Imperious man, who rules the bestial crowd, + Of language, reason, and reflection proud, + With brow erect, who scorns this earthy sod, + And styles himself the image of his God— + Arose from rudiments of form and sense, + An embryon point or microscopic ens!"(2) +</pre> + <p> + Here, clearly enough, is the idea of evolution. But in that day there was + little proof forthcoming of its validity that could satisfy any one but a + poet, and when Erasmus Darwin died, in 1802, the idea of transmutation of + species was still but an unsubstantiated dream. + </p> + <p> + It was a dream, however, which was not confined to Goethe and Darwin. Even + earlier the idea had come more or less vaguely to another great dreamer—and + worker—of Germany, Immanuel Kant, and to several great Frenchmen, + including De Maillet, Maupertuis, Robinet, and the famous naturalist + Buffon—a man who had the imagination of a poet, though his message + was couched in most artistic prose. Not long after the middle of the + eighteenth century Buffon had put forward the idea of transmutation of + species, and he reiterated it from time to time from then on till his + death in 1788. But the time was not yet ripe for the idea of transmutation + of species to burst its bonds. + </p> + <p> + And yet this idea, in a modified or undeveloped form, had taken strange + hold upon the generation that was upon the scene at the close of the + eighteenth century. Vast numbers of hitherto unknown species of animals + had been recently discovered in previously unexplored regions of the + globe, and the wise men were sorely puzzled to account for the disposal of + all of these at the time of the deluge. It simplified matters greatly to + suppose that many existing species had been developed since the episode of + the ark by modification of the original pairs. The remoter bearings of + such a theory were overlooked for the time, and the idea that American + animals and birds, for example, were modified descendants of Old-World + forms—the jaguar of the leopard, the puma of the lion, and so on—became + a current belief with that class of humanity who accept almost any + statement as true that harmonizes with their prejudices without realizing + its implications. + </p> + <p> + Thus it is recorded with eclat that the discovery of the close proximity + of America at the northwest with Asia removes all difficulties as to the + origin of the Occidental faunas and floras, since Oriental species might + easily have found their way to America on the ice, and have been modified + as we find them by "the well-known influence of climate." And the persons + who gave expression to this idea never dreamed of its real significance. + In truth, here was the doctrine of evolution in a nutshell, and, because + its ultimate bearings were not clear, it seemed the most natural of + doctrines. But most of the persons who advanced it would have turned from + it aghast could they have realized its import. As it was, however, only + here and there a man like Buffon reasoned far enough to inquire what might + be the limits of such assumed transmutation; and only here and there a + Darwin or a Goethe reached the conviction that there are no limits. + </p> + <p> + LAMARCK VERSUS CUVIER + </p> + <p> + And even Goethe and Darwin had scarcely passed beyond that tentative stage + of conviction in which they held the thought of transmutation of species + as an ancillary belief not ready for full exposition. There was one of + their contemporaries, however, who, holding the same conception, was moved + to give it full explication. This was the friend and disciple of Buffon, + Jean Baptiste de Lamarck. Possessed of the spirit of a poet and + philosopher, this great Frenchman had also the widest range of technical + knowledge, covering the entire field of animate nature. The first half of + his long life was devoted chiefly to botany, in which he attained high + distinction. Then, just at the beginning of the nineteenth century, he + turned to zoology, in particular to the lower forms of animal life. + Studying these lowly organisms, existing and fossil, he was more and more + impressed with the gradations of form everywhere to be seen; the linking + of diverse families through intermediate ones; and in particular with the + predominance of low types of life in the earlier geological strata. Called + upon constantly to classify the various forms of life in the course of his + systematic writings, he found it more and more difficult to draw sharp + lines of demarcation, and at last the suspicion long harbored grew into a + settled conviction that there is really no such thing as a species of + organism in nature; that "species" is a figment of the human imagination, + whereas in nature there are only individuals. + </p> + <p> + That certain sets of individuals are more like one another than like other + sets is of course patent, but this only means, said Lamarck, that these + similar groups have had comparatively recent common ancestors, while + dissimilar sets of beings are more remotely related in consanguinity. But + trace back the lines of descent far enough, and all will culminate in one + original stock. All forms of life whatsoever are modified descendants of + an original organism. From lowest to highest, then, there is but one race, + one species, just as all the multitudinous branches and twigs from one + root are but one tree. For purposes of convenience of description, we may + divide organisms into orders, families, genera, species, just as we divide + a tree into root, trunk, branches, twigs, leaves; but in the one case, as + in the other, the division is arbitrary and artificial. + </p> + <p> + In Philosophie Zoologique (1809), Lamarck first explicitly formulated his + ideas as to the transmutation of species, though he had outlined them as + early as 1801. In this memorable publication not only did he state his + belief more explicitly and in fuller detail than the idea had been + expressed by any predecessor, but he took another long forward step, + carrying him far beyond all his forerunners except Darwin, in that he made + an attempt to explain the way in which the transmutation of species had + been brought about. The changes have been wrought, he said, through the + unceasing efforts of each organism to meet the needs imposed upon it by + its environment. Constant striving means the constant use of certain + organs. Thus a bird running by the seashore is constantly tempted to wade + deeper and deeper in pursuit of food; its incessant efforts tend to + develop its legs, in accordance with the observed principle that the use + of any organ tends to strengthen and develop it. But such slightly + increased development of the legs is transmitted to the off spring of the + bird, which in turn develops its already improved legs by its individual + efforts, and transmits the improved tendency. Generation after generation + this is repeated, until the sum of the infinitesimal variations, all in + the same direction, results in the production of the long-legged + wading-bird. In a similar way, through individual effort and transmitted + tendency, all the diversified organs of all creatures have been developed—the + fin of the fish, the wing of the bird, the hand of man; nay, more, the + fish itself, the bird, the man, even. Collectively the organs make up the + entire organism; and what is true of the individual organs must be true + also of their ensemble, the living being. + </p> + <p> + Whatever might be thought of Lamarck's explanation of the cause of + transmutation—which really was that already suggested by Erasmus + Darwin—the idea of the evolution for which he contended was but the + logical extension of the conception that American animals are the modified + and degenerated descendants of European animals. But people as a rule are + little prone to follow ideas to their logical conclusions, and in this + case the conclusions were so utterly opposed to the proximal bearings of + the idea that the whole thinking world repudiated them with acclaim. The + very persons who had most eagerly accepted the idea of transmutation of + European species into American species, and similar limited variations + through changed environment, because of the relief thus given the + otherwise overcrowded ark, were now foremost in denouncing such an + extension of the doctrine of transmutation as Lamarck proposed. + </p> + <p> + And, for that matter, the leaders of the scientific world were equally + antagonistic to the Lamarckian hypothesis. Cuvier in particular, once the + pupil of Lamarck, but now his colleague, and in authority more than his + peer, stood out against the transmutation doctrine with all his force. He + argued for the absolute fixity of species, bringing to bear the resources + of a mind which, as a mere repository of facts, perhaps never was + excelled. As a final and tangible proof of his position, he brought + forward the bodies of ibises that had been embalmed by the ancient + Egyptians, and showed by comparison that these do not differ in the + slightest particular from the ibises that visit the Nile to-day. + </p> + <p> + Cuvier's reasoning has such great historical interest—being the + argument of the greatest opponent of evolution of that day—that we + quote it at some length. + </p> + <p> + "The following objections," he says, "have already been started against my + conclusions. Why may not the presently existing races of mammiferous land + quadrupeds be mere modifications or varieties of those ancient races which + we now find in the fossil state, which modifications may have been + produced by change of climate and other local circumstances, and since + raised to the present excessive difference by the operations of similar + causes during a long period of ages? + </p> + <p> + "This objection may appear strong to those who believe in the indefinite + possibility of change of form in organized bodies, and think that, during + a succession of ages and by alterations of habitudes, all the species may + change into one another, or one of them give birth to all the rest. Yet to + these persons the following answer may be given from their own system: If + the species have changed by degrees, as they assume, we ought to find + traces of this gradual modification. Thus, between the palaeotherium and + the species of our own day, we should be able to discover some + intermediate forms; and yet no such discovery has ever been made. Since + the bowels of the earth have not preserved monuments of this strange + genealogy, we have no right to conclude that the ancient and now extinct + species were as permanent in their forms and characters as those which + exist at present; or, at least, that the catastrophe which destroyed them + did not leave sufficient time for the productions of the changes that are + alleged to have taken place. + </p> + <p> + "In order to reply to those naturalists who acknowledge that the varieties + of animals are restrained by nature within certain limits, it would be + necessary to examine how far these limits extend. This is a very curious + inquiry, and in itself exceedingly interesting under a variety of + relations, but has been hitherto very little attended to.... + </p> + <p> + "Wild animals which subsist upon herbage feel the influence of climate a + little more extensively, because there is added to it the influence of + food, both in regard to its abundance and its quality. Thus the elephants + of one forest are larger than those of another; their tusks also grow + somewhat longer in places where their food may happen to be more favorable + for the production of the substance of ivory. The same may take place in + regard to the horns of stags and reindeer. But let us examine two + elephants, the most dissimilar that can be conceived, we shall not + discover the smallest difference in the number and articulations of the + bones, the structure of the teeth, etc......... + </p> + <p> + "Nature appears also to have guarded against the alterations of species + which might proceed from mixture of breeds by influencing the various + species of animals with mutual aversion from one another. Hence all the + cunning and all the force that man is able to exert is necessary to + accomplish such unions, even between species that have the nearest + resemblances. And when the mule breeds that are thus produced by these + forced conjunctions happen to be fruitful, which is seldom the case, this + fecundity never continues beyond a few generations, and would not probably + proceed so far without a continuance of the same cares which excited it at + first. Thus we never see in a wild state intermediate productions between + the hare and the rabbit, between the stag and the doe, or between the + marten and the weasel. But the power of man changes this established + order, and continues to produce all these intermixtures of which the + various species are susceptible, but which they would never produce if + left to themselves. + </p> + <p> + "The degrees of these variations are proportional to the intensity of the + causes that produced them—namely, the slavery or subjection under + which those animals are to man. They do not proceed far in + half-domesticated species. In the cat, for example, a softer or harsher + fur, more brilliant or more varied colors, greater or less size—these + form the whole extent of variety in the species; the skeleton of the cat + of Angora differs in no regular and constant circumstances from the + wild-cat of Europe...." + </p> + <p> + The most remarkable effects of the influence of man are produced upon that + animal which he has reduced most completely under subjection. Dogs have + been transported by mankind into every part of the world and have + submitted their action to his entire direction. Regulated in their unions + by the pleasure or caprice of their masters, the almost endless varieties + of dogs differ from one another in color, in length, and abundance of + hair, which is sometimes entirely wanting; in their natural instincts; in + size, which varies in measure as one to five, mounting in some instances + to more than a hundredfold in bulk; in the form of their ears, noses, and + tails; in the relative length of their legs; in the progressive + development of the brain, in several of the domesticated varieties + occasioning alterations even in the form of the head, some of them having + long, slender muzzles with a flat forehead, others having short muzzles + with a forehead convex, etc., insomuch that the apparent difference + between a mastiff and a water-spaniel and between a greyhound and a pugdog + are even more striking than between almost any of the wild species of a + genus........ + </p> + <p> + It follows from these observations that animals have certain fixed and + natural characters which resist the effects of every kind of influence, + whether proceeding from natural causes or human interference; and we have + not the smallest reason to suspect that time has any more effect on them + than climate. + </p> + <p> + "I am aware that some naturalists lay prodigious stress upon the thousands + which they can call into action by a dash of their pens. In such matters, + however, our only way of judging as to the effects which may be produced + by a long period of time is by multiplying, as it were, such as are + produced by a shorter time. With this view I have endeavored to collect + all the ancient documents respecting the forms of animals; and there are + none equal to those furnished by the Egyptians, both in regard to their + antiquity and abundance. They have not only left us representatives of + animals, but even their identical bodies embalmed and preserved in the + catacombs. + </p> + <p> + "I have examined, with the greatest attention, the engraved figures of + quadrupeds and birds brought from Egypt to ancient Rome, and all these + figures, one with another, have a perfect resemblance to their intended + objects, such as they still are to-day. + </p> + <p> + "From all these established facts, there does not seem to be the smallest + foundation for supposing that the new genera which I have discovered or + established among extraneous fossils, such as the paleoetherium, + anoplotherium, megalonyx, mastodon, pterodactylis, etc., have ever been + the sources of any of our present animals, which only differ so far as + they are influenced by time or climate. Even if it should prove true, + which I am far from believing to be the case, that the fossil elephants, + rhinoceroses, elks, and bears do not differ further from the existing + species of the same genera than the present races of dogs differ among + themselves, this would by no means be a sufficient reason to conclude that + they were of the same species; since the races or varieties of dogs have + been influenced by the trammels of domesticity, which those other animals + never did, and indeed never could, experience."(3) + </p> + <p> + To Cuvier's argument from the fixity of Egyptian mummified birds and + animals, as above stated, Lamarck replied that this proved nothing except + that the ibis had become perfectly adapted to its Egyptian surroundings in + an early day, historically speaking, and that the climatic and other + conditions of the Nile Valley had not since then changed. His theory, he + alleged, provided for the stability of species under fixed conditions + quite as well as for transmutation under varying conditions. + </p> + <p> + But, needless to say, the popular verdict lay with Cuvier; talent won for + the time against genius, and Lamarck was looked upon as an impious + visionary. His faith never wavered, however. He believed that he had + gained a true insight into the processes of animate nature, and he + reiterated his hypotheses over and over, particularly in the introduction + to his Histoire Naturelle des Animaux sans Vertebres, in 1815, and in his + Systeme des Connaissances Positives de l'Homme, in 1820. He lived on till + 1829, respected as a naturalist, but almost unrecognized as a prophet. + </p> + <p> + TENTATIVE ADVANCES + </p> + <p> + While the names of Darwin and Goethe, and in particular that of Lamarck, + must always stand out in high relief in this generation as the exponents + of the idea of transmutation of species, there are a few others which must + not be altogether overlooked in this connection. Of these the most + conspicuous is that of Gottfried Reinhold Treviranus, a German naturalist + physician, professor of mathematics in the lyceum at Bremen. + </p> + <p> + It was an interesting coincidence that Treviranus should have published + the first volume of his Biologie, oder Philosophie der lebenden Natur, in + which his views on the transmutation of species were expounded, in 1802, + the same twelvemonth in which Lamarck's first exposition of the same + doctrine appeared in his Recherches sur l'Organisation des Corps Vivants. + It is singular, too, that Lamarck, in his Hydrogelogie of the same date, + should independently have suggested "biology" as an appropriate word to + express the general science of living things. It is significant of the + tendency of thought of the time that the need of such a unifying word + should have presented itself simultaneously to independent thinkers in + different countries. + </p> + <p> + That same memorable year, Lorenz Oken, another philosophical naturalist, + professor in the University of Zurich, published the preliminary outlines + of his Philosophie der Natur, which, as developed through later + publications, outlined a theory of spontaneous generation and of evolution + of species. Thus it appears that this idea was germinating in the minds of + several of the ablest men of the time during the first decade of our + century. But the singular result of their various explications was to give + sudden check to that undercurrent of thought which for some time had been + setting towards this conception. As soon as it was made clear whither the + concession that animals may be changed by their environment must logically + trend, the recoil from the idea was instantaneous and fervid. Then for a + generation Cuvier was almost absolutely dominant, and his verdict was + generally considered final. + </p> + <p> + There was, indeed, one naturalist of authority in France who had the + hardihood to stand out against Cuvier and his school, and who was in a + position to gain a hearing, though by no means to divide the following. + This was Etienne Geoffroy Saint-Hilaire, the famous author of the + Philosophie Anatomique, and for many years the colleague of Lamarck at the + Jardin des Plantes. Like Goethe, Geoffroy was pre-eminently an anatomist, + and, like the great German, he had early been impressed with the + resemblances between the analogous organs of different classes of beings. + He conceived the idea that an absolute unity of type prevails throughout + organic nature as regards each set of organs. Out of this idea grew his + gradually formed belief that similarity of structure might imply identity + of origin—that, in short, one species of animal might have developed + from another. + </p> + <p> + Geoffroy's grasp of this idea of transmutation was by no means so complete + as that of Lamarck, and he seems never to have fully determined in his own + mind just what might be the limits of such development of species. + Certainly he nowhere includes all organic creatures in one line of + descent, as Lamarck had done; nevertheless, he held tenaciously to the + truth as he saw it, in open opposition to Cuvier, with whom he held a + memorable debate at the Academy of Sciences in 1830—the debate which + so aroused the interest and enthusiasm of Goethe, but which, in the + opinion of nearly every one else, resulted in crushing defeat for + Geoffrey, and brilliant, seemingly final, victory for the advocate of + special creation and the fixity of species. + </p> + <p> + With that all ardent controversy over the subject seemed to end, and for + just a quarter of a century to come there was published but a single + argument for transmutation of species which attracted any general + attention whatever. This oasis in a desert generation was a little book + called Vestiges of the Natural History of Creation, which appeared + anonymously in England in 1844, and which passed through numerous + editions, and was the subject of no end of abusive and derisive comment. + This book, the authorship of which remained for forty years a secret, is + now conceded to have been the work of Robert Chambers, the well-known + English author and publisher. The book itself is remarkable as being an + avowed and unequivocal exposition of a general doctrine of evolution, its + view being as radical and comprehensive as that of Lamarck himself. But it + was a resume of earlier efforts rather than a new departure, to say + nothing of its technical shortcomings, which may best be illustrated by a + quotation. + </p> + <p> + "The whole question," says Chambers, "stands thus: For the theory of + universal order—that is, order as presiding in both the origin and + administration of the world—we have the testimony of a vast number + of facts in nature, and this one in addition—that whatever is left + from the domain of ignorance, and made undoubted matter of science, forms + a new support to the same doctrine. The opposite view, once predominant, + has been shrinking for ages into lesser space, and now maintains a footing + only in a few departments of nature which happen to be less liable than + others to a clear investigation. The chief of these, if not almost the + only one, is the origin of the organic kingdoms. So long as this remains + obscure, the supernatural will have a certain hold upon enlightened + persons. Should it ever be cleared up in a way that leaves no doubt of a + natural origin of plants and animals, there must be a complete revolution + in the view which is generally taken of the relation of the Father of our + being. + </p> + <p> + "This prepares the way for a few remarks on the present state of opinion + with regard to the origin of organic nature. The great difficulty here is + the apparent determinateness of species. These forms of life being + apparently unchangeable, or at least always showing a tendency to return + to the character from which they have diverged, the idea arises that there + can have been no progression from one to another; each must have taken its + special form, independently of other forms, directly from the appointment + of the Creator. The Edinburgh Review writer says, 'they were created by + the hand of God and adapted to the conditions of the period.' Now it is, + in the first place, not certain that species constantly maintain a fixed + character, for we have seen that what were long considered as determinate + species have been transmuted into others. Passing, however, from this + fact, as it is not generally received among men of science, there remain + some great difficulties in connection with the idea of special creation. + First we should have to suppose, as pointed out in my former volume, a + most startling diversity of plan in the divine workings, a great general + plan or system of law in the leading events of world-making, and a plan of + minute, nice operation, and special attention in some of the mere details + of the process. The discrepancy between the two conceptions is surely + overpowering, when we allow ourselves to see the whole matter in a steady + and rational light. There is, also, the striking fact of an ascertained + historical progress of plants and animals in the order of their + organization; marine and cellular plants and invertebrated animals first, + afterwards higher examples of both. In an arbitrary system we had surely + no reason to expect mammals after reptiles; yet in this order they came. + The writer in the Edinburgh Review speaks of animals as coming in + adaptation to conditions, but this is only true in a limited sense. The + groves which formed the coal-beds might have been a fitting habitation for + reptiles, birds, and mammals, as such groves are at the present day; yet + we see none of the last of these classes and hardly any traces of the two + first at that period of the earth. Where the iguanodon lived the elephant + might have lived, but there was no elephant at that time. The sea of the + Lower Silurian era was capable of supporting fish, but no fish existed. It + hence forcibly appears that theatres of life must have remained + unserviceable, or in the possession of a tenantry inferior to what might + have enjoyed them, for many ages: there surely would have been no such + waste allowed in a system where Omnipotence was working upon the plan of + minute attention to specialities. The fact seems to denote that the actual + procedure of the peopling of the earth was one of a natural kind, + requiring a long space of time for its evolution. In this supposition the + long existence of land without land animals, and more particularly without + the noblest classes and orders, is only analogous to the fact, not nearly + enough present to the minds of a civilized people, that to this day the + bulk of the earth is a waste as far as man is concerned. + </p> + <p> + "Another startling objection is in the infinite local variation of organic + forms. Did the vegetable and animal kingdoms consist of a definite number + of species adapted to peculiarities of soil and climate, and universally + distributed, the fact would be in harmony with the idea of special + exertion. But the truth is that various regions exhibit variations + altogether without apparent end or purpose. Professor Henslow enumerates + forty-five distinct flowers or sets of plants upon the surface of the + earth, notwithstanding that many of these would be equally suitable + elsewhere. The animals of different continents are equally various, few + species being the same in any two, though the general character may + conform. The inference at present drawn from this fact is that there must + have been, to use the language of the Rev. Dr. Pye Smith, 'separate and + original creations, perhaps at different and respectively distinct + epochs.' It seems hardly conceivable that rational men should give an + adherence to such a doctrine when we think of what it involves. In the + single fact that it necessitates a special fiat of the inconceivable + Author of this sand-cloud of worlds to produce the flora of St. Helena, we + read its more than sufficient condemnation. It surely harmonizes far + better with our general ideas of nature to suppose that, just as all else + in this far-spread science was formed on the laws impressed upon it at + first by its Author, so also was this. An exception presented to us in + such a light appears admissible only when we succeed in forbidding our + minds to follow out those reasoning processes to which, by another law of + the Almighty, they tend, and for which they are adapted."(4) + </p> + <p> + Such reasoning as this naturally aroused bitter animadversions, and cannot + have been without effect in creating an undercurrent of thought in + opposition to the main trend of opinion of the time. But the book can + hardly be said to have done more than that. Indeed, some critics have + denied it even this merit. After its publication, as before, the + conception of transmutation of species remained in the popular estimation, + both lay and scientific, an almost forgotten "heresy." + </p> + <p> + It is true that here and there a scientist of greater or less repute—as + Von Buch, Meckel, and Von Baer in Germany, Bory Saint-Vincent in France, + Wells, Grant, and Matthew in England, and Leidy in America—had + expressed more or less tentative dissent from the doctrine of special + creation and immutability of species, but their unaggressive suggestions, + usually put forward in obscure publications, and incidentally, were + utterly overlooked and ignored. And so, despite the scientific advances + along many lines at the middle of the century, the idea of the + transmutability of organic races had no such prominence, either in + scientific or unscientific circles, as it had acquired fifty years before. + Special creation held the day, seemingly unopposed. + </p> + <p> + DARWIN AND THE ORIGIN OF SPECIES + </p> + <p> + But even at this time the fancied security of the special-creation + hypothesis was by no means real. Though it seemed so invincible, its real + position was that of an apparently impregnable fortress beneath which, all + unbeknown to the garrison, a powder-mine has been dug and lies ready for + explosion. For already there existed in the secluded work-room of an + English naturalist, a manuscript volume and a portfolio of notes which + might have sufficed, if given publicity, to shatter the entire structure + of the special-creation hypothesis. The naturalist who, by dint of long + and patient effort, had constructed this powder-mine of facts was Charles + Robert Darwin, grandson of the author of Zoonomia. + </p> + <p> + As long ago as July 1, 1837, young Darwin, then twenty-eight years of age, + had opened a private journal, in which he purposed to record all facts + that came to him which seemed to have any bearing on the moot point of the + doctrine of transmutation of species. Four or five years earlier, during + the course of that famous trip around the world with Admiral Fitzroy, as + naturalist to the Beagle, Darwin had made the personal observations which + first tended to shake his belief of the fixity of species. In South + America, in the Pampean formation, he had discovered "great fossil animals + covered with armor like that on the existing armadillos," and had been + struck with this similarity of type between ancient and existing faunas of + the same region. He was also greatly impressed by the manner in which + closely related species of animals were observed to replace one another as + he proceeded southward over the continent; and "by the South-American + character of most of the productions of the Galapagos Archipelago, and + more especially by the manner in which they differ slightly on each island + of the group, none of the islands appearing to be very ancient in a + geological sense." + </p> + <p> + At first the full force of these observations did not strike him; for, + under sway of Lyell's geological conceptions, he tentatively explained the + relative absence of life on one of the Galapagos Islands by suggesting + that perhaps no species had been created since that island arose. But + gradually it dawned upon him that such facts as he had observed "could + only be explained on the supposition that species gradually become + modified." From then on, as he afterwards asserted, the subject haunted + him; hence the journal of 1837. + </p> + <p> + It will thus be seen that the idea of the variability of species came to + Charles Darwin as an inference from personal observations in the field, + not as a thought borrowed from books. He had, of course, read the works of + his grandfather much earlier in life, but the arguments of Zoonomia and + The Temple of Nature had not served in the least to weaken his acceptance + of the current belief in fixity of species. Nor had he been more impressed + with the doctrine of Lamarck, so closely similar to that of his + grandfather. Indeed, even after his South-American experience had aroused + him to a new point of view he was still unable to see anything of value in + these earlier attempts at an explanation of the variation of species. In + opening his journal, therefore, he had no preconceived notion of upholding + the views of these or any other makers of hypotheses, nor at the time had + he formulated any hypothesis of his own. His mind was open and receptive; + he was eager only for facts which might lead him to an understanding of a + problem which seemed utterly obscure. It was something to feel sure that + species have varied; but how have such variations been brought about? + </p> + <p> + It was not long before Darwin found a clew which he thought might lead to + the answer he sought. In casting about for facts he had soon discovered + that the most available field for observation lay among domesticated + animals, whose numerous variations within specific lines are familiar to + every one. Thus under domestication creatures so tangibly different as a + mastiff and a terrier have sprung from a common stock. So have the + Shetland pony, the thoroughbred, and the draught-horse. In short, there is + no domesticated animal that has not developed varieties deviating more or + less widely from the parent stock. Now, how has this been accomplished? + Why, clearly, by the preservation, through selective breeding, of + seemingly accidental variations. Thus one horseman, by constantly + selecting animals that "chance" to have the right build and stamina, + finally develops a race of running-horses; while another horseman, by + selecting a different series of progenitors, has developed a race of slow, + heavy draught animals. + </p> + <p> + So far, so good; the preservation of "accidental" variations through + selective breeding is plainly a means by which races may be developed that + are very different from their original parent form. But this is under + man's supervision and direction. By what process could such selection be + brought about among creatures in a state of nature? Here surely was a + puzzle, and one that must be solved before another step could be taken in + this direction. + </p> + <p> + The key to the solution of this puzzle came into Darwin's mind through a + chance reading of the famous essay on "Population" which Thomas Robert + Malthus had published almost half a century before. This essay, expositing + ideas by no means exclusively original with Malthus, emphasizes the fact + that organisms tend to increase at a geometrical ratio through successive + generations, and hence would overpopulate the earth if not somehow kept in + check. Cogitating this thought, Darwin gained a new insight into the + processes of nature. He saw that in virtue of this tendency of each race + of beings to overpopulate the earth, the entire organic world, animal and + vegetable, must be in a state of perpetual carnage and strife, individual + against individual, fighting for sustenance and life. + </p> + <p> + That idea fully imagined, it becomes plain that a selective influence is + all the time at work in nature, since only a few individuals, relatively, + of each generation can come to maturity, and these few must, naturally, be + those best fitted to battle with the particular circumstances in the midst + of which they are placed. In other words, the individuals best adapted to + their surroundings will, on the average, be those that grow to maturity + and produce offspring. To these offspring will be transmitted the + favorable peculiarities. Thus these peculiarities will become permanent, + and nature will have accomplished precisely what the human breeder is seen + to accomplish. Grant that organisms in a state of nature vary, however + slightly, one from another (which is indubitable), and that such + variations will be transmitted by a parent to its offspring (which no one + then doubted); grant, further, that there is incessant strife among the + various organisms, so that only a small proportion can come to maturity—grant + these things, said Darwin, and we have an explanation of the preservation + of variations which leads on to the transmutation of species themselves. + </p> + <p> + This wonderful coign of vantage Darwin had reached by 1839. Here was the + full outline of his theory; here were the ideas which afterwards came to + be embalmed in familiar speech in the phrases "spontaneous variation," and + the "survival of the fittest," through "natural selection." After such a + discovery any ordinary man would at once have run through the streets of + science, so to speak, screaming "Eureka!" Not so Darwin. He placed the + manuscript outline of his theory in his portfolio, and went on gathering + facts bearing on his discovery. In 1844 he made an abstract in a + manuscript book of the mass of facts by that time accumulated. He showed + it to his friend Hooker, made careful provision for its publication in the + event of his sudden death, then stored it away in his desk and went ahead + with the gathering of more data. This was the unexploded powder-mine to + which I have just referred. + </p> + <p> + Twelve years more elapsed—years during which the silent worker + gathered a prodigious mass of facts, answered a multitude of objections + that arose in his own mind, vastly fortified his theory. All this time the + toiler was an invalid, never knowing a day free from illness and + discomfort, obliged to husband his strength, never able to work more than + an hour and a half at a stretch; yet he accomplished what would have been + vast achievements for half a dozen men of robust health. Two friends among + the eminent scientists of the day knew of his labors—Sir Joseph + Hooker, the botanist, and Sir Charles Lyell, the geologist. Gradually + Hooker had come to be more than half a convert to Darwin's views. Lyell + was still sceptical, yet he urged Darwin to publish his theory without + further delay lest he be forestalled. At last the patient worker decided + to comply with this advice, and in 1856 he set to work to make another and + fuller abstract of the mass of data he had gathered. + </p> + <p> + And then a strange thing happened. After Darwin had been at work on his + "abstract" about two years, but before he had published a line of it, + there came to him one day a paper in manuscript, sent for his approval by + a naturalist friend named Alfred Russel Wallace, who had been for some + time at work in the East India Archipelago. He read the paper, and, to his + amazement, found that it contained an outline of the same theory of + "natural selection" which he himself had originated and for twenty years + had worked upon. Working independently, on opposite sides of the globe, + Darwin and Wallace had hit upon the same explanation of the cause of + transmutation of species. "Were Wallace's paper an abstract of my + unpublished manuscript of 1844," said Darwin, "it could not better express + my ideas." + </p> + <p> + Here was a dilemma. To publish this paper with no word from Darwin would + give Wallace priority, and wrest from Darwin the credit of a discovery + which he had made years before his codiscoverer entered the field. Yet, on + the other hand, could Darwin honorably do otherwise than publish his + friend's paper and himself remain silent? It was a complication well + calculated to try a man's soul. Darwin's was equal to the test. Keenly + alive to the delicacy of the position, he placed the whole matter before + his friends Hooker and Lyell, and left the decision as to a course of + action absolutely to them. Needless to say, these great men did the one + thing which insured full justice to all concerned. They counselled a joint + publication, to include on the one hand Wallace's paper, and on the other + an abstract of Darwin's ideas, in the exact form in which it had been + outlined by the author in a letter to Asa Gray in the previous year—an + abstract which was in Gray's hands before Wallace's paper was in + existence. This joint production, together with a full statement of the + facts of the case, was presented to the Linnaean Society of London by + Hooker and Lyell on the evening of July 1, 1858, this being, by an odd + coincidence, the twenty-first anniversary of the day on which Darwin had + opened his journal to collect facts bearing on the "species question." Not + often before in the history of science has it happened that a great theory + has been nurtured in its author's brain through infancy and adolescence to + its full legal majority before being sent out into the world. + </p> + <p> + Thus the fuse that led to the great powder-mine had been lighted. The + explosion itself came more than a year later, in November, 1859, when + Darwin, after thirteen months of further effort, completed the outline of + his theory, which was at first begun as an abstract for the Linnaean + Society, but which grew to the size of an independent volume despite his + efforts at condensation, and which was given that ever-to-be-famous title, + The Origin of Species by Means of Natural Selection, or the Preservation + of Favored Races in the Struggle for Life. And what an explosion it was! + The joint paper of 1858 had made a momentary flare, causing the hearers, + as Hooker said, to "speak of it with bated breath," but beyond that it + made no sensation. What the result was when the Origin itself appeared no + one of our generation need be told. The rumble and roar that it made in + the intellectual world have not yet altogether ceased to echo after more + than forty years of reverberation. + </p> + <p> + NEW CHAMPIONS + </p> + <p> + To the Origin of Species, then, and to its author, Charles Darwin, must + always be ascribed chief credit for that vast revolution in the + fundamental beliefs of our race which has come about since 1859, and which + made the second half of the century memorable. But it must not be + overlooked that no such sudden metamorphosis could have been effected had + it not been for the aid of a few notable lieutenants, who rallied to the + standards of the leader immediately after the publication of the Origin. + Darwin had all along felt the utmost confidence in the ultimate triumph of + his ideas. "Our posterity," he declared, in a letter to Hooker, "will + marvel as much about the current belief (in special creation) as we do + about fossil shells having been thought to be created as we now see them." + But he fully realized that for the present success of his theory of + transmutation the championship of a few leaders of science was + all-essential. He felt that if he could make converts of Hooker and Lyell + and of Thomas Henry Huxley at once, all would be well. + </p> + <p> + His success in this regard, as in others, exceeded his expectations. + Hooker was an ardent disciple from reading the proof-sheets before the + book was published; Lyell renounced his former beliefs and fell into line + a few months later; while Huxley, so soon as he had mastered the central + idea of natural selection, marvelled that so simple yet all-potent a + thought had escaped him so long, and then rushed eagerly into the fray, + wielding the keenest dialectic blade that was drawn during the entire + controversy. Then, too, unexpected recruits were found in Sir John Lubbock + and John Tyndall, who carried the war eagerly into their respective + territories; while Herbert Spencer, who had advocated a doctrine of + transmutation on philosophic grounds some years before Darwin published + the key to the mystery—and who himself had barely escaped + independent discovery of that key—lent his masterful influence to + the cause. In America the famous botanist Asa Gray, who had long been a + correspondent of Darwin's but whose advocacy of the new theory had not + been anticipated, became an ardent propagandist; while in Germany Ernst + Heinrich Haeckel, the youthful but already noted zoologist, took up the + fight with equal enthusiasm. + </p> + <p> + Against these few doughty champions—with here and there another of + less general renown—was arrayed, at the outset, practically all + Christendom. The interest of the question came home to every person of + intelligence, whatever his calling, and the more deeply as it became more + and more clear how far-reaching are the real bearings of the doctrine of + natural selection. Soon it was seen that should the doctrine of the + survival of the favored races through the struggle for existence win, + there must come with it as radical a change in man's estimate of his own + position as had come in the day when, through the efforts of Copernicus + and Galileo, the world was dethroned from its supposed central position in + the universe. The whole conservative majority of mankind recoiled from + this necessity with horror. And this conservative majority included not + laymen merely, but a vast preponderance of the leaders of science also. + </p> + <p> + With the open-minded minority, on the other hand, the theory of natural + selection made its way by leaps and bounds. Its delightful simplicity—which + at first sight made it seem neither new nor important—coupled with + the marvellous comprehensiveness of its implications, gave it a hold on + the imagination, and secured it a hearing where other theories of + transmutation of species had been utterly scorned. Men who had found + Lamarck's conception of change through voluntary effort ridiculous, and + the vaporings of the Vestiges altogether despicable, men whose scientific + cautions held them back from Spencer's deductive argument, took eager hold + of that tangible, ever-present principle of natural selection, and were + led on and on to its goal. Hour by hour the attitude of the thinking world + towards this new principle changed; never before was so great a revolution + wrought so suddenly. + </p> + <p> + Nor was this merely because "the times were ripe" or "men's minds prepared + for evolution." Darwin himself bears witness that this was not altogether + so. All through the years in which he brooded this theory he sounded his + scientific friends, and could find among them not one who acknowledged a + doctrine of transmutation. The reaction from the stand-point of Lamarck + and Erasmus Darwin and Goethe had been complete, and when Charles Darwin + avowed his own conviction he expected always to have it met with ridicule + or contempt. In 1857 there was but one man speaking with any large degree + of authority in the world who openly avowed a belief in transmutation of + species—that man being Herbert Spencer. But the Origin of Species + came, as Huxley has said, like a flash in the darkness, enabling the + benighted voyager to see the way. The score of years during which its + author had waited and worked had been years well spent. Darwin had become, + as he himself says, a veritable Croesus, "overwhelmed with his riches in + facts"—facts of zoology, of selective artificial breeding, of + geographical distribution of animals, of embryology, of paleontology. He + had massed his facts about his theory, condensed them and recondensed, + until his volume of five hundred pages was an encyclopaedia in scope. + During those long years of musing he had thought out almost every + conceivable objection to his theory, and in his book every such objection + was stated with fullest force and candor, together with such reply as the + facts at command might dictate. It was the force of those twenty years of + effort of a master-mind that made the sudden breach in the breaswtork{sic} + of current thought. + </p> + <p> + Once this breach was effected the work of conquest went rapidly on. Day by + day squads of the enemy capitulated and struck their arms. By the time + another score of years had passed the doctrine of evolution had become the + working hypothesis of the scientific world. The revolution had been + effected. + </p> + <p> + And from amid the wreckage of opinion and belief stands forth the figure + of Charles Darwin, calm, imperturbable, serene; scatheless to ridicule, + contumely, abuse; unspoiled by ultimate success; unsullied alike by the + strife and the victory—take him for all in all, for character, for + intellect, for what he was and what he did, perhaps the most Socratic + figure of the century. When, in 1882, he died, friend and foe alike + conceded that one of the greatest sons of men had rested from his labors, + and all the world felt it fitting that the remains of Charles Darwin + should be entombed in Westminster Abbey close beside the honored grave of + Isaac Newton. Nor were there many who would dispute the justice of + Huxley's estimate of his accomplishment: "He found a great truth trodden + under foot. Reviled by bigots, and ridiculed by all the world, he lived + long enough to see it, chiefly by his own efforts, irrefragably + established in science, inseparably incorporated with the common thoughts + of men, and only hated and feared by those who would revile but dare not." + </p> + <p> + THE ORIGIN OF THE FITTEST + </p> + <p> + Wide as are the implications of the great truth which Darwin and his + co-workers established, however, it leaves quite untouched the problem of + the origin of those "favored variations" upon which it operates. That such + variations are due to fixed and determinate causes no one understood + better than Darwin; but in his original exposition of his doctrine he made + no assumption as to what these causes are. He accepted the observed fact + of variation—as constantly witnessed, for example, in the + differences between parents and offspring—and went ahead from this + assumption. + </p> + <p> + But as soon as the validity of the principle of natural selection came to + be acknowledged speculators began to search for the explanation of those + variations which, for purposes of argument, had been provisionally called + "spontaneous." Herbert Spencer had all along dwelt on this phase of the + subject, expounding the Lamarckian conceptions of the direct influence of + the environment (an idea which had especially appealed to Buffon and to + Geoffroy Saint-Hilaire), and of effort in response to environment and + stimulus as modifying the individual organism, and thus supplying the + basis for the operation of natural selection. Haeckel also became an + advocate of this idea, and presently there arose a so-called school of + neo-Lamarckians, which developed particular strength and prominence in + America under the leadership of Professors A. Hyatt and E. D. Cope. + </p> + <p> + But just as the tide of opinion was turning strongly in this direction, an + utterly unexpected obstacle appeared in the form of the theory of + Professor August Weismann, put forward in 1883, which antagonized the + Lamarckian conception (though not touching the Darwinian, of which + Weismann is a firm upholder) by denying that individual variations, + however acquired by the mature organism, are transmissible. The flurry + which this denial created has not yet altogether subsided, but subsequent + observations seem to show that it was quite disproportionate to the real + merits of the case. Notwithstanding Professor Weismann's objections, the + balance of evidence appears to favor the view that the Lamarckian factor + of acquired variations stands as the complement of the Darwinian factor of + natural selection in effecting the transmutation of species. + </p> + <p> + Even though this partial explanation of what Professor Cope calls the + "origin of the fittest" be accepted, there still remains one great life + problem which the doctrine of evolution does not touch. The origin of + species, genera, orders, and classes of beings through endless + transmutations is in a sense explained; but what of the first term of this + long series? Whence came that primordial organism whose transmuted + descendants make up the existing faunas and floras of the globe? + </p> + <p> + There was a time, soon after the doctrine of evolution gained a hearing, + when the answer to that question seemed to some scientists of authority to + have been given by experiment. Recurring to a former belief, and repeating + some earlier experiments, the director of the Museum of Natural History at + Rouen, M. F. A. Pouchet, reached the conclusion that organic beings are + spontaneously generated about us constantly, in the familiar processes of + putrefaction, which were known to be due to the agency of microscopic + bacteria. But in 1862 Louis Pasteur proved that this seeming spontaneous + generation is in reality due to the existence of germs in the air. + Notwithstanding the conclusiveness of these experiments, the claims of + Pouchet were revived in England ten years later by Professor Bastian; but + then the experiments of John Tyndall, fully corroborating the results of + Pasteur, gave a final quietus to the claim of "spontaneous generation" as + hitherto formulated. + </p> + <p> + There for the moment the matter rests. But the end is not yet. Fauna and + flora are here, and, thanks to Lamarck and Wallace and Darwin, their + development, through the operation of those "secondary causes" which we + call laws of nature, has been proximally explained. The lowest forms of + life have been linked with the highest in unbroken chains of descent. + Meantime, through the efforts of chemists and biologists, the gap between + the inorganic and the organic worlds, which once seemed almost infinite, + has been constantly narrowed. Already philosophy can throw a bridge across + that gap. But inductive science, which builds its own bridges, has not yet + spanned the chasm, small though it appear. Until it shall have done so, + the bridge of organic evolution is not quite complete; yet even as it + stands to-day it is perhaps the most stupendous scientific structure of + the nineteenth century. + </p> + <p> + <a name="link2H_4_0008" id="link2H_4_0008"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + VII. EIGHTEENTH-CENTURY MEDICINE + </h2> + <h3> + THE SYSTEM OF BOERHAAVE + </h3> + <p> + At least two pupils of William Harvey distinguished themselves in + medicine, Giorgio Baglivi (1669-1707), who has been called the "Italian + Sydenham," and Hermann Boerhaave (1668-1738). The work of Baglivi was + hardly begun before his early death removed one of the most promising of + the early eighteenth-century physicians. Like Boerhaave, he represents a + type of skilled, practical clinitian rather than the abstract scientist. + One of his contributions to medical literature is the first accurate + description of typhoid, or, as he calls it, mesenteric fever. + </p> + <p> + If for nothing else, Boerhaave must always be remembered as the teacher of + Von Haller, but in his own day he was the widest known and the most + popular teacher in the medical world. He was the idol of his pupils at + Leyden, who flocked to his lectures in such numbers that it became + necessary to "tear down the walls of Leyden to accommodate them." His fame + extended not only all over Europe but to Asia, North America, and even + into South America. A letter sent him from China was addressed to + "Boerhaave in Europe." His teachings represent the best medical knowledge + of his day, a high standard of morality, and a keen appreciation of the + value of observation; and it was through such teachings imparted to his + pupils and advanced by them, rather than to any new discoveries, that his + name is important in medical history. His arrangement and classification + of the different branches of medicine are interesting as representing the + attitude of the medical profession towards these various branches at that + time. + </p> + <p> + "In the first place we consider Life; then Health, afterwards Diseases; + and lastly their several Remedies. + </p> + <p> + "Health the first general branch of Physic in our Institutions is termed + Physiology, or the Animal Oeconomy; demonstrating the several Parts of the + human Body, with their Mechanism and Actions. + </p> + <p> + "The second branch of Physic is called Pathology, treating of Diseases, + their Differences, Causes and Effects, or Symptoms; by which the human + Body is known to vary from its healthy state. + </p> + <p> + "The third part of Physic is termed Semiotica, which shows the Signs + distinguishing between sickness and Health, Diseases and their Causes in + the human Body; it also imports the State and Degrees of Health and + Diseases, and presages their future Events. + </p> + <p> + "The fourth general branch of Physic is termed Hygiene, or Prophylaxis. + </p> + <p> + "The fifth and last part of Physic is called Therapeutica; which instructs + us in the Nature, Preparation and uses of the Materia Medica; and the + methods of applying the same, in order to cure Diseases and restore lost + Health."(1) + </p> + <p> + From this we may gather that his general view of medicine was not unlike + that taken at the present time. + </p> + <p> + Boerhaave's doctrines were arranged into a "system" by Friedrich Hoffmann, + of Halle (1660-1742), this system having the merit of being simple and + more easily comprehended than many others. In this system forces were + considered inherent in matter, being expressed as mechanical movements, + and determined by mass, number, and weight. Similarly, forces express + themselves in the body by movement, contraction, and relaxation, etc., and + life itself is movement, "particularly movement of the heart." Life and + death are, therefore, mechanical phenomena, health is determined by + regularly recurring movements, and disease by irregularity of them. The + body is simply a large hydraulic machine, controlled by "the aether" or + "sensitive soul," and the chief centre of this soul lies in the medulla. + </p> + <p> + In the practical application of medicines to diseases Hoffman used simple + remedies, frequently with happy results, for whatever the medical man's + theory may be he seldom has the temerity to follow it out logically, and + use the remedies indicated by his theory to the exclusion of + long-established, although perhaps purely empirical, remedies. + Consequently, many vague theorists have been excellent practitioners, and + Hoffman was one of these. Some of the remedies he introduced are still in + use, notably the spirits of ether, or "Hoffman's anodyne." + </p> + <p> + ANIMISTS, VITALISTS, AND ORGANICISTS + </p> + <p> + Besides Hoffman's system of medicine, there were numerous others during + the eighteenth century, most of which are of no importance whatever; but + three, at least, that came into existence and disappeared during the + century are worthy of fuller notice. One of these, the Animists, had for + its chief exponent Georg Ernst Stahl of "phlogiston" fame; another, the + Vitalists, was championed by Paul Joseph Barthez (1734-1806); and the + third was the Organicists. This last, while agreeing with the other two + that vital activity cannot be explained by the laws of physics and + chemistry, differed in not believing that life "was due to some spiritual + entity," but rather to the structure of the body itself. + </p> + <p> + The Animists taught that the soul performed functions of ordinary life in + man, while the life of lower animals was controlled by ordinary mechanical + principles. Stahl supported this theory ardently, sometimes violently, at + times declaring that there were "no longer any doctors, only mechanics and + chemists." He denied that chemistry had anything to do with medicine, and, + in the main, discarded anatomy as useless to the medical man. The soul, he + thought, was the source of all vital movement; and the immediate cause of + death was not disease but the direct action of the soul. When through some + lesion, or because the machinery of the body has become unworkable, as in + old age, the soul leaves the body and death is produced. The soul + ordinarily selects the channels of the circulation, and the contractile + parts, as the route for influencing the body. Hence in fever the pulse is + quickened, due to the increased activity of the soul, and convulsions and + spasmodic movements in disease are due, to the, same cause. Stagnation of + the blood was supposed to be a fertile cause of diseases, and such + diseases were supposed to arise mostly from "plethora"—an + all-important element in Stahl's therapeutics. By many this theory is + regarded as an attempt on the part of the pious Stahl to reconcile + medicine and theology in a way satisfactory to both physicians and + theologians, but, like many conciliatory attempts, it was violently + opposed by both doctors and ministers. + </p> + <p> + A belief in such a theory would lead naturally to simplicity in + therapeutics, and in this respect at least Stahl was consistent. Since the + soul knew more about the body than any physician could know, Stahl + conceived that it would be a hinderance rather than a help for the + physician to interfere with complicated doses of medicine. As he advanced + in age this view of the administration of drugs grew upon him, until after + rejecting quinine, and finally opium, he at last used only salt and water + in treating his patients. From this last we may judge that his "system," + if not doing much good, was at least doing little harm. + </p> + <p> + The theory of the Vitalists was closely allied to that of the Animists, + and its most important representative, Paul Joseph Barthez, was a cultured + and eager scientist. After an eventful and varied career as physician, + soldier, editor, lawyer, and philosopher in turn, he finally returned to + the field of medicine, was made consulting physician by Napoleon in 1802, + and died in Paris four years later. + </p> + <p> + The theory that he championed was based on the assumption that there was a + "vital principle," the nature of which was unknown, but which differed + from the thinking mind, and was the cause of the phenomena of life. This + "vital principle" differed from the soul, and was not exhibited in human + beings alone, but even in animals and plants. This force, or whatever it + might be called, was supposed to be present everywhere in the body, and + all diseases were the results of it. + </p> + <p> + The theory of the Organicists, like that of the Animists and Vitalists, + agreed with the other two that vital activity could not be explained by + the laws of physics and chemistry, but, unlike them, it held that it was a + part of the structure of the body itself. Naturally the practical + physicians were more attracted by this tangible doctrine than by vague + theories "which converted diseases into unknown derangements of some + equally unknown 'principle.'" + </p> + <p> + It is perhaps straining a point to include this brief description of these + three schools of medicine in the history of the progress of the science. + But, on the whole, they were negatively at least prominent factors in + directing true progress along its proper channel, showing what courses + were not to be pursued. Some one has said that science usually stumbles + into the right course only after stumbling into all the wrong ones; and if + this be only partially true, the wrong ones still play a prominent if not + a very creditable part. Thus the medical systems of William Cullen + (1710-1790), and John Brown (1735-1788), while doing little towards the + actual advancement of scientific medicine, played so conspicuous a part in + so wide a field that the "Brunonian system" at least must be given some + little attention. + </p> + <p> + According to Brown's theory, life, diseases, and methods of cure are + explained by the property of "excitability." All exciting powers were + supposed to be stimulating, the apparent debilitating effects of some + being due to a deficiency in the amount of stimulus. Thus "the whole + phenomena of life, health, as well as disease, were supposed to consist of + stimulus and nothing else." This theory created a great stir in the + medical world, and partisans and opponents sprang up everywhere. In Italy + it was enthusiastically supported; in England it was strongly opposed; + while in Scotland riots took place between the opposing factions. Just why + this system should have created any stir, either for or against it, is not + now apparent. + </p> + <p> + Like so many of the other "theorists" of his century, Brown's practical + conclusions deduced from his theory (or perhaps in spite of it) were + generally beneficial to medicine, and some of them extremely valuable in + the treatment of diseases. He first advocated the modern stimulant, or + "feeding treatment" of fevers, and first recognized the usefulness of + animal soups and beef-tea in certain diseases. + </p> + <p> + THE SYSTEM OF HAHNEMANN + </p> + <p> + Just at the close of the century there came into prominence the school of + homoeopathy, which was destined to influence the practice of medicine very + materially and to outlive all the other eighteenth-century schools. It was + founded by Christian Samuel Friedrich Hahnemann (1755-1843), a most + remarkable man, who, after propounding a theory in his younger days which + was at least as reasonable as most of the existing theories, had the + misfortune to outlive his usefulness and lay his doctrine open to ridicule + by the unreasonable teachings of his dotage. + </p> + <p> + Hahnemann rejected all the teachings of morbid anatomy and pathology as + useless in practice, and propounded his famous "similia similibus + curantur"—that all diseases were to be cured by medicine which in + health produced symptoms dynamically similar to the disease under + treatment. If a certain medicine produced a headache when given to a + healthy person, then this medicine was indicated in case of headaches, + etc. At the present time such a theory seems crude enough, but in the + latter part of the eighteenth century almost any theory was as good as the + ones propounded by Animists, Vitalists, and other such schools. It + certainly had the very commendable feature of introducing simplicity in + the use of drugs in place of the complicated prescriptions then in vogue. + Had Hahnemann stopped at this point he could not have been held up to the + indefensible ridicule that was brought upon him, with considerable + justice, by his later theories. But he lived onto propound his + extraordinary theory of "potentiality"—that medicines gained + strength by being diluted—and his even more extraordinary theory + that all chronic diseases are caused either by the itch, syphilis, or + fig-wart disease, or are brought on by medicines. + </p> + <p> + At the time that his theory of potentialities was promulgated, the medical + world had gone mad in its administration of huge doses of compound + mixtures of drugs, and any reaction against this was surely an + improvement. In short, no medicine at all was much better than the heaping + doses used in common practice; and hence one advantage, at least, of + Hahnemann's methods. Stated briefly, his theory was that if a tincture be + reduced to one-fiftieth in strength, and this again reduced to + one-fiftieth, and this process repeated up to thirty such dilutions, the + potency of such a medicine will be increased by each dilution, Hahnemann + himself preferring the weakest, or, as he would call it, the strongest + dilution. The absurdity of such a theory is apparent when it is understood + that long before any drug has been raised to its thirtieth dilution it has + been so reduced in quantity that it cannot be weighed, measured, or + recognized as being present in the solution at all by any means known to + chemists. It is but just to modern followers of homoeopathy to say that + while most of them advocate small dosage, they do not necessarily follow + the teachings of Hahnemann in this respect, believing that the theory of + the dose "has nothing more to do with the original law of cure than the + psora (itch) theory has; and that it was one of the later creations of + Hahnemann's mind." + </p> + <p> + Hahnemann's theory that all chronic diseases are derived from either itch, + syphilis, or fig-wart disease is no longer advocated by his followers, + because it is so easily disproved, particularly in the case of itch. + Hahnemann taught that fully three-quarters of all diseases were caused by + "itch struck in," and yet it had been demonstrated long before his day, + and can be demonstrated any time, that itch is simply a local skin disease + caused by a small parasite. + </p> + <p> + JENNER AND VACCINATION + </p> + <p> + All advances in science have a bearing, near or remote, on the welfare of + our race; but it remains to credit to the closing decade of the eighteenth + century a discovery which, in its power of direct and immediate benefit to + humanity, surpasses any other discovery of this or any previous epoch. + Needless to say, I refer to Jenner's discovery of the method of preventing + smallpox by inoculation with the virus of cow-pox. It detracts nothing + from the merit of this discovery to say that the preventive power of + accidental inoculation had long been rumored among the peasantry of + England. Such vague, unavailing half-knowledge is often the forerunner of + fruitful discovery. + </p> + <p> + To all intents and purposes Jenner's discovery was original and unique. + Nor, considered as a perfect method, was it in any sense an accident. It + was a triumph of experimental science. The discoverer was no novice in + scientific investigation, but a trained observer, who had served a long + apprenticeship in scientific observation under no less a scientist than + the celebrated John Hunter. At the age of twenty-one Jenner had gone to + London to pursue his medical studies, and soon after he proved himself so + worthy a pupil that for two years he remained a member of Hunter's + household as his favorite pupil. His taste for science and natural history + soon attracted the attention of Sir Joseph Banks, who intrusted him with + the preparation of the zoological specimens brought back by Captain Cook's + expedition in 1771. He performed this task so well that he was offered the + position of naturalist to the second expedition, but declined it, + preferring to take up the practice of his profession in his native town of + Berkeley. + </p> + <p> + His many accomplishments and genial personality soon made him a favorite + both as a physician and in society. He was a good singer, a fair violinist + and flute-player, and a very successful writer of prose and verse. But + with all his professional and social duties he still kept up his + scientific investigations, among other things making some careful + observations on the hibernation of hedgehogs at the instigation of Hunter, + the results of which were laid before the Royal Society. He also made + quite extensive investigations as to the geological formations and fossils + found in his neighborhood. + </p> + <p> + Even during his student days with Hunter he had been much interested in + the belief, current in the rural districts of Gloucestershire, of the + antagonism between cow-pox and small-pox, a person having suffered from + cow-pox being immuned to small-pox. At various times Jenner had mentioned + the subject to Hunter, and he was constantly making inquiries of his + fellow-practitioners as to their observations and opinions on the subject. + Hunter was too fully engrossed in other pursuits to give the matter much + serious attention, however, and Jenner's brothers of the profession gave + scant credence to the rumors, although such rumors were common enough. + </p> + <p> + At this time the practice of inoculation for preventing small-pox, or + rather averting the severer forms of the disease, was widely practised. It + was customary, when there was a mild case of the disease, to take some of + the virus from the patient and inoculate persons who had never had the + disease, producing a similar attack in them. Unfortunately there were many + objections to this practice. The inoculated patient frequently developed a + virulent form of the disease and died; or if he recovered, even after a + mild attack, he was likely to be "pitted" and disfigured. But, perhaps + worst of all, a patient so inoculated became the source of infection to + others, and it sometimes happened that disastrous epidemics were thus + brought about. The case was a most perplexing one, for the awful scourge + of small-pox hung perpetually over the head of every person who had not + already suffered and recovered from it. The practice of inoculation was + introduced into England by Lady Mary Wortley Montague (1690-1762), who had + seen it practised in the East, and who announced her intention of + "introducing it into England in spite of the doctors." + </p> + <p> + From the fact that certain persons, usually milkmaids, who had suffered + from cow-pox seemed to be immuned to small-pox, it would seem a very + simple process of deduction to discover that cow-pox inoculation was the + solution of the problem of preventing the disease. But there was another + form of disease which, while closely resembling cow-pox and quite + generally confounded with it, did not produce immunity. The confusion of + these two forms of the disease had constantly misled investigations as to + the possibility of either of them immunizing against smallpox, and the + confusion of these two diseases for a time led Jenner to question the + possibility of doing so. After careful investigations, however, he reached + the conclusion that there was a difference in the effects of the two + diseases, only one of which produced immunity from small-pox. + </p> + <p> + "There is a disease to which the horse, from his state of domestication, + is frequently subject," wrote Jenner, in his famous paper on vaccination. + "The farriers call it the grease. It is an inflammation and swelling in + the heel, accompanied at its commencement with small cracks or fissures, + from which issues a limpid fluid possessing properties of a very peculiar + kind. This fluid seems capable of generating a disease in the human body + (after it has undergone the modification I shall presently speak of) which + bears so strong a resemblance to small-pox that I think it highly probable + it may be the source of that disease. + </p> + <p> + "In this dairy country a great number of cows are kept, and the office of + milking is performed indiscriminately by men and maid servants. One of the + former having been appointed to apply dressings to the heels of a horse + affected with the malady I have mentioned, and not paying due attention to + cleanliness, incautiously bears his part in milking the cows with some + particles of the infectious matter adhering to his fingers. When this is + the case it frequently happens that a disease is communicated to the cows, + and from the cows to the dairy-maids, which spreads through the farm until + most of the cattle and domestics feel its unpleasant consequences. This + disease has obtained the name of Cow-Pox. It appears on the nipples of the + cows in the form of irregular pustules. At their first appearance they are + commonly of a palish blue, or rather of a color somewhat approaching to + livid, and are surrounded by an inflammation. These pustules, unless a + timely remedy be applied, frequently degenerate into phagedenic ulcers, + which prove extremely troublesome. The animals become indisposed, and the + secretion of milk is much lessened. Inflamed spots now begin to appear on + different parts of the hands of the domestics employed in milking, and + sometimes on the wrists, which run on to suppuration, first assuming the + appearance of the small vesications produced by a burn. Most commonly they + appear about the joints of the fingers and at their extremities; but + whatever parts are affected, if the situation will admit the superficial + suppurations put on a circular form with their edges more elevated than + their centre and of a color distinctly approaching to blue. Absorption + takes place, and tumors appear in each axilla. The system becomes + affected, the pulse is quickened; shiverings, succeeded by heat, general + lassitude, and pains about the loins and limbs, with vomiting, come on. + The head is painful, and the patient is now and then even affected with + delirium. These symptoms, varying in their degrees of violence, generally + continue from one day to three or four, leaving ulcerated sores about the + hands which, from the sensibility of the parts, are very troublesome and + commonly heal slowly, frequently becoming phagedenic, like those from + which they sprang. During the progress of the disease the lips, nostrils, + eyelids, and other parts of the body are sometimes affected with sores; + but these evidently arise from their being heedlessly rubbed or scratched + by the patient's infected fingers. No eruptions on the skin have followed + the decline of the feverish symptoms in any instance that has come under + my inspection, one only excepted, and in this case a very few appeared on + the arms: they were very minute, of a vivid red color, and soon died away + without advancing to maturation, so that I cannot determine whether they + had any connection with the preceding symptoms. + </p> + <p> + "Thus the disease makes its progress from the horse (as I conceive) to the + nipple of the cow, and from the cow to the human subject. + </p> + <p> + "Morbid matter of various kinds, when absorbed into the system, may + produce effects in some degree similar; but what renders the cow-pox virus + so extremely singular is that the person that has been thus affected is + forever after secure from the infection of small-pox, neither exposure to + the variolous effluvia nor the insertion of the matter into the skin + producing this distemper."(2) + </p> + <p> + In 1796 Jenner made his first inoculation with cowpox matter, and two + months later the same subject was inoculated with small-pox matter. But, + as Jenner had predicted, no attack of small-pox followed. Although fully + convinced by this experiment that the case was conclusively proven, he + continued his investigations, waiting two years before publishing his + discovery. Then, fortified by indisputable proofs, he gave it to the + world. The immediate effects of his announcement have probably never been + equalled in the history of scientific discovery, unless, perhaps, in the + single instance of the discovery of anaesthesia. In Geneva and Holland + clergymen advocated the practice of vaccination from their pulpits; in + some of the Latin countries religious processions were formed for + receiving vaccination; Jenner's birthday was celebrated as a feast in + Germany; and the first child vaccinated in Russia was named "Vaccinov" and + educated at public expense. In six years the discovery had penetrated to + the most remote corners of civilization; it had even reached some savage + nations. And in a few years small-pox had fallen from the position of the + most dreaded of all diseases to that of being practically the only disease + for which a sure and easy preventive was known. + </p> + <p> + Honors were showered upon Jenner from the Old and the New World, and even + Napoleon, the bitter hater of the English, was among the others who + honored his name. On one occasion Jenner applied to the Emperor for the + release of certain Englishmen detained in France. The petition was about + to be rejected when the name of the petitioner was mentioned. "Ah," said + Napoleon, "we can refuse nothing to that name!" + </p> + <p> + It is difficult for us of to-day clearly to conceive the greatness of + Jenner's triumph, for we can only vaguely realize what a ruthless and + ever-present scourge smallpox had been to all previous generations of men + since history began. Despite all efforts to check it by medication and by + direct inoculation, it swept now and then over the earth as an + all-devastating pestilence, and year by year it claimed one-tenth of all + the beings in Christendom by death as its average quota of victims. "From + small-pox and love but few remain free," ran the old saw. A pitted face + was almost as much a matter of course a hundred years ago as a smooth one + is to-day. + </p> + <p> + Little wonder, then, that the world gave eager acceptance to Jenner's + discovery. No urging was needed to induce the majority to give it trial; + passengers on a burning ship do not hold aloof from the life-boats. Rich + and poor, high and low, sought succor in vaccination and blessed the name + of their deliverer. Of all the great names that were before the world in + the closing days of the century, there was perhaps no other one at once so + widely known and so uniformly reverenced as that of the great English + physician Edward Jenner. Surely there was no other one that should be + recalled with greater gratitude by posterity. + </p> + <p> + <a name="link2H_4_0009" id="link2H_4_0009"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + VIII. NINETEENTH-CENTURY MEDICINE + </h2> + <h3> + PHYSICAL DIAGNOSIS + </h3> + <p> + Although Napoleon Bonaparte, First Consul, was not lacking in + self-appreciation, he probably did not realize that in selecting a + physician for his own needs he was markedly influencing the progress of + medical science as a whole. Yet so strangely are cause and effect adjusted + in human affairs that this simple act of the First Consul had that very + unexpected effect. For the man chosen was the envoy of a new method in + medical practice, and the fame which came to him through being physician + to the First Consul, and subsequently to the Emperor, enabled him to + promulgate the method in a way otherwise impracticable. Hence the indirect + but telling value to medical science of Napoleon's selection. + </p> + <p> + The physician in question was Jean Nicolas de Corvisart. His novel method + was nothing more startling than the now-familiar procedure of tapping the + chest of a patient to elicit sounds indicative of diseased tissues within. + Every one has seen this done commonly enough in our day, but at the + beginning of the century Corvisart, and perhaps some of his pupils, were + probably the only physicians in the world who resorted to this simple and + useful procedure. Hence Napoleon's surprise when, on calling in Corvisart, + after becoming somewhat dissatisfied with his other physicians Pinel and + Portal, his physical condition was interrogated in this strange manner. + With characteristic shrewdness Bonaparte saw the utility of the method, + and the physician who thus attempted to substitute scientific method for + guess-work in the diagnosis of disease at once found favor in his eyes and + was installed as his regular medical adviser. + </p> + <p> + For fifteen years before this Corvisart had practised percussion, as the + chest-tapping method is called, without succeeding in convincing the + profession of its value. The method itself, it should be added, had not + originated with Corvisart, nor did the French physician for a moment claim + it as his own. The true originator of the practice was the German + physician Avenbrugger, who published a book about it as early as 1761. + This book had even been translated into French, then the language of + international communication everywhere, by Roziere de la Chassagne, of + Montpellier, in 1770; but no one other than Corvisart appears to have paid + any attention to either original or translation. It was far otherwise, + however, when Corvisart translated Avenbrugger's work anew, with important + additions of his own, in 1808. + </p> + <p> + "I know very well how little reputation is allotted to translator and + commentators," writes Corvisart, "and I might easily have elevated myself + to the rank of an author if I had elaborated anew the doctrine of + Avenbrugger and published an independent work on percussion. In this way, + however, I should have sacrificed the name of Avenbrugger to my own + vanity, a thing which I am unwilling to do. It is he, and the beautiful + invention which of right belongs to him, that I desire to recall to + life."(1) + </p> + <p> + By this time a reaction had set in against the metaphysical methods in + medicine that had previously been so alluring; the scientific spirit of + the time was making itself felt in medical practice; and this, combined + with Corvisart's fame, brought the method of percussion into immediate and + well-deserved popularity. Thus was laid the foundation for the method of + so-called physical diagnosis, which is one of the corner-stones of modern + medicine. + </p> + <p> + The method of physical diagnosis as practised in our day was by no means + completed, however, with the work of Corvisart. Percussion alone tells + much less than half the story that may be elicited from the organs of the + chest by proper interrogation. The remainder of the story can only be + learned by applying the ear itself to the chest, directly or indirectly. + Simple as this seems, no one thought of practising it for some years after + Corvisart had shown the value of percussion. + </p> + <p> + Then, in 1815, another Paris physician, Rene Theophile Hyacinthe Laennec, + discovered, almost by accident, that the sound of the heart-beat could be + heard surprisingly through a cylinder of paper held to the ear and against + the patient's chest. Acting on the hint thus received, Laennec substituted + a hollow cylinder of wood for the paper, and found himself provided with + an instrument through which not merely heart sounds but murmurs of the + lungs in respiration could be heard with almost startling distinctness. + </p> + <p> + The possibility of associating the varying chest sounds with diseased + conditions of the organs within appealed to the fertile mind of Laennec as + opening new vistas in therapeutics, which he determined to enter to the + fullest extent practicable. His connection with the hospitals of Paris + gave him full opportunity in this direction, and his labors of the next + few years served not merely to establish the value of the new method as an + aid to diagnosis, but laid the foundation also for the science of morbid + anatomy. In 1819 Laennec published the results of his labors in a work + called Traite d'Auscultation Mediate,(2) a work which forms one of the + landmarks of scientific medicine. By mediate auscultation is meant, of + course, the interrogation of the chest with the aid of the little + instrument already referred to, an instrument which its originator thought + hardly worth naming until various barbarous appellations were applied to + it by others, after which Laennec decided to call it the stethoscope, a + name which it has ever since retained. + </p> + <p> + In subsequent years the form of the stethoscope, as usually employed, was + modified and its value augmented by a binauricular attachment, and in very + recent years a further improvement has been made through application of + the principle of the telephone; but the essentials of auscultation with + the stethoscope were established in much detail by Laennec, and the honor + must always be his of thus taking one of the longest single steps by which + practical medicine has in our century acquired the right to be considered + a rational science. Laennec's efforts cost him his life, for he died in + 1826 of a lung disease acquired in the course of his hospital practice; + but even before this his fame was universal, and the value of his method + had been recognized all over the world. Not long after, in 1828, yet + another French physician, Piorry, perfected the method of percussion by + introducing the custom of tapping, not the chest directly, but the finger + or a small metal or hard-rubber plate held against the chest-mediate + percussion, in short. This perfected the methods of physical diagnosis of + diseases of the chest in all essentials; and from that day till this + percussion and auscultation have held an unquestioned place in the regular + armamentarium of the physician. + </p> + <p> + Coupled with the new method of physical diagnosis in the effort to + substitute knowledge for guess-work came the studies of the experimental + physiologists—in particular, Marshall Hall in England and Francois + Magendie in France; and the joint efforts of these various workers led + presently to the abandonment of those severe and often irrational + depletive methods—blood-letting and the like—that had + previously dominated medical practice. To this end also the "statistical + method," introduced by Louis and his followers, largely contributed; and + by the close of the first third of our century the idea was gaining ground + that the province of therapeutics is to aid nature in combating disease, + and that this may often be accomplished better by simple means than by the + heroic measures hitherto thought necessary. In a word, scientific + empiricism was beginning to gain a hearing in medicine as against the + metaphysical preconceptions of the earlier generations. + </p> + <p> + PARASITIC DISEASES + </p> + <p> + I have just adverted to the fact that Napoleon Bonaparte, as First Consul + and as Emperor, was the victim of a malady which caused him to seek the + advice of the most distinguished physicians of Paris. It is a little + shocking to modern sensibilities to read that these physicians, except + Corvisart, diagnosed the distinguished patient's malady as "gale + repercutee"—that is to say, in idiomatic English, the itch "struck + in." It is hardly necessary to say that no physician of today would make + so inconsiderate a diagnosis in the case of a royal patient. If by any + chance a distinguished patient were afflicted with the itch, the sagacious + physician would carefully hide the fact behind circumlocutions and proceed + to eradicate the disease with all despatch. That the physicians of + Napoleon did otherwise is evidence that at the beginning of the century + the disease in question enjoyed a very different status. At that time + itch, instead of being a most plebeian malady, was, so to say, a court + disease. It enjoyed a circulation, in high circles and in low, that modern + therapeutics has quite denied it; and the physicians of the time gave it a + fictitious added importance by ascribing to its influence the existence of + almost any obscure malady that came under their observation. Long after + Napoleon's time gale continued to hold this proud distinction. For + example, the imaginative Dr. Hahnemann did not hesitate to affirm, as a + positive maxim, that three-fourths of all the ills that flesh is heir to + were in reality nothing but various forms of "gale repercutee." + </p> + <p> + All of which goes to show how easy it may be for a masked pretender to + impose on credulous humanity, for nothing is more clearly established in + modern knowledge than the fact that "gale repercutee" was simply a name to + hide a profound ignorance; no such disease exists or ever did exist. Gale + itself is a sufficiently tangible reality, to be sure, but it is a purely + local disease of the skin, due to a perfectly definite cause, and the dire + internal conditions formerly ascribed to it have really no causal + connection with it whatever. This definite cause, as every one nowadays + knows, is nothing more or less than a microscopic insect which has found + lodgment on the skin, and has burrowed and made itself at home there. Kill + that insect and the disease is no more; hence it has come to be an axiom + with the modern physician that the itch is one of the three or four + diseases that he positively is able to cure, and that very speedily. But + it was far otherwise with the physicians of the first third of our + century, because to them the cause of the disease was an absolute mystery. + </p> + <p> + It is true that here and there a physician had claimed to find an insect + lodged in the skin of a sufferer from itch, and two or three times the + claim had been made that this was the cause of the malady, but such views + were quite ignored by the general profession, and in 1833 it was stated in + an authoritative medical treatise that the "cause of gale is absolutely + unknown." But even at this time, as it curiously happened, there were + certain ignorant laymen who had attained to a bit of medical knowledge + that was withheld from the inner circles of the profession. As the + peasantry of England before Jenner had known of the curative value of + cow-pox over small-pox, so the peasant women of Poland had learned that + the annoying skin disease from which they suffered was caused by an almost + invisible insect, and, furthermore, had acquired the trick of dislodging + the pestiferous little creature with the point of a needle. From them a + youth of the country, F. Renucci by name, learned the open secret. He + conveyed it to Paris when he went there to study medicine, and in 1834 + demonstrated it to his master Alibert. This physician, at first sceptical, + soon was convinced, and gave out the discovery to the medical world with + an authority that led to early acceptance. + </p> + <p> + Now the importance of all this, in the present connection, is not at all + that it gave the clew to the method of cure of a single disease. What + makes the discovery epochal is the fact that it dropped a brand-new idea + into the medical ranks—an idea destined, in the long-run, to prove + itself a veritable bomb—the idea, namely, that a minute and quite + unsuspected animal parasite may be the cause of a well-known, widely + prevalent, and important human disease. Of course the full force of this + idea could only be appreciated in the light of later knowledge; but even + at the time of its coming it sufficed to give a great impetus to that new + medical knowledge, based on microscopical studies, which had but recently + been made accessible by the inventions of the lens-makers. The new + knowledge clarified one very turbid medical pool and pointed the way to + the clarification of many others. + </p> + <p> + Almost at the same time that the Polish medical student was demonstrating + the itch mite in Paris, it chanced, curiously enough, that another medical + student, this time an Englishman, made an analogous discovery of perhaps + even greater importance. Indeed, this English discovery in its initial + stages slightly antedated the other, for it was in 1833 that the student + in question, James Paget, interne in St. Bartholomew's Hospital, London, + while dissecting the muscular tissues of a human subject, found little + specks of extraneous matter, which, when taken to the professor of + comparative anatomy, Richard Owen, were ascertained, with the aid of the + microscope, to be the cocoon of a minute and hitherto unknown insect. Owen + named the insect Trichina spiralis. After the discovery was published it + transpired that similar specks had been observed by several earlier + investigators, but no one had previously suspected or, at any rate, + demonstrated their nature. Nor was the full story of the trichina made out + for a long time after Owen's discovery. It was not till 1847 that the + American anatomist Dr. Joseph Leidy found the cysts of trichina in the + tissues of pork; and another decade or so elapsed after that before German + workers, chief among whom were Leuckart, Virchow, and Zenker, proved that + the parasite gets into the human system through ingestion of infected + pork, and that it causes a definite set of symptoms of disease which + hitherto had been mistaken for rheumatism, typhoid fever, and other + maladies. Then the medical world was agog for a time over the subject of + trichinosis; government inspection of pork was established in some parts + of Germany; American pork was excluded altogether from France; and the + whole subject thus came prominently to public attention. But important as + the trichina parasite proved on its own account in the end, its greatest + importance, after all, was in the share it played in directing attention + at the time of its discovery in 1833 to the subject of microscopic + parasites in general. + </p> + <p> + The decade that followed that discovery was a time of great activity in + the study of microscopic organisms and microscopic tissues, and such men + as Ehrenberg and Henle and Bory Saint-Vincent and Kolliker and Rokitansky + and Remak and Dujardin were widening the bounds of knowledge of this new + subject with details that cannot be more than referred to here. But the + crowning achievement of the period in this direction was the discovery + made by the German, J. L. Schoenlein, in 1839, that a very common and most + distressing disease of the scalp, known as favus, is really due to the + presence and growth on the scalp of a vegetable organism of microscopic + size. Thus it was made clear that not merely animal but also vegetable + organisms of obscure, microscopic species have causal relations to the + diseases with which mankind is afflicted. This knowledge of the parasites + was another long step in the direction of scientific medical knowledge; + but the heights to which this knowledge led were not to be scaled, or even + recognized, until another generation of workers had entered the field. + </p> + <p> + PAINLESS SURGERY + </p> + <p> + Meantime, in quite another field of medicine, events were developing which + led presently to a revelation of greater immediate importance to humanity + than any other discovery that had come in the century, perhaps in any + field of science whatever. This was the discovery of the pain-dispelling + power of the vapor of sulphuric ether inhaled by a patient undergoing a + surgical operation. This discovery came solely out of America, and it + stands curiously isolated, since apparently no minds in any other country + were trending towards it even vaguely. Davy, in England, had indeed + originated the method of medication by inhalation, and earned out some + most interesting experiments fifty years earlier, and it was doubtless his + experiments with nitrous oxide gas that gave the clew to one of the + American investigators; but this was the sole contribution of preceding + generations to the subject, and since the beginning of the century, when + Davy turned his attention to other matters, no one had made the slightest + advance along the same line until an American dentist renewed the + investigation. + </p> + <p> + In view of the sequel, Davy's experiments merit full attention. Here is + his own account of them, as written in 1799: + </p> + <p> + "Immediately after a journey of one hundred and twenty-six miles, in which + I had no sleep the preceding night, being much exhausted, I respired seven + quarts of nitrous oxide gas for near three minutes. It produced the usual + pleasurable effects and slight muscular motion. I continued exhilarated + for some minutes afterwards, but in half an hour found myself neither more + nor less exhausted than before the experiment. I had a great propensity to + sleep. + </p> + <p> + "To ascertain with certainty whether the more extensive action of nitrous + oxide compatible with life was capable of producing debility, I resolved + to breathe the gas for such a time, and in such quantities, as to produce + excitement equal in duration and superior in intensity to that occasioned + by high intoxication from opium or alcohol. + </p> + <p> + "To habituate myself to the excitement, and to carry it on gradually, on + December 26th I was enclosed in an air-tight breathing-box, of the + capacity of about nine and one-half cubic feet, in the presence of Dr. + Kinglake. After I had taken a situation in which I could by means of a + curved thermometer inserted under the arm, and a stop-watch, ascertain the + alterations in my pulse and animal heat, twenty quarts of nitrous oxide + were thrown into the box. + </p> + <p> + "For three minutes I experienced no alteration in my sensations, though + immediately after the introduction of the nitrous oxide the smell and + taste of it were very evident. In four minutes I began to feel a slight + glow in the cheeks and a generally diffused warmth over the chest, though + the temperature of the box was not quite 50 degrees.... In twenty-five + minutes the animal heat was 100 degrees, pulse 124. In thirty minutes + twenty quarts more of gas were introduced. + </p> + <p> + "My sensations were now pleasant; I had a generally diffused warmth + without the slightest moisture of the skin, a sense of exhilaration + similar to that produced by a small dose of wine, and a disposition to + muscular motion and to merriment. + </p> + <p> + "In three-quarters of an hour the pulse was 104 and the animal heat not + 99.5 degrees, the temperature of the chamber 64 degrees. The pleasurable + feelings continued to increase, the pulse became fuller and slower, till + in about an hour it was 88, when the animal heat was 99 degrees. Twenty + quarts more of air were admitted. I had now a great disposition to laugh, + luminous points seemed frequently to pass before my eyes, my hearing was + certainly more acute, and I felt a pleasant lightness and power of + exertion in my muscles. In a short time the symptoms became stationary; + breathing was rather oppressed, and on account of the great desire for + action rest was painful. + </p> + <p> + "I now came out of the box, having been in precisely an hour and a + quarter. The moment after I began to respire twenty quarts of unmingled + nitrous oxide. A thrilling extending from the chest to the extremities was + almost immediately produced. I felt a sense of tangible extension highly + pleasurable in every limb; my visible impressions were dazzling and + apparently magnified, I heard distinctly every sound in the room, and was + perfectly aware of my situation. By degrees, as the pleasurable sensations + increased, I lost all connection with external things; trains of vivid + visible images rapidly passed through my mind and were connected with + words in such a manner as to produce perceptions perfectly novel. + </p> + <p> + "I existed in a world of newly connected and newly modified ideas. I + theorized; I imagined that I made discoveries. When I was awakened from + this semi-delirious trance by Dr. Kinglake, who took the bag from my + mouth, indignation and pride were the first feelings produced by the sight + of persons about me. My emotions were enthusiastic and sublime; and for a + minute I walked about the room perfectly regardless of what was said to + me. As I recovered my former state of mind, I felt an inclination to + communicate the discoveries I had made during the experiment. I endeavored + to recall the ideas—they were feeble and indistinct; one collection + of terms, however, presented itself, and, with most intense belief and + prophetic manner, I exclaimed to Dr. Kinglake, 'Nothing exists but + thoughts!—the universe is composed of impressions, ideas, pleasures, + and pains.' "(3) + </p> + <p> + From this account we see that Davy has anaesthetized himself to a point + where consciousness of surroundings was lost, but not past the stage of + exhilaration. Had Dr. Kinglake allowed the inhaling-bag to remain in + Davy's mouth for a few moments longer complete insensibility would have + followed. As it was, Davy appears to have realized that sensibility was + dulled, for he adds this illuminative suggestion: "As nitrous oxide in its + extensive operation appears capable of destroying physical pain, it may + probably be used with advantage during surgical operations in which no + great effusion of blood takes place."(4) + </p> + <p> + Unfortunately no one took advantage of this suggestion at the time, and + Davy himself became interested in other fields of science and never + returned to his physiological studies, thus barely missing one of the + greatest discoveries in the entire field of science. In the generation + that followed no one seems to have thought of putting Davy's suggestion to + the test, and the surgeons of Europe had acknowledged with one accord that + all hope of finding a means to render operations painless must be utterly + abandoned—that the surgeon's knife must ever remain a synonym for + slow and indescribable torture. By an odd coincidence it chanced that Sir + Benjamin Brodie, the acknowledged leader of English surgeons, had publicly + expressed this as his deliberate though regretted opinion at a time when + the quest which he considered futile had already led to the most brilliant + success in America, and while the announcement of the discovery, which + then had no transatlantic cable to convey it, was actually on its way to + the Old World. + </p> + <p> + The American dentist just referred to, who was, with one exception to be + noted presently, the first man in the world to conceive that the + administration of a definite drug might render a surgical operation + painless and to give the belief application was Dr. Horace Wells, of + Hartford, Connecticut. The drug with which he experimented was nitrous + oxide—the same that Davy had used; the operation that he rendered + painless was no more important than the extraction of a tooth—yet it + sufficed to mark a principle; the year of the experiment was 1844. + </p> + <p> + The experiments of Dr. Wells, however, though important, were not + sufficiently demonstrative to bring the matter prominently to the + attention of the medical world. The drug with which he experimented proved + not always reliable, and he himself seems ultimately to have given the + matter up, or at least to have relaxed his efforts. But meantime a friend, + to whom he had communicated his belief and expectations, took the matter + up, and with unremitting zeal carried forward experiments that were + destined to lead to more tangible results. This friend was another + dentist, Dr. W. T. G. Morton, of Boston, then a young man full of youthful + energy and enthusiasm. He seems to have felt that the drug with which + Wells had experimented was not the most practicable one for the purpose, + and so for several months he experimented with other allied drugs, until + finally he hit upon sulphuric ether, and with this was able to make + experiments upon animals, and then upon patients in the dental chair, that + seemed to him absolutely demonstrative. + </p> + <p> + Full of eager enthusiasm, and absolutely confident of his results, he at + once went to Dr. J. C. Warren, one of the foremost surgeons of Boston, and + asked permission to test his discovery decisively on one of the patients + at the Boston Hospital during a severe operation. The request was granted; + the test was made on October 16, 1846, in the presence of several of the + foremost surgeons of the city and of a body of medical students. The + patient slept quietly while the surgeon's knife was plied, and awoke to + astonished comprehension that the ordeal was over. The impossible, the + miraculous, had been accomplished.(5) + </p> + <p> + Swiftly as steam could carry it—slowly enough we should think it + to-day—the news was heralded to all the world. It was received in + Europe with incredulity, which vanished before repeated experiments. + Surgeons were loath to believe that ether, a drug that had long held a + place in the subordinate armamentarium of the physician, could accomplish + such a miracle. But scepticism vanished before the tests which any surgeon + might make, and which surgeons all over the world did make within the next + few weeks. Then there came a lingering outcry from a few surgeons, notably + some of the Parisians, that the shock of pain was beneficial to the + patient, hence that anaesthesia—as Dr. Oliver Wendell Holmes had + christened the new method—was a procedure not to be advised. Then, + too, there came a hue-and-cry from many a pulpit that pain was God-given, + and hence, on moral grounds, to be clung to rather than renounced. But the + outcry of the antediluvians of both hospital and pulpit quickly received + its quietus; for soon it was clear that the patient who did not suffer the + shock of pain during an operation rallied better than the one who did so + suffer, while all humanity outside the pulpit cried shame to the spirit + that would doom mankind to suffer needless agony. And so within a few + months after that initial operation at the Boston Hospital in 1846, ether + had made good its conquest of pain throughout the civilized world. Only by + the most active use of the imagination can we of this present day realize + the full meaning of that victory. + </p> + <p> + It remains to be added that in the subsequent bickerings over the + discovery—such bickerings as follow every great advance—two + other names came into prominent notice as sharers in the glory of the new + method. Both these were Americans—the one, Dr. Charles T. Jackson, + of Boston; the other, Dr. Crawford W. Long, of Alabama. As to Dr. Jackson, + it is sufficient to say that he seems to have had some vague inkling of + the peculiar properties of ether before Morton's discovery. He even + suggested the use of this drug to Morton, not knowing that Morton had + already tried it; but this is the full measure of his association with the + discovery. Hence it is clear that Jackson's claim to equal share with + Morton in the discovery was unwarranted, not to say absurd. + </p> + <p> + Dr. Long's association with the matter was far different and altogether + honorable. By one of those coincidences so common in the history of + discovery, he was experimenting with ether as a pain-destroyer + simultaneously with Morton, though neither so much as knew of the + existence of the other. While a medical student he had once inhaled ether + for the intoxicant effects, as other medical students were wont to do, and + when partially under influence of the drug he had noticed that a chance + blow to his shins was painless. This gave him the idea that ether might be + used in surgical operations; and in subsequent years, in the course of his + practice in a small Georgia town, he put the idea into successful + execution. There appears to be no doubt whatever that he performed + successful minor operations under ether some two or three years before + Morton's final demonstration; hence that the merit of first using the + drug, or indeed any drug, in this way belongs to him. But, unfortunately, + Dr. Long did not quite trust the evidence of his own experiments. Just at + that time the medical journals were full of accounts of experiments in + which painless operations were said to be performed through practice of + hypnotism, and Dr. Long feared that his own success might be due to an + incidental hypnotic influence rather than to the drug. Hence he delayed + announcing his apparent discovery until he should have opportunity for + further tests—and opportunities did not come every day to the + country practitioner. And while he waited, Morton anticipated him, and the + discovery was made known to the world without his aid. It was a true + scientific caution that actuated Dr. Long to this delay, but the caution + cost him the credit, which might otherwise have been his, of giving to the + world one of the greatest blessings—dare we not, perhaps, say the + very greatest?—that science has ever conferred upon humanity. + </p> + <p> + A few months after the use of ether became general, the Scotch surgeon Sir + J. Y. Simpson(6) discovered that another drug, chloroform, could be + administered with similar effects; that it would, indeed, in many cases + produce anaesthesia more advantageously even than ether. From that day + till this surgeons have been more or less divided in opinion as to the + relative merits of the two drugs; but this fact, of course, has no bearing + whatever upon the merit of the first discovery of the method of + anaesthesia. Even had some other drug subsequently quite banished ether, + the honor of the discovery of the beneficent method of anaesthesia would + have been in no wise invalidated. And despite all cavillings, it is + unequivocally established that the man who gave that method to the world + was William T. G. Morton. + </p> + <p> + PASTEUR AND THE GERM THEORY OF DISEASE + </p> + <p> + The discovery of the anaesthetic power of drugs was destined presently, in + addition to its direct beneficences, to aid greatly in the progress of + scientific medicine, by facilitating those experimental studies of animals + from which, before the day of anaesthesia, many humane physicians were + withheld, and which in recent years have led to discoveries of such + inestimable value to humanity. But for the moment this possibility was + quite overshadowed by the direct benefits of anaesthesia, and the long + strides that were taken in scientific medicine during the first fifteen + years after Morton's discovery were mainly independent of such aid. These + steps were taken, indeed, in a field that at first glance might seem to + have a very slight connection with medicine. Moreover, the chief worker in + the field was not himself a physician. He was a chemist, and the work in + which he was now engaged was the study of alcoholic fermentation in vinous + liquors. Yet these studies paved the way for the most important advances + that medicine has made in any century towards the plane of true science; + and to this man more than to any other single individual—it might + almost be said more than to all other individuals—was due this + wonderful advance. It is almost superfluous to add that the name of this + marvellous chemist was Louis Pasteur. + </p> + <p> + The studies of fermentation which Pasteur entered upon in 1854 were aimed + at the solution of a controversy that had been waging in the scientific + world with varying degrees of activity for a quarter of a century. Back in + the thirties, in the day of the early enthusiasm over the perfected + microscope, there had arisen a new interest in the minute forms of life + which Leeuwenhoek and some of the other early workers with the lens had + first described, and which now were shown to be of almost universal + prevalence. These minute organisms had been studied more or less by a host + of observers, but in particular by the Frenchman Cagniard Latour and the + German of cell-theory fame, Theodor Schwann. These men, working + independently, had reached the conclusion, about 1837, that the + micro-organisms play a vastly more important role in the economy of nature + than any one previously had supposed. They held, for example, that the + minute specks which largely make up the substance of yeast are living + vegetable organisms, and that the growth of these organisms is the cause + of the important and familiar process of fermentation. They even came to + hold, at least tentatively, the opinion that the somewhat similar + micro-organisms to be found in all putrefying matter, animal or vegetable, + had a causal relation to the process of putrefaction. + </p> + <p> + This view, particularly as to the nature of putrefaction, was expressed + even more outspokenly a little later by the French botanist Turpin. Views + so supported naturally gained a following; it was equally natural that so + radical an innovation should be antagonized. In this case it chanced that + one of the most dominating scientific minds of the time, that of Liebig, + took a firm and aggressive stand against the new doctrine. In 1839 he + promulgated his famous doctrine of fermentation, in which he stood out + firmly against any "vitalistic" explanation of the phenomena, alleging + that the presence of micro-organisms in fermenting and putrefying + substances was merely incidental, and in no sense causal. This opinion of + the great German chemist was in a measure substantiated by experiments of + his compatriot Helmholtz, whose earlier experiments confirmed, but later + ones contradicted, the observations of Schwann, and this combined + authority gave the vitalistic conception a blow from which it had not + rallied at the time when Pasteur entered the field. Indeed, it was + currently regarded as settled that the early students of the subject had + vastly over-estimated the importance of micro-organisms. + </p> + <p> + And so it came as a new revelation to the generality of scientists of the + time, when, in 1857 and the succeeding half-decade, Pasteur published the + results of his researches, in which the question had been put to a series + of altogether new tests, and brought to unequivocal demonstration. + </p> + <p> + He proved that the micro-organisms do all that his most imaginative + predecessors had suspected, and more. Without them, he proved, there would + be no fermentation, no putrefaction—no decay of any tissues, except + by the slow process of oxidation. It is the microscopic yeast-plant which, + by seizing on certain atoms of the molecule, liberates the remaining atoms + in the form of carbonic-acid and alcohol, thus effecting fermentation; it + is another microscopic plant—a bacterium, as Devaine had christened + it—which in a similar way effects the destruction of organic + molecules, producing the condition which we call putrefaction. Pasteur + showed, to the amazement of biologists, that there are certain forms of + these bacteria which secure the oxygen which all organic life requires, + not from the air, but by breaking up unstable molecules in which oxygen is + combined; that putrefaction, in short, has its foundation in the + activities of these so-called anaerobic bacteria. + </p> + <p> + In a word, Pasteur showed that all the many familiar processes of the + decay of organic tissues are, in effect, forms of fermentation, and would + not take place at all except for the presence of the living + micro-organisms. A piece of meat, for example, suspended in an atmosphere + free from germs, will dry up gradually, without the slightest sign of + putrefaction, regardless of the temperature or other conditions to which + it may have been subjected. Let us witness one or two series of these + experiments as presented by Pasteur himself in one of his numerous papers + before the Academy of Sciences. + </p> + <p> + EXPERIMENTS WITH GRAPE SUGAR + </p> + <p> + "In the course of the discussion which took place before the Academy upon + the subject of the generation of ferments properly so-called, there was a + good deal said about that of wine, the oldest fermentation known. On this + account I decided to disprove the theory of M. Fremy by a decisive + experiment bearing solely upon the juice of grapes. + </p> + <p> + "I prepared forty flasks of a capacity of from two hundred and fifty to + three hundred cubic centimetres and filled them half full with filtered + grape-must, perfectly clear, and which, as is the case of all acidulated + liquids that have been boiled for a few seconds, remains uncontaminated + although the curved neck of the flask containing them remain constantly + open during several months or years. + </p> + <p> + "In a small quantity of water I washed a part of a bunch of grapes, the + grapes and the stalks together, and the stalks separately. This washing + was easily done by means of a small badger's-hair brush. The washing-water + collected the dust upon the surface of the grapes and the stalks, and it + was easily shown under the microscope that this water held in suspension a + multitude of minute organisms closely resembling either fungoid spores, or + those of alcoholic Yeast, or those of Mycoderma vini, etc. This being + done, ten of the forty flasks were preserved for reference; in ten of the + remainder, through the straight tube attached to each, some drops of the + washing-water were introduced; in a third series of ten flasks a few drops + of the same liquid were placed after it had been boiled; and, finally, in + the ten remaining flasks were placed some drops of grape-juice taken from + the inside of a perfect fruit. In order to carry out this experiment, the + straight tube of each flask was drawn out into a fine and firm point in + the lamp, and then curved. This fine and closed point was filed round near + the end and inserted into the grape while resting upon some hard + substance. When the point was felt to touch the support of the grape it + was by a slight pressure broken off at the point file mark. Then, if care + had been taken to create a slight vacuum in the flask, a drop of the juice + of the grape got into it, the filed point was withdrawn, and the aperture + immediately closed in the alcohol lamp. This decreased pressure of the + atmosphere in the flask was obtained by the following means: After warming + the sides of the flask either in the hands or in the lamp-flame, thus + causing a small quantity of air to be driven out of the end of the curved + neck, this end was closed in the lamp. After the flask was cooled, there + was a tendency to suck in the drop of grape-juice in the manner just + described. + </p> + <p> + "The drop of grape-juice which enters into the flask by this suction + ordinarily remains in the curved part of the tube, so that to mix it with + the must it was necessary to incline the flask so as to bring the must + into contact with the juice and then replace the flask in its normal + position. The four series of comparative experiments produced the + following results: + </p> + <p> + "The first ten flasks containing the grape-must boiled in pure air did not + show the production of any organism. The grape-must could possibly remain + in them for an indefinite number of years. Those in the second series, + containing the water in which the grapes had been washed separately and + together, showed without exception an alcoholic fermentation which in + several cases began to appear at the end of forty-eight hours when the + experiment took place at ordinary summer temperature. At the same time + that the yeast appeared, in the form of white traces, which little by + little united themselves in the form of a deposit on the sides of all the + flasks, there were seen to form little flakes of Mycellium, often as a + single fungoid growth or in combination, these fungoid growths being quite + independent of the must or of any alcoholic yeast. Often, also, the + Mycoderma vini appeared after some days upon the surface of the liquid. + The Vibria and the lactic ferments properly so called did not appear on + account of the nature of the liquid. + </p> + <p> + "The third series of flasks, the washing-water in which had been + previously boiled, remained unchanged, as in the first series. Those of + the fourth series, in which was the juice of the interior of the grapes, + remained equally free from change, although I was not always able, on + account of the delicacy of the experiment, to eliminate every chance of + error. These experiments cannot leave the least doubt in the mind as to + the following facts: + </p> + <p> + "Grape-must, after heating, never ferments on contact with the air, when + the air has been deprived of the germs which it ordinarily holds in a + state of suspension. + </p> + <p> + "The boiled grape-must ferments when there is introduced into it a very + small quantity of water in which the surface of the grapes or their stalks + have been washed. + </p> + <p> + "The grape-must does not ferment when this washing-water has been boiled + and afterwards cooled. + </p> + <p> + "The grape-must does not ferment when there is added to it a small + quantity of the juice of the inside of the grape. + </p> + <p> + "The yeast, therefore, which causes the fermentation of the grapes in the + vintage-tub comes from the outside and not from the inside of the grapes. + Thus is destroyed the hypothesis of MM. Trecol and Fremy, who surmised + that the albuminous matter transformed itself into yeast on account of the + vital germs which were natural to it. With greater reason, therefore, + there is no longer any question of the theory of Liebig of the + transformation of albuminoid matter into ferments on account of the + oxidation." + </p> + <p> + FOREIGN ORGANISMS AND THE WORT OF BEER + </p> + <p> + "The method which I have just followed," Pasteur continues, "in order to + show that there exists a correlation between the diseases of beer and + certain microscopic organisms leaves no room for doubt, it seems to me, in + regard to the principles I am expounding. + </p> + <p> + "Every time that the microscope reveals in the leaven, and especially in + the active yeast, the production of organisms foreign to the alcoholic + yeast properly so called, the flavor of the beer leaves something to be + desired, much or little, according to the abundance and the character of + these little germs. Moreover, when a finished beer of good quality loses + after a time its agreeable flavor and becomes sour, it can be easily shown + that the alcoholic yeast deposited in the bottles or the casks, although + originally pure, at least in appearance, is found to be contaminated + gradually with these filiform or other ferments. All this can be deduced + from the facts already given, but some critics may perhaps declare that + these foreign ferments are the consequences of the diseased condition, + itself produced by unknown causes. + </p> + <p> + "Although this gratuitous hypothesis may be difficult to uphold, I will + endeavor to corroborate the preceding observations by a clearer method of + investigation. This consists in showing that the beer never has any + unpleasant taste in all cases when the alcoholic ferment properly so + called is not mixed with foreign ferments; that it is the same in the case + of wort, and that wort, liable to changes as it is, can be preserved + unaltered if it is kept from those microscopic parasites which find in it + a suitable nourishment and a field for growth. + </p> + <p> + "The employment of this second method has, moreover, the advantage of + proving with certainty the proposition that I advanced at first—namely, + that the germs of these organisms are derived from the dust of the + atmosphere, carried about and deposited upon all objects, or scattered + over the utensils and the materials used in a brewery-materials naturally + charged with microscopic germs, and which the various operations in the + store-rooms and the malt-house may multiply indefinitely. + </p> + <p> + "Let us take a glass flask with a long neck of from two hundred and fifty + to three hundred cubic centimetres capacity, and place in it some wort, + with or without hops, and then in the flame of a lamp draw out the neck of + the flask to a fine point, afterwards heating the liquid until the steam + comes out of the end of the neck. It can then be allowed to cool without + any other precautions; but for additional safety there can be introduced + into the little point a small wad of asbestos at the moment that the flame + is withdrawn from beneath the flask. Before thus placing the asbestos it + also can be passed through the flame, as well as after it has been put + into the end of the tube. The air which then first re-enters the flask + will thus come into contact with the heated glass and the heated liquid, + so as to destroy the vitality of any dust germs that may exist in the air. + The air itself will re-enter very gradually, and slowly enough to enable + any dust to be taken up by the drop of water which the air forces up the + curvature of the tube. Ultimately the tube will be dry, but the + re-entering of the air will be so slow that the particles of dust will + fall upon the sides of the tube. The experiments show that with this kind + of vessel, allowing free communication with the air, and the dust not + being allowed to enter, the dust will not enter at all events for a period + of ten or twelve years, which has been the longest period devoted to these + trials; and the liquid, if it were naturally limpid, will not be in the + least polluted neither on its surface nor in its mass, although the + outside of the flask may become thickly coated with dust. This is a most + irrefutable proof of the impossibility of dust getting inside the flask. + </p> + <p> + "The wort thus prepared remains uncontaminated indefinitely, in spite of + its susceptibility to change when exposed to the air under conditions + which allow it to gather the dusty particles which float in the + atmosphere. It is the same in the case of urine, beef-tea, and grape-must, + and generally with all those putrefactable and fermentable liquids which + have the property when heated to boiling-point of destroying the vitality + of dust germs."(7) + </p> + <p> + There was nothing in these studies bearing directly upon the question of + animal diseases, yet before they were finished they had stimulated + progress in more than one field of pathology. At the very outset they + sufficed to start afresh the inquiry as to the role played by + micro-organisms in disease. In particular they led the French physician + Devaine to return to some interrupted studies which he had made ten years + before in reference to the animal disease called anthrax, or splenic + fever, a disease that cost the farmers of Europe millions of francs + annually through loss of sheep and cattle. In 1850 Devaine had seen + multitudes of bacteria in the blood of animals who had died of anthrax, + but he did not at that time think of them as having a causal relation to + the disease. Now, however, in 1863, stimulated by Pasteur's new + revelations regarding the power of bacteria, he returned to the subject, + and soon became convinced, through experiments by means of inoculation, + that the microscopic organisms he had discovered were the veritable and + the sole cause of the infectious disease anthrax. + </p> + <p> + The publication of this belief in 1863 aroused a furor of controversy. + That a microscopic vegetable could cause a virulent systemic disease was + an idea altogether too startling to be accepted in a day, and the + generality of biologists and physicians demanded more convincing proofs + than Devaine as yet was able to offer. + </p> + <p> + Naturally a host of other investigators all over the world entered the + field. Foremost among these was the German Dr. Robert Koch, who soon + corroborated all that Devaine had observed, and carried the experiments + further in the direction of the cultivation of successive generations of + the bacteria in artificial media, inoculations being made from such pure + cultures of the eighth generation, with the astonishing result that + animals thus inoculated succumbed to the disease. + </p> + <p> + Such experiments seem demonstrative, yet the world was unconvinced, and in + 1876, while the controversy was still at its height, Pasteur was prevailed + upon to take the matter in hand. The great chemist was becoming more and + more exclusively a biologist as the years passed, and in recent years his + famous studies of the silk-worm diseases, which he proved due to bacterial + infection, and of the question of spontaneous generation, had given him + unequalled resources in microscopical technique. And so when, with the aid + of his laboratory associates Duclaux and Chamberland and Roux, he took up + the mooted anthrax question the scientific world awaited the issue with + bated breath. And when, in 1877, Pasteur was ready to report on his + studies of anthrax, he came forward with such a wealth of demonstrative + experiments—experiments the rigid accuracy of which no one would for + a moment think of questioning—going to prove the bacterial origin of + anthrax, that scepticism was at last quieted for all time to come. + </p> + <p> + Henceforth no one could doubt that the contagious disease anthrax is due + exclusively to the introduction into an animal's system of a specific germ—a + microscopic plant—which develops there. And no logical mind could + have a reasonable doubt that what is proved true of one infectious disease + would some day be proved true also of other, perhaps of all, forms of + infectious maladies. + </p> + <p> + Hitherto the cause of contagion, by which certain maladies spread from + individual to individual, had been a total mystery, quite unillumined by + the vague terms "miasm," "humor," "virus," and the like cloaks of + ignorance. Here and there a prophet of science, as Schwann and Henle, had + guessed the secret; but guessing, in science, is far enough from knowing. + Now, for the first time, the world KNEW, and medicine had taken another + gigantic stride towards the heights of exact science. + </p> + <p> + LISTER AND ANTISEPTIC SURGERY + </p> + <p> + Meantime, in a different though allied field of medicine there had been a + complementary growth that led to immediate results of even more practical + importance. I mean the theory and practice of antisepsis in surgery. This + advance, like the other, came as a direct outgrowth of Pasteur's + fermentation studies of alcoholic beverages, though not at the hands of + Pasteur himself. Struck by the boundless implications of Pasteur's + revelations regarding the bacteria, Dr. Joseph Lister (the present Lord + Lister), then of Glasgow, set about as early as 1860 to make a wonderful + application of these ideas. If putrefaction is always due to bacterial + development, he argued, this must apply as well to living as to dead + tissues; hence the putrefactive changes which occur in wounds and after + operations on the human subject, from which blood-poisoning so often + follows, might be absolutely prevented if the injured surfaces could be + kept free from access of the germs of decay. + </p> + <p> + In the hope of accomplishing this result, Lister began experimenting with + drugs that might kill the bacteria without injury to the patient, and with + means to prevent further access of germs once a wound was freed from them. + How well he succeeded all the world knows; how bitterly he was antagonized + for about a score of years, most of the world has already forgotten. As + early as 1867 Lister was able to publish results pointing towards success + in his great project; yet so incredulous were surgeons in general that + even some years later the leading surgeons on the Continent had not so + much as heard of his efforts. In 1870 the soldiers of Paris died, as of + old, of hospital gangrene; and when, in 1871, the French surgeon Alphonse + Guerin, stimulated by Pasteur's studies, conceived the idea of dressing + wounds with cotton in the hope of keeping germs from entering them, he was + quite unaware that a British contemporary had preceded him by a full + decade in this effort at prevention and had made long strides towards + complete success. Lister's priority, however, and the superiority of his + method, were freely admitted by the French Academy of Sciences, which in + 1881 officially crowned his achievement, as the Royal Society of London + had done the year before. + </p> + <p> + By this time, to be sure, as everybody knows, Lister's new methods had + made their way everywhere, revolutionizing the practice of surgery and + practically banishing from the earth maladies that hitherto had been the + terror of the surgeon and the opprobrium of his art. And these bedside + studies, conducted in the end by thousands of men who had no knowledge of + microscopy, had a large share in establishing the general belief in the + causal relation that micro-organisms bear to disease, which by about the + year 1880 had taken possession of the medical world. But they did more; + they brought into equal prominence the idea that, the cause of a diseased + condition being known, it maybe possible as never before to grapple with + and eradicate that condition. + </p> + <p> + PREVENTIVE INOCULATION + </p> + <p> + The controversy over spontaneous generation, which, thanks to Pasteur and + Tyndall, had just been brought to a termination, made it clear that no + bacterium need be feared where an antecedent bacterium had not found + lodgment; Listerism in surgery had now shown how much might be + accomplished towards preventing the access of germs to abraded surfaces of + the body and destroying those that already had found lodgment there. As + yet, however, there was no inkling of a way in which a corresponding + onslaught might be made upon those other germs which find their way into + the animal organism by way of the mouth and the nostrils, and which, as + was now clear, are the cause of those contagious diseases which, first and + last, claim so large a proportion of mankind for their victims. How such + means might be found now became the anxious thought of every imaginative + physician, of every working microbiologist. + </p> + <p> + As it happened, the world was not kept long in suspense. Almost before the + proposition had taken shape in the minds of the other leaders, Pasteur had + found a solution. Guided by the empirical success of Jenner, he, like many + others, had long practised inoculation experiments, and on February 9, + 1880, he announced to the French Academy of Sciences that he had found a + method of so reducing the virulence of a disease germ that when introduced + into the system of a susceptible animal it produced only a mild form of + the disease, which, however, sufficed to protect against the usual + virulent form exactly as vaccinia protects against small-pox. The + particular disease experimented with was that infectious malady of poultry + known familiarly as "chicken cholera." In October of the same year Pasteur + announced the method by which this "attenuation of the virus," as he + termed it, had been brought about—by cultivation of the disease + germs in artificial media, exposed to the air, and he did not hesitate to + assert his belief that the method would prove "susceptible of + generalization"—that is to say, of application to other diseases + than the particular one in question. + </p> + <p> + Within a few months he made good this prophecy, for in February, 1881, he + announced to the Academy that with the aid, as before, of his associates + MM. Chamberland and Roux, he had produced an attenuated virus of the + anthrax microbe by the use of which, as he affirmed with great confidence, + he could protect sheep, and presumably cattle, against that fatal malady. + "In some recent publications," said Pasteur, "I announced the first case + of the attenuation of a virus by experimental methods only. Formed of a + special microbe of an extreme minuteness, this virus may be multiplied by + artificial culture outside the animal body. These cultures, left alone + without any possible external contamination, undergo, in the course of + time, modifications of their virulency to a greater or less extent. The + oxygen of the atmosphere is said to be the chief cause of these + attenuations—that is, this lessening of the facilities of + multiplication of the microbe; for it is evident that the difference of + virulence is in some way associated with differences of development in the + parasitic economy. + </p> + <p> + "There is no need to insist upon the interesting character of these + results and the deductions to be made therefrom. To seek to lessen the + virulence by rational means would be to establish, upon an experimental + basis, the hope of preparing from an active virus, easily cultivated + either in the human or animal body, a vaccine-virus of restrained + development capable of preventing the fatal effects of the former. + Therefore, we have applied all our energies to investigate the possible + generalizing action of atmospheric oxygen in the attenuation of virus. + </p> + <p> + "The anthrax virus, being one that has been most carefully studied, seemed + to be the first that should attract our attention. Every time, however, we + encountered a difficulty. Between the microbe of chicken cholera and the + microbe of anthrax there exists an essential difference which does not + allow the new experiment to be verified by the old. The microbes of + chicken cholera do not, in effect, seem to resolve themselves, in their + culture, into veritable germs. The latter are merely cells, or + articulations always ready to multiply by division, except when the + particular conditions in which they become true germs are known. + </p> + <p> + "The yeast of beer is a striking example of these cellular productions, + being able to multiply themselves indefinitely without the apparition of + their original spores. There exist many mucedines (Mucedinae?) of tubular + mushrooms, which in certain conditions of culture produce a chain of more + or less spherical cells called Conidae. The latter, detached from their + branches, are able to reproduce themselves in the form of cells, without + the appearance, at least with a change in the conditions of culture, of + the spores of their respective mucedines. These vegetable organisms can be + compared to plants which are cultivated by slipping, and to produce which + it is not necessary to have the fruits or the seeds of the mother plant. + </p> + <p> + "The anthrax bacterium, in its artificial cultivation, behaves very + differently. Its mycelian filaments, if one may so describe them, have + been produced scarcely for twenty-four or forty-eight hours when they are + seen to transform themselves, those especially which are in free contact + with the air, into very refringent corpuscles, capable of gradually + isolating themselves into true germs of slight organization. Moreover, + observation shows that these germs, formed so quickly in the culture, do + not undergo, after exposure for a time to atmospheric air, any change + either in their vitality or their virulence. I was able to present to the + Academy a tube containing some spores of anthrax bacteria produced four + years ago, on March 21, 1887. Each year the germination of these little + corpuscles has been tried, and each year the germination has been + accomplished with the same facility and the same rapidity as at first. + Each year also the virulence of the new cultures has been tested, and they + have not shown any visible falling off. Therefore, how can we experiment + with the action of the air upon the anthrax virus with any expectation of + making it less virulent? + </p> + <p> + "The crucial difficulty lies perhaps entirely in this rapid reproduction + of the bacteria germs which we have just related. In its form of a + filament, and in its multiplication by division, is not this organism at + all points comparable with the microbe of the chicken cholera? + </p> + <p> + "That a germ, properly so called, that a seed, does not suffer any + modification on account of the air is easily conceived; but it is + conceivable not less easily that if there should be any change it would + occur by preference in the case of a mycelian fragment. It is thus that a + slip which may have been abandoned in the soil in contact with the air + does not take long to lose all vitality, while under similar conditions a + seed is preserved in readiness to reproduce the plant. If these views have + any foundation, we are led to think that in order to prove the action of + the air upon the anthrax bacteria it will be indispensable to submit to + this action the mycelian development of the minute organism under + conditions where there cannot be the least admixture of corpuscular germs. + Hence the problem of submitting the bacteria to the action of oxygen comes + back to the question of presenting entirely the formation of spores. The + question being put in this way, we are beginning to recognize that it is + capable of being solved. + </p> + <p> + "We can, in fact, prevent the appearance of spores in the artificial + cultures of the anthrax parasite by various artifices. At the lowest + temperature at which this parasite can be cultivated—that is to say, + about +16 degrees Centigrade—the bacterium does not produce germs—at + any rate, for a very long time. The shapes of the minute microbe at this + lowest limit of its development are irregular, in the form of balls and + pears—in a word, they are monstrosities—but they are without + spores. In the last regard also it is the same at the highest temperatures + at which the parasite can be cultivated, temperatures which vary slightly + according to the means employed. In neutral chicken bouillon the bacteria + cannot be cultivated above 45 degrees. Culture, however, is easy and + abundant at 42 to 43 degrees, but equally without any formation of spores. + Consequently a culture of mycelian bacteria can be kept entirely free from + germs while in contact with the open air at a temperature of from 42 to 43 + degrees Centigrade. Now appear the three remarkable results. After about + one month of waiting the culture dies—that is to say, if put into a + fresh bouillon it becomes absolutely sterile. + </p> + <p> + "So much for the life and nutrition of this organism. In respect to its + virulence, it is an extraordinary fact that it disappears entirely after + eight days' culture at 42 to 43 degrees Centigrade, or, at any rate, the + cultures are innocuous for the guinea-pig, the rabbit, and the sheep, the + three kinds of animals most apt to contract anthrax. We are thus able to + obtain, not only the attenuation of the virulence, but also its complete + suppression by a simple method of cultivation. Moreover, we see also the + possibility of preserving and cultivating the terrible microbe in an + inoffensive state. What is it that happens in these eight days at 43 + degrees that suffices to take away the virulence of the bacteria? Let us + remember that the microbe of chicken cholera dies in contact with the air, + in a period somewhat protracted, it is true, but after successive + attenuations. Are we justified in thinking that it ought to be the same in + regard to the microbe of anthrax? This hypothesis is confirmed by + experiment. Before the disappearance of its virulence the anthrax microbe + passes through various degrees of attenuation, and, moreover, as is also + the case with the microbe of chicken cholera, each of these attenuated + states of virulence can be obtained by cultivation. Moreover, since, + according to one of our recent Communications, anthrax is not recurrent, + each of our attenuated anthrax microbes is, for the better-developed + microbe, a vaccine—that is to say, a virus producing a + less-malignant malady. What, therefore, is easier than to find in these a + virus that will infect with anthrax sheep, cows, and horses, without + killing them, and ultimately capable of warding off the mortal malady? We + have practised this experiment with great success upon sheep, and when the + season comes for the assembling of the flocks at Beauce we shall try the + experiment on a larger scale. + </p> + <p> + "Already M. Toussaint has announced that sheep can be saved by preventive + inoculations; but when this able observer shall have published his + results; on the subject of which we have made such exhaustive studies, as + yet unpublished, we shall be able to see the whole difference which exists + between the two methods—the uncertainty of the one and the certainty + of the other. That which we announce has, moreover, the very great + advantage of resting upon the existence of a poison vaccine cultivable at + will, and which can be increased indefinitely in the space of a few hours + without having recourse to infected blood."(8) + </p> + <p> + This announcement was immediately challenged in a way that brought it to + the attention of the entire world. The president of an agricultural + society, realizing the enormous importance of the subject, proposed to + Pasteur that his alleged discovery should be submitted to a decisive + public test. He proposed to furnish a drove of fifty sheep half of which + were to be inoculated with the attenuated virus of Pasteur. Subsequently + all the sheep were to be inoculated with virulent virus, all being kept + together in one pen under precisely the same conditions. The "protected" + sheep were to remain healthy; the unprotected ones to die of anthrax; so + read the terms of the proposition. Pasteur accepted the challenge; he even + permitted a change in the programme by which two goats were substituted + for two of the sheep, and ten cattle added, stipulating, however, that + since his experiments had not yet been extended to cattle these should not + be regarded as falling rigidly within the terms of the test. + </p> + <p> + It was a test to try the soul of any man, for all the world looked on + askance, prepared to deride the maker of so preposterous a claim as soon + as his claim should be proved baseless. Not even the fame of Pasteur could + make the public at large, lay or scientific, believe in the possibility of + what he proposed to accomplish. There was time for all the world to be + informed of the procedure, for the first "preventive" inoculation—or + vaccination, as Pasteur termed it—was made on May 5th, the second on + May 17th, and another interval of two weeks must elapse before the final + inoculations with the unattenuated virus. Twenty-four sheep, one goat, and + five cattle were submitted to the preliminary vaccinations. Then, on May + 31 st, all sixty of the animals were inoculated, a protected and + unprotected one alternately, with an extremely virulent culture of anthrax + microbes that had been in Pasteur's laboratory since 1877. This + accomplished, the animals were left together in one enclosure to await the + issue. + </p> + <p> + Two days later, June 2d, at the appointed hour of rendezvous, a vast + crowd, composed of veterinary surgeons, newspaper correspondents, and + farmers from far and near, gathered to witness the closing scenes of this + scientific tourney. What they saw was one of the most dramatic scenes in + the history of peaceful science—a scene which, as Pasteur declared + afterwards, "amazed the assembly." Scattered about the enclosure, dead, + dying, or manifestly sick unto death, lay the unprotected animals, one and + all, while each and every "protected" animal stalked unconcernedly about + with every appearance of perfect health. Twenty of the sheep and the one + goat were already dead; two other sheep expired under the eyes of the + spectators; the remaining victims lingered but a few hours longer. Thus in + a manner theatrical enough, not to say tragic, was proclaimed the + unequivocal victory of science. Naturally enough, the unbelievers struck + their colors and surrendered without terms; the principle of protective + vaccination, with a virus experimentally prepared in the laboratory, was + established beyond the reach of controversy. + </p> + <p> + That memorable scientific battle marked the beginning of a new era in + medicine. It was a foregone conclusion that the principle thus established + would be still further generalized; that it would be applied to human + maladies; that in all probability it would grapple successfully, sooner or + later, with many infectious diseases. That expectation has advanced + rapidly towards realization. Pasteur himself made the application to the + human subject in the disease hydrophobia in 1885, since which time that + hitherto most fatal of maladies has largely lost its terrors. Thousands of + persons bitten by mad dogs have been snatched from the fatal consequences + of that mishap by this method at the Pasteur Institute in Paris, and at + the similar institutes, built on the model of this parent one, that have + been established all over the world in regions as widely separated as New + York and Nha-Trang. + </p> + <p> + SERUM-THERAPY + </p> + <p> + In the production of the rabies vaccine Pasteur and his associates + developed a method of attenuation of a virus quite different from that + which had been employed in the case of the vaccines of chicken cholera and + of anthrax. The rabies virus was inoculated into the system of guinea-pigs + or rabbits and, in effect, cultivated in the systems of these animals. The + spinal cord of these infected animals was found to be rich in the virus, + which rapidly became attenuated when the cord was dried in the air. The + preventive virus, of varying strengths, was made by maceration of these + cords at varying stages of desiccation. This cultivation of a virus within + the animal organism suggested, no doubt, by the familiar Jennerian method + of securing small-pox vaccine, was at the same time a step in the + direction of a new therapeutic procedure which was destined presently to + become of all-absorbing importance—the method, namely, of so-called + serum-therapy, or the treatment of a disease with the blood serum of an + animal that has been subjected to protective inoculation against that + disease. + </p> + <p> + The possibility of such a method was suggested by the familiar + observation, made by Pasteur and numerous other workers, that animals of + different species differ widely in their susceptibility to various + maladies, and that the virus of a given disease may become more and more + virulent when passed through the systems of successive individuals of one + species, and, contrariwise, less and less virulent when passed through the + systems of successive individuals of another species. These facts + suggested the theory that the blood of resistant animals might contain + something directly antagonistic to the virus, and the hope that this + something might be transferred with curative effect to the blood of an + infected susceptible animal. Numerous experimenters all over the world + made investigations along the line of this alluring possibility, the + leaders perhaps being Drs. Behring and Kitasato, closely followed by Dr. + Roux and his associates of the Pasteur Institute of Paris. Definite + results were announced by Behring in 1892 regarding two important diseases—tetanus + and diphtheria—but the method did not come into general notice until + 1894, when Dr. Roux read an epoch-making paper on the subject at the + Congress of Hygiene at Buda-Pesth. + </p> + <p> + In this paper Dr. Roux, after adverting to the labors of Behring, Ehrlich, + Boer, Kossel, and Wasserman, described in detail the methods that had been + developed at the Pasteur Institute for the development of the curative + serum, to which Behring had given the since-familiar name antitoxine. The + method consists, first, of the cultivation, for some months, of the + diphtheria bacillus (called the Klebs-Loeffler bacillus, in honor of its + discoverers) in an artificial bouillon, for the development of a powerful + toxine capable of giving the disease in a virulent form. + </p> + <p> + This toxine, after certain details of mechanical treatment, is injected in + small but increasing doses into the system of an animal, care being taken + to graduate the amount so that the animal does not succumb to the disease. + After a certain course of this treatment it is found that a portion of + blood serum of the animal so treated will act in a curative way if + injected into the blood of another animal, or a human patient, suffering + with diphtheria. In other words, according to theory, an antitoxine has + been developed in the system of the animal subjected to the progressive + inoculations of the diphtheria toxine. In Dr. Roux's experience the animal + best suited for the purpose is the horse, though almost any of the + domesticated animals will serve the purpose. + </p> + <p> + But Dr. Roux's paper did not stop with the description of laboratory + methods. It told also of the practical application of the serum to the + treatment of numerous cases of diphtheria in the hospitals of Paris—applications + that had met with a gratifying measure of success. He made it clear that a + means had been found of coping successfully with what had been one of the + most virulent and intractable of the diseases of childhood. Hence it was + not strange that his paper made a sensation in all circles, medical and + lay alike. + </p> + <p> + Physicians from all over the world flocked to Paris to learn the details + of the open secret, and within a few months the new serum-therapy had an + acknowledged standing with the medical profession everywhere. What it had + accomplished was regarded as but an earnest of what the new method might + accomplish presently when applied to the other infectious diseases. + </p> + <p> + Efforts at such applications were immediately begun in numberless + directions—had, indeed, been under way in many a laboratory for some + years before. It is too early yet to speak of the results in detail. But + enough has been done to show that this method also is susceptible of the + widest generalization. It is not easy at the present stage to sift that + which is tentative from that which will be permanent; but so great an + authority as Behring does not hesitate to affirm that today we possess, in + addition to the diphtheria antitoxine, equally specific antitoxines of + tetanus, cholera, typhus fever, pneumonia, and tuberculosis—a set of + diseases which in the aggregate account for a startling proportion of the + general death-rate. Then it is known that Dr. Yersin, with the + collaboration of his former colleagues of the Pasteur Institute, has + developed, and has used with success, an antitoxine from the microbe of + the plague which recently ravaged China. + </p> + <p> + Dr. Calmette, another graduate of the Pasteur Institute, has extended the + range of the serum-therapy to include the prevention and treatment of + poisoning by venoms, and has developed an antitoxine that has already + given immunity from the lethal effects of snake bites to thousands of + persons in India and Australia. + </p> + <p> + Just how much of present promise is tentative, just what are the limits of + the methods—these are questions for the future to decide. But, in + any event, there seems little question that the serum treatment will stand + as the culminating achievement in therapeutics of our century. It is the + logical outgrowth of those experimental studies with the microscope begun + by our predecessors of the thirties, and it represents the present + culmination of the rigidly experimental method which has brought medicine + from a level of fanciful empiricism to the plane of a rational + experimental science. + </p> + <p> + <a name="link2H_4_0010" id="link2H_4_0010"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + IX. THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY + </h2> + <h3> + BRAIN AND MIND + </h3> + <p> + A little over a hundred years ago a reform movement was afoot in the world + in the interests of the insane. As was fitting, the movement showed itself + first in America, where these unfortunates were humanely cared for at a + time when their treatment elsewhere was worse than brutal; but England and + France quickly fell into line. The leader on this side of the water was + the famous Philadelphian, Dr. Benjamin Rush, "the Sydenham of America"; in + England, Dr. William Tuke inaugurated the movement; and in France, Dr. + Philippe Pinel, single-handed, led the way. Moved by a common spirit, + though acting quite independently, these men raised a revolt against the + traditional custom which, spurning the insane as demon-haunted outcasts, + had condemned these unfortunates to dungeons, chains, and the lash. + Hitherto few people had thought it other than the natural course of events + that the "maniac" should be thrust into a dungeon, and perhaps chained to + the wall with the aid of an iron band riveted permanently about his neck + or waist. Many an unfortunate, thus manacled, was held to the narrow + limits of his chain for years together in a cell to which full daylight + never penetrated; sometimes—iron being expensive—the chain was + so short that the wretched victim could not rise to the upright posture or + even shift his position upon his squalid pallet of straw. + </p> + <p> + In America, indeed, there being no Middle Age precedents to crystallize + into established customs, the treatment accorded the insane had seldom or + never sunk to this level. Partly for this reason, perhaps, the work of Dr. + Rush at the Philadelphia Hospital, in 1784, by means of which the insane + came to be humanely treated, even to the extent of banishing the lash, has + been but little noted, while the work of the European leaders, though + belonging to later decades, has been made famous. And perhaps this is not + as unjust as it seems, for the step which Rush took, from relatively bad + to good, was a far easier one to take than the leap from atrocities to + good treatment which the European reformers were obliged to compass. In + Paris, for example, Pinel was obliged to ask permission of the authorities + even to make the attempt at liberating the insane from their chains, and, + notwithstanding his recognized position as a leader of science, he gained + but grudging assent, and was regarded as being himself little better than + a lunatic for making so manifestly unwise and hopeless an attempt. Once + the attempt had been made, however, and carried to a successful issue, the + amelioration wrought in the condition of the insane was so patent that the + fame of Pinel's work at the Bicetre and the Salpetriere went abroad apace. + It required, indeed, many years to complete it in Paris, and a lifetime of + effort on the part of Pinel's pupil Esquirol and others to extend the + reform to the provinces; but the epochal turning-point had been reached + with Pinel's labors of the closing years of the eighteenth century. + </p> + <p> + The significance of this wise and humane reform, in the present + connection, is the fact that these studies of the insane gave emphasis to + the novel idea, which by-and-by became accepted as beyond question, that + "demoniacal possession" is in reality no more than the outward expression + of a diseased condition of the brain. This realization made it clear, as + never before, how intimately the mind and the body are linked one to the + other. And so it chanced that, in striking the shackles from the insane, + Pinel and his confreres struck a blow also, unwittingly, at time-honored + philosophical traditions. The liberation of the insane from their dungeons + was an augury of the liberation of psychology from the musty recesses of + metaphysics. Hitherto psychology, in so far as it existed at all, was but + the subjective study of individual minds; in future it must become + objective as well, taking into account also the relations which the mind + bears to the body, and in particular to the brain and nervous system. + </p> + <p> + The necessity for this collocation was advocated quite as earnestly, and + even more directly, by another worker of this period, whose studies were + allied to those of alienists, and who, even more actively than they, + focalized his attention upon the brain and its functions. This earliest of + specialists in brain studies was a German by birth but Parisian by + adoption, Dr. Franz Joseph Gall, originator of the since-notorious system + of phrenology. The merited disrepute into which this system has fallen + through the exposition of peripatetic charlatans should not make us forget + that Dr. Gall himself was apparently a highly educated physician, a + careful student of the brain and mind according to the best light of his + time, and, withal, an earnest and honest believer in the validity of the + system he had originated. The system itself, taken as a whole, was + hopelessly faulty, yet it was not without its latent germ of truth, as + later studies were to show. How firmly its author himself believed in it + is evidenced by the paper which he contributed to the French Academy of + Sciences in 1808. The paper itself was referred to a committee of which + Pinel and Cuvier were members. The verdict of this committee was adverse, + and justly so; yet the system condemned had at least one merit which its + detractors failed to realize. It popularized the conception that the brain + is the organ of mind. Moreover, by its insistence it rallied about it a + band of scientific supporters, chief of whom was Dr. Kaspar Spurzlieim, a + man of no mean abilities, who became the propagandist of phrenology in + England and in America. Of course such advocacy and popularity stimulated + opposition as well, and out of the disputations thus arising there grew + presently a general interest in the brain as the organ of mind, quite + aside from any preconceptions whatever as to the doctrines of Gall and + Spurzheim. + </p> + <p> + Prominent among the unprejudiced class of workers who now appeared was the + brilliant young Frenchman Louis Antoine Desmoulins, who studied first + under the tutorage of the famous Magendie, and published jointly with him + a classical work on the nervous system of vertebrates in 1825. Desmoulins + made at least one discovery of epochal importance. He observed that the + brains of persons dying in old age were lighter than the average and gave + visible evidence of atrophy, and he reasoned that such decay is a normal + accompaniment of senility. No one nowadays would question the accuracy of + this observation, but the scientific world was not quite ready for it in + 1825; for when Desmoulins announced his discovery to the French Academy, + that august and somewhat patriarchal body was moved to quite unscientific + wrath, and forbade the young iconoclast the privilege of further hearings. + From which it is evident that the partially liberated spirit of the new + psychology had by no means freed itself altogether, at the close of the + first quarter of the nineteenth century, from the metaphysical cobwebs of + its long incarceration. + </p> + <p> + FUNCTIONS OF THE NERVES + </p> + <p> + While studies of the brain were thus being inaugurated, the nervous + system, which is the channel of communication between the brain and the + outside world, was being interrogated with even more tangible results. The + inaugural discovery was made in 1811 by Dr. (afterwards Sir Charles) + Bell,(1) the famous English surgeon and experimental physiologist. It + consisted of the observation that the anterior roots of the spinal nerves + are given over to the function of conveying motor impulses from the brain + outward, whereas the posterior roots convey solely sensory impulses to the + brain from without. Hitherto it had been supposed that all nerves have a + similar function, and the peculiar distribution of the spinal nerves had + been an unsolved puzzle. + </p> + <p> + Bell's discovery was epochal; but its full significance was not + appreciated for a decade, nor, indeed, was its validity at first admitted. + In Paris, in particular, then the court of final appeal in all matters + scientific, the alleged discovery was looked at askance, or quite ignored. + But in 1823 the subject was taken up by the recognized leader of French + physiology—Francois Magendie—in the course of his + comprehensive experimental studies of the nervous system, and Bell's + conclusions were subjected to the most rigid experimental tests and found + altogether valid. Bell himself, meanwhile, had turned his attention to the + cranial nerves, and had proved that these also are divisible into two sets—sensory + and motor. Sometimes, indeed, the two sets of filaments are combined into + one nerve cord, but if traced to their origin these are found to arise + from different brain centres. Thus it was clear that a hitherto + unrecognized duality of function pertains to the entire extra-cranial + nervous system. Any impulse sent from the periphery to the brain must be + conveyed along a perfectly definite channel; the response from the brain, + sent out to the peripheral muscles, must traverse an equally definite and + altogether different course. If either channel is interrupted—as by + the section of its particular nerve tract—the corresponding message + is denied transmission as effectually as an electric current is stopped by + the section of the transmitting wire. + </p> + <p> + Experimenters everywhere soon confirmed the observations of Bell and + Magendie, and, as always happens after a great discovery, a fresh impulse + was given to investigations in allied fields. Nevertheless, a full decade + elapsed before another discovery of comparable importance was made. Then + Marshall Hall, the most famous of English physicians of his day, made his + classical observations on the phenomena that henceforth were to be known + as reflex action. In 1832, while experimenting one day with a decapitated + newt, he observed that the headless creature's limbs would contract in + direct response to certain stimuli. Such a response could no longer be + secured if the spinal nerves supplying a part were severed. Hence it was + clear that responsive centres exist in the spinal cord capable of + receiving a sensory message and of transmitting a motor impulse in reply—a + function hitherto supposed to be reserved for the brain. Further studies + went to show that such phenomena of reflex action on the part of centres + lying outside the range of consciousness, both in the spinal cord and in + the brain itself, are extremely common; that, in short, they enter + constantly into the activities of every living organism and have a most + important share in the sum total of vital movements. Hence, Hall's + discovery must always stand as one of the great mile-stones of the advance + of neurological science. + </p> + <p> + Hall gave an admirably clear and interesting account of his experiments + and conclusions in a paper before the Royal Society, "On the Reflex + Functions of the Medulla Oblongata and the Medulla Spinalis," from which, + as published in the Transactions of the society for 1833, we may quote at + some length: + </p> + <p> + "In the entire animal, sensation and voluntary motion, functions of the + cerebrum, combine with the functions of the medulla oblongata and medulla + spinalis, and may therefore render it difficult or impossible to determine + those which are peculiar to each; if, in an animal deprived of the brain, + the spinal marrow or the nerves supplying the muscles be stimulated, those + muscles, whether voluntary or respiratory, are equally thrown into + contraction, and, it may be added, equally in the complete and in the + mutilated animal; and, in the case of the nerves, equally in limbs + connected with and detached from the spinal marrow. + </p> + <p> + "The operation of all these various causes may be designated centric, as + taking place AT, or at least in a direction FROM, central parts of the + nervous system. But there is another function the phenomena of which are + of a totally different order and obey totally different laws, being + excited by causes in a situation which is EXCENTRIC in the nervous system—that + is, distant from the nervous centres. This mode of action has not, I + think, been hitherto distinctly understood by physiologists. + </p> + <p> + "Many of the phenomena of this principle of action, as they occur in the + limbs, have certainly been observed. But, in the first place, this + function is by no means confined to the limbs; for, while it imparts to + each muscle its appropriate tone, and to each system of muscles its + appropriate equilibrium or balance, it performs the still more important + office of presiding over the orifices and terminations of each of the + internal canals in the animal economy, giving them their due form and + action; and, in the second place, in the instances in which the phenomena + of this function have been noticed, they have been confounded, as I have + stated, with those of sensation and volition; or, if they have been + distinguished from these, they have been too indefinitely denominated + instinctive, or automatic. I have been compelled, therefore, to adopt some + new designation for them, and I shall now give the reasons for my choice + of that which is given in the title of this paper—'Reflex + Functions.' + </p> + <p> + "This property is characterized by being EXCITED in its action and REFLEX + in its course: in every instance in which it is exerted an impression made + upon the extremities of certain nerves is conveyed to the medulla + oblongata or the medulla spinalis, and is reflected along the nerves to + parts adjacent to, or remote from, that which has received the impression. + </p> + <p> + "It is by this reflex character that the function to which I have alluded + is to be distinguished from every other. There are, in the animal economy, + four modes of muscular action, of muscular contraction. The first is that + designated VOLUNTARY: volition, originated in the cerebrum and spontaneous + in its acts, extends its influence along the spinal marrow and the motor + nerves in a DIRECT LINE to the voluntary muscles. The SECOND is that of + RESPIRATION: like volition, the motive influence in respiration passes in + a DIRECT LINE from one point of the nervous system to certain muscles; but + as voluntary motion seems to originate in the cerebrum, so the respiratory + motions originate in the medulla oblongata: like the voluntary motions, + the motions of respirations are spontaneous; they continue, at least, + after the eighth pair of nerves have been divided. The THIRD kind of + muscular action in the animal economy is that termed involuntary: it + depends upon the principle of irritability and requires the IMMEDIATE + application of a stimulus to the nervo-muscular fibre itself. These three + kinds of muscular motion are well known to physiologists; and I believe + they are all which have been hitherto pointed out. There is, however, a + FOURTH, which subsists, in part, after the voluntary and respiratory + motions have ceased, by the removal of the cerebrum and medulla oblongata, + and which is attached to the medulla spinalis, ceasing itself when this is + removed, and leaving the irritability undiminished. In this kind of + muscular motion the motive influence does not originate in any central + part of the nervous system, but from a distance from that centre; it is + neither spontaneous in its action nor direct in its course; it is, on the + contrary, EXCITED by the application of appropriate stimuli, which are + not, however, applied immediately to the muscular or nervo-muscular fibre, + but to certain membraneous parts, whence the impression is carried through + the medulla, REFLECTED and reconducted to the part impressed, or conducted + to a part remote from it in which muscular contraction is effected. + </p> + <p> + "The first three modes of muscular action are known only by actual + movements of muscular contractions. But the reflex function exists as a + continuous muscular action, as a power presiding over organs not actually + in a state of motion, preserving in some, as the glottis, an open, in + others, as the sphincters, a closed form, and in the limbs a due degree of + equilibrium or balanced muscular action—a function not, I think, + hitherto recognized by physiologists. + </p> + <p> + "The three kinds of muscular motion hitherto known may be distinguished in + another way. The muscles of voluntary motion and of respiration may be + excited by stimulating the nerves which supply them, in any part of their + course, whether at their source as a part of the medulla oblongata or the + medulla spinalis or exterior to the spinal canal: the muscles of + involuntary motion are chiefly excited by the actual contact of stimuli. + In the case of the reflex function alone the muscles are excited by a + stimulus acting mediately and indirectly in a curved and reflex course, + along superficial subcutaneous or submucous nerves proceeding from the + medulla. The first three of these causes of muscular motion may act on + detached limbs or muscles. The last requires the connection with the + medulla to be preserved entire. + </p> + <p> + "All the kinds of muscular motion may be unduly excited, but the reflex + function is peculiar in being excitable in two modes of action, not + previously subsisting in the animal economy, as in the case of sneezing, + coughing, vomiting, etc. The reflex function also admits of being + permanently diminished or augmented and of taking on some other morbid + forms, of which I shall treat hereafter. + </p> + <p> + "Before I proceed to the details of the experiments upon which this + disposition rests, it may be well to point out several instances in + illustration of the various sources of and the modes of muscular action + which have been enumerated. None can be more familiar than the act of + swallowing. Yet how complicated is the act! The apprehension of the food + by the teeth and tongue, etc., is voluntary, and cannot, therefore, take + place in an animal from which the cerebrum is removed. The transition of + food over the glottis and along the middle and lower part of the pharynx + depends upon the reflex action: it can take place in animals from which + the cerebrum has been removed or the ninth pair of nerves divided; but it + requires the connection with the medulla oblongata to be preserved + entirely; and the actual contact of some substance which may act as a + stimulus: it is attended by the accurate closure of the glottis and by the + contraction of the pharynx. The completion of the act of deglutition is + dependent upon the stimulus immediately impressed upon the muscular fibre + of the oesophagus, and is the result of excited irritability. + </p> + <p> + "However plain these observations may have made the fact that there is a + function of the nervous muscular system distinct from sensation, from the + voluntary and respiratory motions, and from irritability, it is right, in + every such inquiry as the present, that the statements and reasonings + should be made with the experiment, as it were, actually before us. It has + already been remarked that the voluntary and respiratory motions are + spontaneous, not necessarily requiring the agency of a stimulus. If, then, + an animal can be placed in such circumstances that such motions will + certainly not take place, the power of moving remaining, it may be + concluded that volition and the motive influence of respiration are + annihilated. Now this is effected by removing the cerebrum and the medulla + oblongata. These facts are fully proved by the experiments of Legallois + and M. Flourens, and by several which I proceed to detail, for the sake of + the opportunity afforded by doing so of stating the arguments most + clearly. + </p> + <p> + "I divided the spinal marrow of a very lively snake between the second and + third vertebrae. The movements of the animal were immediately before + extremely vigorous and unintermitted. From the moment of the division of + the spinal marrow it lay perfectly tranquil and motionless, with the + exception of occasional gaspings and slight movements of the head. It + became quite evident that this state of quiescence would continue + indefinitely were the animal secured from all external impressions. + </p> + <p> + "Being now stimulated, the body began to move with great activity, and + continued to do so for a considerable time, each change of position or + situation bringing some fresh part of the surface of the animal into + contact with the table or other objects and renewing the application of + stimulants. + </p> + <p> + "At length the animal became again quiescent; and being carefully + protected from all external impressions it moved no more, but died in the + precise position and form which it had last assumed. + </p> + <p> + "It requires a little manoeuvre to perform this experiment successfully: + the motions of the animal must be watched and slowly and cautiously + arrested by opposing some soft substance, as a glove or cotton wool; they + are by this means gradually lulled into quiescence. The slightest touch + with a hard substance, the slightest stimulus, will, on the other hand, + renew the movements on the animal in an active form. But that this + phenomenon does not depend upon sensation is further fully proved by the + facts that the position last assumed, and the stimuli, may be such as + would be attended by extreme or continued pain, if the sensibility were + undestroyed: in one case the animal remained partially suspended over the + acute edge of the table; in others the infliction of punctures and the + application of a lighted taper did not prevent the animal, still possessed + of active powers of motion, from passing into a state of complete and + permanent quiescence." + </p> + <p> + In summing up this long paper Hall concludes with this sentence: "The + reflex function appears in a word to be the COMPLEMENT of the functions of + the nervous system hitherto known."(2) + </p> + <p> + All these considerations as to nerve currents and nerve tracts becoming + stock knowledge of science, it was natural that interest should become + stimulated as to the exact character of these nerve tracts in themselves, + and all the more natural in that the perfected microscope was just now + claiming all fields for its own. A troop of observers soon entered upon + the study of the nerves, and the leader here, as in so many other lines of + microscopical research, was no other than Theodor Schwann. Through his + efforts, and with the invaluable aid of such other workers as Remak, + Purkinje, Henle, Muller, and the rest, all the mystery as to the general + characteristics of nerve tracts was cleared away. It came to be known that + in its essentials a nerve tract is a tenuous fibre or thread of protoplasm + stretching between two terminal points in the organism, one of such + termini being usually a cell of the brain or spinal cord, the other a + distribution-point at or near the periphery—for example, in a muscle + or in the skin. Such a fibril may have about it a protective covering, + which is known as the sheath of Schwann; but the fibril itself is the + essential nerve tract; and in many cases, as Remak presently discovered, + the sheath is dispensed with, particularly in case of the nerves of the + so-called sympathetic system. + </p> + <p> + This sympathetic system of ganglia and nerves, by-the-bye, had long been a + puzzle to the physiologists. Its ganglia, the seeming centre of the + system, usually minute in size and never very large, are found everywhere + through the organism, but in particular are gathered into a long double + chain which lies within the body cavity, outside the spinal column, and + represents the sole nervous system of the non-vertebrated organisms. + Fibrils from these ganglia were seen to join the cranial and spinal nerve + fibrils and to accompany them everywhere, but what special function they + subserved was long a mere matter of conjecture and led to many absurd + speculations. Fact was not substituted for conjecture until about the year + 1851, when the great Frenchman Claude Bernard conclusively proved that at + least one chief function of the sympathetic fibrils is to cause + contraction of the walls of the arterioles of the system, thus regulating + the blood-supply of any given part. Ten years earlier Henle had + demonstrated the existence of annular bands of muscle fibres in the + arterioles, hitherto a much-mooted question, and several tentative + explanations of the action of these fibres had been made, particularly by + the brothers Weber, by Stilling, who, as early as 1840, had ventured to + speak of "vaso-motor" nerves, and by Schiff, who was hard upon the same + track at the time of Bernard's discovery. But a clear light was not thrown + on the subject until Bernard's experiments were made in 1851. The + experiments were soon after confirmed and extended by Brown-Sequard, + Waller, Budge, and numerous others, and henceforth physiologists felt that + they understood how the blood-supply of any given part is regulated by the + nervous system. + </p> + <p> + In reality, however, they had learned only half the story, as Bernard + himself proved only a few years later by opening up a new and quite + unsuspected chapter. While experimenting in 1858 he discovered that there + are certain nerves supplying the heart which, if stimulated, cause that + organ to relax and cease beating. As the heart is essentially nothing more + than an aggregation of muscles, this phenomenon was utterly puzzling and + without precedent in the experience of physiologists. An impulse + travelling along a motor nerve had been supposed to be able to cause a + muscular contraction and to do nothing else; yet here such an impulse had + exactly the opposite effect. The only tenable explanation seemed to be + that this particular impulse must arrest or inhibit the action of the + impulses that ordinarily cause the heart muscles to contract. But the idea + of such inhibition of one impulse by another was utterly novel and at + first difficult to comprehend. Gradually, however, the idea took its place + in the current knowledge of nerve physiology, and in time it came to be + understood that what happens in the case of the heart nerve-supply is only + a particular case under a very general, indeed universal, form of nervous + action. Growing out of Bernard's initial discovery came the final + understanding that the entire nervous system is a mechanism of centres + subordinate and centres superior, the action of the one of which may be + counteracted and annulled in effect by the action of the other. This + applies not merely to such physical processes as heart-beats and arterial + contraction and relaxing, but to the most intricate functionings which + have their counterpart in psychical processes as well. Thus the + observation of the inhibition of the heart's action by a nervous impulse + furnished the point of departure for studies that led to a better + understanding of the modus operandi of the mind's activities than had ever + previously been attained by the most subtle of psychologists. + </p> + <p> + PSYCHO-PHYSICS + </p> + <p> + The work of the nerve physiologists had thus an important bearing on + questions of the mind. But there was another company of workers of this + period who made an even more direct assault upon the "citadel of thought." + A remarkable school of workers had been developed in Germany, the leaders + being men who, having more or less of innate metaphysical bias as a + national birthright, had also the instincts of the empirical scientist, + and whose educational equipment included a profound knowledge not alone of + physiology and psychology, but of physics and mathematics as well. These + men undertook the novel task of interrogating the relations of body and + mind from the standpoint of physics. They sought to apply the vernier and + the balance, as far as might be, to the intangible processes of mind. + </p> + <p> + The movement had its precursory stages in the early part of the century, + notably in the mathematical psychology of Herbart, but its first definite + output to attract general attention came from the master-hand of Hermann + Helmholtz in 1851. It consisted of the accurate measurement of the speed + of transit of a nervous impulse along a nerve tract. To make such + measurement had been regarded as impossible, it being supposed that the + flight of the nervous impulse was practically instantaneous. But Helmholtz + readily demonstrated the contrary, showing that the nerve cord is a + relatively sluggish message-bearer. According to his experiments, first + performed upon the frog, the nervous "current" travels less than one + hundred feet per second. Other experiments performed soon afterwards by + Helmholtz himself, and by various followers, chief among whom was Du + Bois-Reymond, modified somewhat the exact figures at first obtained, but + did not change the general bearings of the early results. Thus the nervous + impulse was shown to be something far different, as regards speed of + transit, at any rate, from the electric current to which it had been so + often likened. An electric current would flash halfway round the globe + while a nervous impulse could travel the length of the human body—from + a man's foot to his brain. + </p> + <p> + The tendency to bridge the gulf that hitherto had separated the physical + from the psychical world was further evidenced in the following decade by + Helmholtz's remarkable but highly technical study of the sensations of + sound and of color in connection with their physical causes, in the course + of which he revived the doctrine of color vision which that other great + physiologist and physicist, Thomas Young, had advanced half a century + before. The same tendency was further evidenced by the appearance, in + 1852, of Dr. Hermann Lotze's famous Medizinische Psychologie, oder + Physiologie der Seele, with its challenge of the old myth of a "vital + force." But the most definite expression of the new movement was + signalized in 1860, when Gustav Fechner published his classical work + called Psychophysik. That title introduced a new word into the vocabulary + of science. Fechner explained it by saying, "I mean by psychophysics an + exact theory of the relation between spirit and body, and, in a general + way, between the physical and the psychic worlds." The title became famous + and the brunt of many a controversy. So also did another phrase which + Fechner introduced in the course of his book—the phrase + "physiological psychology." In making that happy collocation of words + Fechner virtually christened a new science. + </p> + <p> + FECHNER EXPOUNDS WEBER'S LAW + </p> + <p> + The chief purport of this classical book of the German psycho-physiologist + was the elaboration and explication of experiments based on a method + introduced more than twenty years earlier by his countryman E. H. Weber, + but which hitherto had failed to attract the attention it deserved. The + method consisted of the measurement and analysis of the definite relation + existing between external stimuli of varying degrees of intensity (various + sounds, for example) and the mental states they induce. Weber's + experiments grew out of the familiar observation that the nicety of our + discriminations of various sounds, weights, or visual images depends upon + the magnitude of each particular cause of a sensation in its relation with + other similar causes. Thus, for example, we cannot see the stars in the + daytime, though they shine as brightly then as at night. Again, we seldom + notice the ticking of a clock in the daytime, though it may become almost + painfully audible in the silence of the night. Yet again, the difference + between an ounce weight and a two-ounce weight is clearly enough + appreciable when we lift the two, but one cannot discriminate in the same + way between a five-pound weight and a weight of one ounce over five + pounds. + </p> + <p> + This last example, and similar ones for the other senses, gave Weber the + clew to his novel experiments. Reflection upon every-day experiences made + it clear to him that whenever we consider two visual sensations, or two + auditory sensations, or two sensations of weight, in comparison one with + another, there is always a limit to the keenness of our discrimination, + and that this degree of keenness varies, as in the case of the weights + just cited, with the magnitude of the exciting cause. + </p> + <p> + Weber determined to see whether these common experiences could be brought + within the pale of a general law. His method consisted of making long + series of experiments aimed at the determination, in each case, of what + came to be spoken of as the least observable difference between the + stimuli. Thus if one holds an ounce weight in each hand, and has tiny + weights added to one of them, grain by grain, one does not at first + perceive a difference; but presently, on the addition of a certain grain, + he does become aware of the difference. Noting now how many grains have + been added to produce this effect, we have the weight which represents the + least appreciable difference when the standard is one ounce. + </p> + <p> + Now repeat the experiment, but let the weights be each of five pounds. + Clearly in this case we shall be obliged to add not grains, but drachms, + before a difference between the two heavy weights is perceived. But + whatever the exact amount added, that amount represents the stimulus + producing a just-perceivable sensation of difference when the standard is + five pounds. And so on for indefinite series of weights of varying + magnitudes. Now came Weber's curious discovery. Not only did he find that + in repeated experiments with the same pair of weights the measure of + "just-{p}erceivable difference" remained approximately fixed, but he + found, further, that a remarkable fixed relation exists between the + stimuli of different magnitude. If, for example, he had found it + necessary, in the case of the ounce weights, to add one-fiftieth of an + ounce to the one before a difference was detected, he found also, in the + case of the five-pound weights, that one-fiftieth of five pounds must be + added before producing the same result. And so of all other weights; the + amount added to produce the stimulus of "least-appreciable difference" + always bore the same mathematical relation to the magnitude of the weight + used, be that magnitude great or small. + </p> + <p> + Weber found that the same thing holds good for the stimuli of the + sensations of sight and of hearing, the differential stimulus bearing + always a fixed ratio to the total magnitude of the stimuli. Here, then, + was the law he had sought. + </p> + <p> + Weber's results were definite enough and striking enough, yet they failed + to attract any considerable measure of attention until they were revived + and extended by Fechner and brought before the world in the famous work on + psycho-physics. Then they precipitated a veritable melee. Fechner had not + alone verified the earlier results (with certain limitations not essential + to the present consideration), but had invented new methods of making + similar tests, and had reduced the whole question to mathematical + treatment. He pronounced Weber's discovery the fundamental law of + psycho-physics. In honor of the discoverer, he christened it Weber's Law. + He clothed the law in words and in mathematical formulae, and, so to say, + launched it full tilt at the heads of the psychological world. It made a + fine commotion, be assured, for it was the first widely heralded bulletin + of the new psychology in its march upon the strongholds of the + time-honored metaphysics. The accomplishments of the microscopists and the + nerve physiologists had been but preliminary—mere border skirmishes + of uncertain import. But here was proof that the iconoclastic movement + meant to invade the very heart of the sacred territory of mind—a + territory from which tangible objective fact had been supposed to be + forever barred. + </p> + <p> + PHYSIOLOGICAL PSYCHOLOGY + </p> + <p> + Hardly had the alarm been sounded, however, before a new movement was + made. While Fechner's book was fresh from the press, steps were being + taken to extend the methods of the physicist in yet another way to the + intimate processes of the mind. As Helmholtz had shown the rate of nervous + impulsion along the nerve tract to be measurable, it was now sought to + measure also the time required for the central nervous mechanism to + perform its work of receiving a message and sending out a response. This + was coming down to the very threshold of mind. The attempt was first made + by Professor Donders in 1861, but definitive results were only obtained + after many years of experiment on the part of a host of observers. The + chief of these, and the man who has stood in the forefront of the new + movement and has been its recognized leader throughout the remainder of + the century, is Dr. Wilhelm Wundt, of Leipzig. + </p> + <p> + The task was not easy, but, in the long run, it was accomplished. Not + alone was it shown that the nerve centre requires a measurable time for + its operations, but much was learned as to conditions that modify this + time. Thus it was found that different persons vary in the rate of their + central nervous activity—which explained the "personal equation" + that the astronomer Bessel had noted a half-century before. It was found, + too, that the rate of activity varies also for the same person under + different conditions, becoming retarded, for example, under influence of + fatigue, or in case of certain diseases of the brain. All details aside, + the essential fact emerges, as an experimental demonstration, that the + intellectual processes—sensation, apperception, volition—are + linked irrevocably with the activities of the central nervous tissues, and + that these activities, like all other physical processes, have a time + element. To that old school of psychologists, who scarcely cared more for + the human head than for the heels—being interested only in the mind—such + a linking of mind and body as was thus demonstrated was naturally + disquieting. But whatever the inferences, there was no escaping the facts. + </p> + <p> + Of course this new movement has not been confined to Germany. Indeed, it + had long had exponents elsewhere. Thus in England, a full century earlier, + Dr. Hartley had championed the theory of the close and indissoluble + dependence of the mind upon the brain, and formulated a famous vibration + theory of association that still merits careful consideration. Then, too, + in France, at the beginning of the century, there was Dr. Cabanis with his + tangible, if crudely phrased, doctrine that the brain digests impressions + and secretes thought as the stomach digests food and the liver secretes + bile. Moreover, Herbert Spencer's Principles of Psychology, with its + avowed co-ordination of mind and body and its vitalizing theory of + evolution, appeared in 1855, half a decade before the work of Fechner. But + these influences, though of vast educational value, were theoretical + rather than demonstrative, and the fact remains that the experimental work + which first attempted to gauge mental operations by physical principles + was mainly done in Germany. Wundt's Physiological Psychology, with its + full preliminary descriptions of the anatomy of the nervous system, gave + tangible expression to the growth of the new movement in 1874; and four + years later, with the opening of his laboratory of physiological + psychology at the University of Leipzig, the new psychology may be said to + have gained a permanent foothold and to have forced itself into official + recognition. From then on its conquest of the world was but a matter of + time. + </p> + <p> + It should be noted, however, that there is one other method of strictly + experimental examination of the mental field, latterly much in vogue, + which had a different origin. This is the scientific investigation of the + phenomena of hypnotism. This subject was rescued from the hands of + charlatans, rechristened, and subjected to accurate investigation by Dr. + James Braid, of Manchester, as early as 1841. But his results, after + attracting momentary attention, fell from view, and, despite desultory + efforts, the subject was not again accorded a general hearing from the + scientific world until 1878, when Dr. Charcot took it up at the + Salpetriere, in Paris, followed soon afterwards by Dr. Rudolf Heidenhain, + of Breslau, and a host of other experimenters. The value of the method in + the study of mental states was soon apparent. Most of Braid's experiments + were repeated, and in the main his results were confirmed. His explanation + of hypnotism, or artificial somnambulism, as a self-induced state, + independent of any occult or supersensible influence, soon gained general + credence. His belief that the initial stages are due to fatigue of nervous + centres, usually from excessive stimulation, has not been supplanted, + though supplemented by notions growing out of the new knowledge as to + subconscious mentality in general, and the inhibitory influence of one + centre over another in the central nervous mechanism. + </p> + <p> + THE BRAIN AS THE ORGAN OF MIND + </p> + <p> + These studies of the psychologists and pathologists bring the relations of + mind and body into sharp relief. But even more definite in this regard was + the work of the brain physiologists. Chief of these, during the middle + period of the century, was the man who is sometimes spoken of as the + "father of brain physiology," Marie Jean Pierre Flourens, of the Jardin + des Plantes of Paris, the pupil and worthy successor of Magendie. His + experiments in nerve physiology were begun in the first quarter of the + century, but his local experiments upon the brain itself were not + culminated until about 1842. At this time the old dispute over phrenology + had broken out afresh, and the studies of Flourens were aimed, in part at + least, at the strictly scientific investigation of this troublesome topic. + </p> + <p> + In the course of these studies Flourens discovered that in the medulla + oblongata, the part of the brain which connects that organ with the spinal + cord, there is a centre of minute size which cannot be injured in the + least without causing the instant death of the animal operated upon. It + may be added that it is this spot which is reached by the needle of the + garroter in Spanish executions, and that the same centre also is destroyed + when a criminal is "successfully" hanged, this time by the forced + intrusion of a process of the second cervical vertebra. Flourens named + this spot the "vital knot." Its extreme importance, as is now understood, + is due to the fact that it is the centre of nerves that supply the heart; + but this simple explanation, annulling the conception of a specific "life + centre," was not at once apparent. + </p> + <p> + Other experiments of Flourens seemed to show that the cerebellum is the + seat of the centres that co-ordinate muscular activities, and that the + higher intellectual faculties are relegated to the cerebrum. But beyond + this, as regards localization, experiment faltered. Negative results, as + regards specific faculties, were obtained from all localized irritations + of the cerebrum, and Flourens was forced to conclude that the cerebral + lobe, while being undoubtedly the seat of higher intellection, performs + its functions with its entire structure. This conclusion, which + incidentally gave a quietus to phrenology, was accepted generally, and + became the stock doctrine of cerebral physiology for a generation. + </p> + <p> + It will be seen, however, that these studies of Flourens had a double + bearing. They denied localization of cerebral functions, but they + demonstrated the localization of certain nervous processes in other + portions of the brain. On the whole, then, they spoke positively for the + principle of localization of function in the brain, for which a certain + number of students contended; while their evidence against cerebral + localization was only negative. There was here and there an observer who + felt that this negative testimony was not conclusive. In particular, the + German anatomist Meynert, who had studied the disposition of nerve tracts + in the cerebrum, was led to believe that the anterior portions of the + cerebrum must have motor functions in preponderance; the posterior + positions, sensory functions. Somewhat similar conclusions were reached + also by Dr. Hughlings-Jackson, in England, from his studies of epilepsy. + But no positive evidence was forthcoming until 1861, when Dr. Paul Broca + brought before the Academy of Medicine in Paris a case of brain lesion + which he regarded as having most important bearings on the question of + cerebral localization. + </p> + <p> + The case was that of a patient at the Bicetre, who for twenty years had + been deprived of the power of speech, seemingly through loss of memory of + words. In 1861 this patient died, and an autopsy revealed that a certain + convolution of the left frontal lobe of his cerebrum had been totally + destroyed by disease, the remainder of his brain being intact. Broca felt + that this observation pointed strongly to a localization of the memory of + words in a definite area of the brain. Moreover, it transpired that the + case was not without precedent. As long ago as 1825 Dr. Boillard had been + led, through pathological studies, to locate definitely a centre for the + articulation of words in the frontal lobe, and here and there other + observers had made tentatives in the same direction. Boillard had even + followed the matter up with pertinacity, but the world was not ready to + listen to him. Now, however, in the half-decade that followed Broca's + announcements, interest rose to fever-beat, and through the efforts of + Broca, Boillard, and numerous others it was proved that a veritable centre + having a strange domination over the memory of articulate words has its + seat in the third convolution of the frontal lobe of the cerebrum, usually + in the left hemisphere. That part of the brain has since been known to the + English-speaking world as the convolution of Broca, a name which, + strangely enough, the discoverer's compatriots have been slow to accept. + </p> + <p> + This discovery very naturally reopened the entire subject of brain + localization. It was but a short step to the inference that there must be + other definite centres worth the seeking, and various observers set about + searching for them. In 1867 a clew was gained by Eckhard, who, repeating a + forgotten experiment by Haller and Zinn of the previous century, removed + portions of the brain cortex of animals, with the result of producing + convulsions. But the really vital departure was made in 1870 by the German + investigators Fritsch and Hitzig, who, by stimulating definite areas of + the cortex of animals with a galvanic current, produced contraction of + definite sets of muscles of the opposite side of the body. These most + important experiments, received at first with incredulity, were repeated + and extended in 1873 by Dr. David Ferrier, of London, and soon afterwards + by a small army of independent workers everywhere, prominent among whom + were Franck and Pitres in France, Munck and Goltz in Germany, and Horsley + and Schafer in England. The detailed results, naturally enough, were not + at first all in harmony. Some observers, as Goltz, even denied the + validity of the conclusions in toto. But a consensus of opinion, based on + multitudes of experiments, soon placed the broad general facts for which + Fritsch and Hitzig contended beyond controversy. It was found, indeed, + that the cerebral centres of motor activities have not quite the finality + at first ascribed to them by some observers, since it may often happen + that after the destruction of a centre, with attending loss of function, + there may be a gradual restoration of the lost function, proving that + other centres have acquired the capacity to take the place of the one + destroyed. There are limits to this capacity for substitution, however, + and with this qualification the definiteness of the localization of motor + functions in the cerebral cortex has become an accepted part of brain + physiology. + </p> + <p> + Nor is such localization confined to motor centres. Later experiments, + particularly of Ferrier and of Munck, proved that the centres of vision + are equally restricted in their location, this time in the posterior lobes + of the brain, and that hearing has likewise its local habitation. Indeed, + there is every reason to believe that each form of primary sensation is + based on impressions which mainly come to a definitely localized goal in + the brain. But all this, be it understood, has no reference to the higher + forms of intellection. All experiment has proved futile to localize these + functions, except indeed to the extent of corroborating the familiar fact + of their dependence upon the brain, and, somewhat problematically, upon + the anterior lobes of the cerebrum in particular. But this is precisely + what should be expected, for the clearer insight into the nature of mental + processes makes it plain that in the main these alleged "faculties" are + not in themselves localized. Thus, for example, the "faculty" of language + is associated irrevocably with centres of vision, of hearing, and of + muscular activity, to go no further, and only becomes possible through the + association of these widely separated centres. The destruction of Broca's + centre, as was early discovered, does not altogether deprive a patient of + his knowledge of language. He may be totally unable to speak (though as to + this there are all degrees of variation), and yet may comprehend what is + said to him, and be able to read, think, and even write correctly. Thus it + appears that Broca's centre is peculiarly bound up with the capacity for + articulate speech, but is far enough from being the seat of the faculty of + language in its entirety. + </p> + <p> + In a similar way, most of the supposed isolated "faculties" of higher + intellection appear, upon clearer analysis, as complex aggregations of + primary sensations, and hence necessarily dependent upon numerous and + scattered centres. Some "faculties," as memory and volition, may be said + in a sense to be primordial endowments of every nerve cell—even of + every body cell. Indeed, an ultimate analysis relegates all intellection, + in its primordial adumbrations, to every particle of living matter. But + such refinements of analysis, after all, cannot hide the fact that certain + forms of higher intellection involve a pretty definite collocation and + elaboration of special sensations. Such specialization, indeed, seems a + necessary accompaniment of mental evolution. That every such specialized + function has its localized centres of co-ordination, of some such + significance as the demonstrated centres of articulate speech, can hardly + be in doubt—though this, be it understood, is an induction, not as + yet a demonstration. In other words, there is every reason to believe that + numerous "centres," in this restricted sense, exist in the brain that have + as yet eluded the investigator. Indeed, the current conception regards the + entire cerebral cortex as chiefly composed of centres of ultimate + co-ordination of impressions, which in their cruder form are received by + more primitive nervous tissues—the basal ganglia, the cerebellum and + medulla, and the spinal cord. + </p> + <p> + This, of course, is equivalent to postulating the cerebral cortex as the + exclusive seat of higher intellection. This proposition, however, to which + a safe induction seems to lead, is far afield from the substantiation of + the old conception of brain localization, which was based on faulty + psychology and equally faulty inductions from few premises. The details of + Gall's system, as propounded by generations of his mostly unworthy + followers, lie quite beyond the pale of scientific discussion. Yet, as I + have said, a germ of truth was there—the idea of specialization of + cerebral functions—and modern investigators have rescued that + central conception from the phrenological rubbish heap in which its + discoverer unfortunately left it buried. + </p> + <p> + THE MINUTE STRUCTURE OF THE BRAIN + </p> + <p> + The common ground of all these various lines of investigations of + pathologist, anatomist, physiologist, physicist, and psychologist is, + clearly, the central nervous system—the spinal cord and the brain. + The importance of these structures as the foci of nervous and mental + activities has been recognized more and more with each new accretion of + knowledge, and the efforts to fathom the secrets of their intimate + structure has been unceasing. For the earlier students, only the crude + methods of gross dissections and microscopical inspection were available. + These could reveal something, but of course the inner secrets were for the + keener insight of the microscopist alone. And even for him the task of + investigation was far from facile, for the central nervous tissues are the + most delicate and fragile, and on many accounts the most difficult of + manipulation of any in the body. + </p> + <p> + Special methods, therefore, were needed for this essay, and brain + histology has progressed by fitful impulses, each forward jet marking the + introduction of some ingenious improvement of mechanical technique, which + placed a new weapon in the hands of the investigators. + </p> + <p> + The very beginning was made in 1824 by Rolando, who first thought of + cutting chemically hardened pieces of brain tissues into thin sections for + microscopical examination—the basal structure upon which almost all + the later advances have been conducted. Muller presently discovered that + bichromate of potassium in solution makes the best of fluids for the + preliminary preservation and hardening of the tissues. Stilling, in 1842, + perfected the method by introducing the custom of cutting a series of + consecutive sections of the same tissue, in order to trace nerve tracts + and establish spacial relations. Then from time to time mechanical + ingenuity added fresh details of improvement. It was found that pieces of + hardened tissue of extreme delicacy can be made better subject to + manipulation by being impregnated with collodion or celloidine and + embedded in paraffine. Latterly it has become usual to cut sections also + from fresh tissues, unchanged by chemicals, by freezing them suddenly with + vaporized ether or, better, carbonic acid. By these methods, and with the + aid of perfected microtomes, the worker of recent periods avails himself + of sections of brain tissues of a tenuousness which the early + investigators could not approach. + </p> + <p> + But more important even than the cutting of thin sections is the process + of making the different parts of the section visible, one tissue + differentiated from another. The thin section, as the early workers + examined it, was practically colorless, and even the crudest details of + its structure were made out with extreme difficulty. Remak did, indeed, + manage to discover that the brain tissue is cellular, as early as 1833, + and Ehrenberg in the same year saw that it is also fibrillar, but beyond + this no great advance was made until 1858, when a sudden impulse was + received from a new process introduced by Gerlach. The process itself was + most simple, consisting essentially of nothing more than the treatment of + a microscopical section with a solution of carmine. But the result was + wonderful, for when such a section was placed under the lens it no longer + appeared homogeneous. Sprinkled through its substance were seen irregular + bodies that had taken on a beautiful color, while the matrix in which they + were embedded remained unstained. In a word, the central nerve cell had + sprung suddenly into clear view. + </p> + <p> + A most interesting body it proved, this nerve cell, or ganglion cell, as + it came to be called. It was seen to be exceedingly minute in size, + requiring high powers of the microscope to make it visible. It exists in + almost infinite numbers, not, however, scattered at random through the + brain and spinal cord. On the contrary, it is confined to those portions + of the central nervous masses which to the naked eye appear gray in color, + being altogether wanting in the white substance which makes up the chief + mass of the brain. Even in the gray matter, though sometimes thickly + distributed, the ganglion cells are never in actual contact one with + another; they always lie embedded in intercellular tissues, which came to + be known, following Virchow, as the neuroglia. + </p> + <p> + Each ganglion cell was seen to be irregular in contour, and to have + jutting out from it two sets of minute fibres, one set relatively short, + indefinitely numerous, and branching in every direction; the other set + limited in number, sometimes even single, and starting out directly from + the cell as if bent on a longer journey. The numerous filaments came to be + known as protoplasmic processes; the other fibre was named, after its + discoverer, the axis cylinder of Deiters. It was a natural inference, + though not clearly demonstrable in the sections, that these filamentous + processes are the connecting links between the different nerve cells and + also the channels of communication between nerve cells and the periphery + of the body. The white substance of brain and cord, apparently, is made up + of such connecting fibres, thus bringing the different ganglion cells + everywhere into communication one with another. + </p> + <p> + In the attempt to trace the connecting nerve tracts through this white + substance by either macroscopical or microscopical methods, most important + aid is given by a method originated by Waller in 1852. Earlier than that, + in 1839, Nasse had discovered that a severed nerve cord degenerates in its + peripheral portions. Waller discovered that every nerve fibre, sensory or + motor, has a nerve cell to or from which it leads, which dominates its + nutrition, so that it can only retain its vitality while its connection + with that cell is intact. Such cells he named trophic centres. Certain + cells of the anterior part of the spinal cord, for example, are the + trophic centres of the spinal motor nerves. Other trophic centres, + governing nerve tracts in the spinal cord itself, are in the various + regions of the brain. It occurred to Waller that by destroying such + centres, or by severing the connection at various regions between a + nervous tract and its trophic centre, sharply defined tracts could be made + to degenerate, and their location could subsequently be accurately + defined, as the degenerated tissues take on a changed aspect, both to + macroscopical and microscopical observation. Recognition of this principle + thus gave the experimenter a new weapon of great efficiency in tracing + nervous connections. Moreover, the same principle has wide application in + case of the human subject in disease, such as the lesion of nerve tracts + or the destruction of centres by localized tumors, by embolisms, or by + traumatisms. + </p> + <p> + All these various methods of anatomical examination combine to make the + conclusion almost unavoidable that the central ganglion cells are the + veritable "centres" of nervous activity to which so many other lines of + research have pointed. The conclusion was strengthened by experiments of + the students of motor localization, which showed that the veritable + centres of their discovery lie, demonstrably, in the gray cortex of the + brain, not in the white matter. But the full proof came from pathology. At + the hands of a multitude of observers it was shown that in certain + well-known diseases of the spinal cord, with resulting paralysis, it is + the ganglion cells themselves that are found to be destroyed. Similarly, + in the case of sufferers from chronic insanities, with marked dementia, + the ganglion cells of the cortex of the brain are found to have undergone + degeneration. The brains of paretics in particular show such degeneration, + in striking correspondence with their mental decadence. The position of + the ganglion cell as the ultimate centre of nervous activities was thus + placed beyond dispute. + </p> + <p> + Meantime, general acceptance being given the histological scheme of + Gerlach, according to which the mass of the white substance of the brain + is a mesh-work of intercellular fibrils, a proximal idea seemed attainable + of the way in which the ganglionic activities are correlated, and, through + association, built up, so to speak, into the higher mental processes. Such + a conception accorded beautifully with the ideas of the associationists, + who had now become dominant in psychology. But one standing puzzle + attended this otherwise satisfactory correlation of anatomical + observations and psychic analyses. It was this: Since, according to the + histologist, the intercellular fibres, along which impulses are conveyed, + connect each brain cell, directly or indirectly, with every other brain + cell in an endless mesh-work, how is it possible that various sets of + cells may at times be shut off from one another? Such isolation must take + place, for all normal ideation depends for its integrity quite as much + upon the shutting-out of the great mass of associations as upon the + inclusion of certain other associations. For example, a student in solving + a mathematical problem must for the moment become quite oblivious to the + special associations that have to do with geography, natural history, and + the like. But does histology give any clew to the way in which such + isolation may be effected? + </p> + <p> + Attempts were made to find an answer through consideration of the very + peculiar character of the blood-supply in the brain. Here, as nowhere + else, the terminal twigs of the arteries are arranged in closed systems, + not anastomosing freely with neighboring systems. Clearly, then, a + restricted area of the brain may, through the controlling influence of the + vasomotor nerves, be flushed with arterial blood while neighboring parts + remain relatively anaemic. And since vital activities unquestionably + depend in part upon the supply of arterial blood, this peculiar + arrangement of the vascular mechanism may very properly be supposed to aid + in the localized activities of the central nervous ganglia. But this + explanation left much to be desired—in particular when it is + recalled that all higher intellection must in all probability involve + multitudes of widely scattered centres. + </p> + <p> + No better explanation was forthcoming, however, until the year 1889, when + of a sudden the mystery was cleared away by a fresh discovery. Not long + before this the Italian histologist Dr. Camille Golgi had discovered a + method of impregnating hardened brain tissues with a solution of nitrate + of silver, with the result of staining the nerve cells and their processes + almost infinitely better than was possible by the methods of Gerlach, or + by any of the multiform methods that other workers had introduced. Now for + the first time it became possible to trace the cellular prolongations + definitely to their termini, for the finer fibrils had not been rendered + visible by any previous method of treatment. Golgi himself proved that the + set of fibrils known as protoplasmic prolongations terminate by free + extremities, and have no direct connection with any cell save the one from + which they spring. He showed also that the axis cylinders give off + multitudes of lateral branches not hitherto suspected. But here he paused, + missing the real import of the discovery of which he was hard on the + track. It remained for the Spanish histologist Dr. S. Ramon y Cajal to + follow up the investigation by means of an improved application of Golgi's + method of staining, and to demonstrate that the axis cylinders, together + with all their collateral branches, though sometimes extending to a great + distance, yet finally terminate, like the other cell prolongations, in + arborescent fibrils having free extremities. In a word, it was shown that + each central nerve cell, with its fibrillar offshoots, is an isolated + entity. Instead of being in physical connection with a multitude of other + nerve cells, it has no direct physical connection with any other nerve + cell whatever. + </p> + <p> + When Dr. Cajal announced his discovery, in 1889, his revolutionary claims + not unnaturally amazed the mass of histologists. There were some few of + them, however, who were not quite unprepared for the revelation; in + particular His, who had half suspected the independence of the cells, + because they seemed to develop from dissociated centres; and Forel, who + based a similar suspicion on the fact that he had never been able actually + to trace a fibre from one cell to another. These observers then came + readily to repeat Cajal's experiments. So also did the veteran histologist + Kolliker, and soon afterwards all the leaders everywhere. The result was a + practically unanimous confirmation of the Spanish histologist's claims, + and within a few months after his announcements the old theory of union of + nerve cells into an endless mesh-work was completely discarded, and the + theory of isolated nerve elements—the theory of neurons, as it came + to be called—was fully established in its place. + </p> + <p> + As to how these isolated nerve cells functionate, Dr. Cajal gave the clew + from the very first, and his explanation has met with universal approval. + </p> + <p> + In the modified view, the nerve cell retains its old position as the + storehouse of nervous energy. Each of the filaments jutting out from the + cell is held, as before, to be indeed a transmitter of impulses, but a + transmitter that operates intermittently, like a telephone wire that is + not always "connected," and, like that wire, the nerve fibril operates by + contact and not by continuity. Under proper stimulation the ends of the + fibrils reach out, come in contact with other end fibrils of other cells, + and conduct their destined impulse. Again they retract, and communication + ceases for the time between those particular cells. Meantime, by a + different arrangement of the various conductors, different sets of cells + are placed in communication, different associations of nervous impulses + induced, different trains of thought engendered. Each fibril when + retracted becomes a non-conductor, but when extended and in contact with + another fibril, or with the body of another cell, it conducts its message + as readily as a continuous filament could do—precisely as in the + case of an electric wire. + </p> + <p> + This conception, founded on a most tangible anatomical basis, enables us + to answer the question as to how ideas are isolated, and also, as Dr. + Cajal points out, throws new light on many other mental processes. One can + imagine, for example, by keeping in mind the flexible nerve prolongations, + how new trains of thought may be engendered through novel associations of + cells; how facility of thought or of action in certain directions is + acquired through the habitual making of certain nerve-cell connections; + how certain bits of knowledge may escape our memory and refuse to be found + for a time because of a temporary incapacity of the nerve cells to make + the proper connections, and so on indefinitely. + </p> + <p> + If one likens each nerve cell to a central telephone office, each of its + filamentous prolongations to a telephone wire, one can imagine a striking + analogy between the modus operandi of nervous processes and of the + telephone system. The utility of new connections at the central office, + the uselessness of the mechanism when the connections cannot be made, the + "wires in use" that retard your message, perhaps even the crossing of + wires, bringing you a jangle of sounds far different from what you desire—all + these and a multiplicity of other things that will suggest themselves to + every user of the telephone may be imagined as being almost ludicrously + paralleled in the operations of the nervous mechanism. And that parallel, + startling as it may seem, is not a mere futile imagining. It is sustained + and rendered plausible by a sound substratum of knowledge of the + anatomical conditions under which the central nervous mechanism exists, + and in default of which, as pathology demonstrates with no less certitude, + its functionings are futile to produce the normal manifestations of higher + intellection. + </p> + <p> + <a name="link2H_4_0011" id="link2H_4_0011"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + X. THE NEW SCIENCE OF ORIENTAL ARCHAEOLOGY + </h2> + <h3> + HOW THE "RIDDLE OF THE SPHINX" WAS READ + </h3> + <p> + Conspicuously placed in the great hall of Egyptian antiquities in the + British Museum is a wonderful piece of sculpture known as the Rosetta + Stone. I doubt if any other piece in the entire exhibit attracts so much + attention from the casual visitor as this slab of black basalt on its + telescope-like pedestal. The hall itself, despite its profusion of + strangely sculptured treasures, is never crowded, but before this stone + you may almost always find some one standing, gazing with more or less of + discernment at the strange characters that are graven neatly across its + upturned, glass-protected face. A glance at this graven surface suffices + to show that three sets of inscriptions are recorded there. The upper one, + occupying about one-fourth of the surface, is a pictured scroll, made up + of chains of those strange outlines of serpents, hawks, lions, and so on, + which are recognized, even by the least initiated, as hieroglyphics. The + middle inscription, made up of lines, angles, and half-pictures, one might + surmise to be a sort of abbreviated or short-hand hieroglyphic. The third + or lower inscription is Greek—obviously a thing of words. If the + screeds above be also made of words, only the elect have any way of + proving the fact. + </p> + <p> + Fortunately, however, even the least scholarly observer is left in no + doubt as to the real import of the thing he sees, for an obliging English + label tells us that these three inscriptions are renderings of the same + message, and that this message is a "decree of the priests of Memphis + conferring divine honors on Ptolemy V. (Epiphenes), King of Egypt, B.C. + 195." The label goes on to state that the upper inscription (of which, + unfortunately, only part of the last dozen lines or so remains, the slab + being broken) is in "the Egyptian language, in hieroglyphics, or writing + of the priests"; the second inscription "in the same language is in + Demotic, or the writing of the people"; and the third "the Greek language + and character." Following this is a brief biography of the Rosetta Stone + itself, as follows: "The stone was found by the French in 1798 among the + ruins of Fort Saint Julien, near the Rosetta mouth of the Nile. It passed + into the hands of the British by the treaty of Alexandria, and was + deposited in the British Museum in the year 1801." There is a whole volume + of history in that brief inscription—and a bitter sting thrown in, + if the reader chance to be a Frenchman. Yet the facts involved could + scarcely be suggested more modestly. They are recorded much more bluntly + in a graven inscription on the side of the stone, which reads: "Captured + in Egypt by the British Army, 1801." No Frenchman could read those words + without a veritable sinking of the heart. + </p> + <p> + The value of the Rosetta Stone depended on the fact that it gave promise, + even when casually inspected, of furnishing a key to the centuries-old + mystery of the hieroglyphics. For two thousand years the secret of these + strange markings had been forgotten. Nowhere in the world—quite as + little in Egypt as elsewhere—had any man the slightest clew to their + meaning; there were those who even doubted whether these droll picturings + really had any specific meaning, questioning whether they were not rather + vague symbols of esoteric religious import and nothing more. And it was + the Rosetta Stone that gave the answer to these doubters and restored to + the world a lost language and a forgotten literature. + </p> + <p> + The trustees of the museum recognized at once that the problem of the + Rosetta Stone was one on which the scientists of the world might well + exhaust their ingenuity, and promptly published to the world a carefully + lithographed copy of the entire inscription, so that foreign scholarship + had equal opportunity with the British to try at the riddle. It was an + Englishman, however, who first gained a clew to the solution. This was + none other than the extraordinary Dr. Thomas Young, the demonstrator of + the vibratory nature of light. + </p> + <p> + Young's specific discoveries were these: (1) That many of the pictures of + the hieroglyphics stand for the names of the objects actually delineated; + (2) that other pictures are sometimes only symbolic; (3) that plural + numbers are represented by repetition; (4) that numerals are represented + by dashes; (5) that hieroglyphics may read either from the right or from + the left, but always from the direction in which the animal and human + figures face; (6) that proper names are surrounded by a graven oval ring, + making what he called a cartouche; (7) that the cartouches of the + preserved portion of the Rosetta Stone stand for the name of Ptolemy + alone; (8) that the presence of a female figure after such cartouches in + other inscriptions always denotes the female sex; (9) that within the + cartouches the hieroglyphic symbols have a positively phonetic value, + either alphabetic or syllabic; and (10) that several different characters + may have the same phonetic value. + </p> + <p> + Just what these phonetic values are Young pointed out in the case of + fourteen characters representing nine sounds, six of which are accepted + to-day as correctly representing the letters to which he ascribed them, + and the three others as being correct regarding their essential or + consonant element. It is clear, therefore, that he was on the right track + thus far, and on the very verge of complete discovery. But, unfortunately, + he failed to take the next step, which would have been to realize that the + same phonetic values which were given to the alphabetic characters within + the cartouches were often ascribed to them also when used in the general + text of an inscription; in other words, that the use of an alphabet was + not confined to proper names. This was the great secret which Young missed + and which his French successor, Jean Francois Champollion, working on the + foundation that Young had laid, was enabled to ferret out. + </p> + <p> + Young's initial studies of the Rosetta Stone were made in 1814; his later + publication bore date of 1819. Champollion's first announcement of results + came in 1822; his second and more important one in 1824. By this time, + through study of the cartouches of other inscriptions, Champollion had + made out almost the complete alphabet, and the "riddle of the Sphinx" was + practically solved. He proved that the Egyptians had developed a + relatively complete alphabet (mostly neglecting the vowels, as early + Semitic alphabets did also) centuries before the Phoenicians were heard of + in history. What relation this alphabet bore to the Phoenician we shall + have occasion to ask in another connection; for the moment it suffices to + know that those strange pictures of the Egyptian scroll are really + letters. + </p> + <p> + Even this statement, however, must be in a measure modified. These + pictures are letters and something more. Some of them are purely + alphabetical in character and some are symbolic in another way. Some + characters represent syllables. Others stand sometimes as mere + representatives of sounds, and again, in a more extended sense, as + representations of things, such as all hieroglyphics doubtless were in the + beginning. In a word, this is an alphabet, but not a perfected alphabet, + such as modern nations are accustomed to; hence the enormous complications + and difficulties it presented to the early investigators. + </p> + <p> + Champollion did not live to clear up all these mysteries. His work was + taken up and extended by his pupil Rossellini, and in particular by Dr. + Richard Lepsius in Germany, followed by M. Bernouf, and by Samuel Birch of + the British Museum, and more recently by such well-known Egyptologists as + MM. Maspero and Mariette and Chabas, in France, Dr. Brugsch, in Germany, + and Dr. E. Wallis Budge, the present head of the Department of Oriental + Antiquities at the British Museum. But the task of later investigators has + been largely one of exhumation and translation of records rather than of + finding methods. + </p> + <p> + TREASURES FROM NINEVEH + </p> + <p> + The most casual wanderer in the British Museum can hardly fail to notice + two pairs of massive sculptures, in the one case winged bulls, in the + other winged lions, both human-headed, which guard the entrance to the + Egyptian hall, close to the Rosetta Stone. Each pair of these weird + creatures once guarded an entrance to the palace of a king in the famous + city of Nineveh. As one stands before them his mind is carried back over + some twenty-seven intervening centuries, to the days when the "Cedar of + Lebanon" was "fair in his greatness" and the scourge of Israel. + </p> + <p> + The very Sculptures before us, for example, were perhaps seen by Jonah + when he made that famous voyage to Nineveh some seven or eight hundred + years B.C. A little later the Babylonian and the Mede revolted against + Assyrian tyranny and descended upon the fair city of Nineveh, and almost + literally levelled it to the ground. But these great sculptures, among + other things, escaped destruction, and at once hidden and preserved by the + accumulating debris of the centuries, they stood there age after age, + their very existence quite forgotten. When Xenophon marched past their + site with the ill-starred expedition of the ten thousand, in the year 400 + B.C., he saw only a mound which seemed to mark the site of some ancient + ruin; but the Greek did not suspect that he looked upon the site of that + city which only two centuries before had been the mistress of the world. + </p> + <p> + So ephemeral is fame! And yet the moral scarcely holds in the sequel; for + we of to-day, in this new, undreamed-of Western world, behold these + mementos of Assyrian greatness fresh from their twenty-five hundred years + of entombment, and with them records which restore to us the history of + that long-forgotten people in such detail as it was not known to any + previous generation since the fall of Nineveh. For two thousand five + hundred years no one saw these treasures or knew that they existed. One + hundred generations of men came and went without once pronouncing the name + of kings Shalmaneser or Asumazirpal or Asurbanipal. And to-day, after + these centuries of oblivion, these names are restored to history, and, + thanks to the character of their monuments, are assured a permanency of + fame that can almost defy time itself. It would be nothing strange, but + rather in keeping with their previous mutations of fortune, if the names + of Asurnazirpal and Asurbanipal should be familiar as household words to + future generations that have forgotten the existence of an Alexander, a + Caesar, and a Napoleon. For when Macaulay's prospective New Zealander + explores the ruins of the British Museum the records of the ancient + Assyrians will presumably still be there unscathed, to tell their story as + they have told it to our generation, though every manuscript and printed + book may have gone the way of fragile textures. + </p> + <p> + But the past of the Assyrian sculptures is quite necromantic enough + without conjuring for them a necromantic future. The story of their + restoration is like a brilliant romance of history. Prior to the middle of + this century the inquiring student could learn in an hour or so all that + was known in fact and in fable of the renowned city of Nineveh. He had but + to read a few chapters of the Bible and a few pages of Diodorus to exhaust + the important literature on the subject. If he turned also to the pages of + Herodotus and Xenophon, of Justin and Aelian, these served chiefly to + confirm the suspicion that the Greeks themselves knew almost nothing more + of the history of their famed Oriental forerunners. The current fables + told of a first King Ninus and his wonderful queen Semiramis; of + Sennacherib the conqueror; of the effeminate Sardanapalus, who neglected + the warlike ways of his ancestors but perished gloriously at the last, + with Nineveh itself, in a self-imposed holocaust. And that was all. How + much of this was history, how much myth, no man could say; and for all any + one suspected to the contrary, no man could ever know. And to-day the + contemporary records of the city are before us in such profusion as no + other nation of antiquity, save Egypt alone, can at all rival. Whole + libraries of Assyrian books are at hand that were written in the seventh + century before our era. These, be it understood, are the original books + themselves, not copies. The author of that remote time appeals to us + directly, hand to eye, without intermediary transcriber. And there is not + a line of any Hebrew or Greek manuscript of a like age that has been + preserved to us; there is little enough that can match these ancient books + by a thousand years. When one reads Moses or Isaiah, Homer, Hesiod, or + Herodotus, he is but following the transcription—often + unquestionably faulty and probably never in all parts perfect—of + successive copyists of later generations. The oldest known copy of the + Bible, for example, dates probably from the fourth century A.D., a + thousand years or more after the last Assyrian records were made and read + and buried and forgotten. + </p> + <p> + There was at least one king of Assyria—namely, Asurbanipal, whose + palace boasted a library of some ten thousand volumes—a library, if + you please, in which the books were numbered and shelved systematically, + and classified and cared for by an official librarian. If you would see + some of the documents of this marvellous library you have but to step past + the winged lions of Asurnazirpal and enter the Assyrian hall just around + the corner from the Rosetta Stone. Indeed, the great slabs of stone from + which the lions themselves are carved are in a sense books, inasmuch as + there are written records inscribed on their surface. A glance reveals the + strange characters in which these records are written, graven neatly in + straight lines across the stone, and looking to casual inspection like + nothing so much as random flights of arrow-heads. The resemblance is so + striking that this is sometimes called the arrow-head character, though it + is more generally known as the wedge or cuneiform character. The + inscriptions on the flanks of the lions are, however, only makeshift + books. But the veritable books are no farther away than the next room + beyond the hall of Asurnazirpal. They occupy part of a series of cases + placed down the centre of this room. Perhaps it is not too much to speak + of this collection as the most extraordinary set of documents of all the + rare treasures of the British Museum, for it includes not books alone, but + public and private letters, business announcements, marriage contracts—in + a word, all the species of written records that enter into the every-day + life of an intelligent and cultured community. + </p> + <p> + But by what miracle have such documents been preserved through all these + centuries? A glance makes the secret evident. It is simply a case of + time-defying materials. Each one of these Assyrian documents appears to + be, and in reality is, nothing more or less than an inscribed fragment of + brick, having much the color and texture of a weathered terra-cotta tile + of modern manufacture. These slabs are usually oval or oblong in shape, + and from two or three to six or eight inches in length and an inch or so + in thickness. Each of them was originally a portion of brick-clay, on + which the scribe indented the flights of arrowheads with some + sharp-cornered instrument, after which the document was made permanent by + baking. They are somewhat fragile, of course, as all bricks are, and many + of them have been more or less crumbled in the destruction of the palace + at Nineveh; but to the ravages of mere time they are as nearly + invulnerable as almost anything in nature. Hence it is that these records + of a remote civilization have been preserved to us, while the similar + records of such later civilizations as the Grecian have utterly perished, + much as the flint implements of the cave-dweller come to us unchanged, + while the iron implements of a far more recent age have crumbled away. + </p> + <p> + HOW THE RECORDS WERE READ + </p> + <p> + After all, then, granted the choice of materials, there is nothing so very + extraordinary in the mere fact of preservation of these ancient records. + To be sure, it is vastly to the credit of nineteenth-century enterprise to + have searched them out and brought them back to light. But the real marvel + in connection with them is the fact that nineteenth-century scholarship + should have given us, not the material documents themselves, but a + knowledge of their actual contents. The flight of arrow-heads on wall or + slab or tiny brick have surely a meaning; but how shall we guess that + meaning? These must be words; but what words? The hieroglyphics of the + Egyptians were mysterious enough in all conscience; yet, after all, their + symbols have a certain suggestiveness, whereas there is nothing that seems + to promise a mental leverage in the unbroken succession of these cuneiform + dashes. Yet the Assyrian scholar of to-day can interpret these strange + records almost as readily and as surely as the classical scholar + interprets a Greek manuscript. And this evidences one of the greatest + triumphs of nineteenth-century scholarship, for within almost two thousand + years no man has lived, prior to our century, to whom these strange + inscriptions would not have been as meaningless as they are to the most + casual stroller who looks on them with vague wonderment here in the museum + to-day. For the Assyrian language, like the Egyptian, was veritably a dead + language; not, like Greek and Latin, merely passed from practical + every-day use to the closet of the scholar, but utterly and absolutely + forgotten by all the world. Such being the case, it is nothing less than + marvellous that it should have been restored. + </p> + <p> + It is but fair to add that this restoration probably never would have been + effected, with Assyrian or with Egyptian, had the language in dying left + no cognate successor; for the powers of modern linguistry, though great, + are not actually miraculous. But, fortunately, a language once developed + is not blotted out in toto; it merely outlives its usefulness and is + gradually supplanted, its successor retaining many traces of its origin. + So, just as Latin, for example, has its living representatives in Italian + and the other Romance tongues, the language of Assyria is represented by + cognate Semitic languages. As it chances, however, these have been of aid + rather in the later stages of Assyrian study than at the very outset; and + the first clew to the message of the cuneiform writing came through a + slightly different channel. + </p> + <p> + Curiously enough, it was a trilingual inscription that gave the clew, as + in the case of the Rosetta Stone, though with very striking difference + withal. The trilingual inscription now in question, instead of being a + small, portable monument, covers the surface of a massive bluff at + Behistun in western Persia. Moreover, all three of its inscriptions are in + cuneiform characters, and all three are in languages that at the beginning + of our century were absolutely unknown. This inscription itself, as a + striking monument of unknown import, had been seen by successive + generations. Tradition ascribed it, as we learn from Ctesias, through + Diodorus, to the fabled Assyrian queen Semiramis. Tradition was quite at + fault in this; but it is only recently that knowledge has availed to set + it right. The inscription, as is now known, was really written about the + year 515 B.C., at the instance of Darius I., King of Persia, some of whose + deeds it recounts in the three chief languages of his widely scattered + subjects. + </p> + <p> + The man who at actual risk of life and limb copied this wonderful + inscription, and through interpreting it became the veritable "father of + Assyriology," was the English general Sir Henry Rawlinson. His feat was + another British triumph over the same rivals who had competed for the + Rosetta Stone; for some French explorers had been sent by their + government, some years earlier, expressly to copy this strange record, and + had reported that it was impossible to reach the inscription. But British + courage did not find it so, and in 1835 Rawlinson scaled the dangerous + height and made a paper cast of about half the inscription. Diplomatic + duties called him away from the task for some years, but in 1848 he + returned to it and completed the copy of all parts of the inscription that + have escaped the ravages of time. And now the material was in hand for a + new science, which General Rawlinson himself soon, assisted by a host of + others, proceeded to elaborate. + </p> + <p> + The key to the value of this unique inscription lies in the fact that its + third language is ancient Persian. It appears that the ancient Persians + had adopted the cuneiform character from their western neighbors, the + Assyrians, but in so doing had made one of those essential modifications + and improvements which are scarcely possible to accomplish except in the + transition from one race to another. Instead of building with the + arrow-head a multitude of syllabic characters, including many homophones, + as had been and continued to be the custom with the Assyrians, the + Persians selected a few of these characters and ascribed to them phonetic + values that were almost purely alphabetic. In a word, while retaining the + wedge as the basal stroke of their script, they developed an alphabet, + making the last wonderful analysis of phonetic sounds which even to this + day has escaped the Chinese, which the Egyptians had only partially + effected, and which the Phoenicians were accredited by the Greeks with + having introduced to the Western world. In addition to this all-essential + step, the Persians had introduced the minor but highly convenient custom + of separating the words of a sentence from one another by a particular + mark, differing in this regard not only from the Assyrians and Egyptians, + but from the early Greek scribes as well. + </p> + <p> + Thanks to these simplifications, the old Persian language had been + practically restored about the beginning of the nineteenth century, + through the efforts of the German Grotefend, and further advances in it + were made just at this time by Renouf, in France, and by Lassen, in + Germany, as well as by Rawlinson himself, who largely solved the problem + of the Persian alphabet independently. So the Persian portion of the + Behistun inscription could be at least partially deciphered. This in + itself, however, would have been no very great aid towards the restoration + of the languages of the other portions had it not chanced, fortunately, + that the inscription is sprinkled with proper names. Now proper names, + generally speaking, are not translated from one language to another, but + transliterated as nearly as the genius of the language will permit. It was + the fact that the Greek word Ptolemaics was transliterated on the Rosetta + Stone that gave the first clew to the sounds of the Egyptian characters. + Had the upper part of the Rosetta Stone been preserved, on which, + originally, there were several other names, Young would not have halted + where he did in his decipherment. + </p> + <p> + But fortune, which had been at once so kind and so tantalizing in the case + of the Rosetta Stone, had dealt more gently with the Behistun + inscriptions; for no fewer than ninety proper names were preserved in the + Persian portion and duplicated, in another character, in the Assyrian + inscription. A study of these gave a clew to the sounds of the Assyrian + characters. The decipherment of this character, however, even with this + aid, proved enormously difficult, for it was soon evident that here it was + no longer a question of a nearly perfect alphabet of a few characters, but + of a syllabary of several hundred characters, including many homophones, + or different forms for representing the same sound. But with the Persian + translation for a guide on the one hand, and the Semitic languages, to + which family the Assyrian belonged, on the other, the appalling task was + gradually accomplished, the leading investigators being General Rawlinson, + Professor Hincks, and Mr. Fox-Talbot, in England, Professor Jules Oppert, + in Paris, and Professor Julian Schrader, in Germany, though a host of + other scholars soon entered the field. + </p> + <p> + This great linguistic feat was accomplished about the middle of the + nineteenth century. But so great a feat was it that many scholars of the + highest standing, including Joseph Erneste Renan, in France, and Sir G. + Cornewall Lewis, in England, declined at first to accept the results, + contending that the Assyriologists had merely deceived themselves by + creating an arbitrary language. The matter was put to a test in 1855 at + the suggestion of Mr. Fox-Talbot, when four scholars, one being Mr. Talbot + himself and the others General Rawlinson, Professor Hincks, and Professor + Oppert, laid before the Royal Asiatic Society their independent + interpretations of a hitherto untranslated Assyrian text. A committee of + the society, including England's greatest historian of the century, George + Grote, broke the seals of the four translations, and reported that they + found them unequivocally in accord as regards their main purport, and even + surprisingly uniform as regards the phraseology of certain passages—in + short, as closely similar as translations from the obscure texts of any + difficult language ever are. This decision gave the work of the + Assyriologists official status, and the reliability of their method has + never since been in question. Henceforth Assyriology was an established + science. + </p> + <p> + <a name="link2H_APPE" id="link2H_APPE"> + <!-- H2 anchor --> </a> + </p> + <div style="height: 4em;"> + <br /><br /><br /><br /> + </div> + <h2> + APPENDIX + </h2> +<pre xml:space="preserve"> + REFERENCE-LIST + + CHAPTER I. MODERN DEVELOPMENT OF THE PHYSICAL SCIENCES + + (1) Robert Boyle, Philosophical Works (3 vols.). London, 1738. + + CHAPTER II. THE BEGINNINGS OF MODERN CHEMISTRY + + (1) For a complete account of the controversy called the "Water + Controversy," see The Life of the Hon. Henry Cavendish, by George + Wilson, M.D., F.R.S.E. London, 1850. + + (2) Henry Cavendish, in Phil. Trans. for 1784, P. 119. + + (3) Lives of the Philosophers of the Time of George III., by Henry, Lord + Brougham, F.R.S., p. 106. London, 1855. + + (4) Experiments and Observations on Different Kinds of Air, by Joseph + Priestley (3 vols.). Birmingham, 790, vol. II, pp. 103-107. + + (5) Lectures on Experimental Philosophy, by Joseph Priestley, lecture + IV., pp. 18, ig. J. Johnson, London, 1794. + + (6) Translated from Scheele's Om Brunsten, eller Magnesia, och dess + Egenakaper. Stockholm, 1774, and published as Alembic Club Reprints, No. + 13, 1897, p. 6. + + (7) According to some writers this was discovered by Berzelius. + + (8) Histoire de la Chimie, par Ferdinand Hoefer. Paris, 1869, Vol. CL, + p. 289. + + (9) Elements of Chemistry, by Anton Laurent Lavoisier, translated by + Robert Kerr, p. 8. London and Edinburgh, 1790. + + (10) Ibid., pp. 414-416. + + CHAPTER III. CHEMISTRY SINCE THE TIME OF DALTON + + (1) Sir Humphry Davy, in Phil. Trans., Vol. VIII. + + CHAPTER IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH CENTURY + + (1) Baas, History of Medicine, p. 692. + + (2) Based on Thomas H. Huxley's Presidential Address to the British + Association for the Advancement of Science, 1870. + + (3) Essays on Digestion, by James Carson. London, 1834, p. 6. + + (4) Ibid., p. 7. + + (5) John Hunter, On the Digestion of the Stomach after Death, first + edition, pp. 183-188. + + (6) Erasmus Darwin, The Botanic Garden, pp. 448-453. London, 1799. + + CHAPTER V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH CENTURY + + (1) Baron de Cuvier's Theory of the Earth. New York, 1818, p. 123. + + (2) On the Organs and Mode of Fecundation of Orchidex and Asclepiadea, + by Robert Brown, Esq., in Miscellaneous Botanical Works. London, 1866, + Vol. I., pp. 511-514. + + (3) Justin Liebig, Animal Chemistry. London, 1843, p. 17f. + + CHAPTER VI. THEORIES OF ORGANIC EVOLUTION + + (1) "Essay on the Metamorphoses of Plants," by Goethe, translated + for the present work from Grundriss einer Geschichte der + Naturwissenschaften, by Friederich Dannemann (2 vols.). Leipzig, 1896, + Vol. I., p. 194. + + (2) The Temple of Nature, or The Origin of Society, by Erasmus Darwin, + edition published in 1807, p. 35. + + (3) Baron de Cuvier, Theory of the Earth. New York, 1818, p.74. (This + was the introduction to Cuvier's great work.) + + (4) Robert Chambers, Explanations: a sequel to Vestiges of Creation. + London, Churchill, 1845, pp. 148-153. + + CHAPTER VII. EIGHTEENTH-CENTURY MEDICINE + + (1) Condensed from Dr. Boerhaave's Academical Lectures on the Theory of + Physic. London, 1751, pp. 77, 78. Boerhaave's lectures were published as + Aphorismi de cognoscendis et curandis Morbis, Leyden, 1709. On this + book Van Swieten wrote commentaries filling five volumes. Another very + celebrated work of Boerhaave is his Institutiones et Experimenta + Chemic, Paris, 1724, the germs of this being given as a lecture on his + appointment to the chair of chemistry in the University of Leyden in + 1718. + + (2) An Inquiry into the Causes and Effects of the Variola Vaccine, etc., + by Edward Jenner, M.D., F.R.S., etc. London, 1799, pp. 2-7. He wrote + several other papers, most of which were communications to the Royal + Society. His last publication was, On the Influence of Artificial + Eruptions in Certain Diseases (London, 1822), a subject to which he had + given much time and study. + + CHAPTER VIII. NINETEENTH-CENTURY MEDICINE + + (1) In the introduction to Corvisart's translation of Avenbrugger's + work. Paris, 1808. + + (2) Laennec, Traite d'Auscultation Mediate. Paris, 1819. This was + Laennec's chief work, and was soon translated into several different + languages. Before publishing this he had written also, Propositions sur + la doctrine midicale d'Hippocrate, Paris, 1804, and Memoires sur les + vers visiculaires, in the same year. + + (3) Researches, Chemical and Philosophical, chiefly concerning Nitrous + Oxide or Dephlogisticated Nitrous Air and its Respiration, by Humphry + Davy. London, 1800, pp. 479-556. + + (4) Ibid. + + (5) For accounts of the discovery of anaesthesia, see Report of the + Board of Trustees of the Massachusetts General Hospital, Boston, 1888. + Also, The Ether Controversy: Vindication of the Hospital Reports of + 1848, by N. L Bowditch, Boston, 1848. An excellent account is given in + Littell's Living Age, for March, 1848, written by R. H. Dana, Jr. There + are also two Congressional Reports on the question of the discovery of + etherization, one for 1848, the other for 11852. + + (6) Simpson made public this discovery of the anaesthetic properties + of chloroform in a paper read before the Medico-Chirurgical Society of + Edinburgh, in March, 1847, about three months after he had first seen + a surgical operation performed upon a patient to whom ether had been + administered. + + (7) Louis Pasteur, Studies on Fermentation. London, 1870. + + (8) Louis Pasteur, in Comptes Rendus des Sciences de L'Academie des + Sciences, vol. XCII., 1881, pp. 429-435. + + CHAPTER IX. THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY + + (1) Bell's communications were made to the Royal Society, but his + studies and his discoveries in the field of anatomy of the nervous + system were collected and published, in 1824, as An Exposition of the + Natural System of Nerves of the Human Body: being a Republication of the + Papers delivered to the Royal Society on the Subject of the Nerves. + + (2) Marshall Hall, M.D., F.R.S.L., On the Reflex Functions of the + Medulla Oblongata and the Medulla Spinalis, in Phil. Trans. of Royal + Soc., vol. XXXIII., 1833. +</pre> + <p> + <br /> <br /> + </p> + <hr /> + <hr /> + <p> + <br /> <br /> + </p> + <h1> + TABLE OF CONTENTS <br /><br /> FOR THE FIVE VOLUMES + </h1> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0002"> <b>BOOK + I</b> </a> + </p> + <table summary="" style="margin-right: auto; margin-left: auto"> + <tr> + <td> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0003"> + I. PREHISTORIC SCIENCE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0004"> + II. EGYPTIAN SCIENCE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0005"> + III. SCIENCE OF BABYLONIA AND ASSYRIA </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0006"> + IV. THE DEVELOPMENT OF THE ALPHABET </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0007"> + V. THE BEGINNINGS OF GREEK SCIENCE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0008"> + VI. THE EARLY GREEK PHILOSOPHERS IN ITALY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0009"> + VII. GREEK SCIENCE IN THE EARLY ATTIC PERIOD </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0010"> + VIII. POST-SOCRATIC SCIENCE AT ATHENS—PLATO, ARISTOTLE, AND + THEOPHRASTUS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0011"> + IX. GREEK SCIENCE OF THE ALEXANDRIAN OR HELLENISTIC PERIOD </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0012"> + X. SCIENCE OF THE ROMAN PERIOD </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1705/1705-h/1705-h.htm#2H_4_0013"> + XI. A RETROSPECTIVE GLANCE AT CLASSICAL SCIENCE </a> + </p> + </td> + </tr> + </table> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0002"> <b>BOOK + II. THE BEGINNINGS OF MODERN SCIENCE</b> </a> + </p> + <table summary="" style="margin-right: auto; margin-left: auto"> + <tr> + <td> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0003"> + I. SCIENCE IN THE DARK AGE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0004"> + II. MEDIAEVAL SCIENCE AMONG THE ARABIANS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0005"> + III. MEDIAEVAL SCIENCE IN THE WEST </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0006"> + IV. THE NEW COSMOLOGY—COPERNICUS TO KEPLER AND GALILEO </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0007"> + V. GALILEO AND THE NEW PHYSICS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0008"> + VI. TWO PSEUDO-SCIENCES—ALCHEMY AND ASTROLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0009"> + VII. FROM PARACELSUS TO HARVEY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0010"> + VIII. MEDICINE IN THE SIXTEENTH AND SEVENTEENTH CENTURIES </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0011"> + IX. PHILOSOPHER-SCIENTISTS AND NEW INSTITUTIONS OF LEARNING </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0012"> + X. THE SUCCESSORS OF GALILEO IN PHYSICAL SCIENCE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0013"> + XI. NEWTON AND THE COMPOSITION OF LIGHT </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0014"> + XII. NEWTON AND THE LAW OF GRAVITATION </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0015"> + XIII. INSTRUMENTS OF PRECISION IN THE AGE OF NEWTON </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0016"> + XIV. PROGRESS IN ELECTRICITY FROM GILBERT AND VON GUERICKE TO + FRANKLIN </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1706/1706-h/1706-h.htm#2H_4_0017"> + XV. NATURAL HISTORY TO THE TIME OF LINNAEUS </a> + </p> + </td> + </tr> + </table> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0001"> <b>BOOK + III. MODERN DEVELOPMENT OF THE PHYSICAL SCIENCES</b> </a> + </p> + <table summary="" style="margin-right: auto; margin-left: auto"> + <tr> + <td> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0002"> + I. THE SUCCESSORS OF NEWTON IN ASTRONOMY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0003"> + II. THE PROGRESS OF MODERN ASTRONOMY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0004"> + III. THE NEW SCIENCE OF PALEONTOLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0005"> + IV. THE ORIGIN AND DEVELOPMENT OF MODERN GEOLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0006"> + V. THE NEW SCIENCE OF METEOROLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0007"> + VI. MODERN THEORIES OF HEAT AND LIGHT </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0008"> + VII. THE MODERN DEVELOPMENT OF ELECTRICITY AND MAGNETISM </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0009"> + VIII. THE CONSERVATION OF ENERGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1707/1707-h/1707-h.htm#2H_4_0010"> + IX. THE ETHER AND PONDERABLE MATTER </a> + </p> + </td> + </tr> + </table> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0001"> <b>BOOK + IV. MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES</b> </a> + </p> + <table summary="" style="margin-right: auto; margin-left: auto"> + <tr> + <td> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0002"> + I. THE PHLOGISTON THEORY IN CHEMISTRY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0003"> + II. THE BEGINNINGS OF MODERN CHEMISTRY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0004"> + III. CHEMISTRY SINCE THE TIME OF DALTON </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0005"> + IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH CENTURY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0006"> + V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH CENTURY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0007"> + VI. THEORIES OF ORGANIC EVOLUTION </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0008"> + VII. EIGHTEENTH-CENTURY MEDICINE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0009"> + VIII. NINETEENTH-CENTURY MEDICINE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0010"> + IX. THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/1708/1708-h/1708-h.htm#2H_4_0011"> + X. THE NEW SCIENCE OF ORIENTAL ARCHAEOLOGY </a> + </p> + </td> + </tr> + </table> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0001"> + <b>BOOK V. ASPECTS OF RECENT SCIENCE</b> </a><br /> + </p> + <table summary="" style="margin-right: auto; margin-left: auto"> + <tr> + <td> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0003"> + I. THE BRITISH MUSEUM </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0004"> + II. THE ROYAL SOCIETY OF LONDON FOR IMPROVING NATURAL KNOWLEDGE </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0005"> + III. THE ROYAL INSTITUTION AND THE LOW-TEMPERATURE RESEARCHES </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0006"> + IV. SOME PHYSICAL LABORATORIES AND PHYSICAL PROBLEMS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0007"> + V. THE MARINE BIOLOGICAL LABORATORY AT NAPLES </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0008"> + VI. ERNST HAECKEL AND THE NEW ZOOLOGY </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0009"> + VII. SOME MEDICAL LABORATORIES AND MEDICAL PROBLEMS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0010"> + VII. SOME UNSOLVED SCIENTIFIC PROBLEMS </a> + </p> + <p class="toc"> + <a + href="http://www.gutenberg.org/files/30495/30495-h/30495-h.htm#2H_4_0011"> + IX. RETROSPECT AND PROSPECT </a> + </p> + </td> + </tr> + </table> + <p> + <br /> <br /> + </p> + <hr /> + <p> + <br /> <br /> + </p> +<pre xml:space="preserve"> + + + + + +End of the Project Gutenberg EBook of A History of Science, Volume 4(of 5), by +Henry Smith Williams + +*** END OF THIS PROJECT GUTENBERG EBOOK HISTORY OF SCIENCE, V4 *** + +***** This file should be named 1708-h.htm or 1708-h.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/1/7/0/1708/ + +Produced by Charles Keller, and David Widger + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: A History of Science, Volume 4(of 5) + +Author: Henry Smith Williams + +Release Date: April, 1999 [Etext #1708] +Posting Date: November 18, 2009 + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK HISTORY OF SCIENCE, V4 *** + + + + +Produced by Charles Keller + + + + + +A HISTORY OF SCIENCE + + +By Henry Smith Williams, M.D., LL.D. + +Assisted By Edward H. Williams, M.D. + +In Five Volumes + +Volume IV. + + +MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES + + + + +BOOK IV. MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES + +AS regards chronology, the epoch covered in the present volume is +identical with that viewed in the preceding one. But now as regards +subject matter we pass on to those diverse phases of the physical world +which are the field of the chemist, and to those yet more intricate +processes which have to do with living organisms. So radical are the +changes here that we seem to be entering new worlds; and yet, here as +before, there are intimations of the new discoveries away back in the +Greek days. The solution of the problem of respiration will remind +us that Anaxagoras half guessed the secret; and in those diversified +studies which tell us of the Daltonian atom in its wonderful +transmutations, we shall be reminded again of the Clazomenian +philosopher and his successor Democritus. + +Yet we should press the analogy much too far were we to intimate that +the Greek of the elder day or any thinker of a more recent period had +penetrated, even in the vaguest way, all of the mysteries that the +nineteenth century has revealed in the fields of chemistry and biology. +At the very most the insight of those great Greeks and of the wonderful +seventeenth-century philosophers who so often seemed on the verge of our +later discoveries did no more than vaguely anticipate their successors +of this later century. To gain an accurate, really specific knowledge of +the properties of elementary bodies was reserved for the chemists of a +recent epoch. The vague Greek questionings as to organic evolution were +world-wide from the precise inductions of a Darwin. If the mediaeval +Arabian endeavored to dull the knife of the surgeon with the use of +drugs, his results hardly merit to be termed even an anticipation +of modern anaesthesia. And when we speak of preventive medicine--of +bacteriology in all its phases--we have to do with a marvellous field of +which no previous generation of men had even the slightest inkling. + +All in all, then, those that lie before us are perhaps the most +wonderful and the most fascinating of all the fields of science. As +the chapters of the preceding book carried us out into a macrocosm of +inconceivable magnitude, our present studies are to reveal a microcosm +of equally inconceivable smallness. As the studies of the physicist +attempted to reveal the very nature of matter and of energy, we have now +to seek the solution of the yet more inscrutable problems of life and of +mind. + + + + +I. THE PHLOGISTON THEORY IN CHEMISTRY + +The development of the science of chemistry from the "science" of +alchemy is a striking example of the complete revolution in the attitude +of observers in the field of science. As has been pointed out in a +preceding chapter, the alchemist, having a preconceived idea of how +things should be, made all his experiments to prove his preconceived +theory; while the chemist reverses this attitude of mind and bases his +conceptions on the results of his laboratory experiments. In short, +chemistry is what alchemy never could be, an inductive science. But +this transition from one point of view to an exactly opposite one was +necessarily a very slow process. Ideas that have held undisputed sway +over the minds of succeeding generations for hundreds of years cannot +be overthrown in a moment, unless the agent of such an overthrow be so +obvious that it cannot be challenged. The rudimentary chemistry that +overthrew alchemy had nothing so obvious and palpable. + +The great first step was the substitution of the one principle, +phlogiston, for the three principles, salt, sulphur, and mercury. We +have seen how the experiment of burning or calcining such a metal +as lead "destroyed" the lead as such, leaving an entirely different +substance in its place, and how the original metal could be restored by +the addition of wheat to the calcined product. To the alchemist this was +"mortification" and "revivification" of the metal. For, as pointed +out by Paracelsus, "anything that could be killed by man could also be +revivified by him, although this was not possible to the things killed +by God." The burning of such substances as wood, wax, oil, etc., was +also looked upon as the same "killing" process, and the fact that the +alchemist was unable to revivify them was regarded as simply the lack of +skill on his part, and in no wise affecting the theory itself. + +But the iconoclastic spirit, if not the acceptance of all the teachings, +of the great Paracelsus had been gradually taking root among the better +class of alchemists, and about the middle of the seventeenth century +Robert Boyle (1626-1691) called attention to the possibility of making +a wrong deduction from the phenomenon of the calcination of the metals, +because of a very important factor, the action of the air, which was +generally overlooked. And he urged his colleagues of the laboratories to +give greater heed to certain other phenomena that might pass unnoticed +in the ordinary calcinating process. In his work, The Sceptical Chemist, +he showed the reasons for doubting the threefold constitution of matter; +and in his General History of the Air advanced some novel and carefully +studied theories as to the composition of the atmosphere. This was an +important step, and although Boyle is not directly responsible for the +phlogiston theory, it is probable that his experiments on the atmosphere +influenced considerably the real founders, Becker and Stahl. + +Boyle gave very definitely his idea of how he thought air might be +composed. "I conjecture that the atmospherical air consists of three +different kinds of corpuscles," he says; "the first, those numberless +particles which, in the form of vapors or dry exhalations, ascend +from the earth, water, minerals, vegetables, animals, etc.; in a word, +whatever substances are elevated by the celestial or subterraneal heat, +and thence diffused into the atmosphere. The second may be yet more +subtle, and consist of those exceedingly minute atoms, the magnetical +effluvia of the earth, with other innumerable particles sent out from +the bodies of the celestial luminaries, and causing, by their influence, +the idea of light in us. The third sort is its characteristic and +essential property, I mean permanently elastic parts. Various hypotheses +may be framed relating to the structure of these later particles of the +air. They might be resembled to the springs of watches, coiled up and +endeavoring to restore themselves; to wool, which, being compressed, +has an elastic force; to slender wires of different substances, +consistencies, lengths, and thickness; in greater curls or less, +near to, or remote from each other, etc., yet all continuing springy, +expansible, and compressible. Lastly, they may also be compared to the +thin shavings of different kinds of wood, various in their lengths, +breadth, and thickness. And this, perhaps, will seem the most eligible +hypothesis, because it, in some measure, illustrates the production +of the elastic particles we are considering. For no art or curious +instruments are required to make these shavings whose curls are in no +wise uniform, but seemingly casual; and what is more remarkable, bodies +that before seemed unelastic, as beams and blocks, will afford them."(1) + +Although this explanation of the composition of the air is most crude, +it had the effect of directing attention to the fact that the +atmosphere is not "mere nothingness," but a "something" with a +definite composition, and this served as a good foundation for future +investigations. To be sure, Boyle was neither the first nor the only +chemist who had suspected that the air was a mixture of gases, and not +a simple one, and that only certain of these gases take part in the +process of calcination. Jean Rey, a French physician, and John Mayow, an +Englishman, had preformed experiments which showed conclusively that the +air was not a simple substance; but Boyle's work was better known, and +in its effect probably more important. But with all Boyle's explanations +of the composition of air, he still believed that there was an +inexplicable something, a "vital substance," which he was unable to +fathom, and which later became the basis of Stahl's phlogiston theory. +Commenting on this mysterious substance, Boyle says: "The difficulty +we find in keeping flame and fire alive, though but for a little time, +without air, renders it suspicious that there be dispersed through the +rest of the atmosphere some odd substance, either of a solar, astral, or +other foreign nature; on account of which the air is so necessary to the +substance of flame!" It was this idea that attracted the attention +of George Ernst Stahl (1660-1734), a professor of medicine in the +University of Halle, who later founded his new theory upon it. Stahl's +theory was a development of an earlier chemist, Johann Joachim Becker +(1635-1682), in whose footsteps he followed and whose experiments he +carried further. + +In many experiments Stahl had been struck with the fact that certain +substances, while differing widely, from one another in many respects, +were alike in combustibility. From this he argued that all combustible +substances must contain a common principle, and this principle he named +phlogiston. This phlogiston he believed to be intimately associated in +combination with other substances in nature, and in that condition not +perceivable by the senses; but it was supposed to escape as a substance +burned, and become apparent to the senses as fire or flame. In other +words, phlogiston was something imprisoned in a combustible structure +(itself forming part of the structure), and only liberated when this +structure was destroyed. Fire, or flame, was FREE phlogiston, while the +imprisoned phlogiston was called COMBINED PHLOGISTON, or combined fire. +The peculiar quality of this strange substance was that it disliked +freedom and was always striving to conceal itself in some combustible +substance. Boyle's tentative suggestion that heat was simply motion was +apparently not accepted by Stahl, or perhaps it was unknown to him. + +According to the phlogistic theory, the part remaining after a substance +was burned was simply the original substance deprived of phlogiston. To +restore the original combustible substance, it was necessary to heat the +residue of the combustion with something that burned easily, so that the +freed phlogiston might again combine with the ashes. This was explained +by the supposition that the more combustible a substance was the more +phlogiston it contained, and since free phlogiston sought always to +combine with some suitable substance, it was only necessary to mix the +phlogisticating agents, such as charcoal, phosphorus, oils, fats, etc., +with the ashes of the original substance, and heat the mixture, the +phlogiston thus freed uniting at once with the ashes. This theory fitted +very nicely as applied to the calcined lead revivified by the grains of +wheat, although with some other products of calcination it did not seem +to apply at all. + +It will be seen from this that the phlogistic theory was a step towards +chemistry and away from alchemy. It led away from the idea of a "spirit" +in metals that could not be seen, felt, or appreciated by any of the +senses, and substituted for it a principle which, although a falsely +conceived one, was still much more tangible than the "spirit," since it +could be seen and felt as free phlogiston and weighed and measured as +combined phlogiston. The definiteness of the statement that a metal, +for example, was composed of phlogiston and an element was much less +enigmatic, even if wrong, than the statement of the alchemist that +"metals are produced by the spiritual action of the three principles, +salt, mercury, sulphur"--particularly when it is explained that salt, +mercury, and sulphur were really not what their names implied, and that +there was no universally accepted belief as to what they really were. + +The metals, which are now regarded as elementary bodies, were considered +compounds by the phlogistians, and they believed that the calcining of +a metal was a process of simplification. They noted, however, that the +remains of calcination weighed more than the original product, and the +natural inference from this would be that the metal must have taken in +some substance rather than have given off anything. But the phlogistians +had not learned the all-important significance of weights, and their +explanation of variation in weight was either that such gain or loss +was an unimportant "accident" at best, or that phlogiston, being light, +tended to lighten any substance containing it, so that driving it out of +the metal by calcination naturally left the residue heavier. + +At first the phlogiston theory seemed to explain in an indisputable way +all the known chemical phenomena. Gradually, however, as experiments +multiplied, it became evident that the plain theory as stated by Stahl +and his followers failed to explain satisfactorily certain laboratory +reactions. To meet these new conditions, certain modifications were +introduced from time to time, giving the theory a flexibility that +would allow it to cover all cases. But as the number of inexplicable +experiments continued to increase, and new modifications to the theory +became necessary, it was found that some of these modifications were +directly contradictory to others, and thus the simple theory became +too cumbersome from the number of its modifications. Its supporters +disagreed among themselves, first as to the explanation of certain +phenomena that did not seem to accord with the phlogistic theory, and +a little later as to the theory itself. But as yet there was no +satisfactory substitute for this theory, which, even if unsatisfactory, +seemed better than anything that had gone before or could be suggested. + +But the good effects of the era of experimental research, to which the +theory of Stahl had given such an impetus, were showing in the attitude +of the experimenters. The works of some of the older writers, such +as Boyle and Hooke, were again sought out in their dusty corners and +consulted, and their surmises as to the possible mixture of various +gases in the air were more carefully considered. Still the phlogiston +theory was firmly grounded in the minds of the philosophers, who can +hardly be censured for adhering to it, at least until some satisfactory +substitute was offered. The foundation for such a theory was finally +laid, as we shall see presently, by the work of Black, Priestley, +Cavendish, and Lavoisier, in the eighteenth century, but the phlogiston +theory cannot be said to have finally succumbed until the opening years +of the nineteenth century. + + + + +II. THE BEGINNINGS OF MODERN CHEMISTRY + +THE "PNEUMATIC" CHEMISTS + +Modern chemistry may be said to have its beginning with the work of +Stephen Hales (1677-1761), who early in the eighteenth century began his +important study of the elasticity of air. Departing from the point of +view of most of the scientists of the time, he considered air to be "a +fine elastic fluid, with particles of very different nature floating in +it"; and he showed that these "particles" could be separated. He pointed +out, also, that various gases, or "airs," as he called them, were +contained in many solid substances. The importance of his work, however, +lies in the fact that his general studies were along lines leading away +from the accepted doctrines of the time, and that they gave the impetus +to the investigation of the properties of gases by such chemists as +Black, Priestley, Cavendish, and Lavoisier, whose specific discoveries +are the foundation-stones of modern chemistry. + + +JOSEPH BLACK + +The careful studies of Hales were continued by his younger confrere, Dr. +Joseph Black (1728-1799), whose experiments in the weights of gases and +other chemicals were first steps in quantitative chemistry. But even +more important than his discoveries of chemical properties in general +was his discovery of the properties of carbonic-acid gas. + +Black had been educated for the medical profession in the University of +Glasgow, being a friend and pupil of the famous Dr. William Cullen. But +his liking was for the chemical laboratory rather than for the practice +of medicine. Within three years after completing his medical course, +and when only twenty-three years of age, he made the discovery of the +properties of carbonic acid, which he called by the name of "fixed air." +After discovering this gas, Black made a long series of experiments, +by which he was able to show how widely it was distributed throughout +nature. Thus, in 1757, he discovered that the bubbles given off in +the process of brewing, where there was vegetable fermentation, were +composed of it. To prove this, he collected the contents of these +bubbles in a bottle containing lime-water. When this bottle was +shaken violently, so that the lime-water and the carbonic acid became +thoroughly mixed, an insoluble white powder was precipitated from the +solution, the carbonic acid having combined chemically with the lime +to form the insoluble calcium carbonate, or chalk. This experiment +suggested another. Fixing a piece of burning charcoal in the end of a +bellows, he arranged a tube so that the gas coming from the charcoal +would pass through the lime-water, and, as in the case of the bubbles +from the brewer's vat, he found that the white precipitate was thrown +down; in short, that carbonic acid was given off in combustion. Shortly +after, Black discovered that by blowing through a glass tube inserted +into lime-water, chalk was precipitated, thus proving that carbonic acid +was being constantly thrown off in respiration. + +The effect of Black's discoveries was revolutionary, and the attitude +of mind of the chemists towards gases, or "airs," was changed from that +time forward. Most of the chemists, however, attempted to harmonize the +new facts with the older theories--to explain all the phenomena on the +basis of the phlogiston theory, which was still dominant. But while many +of Black's discoveries could not be made to harmonize with that +theory, they did not directly overthrow it. It required the additional +discoveries of some of Black's fellow-scientists to complete its +downfall, as we shall see. + + +HENRY CAVENDISH + +This work of Black's was followed by the equally important work of +his former pupil, Henry Cavendish (1731-1810), whose discovery of the +composition of many substances, notably of nitric acid and of water, +was of great importance, adding another link to the important chain of +evidence against the phlogiston theory. Cavendish is one of the most +eccentric figures in the history of science, being widely known in his +own time for his immense wealth and brilliant intellect, and also for +his peculiarities and his morbid sensibility, which made him dread +society, and probably did much in determining his career. Fortunately +for him, and incidentally for the cause of science, he was able to +pursue laboratory investigations without being obliged to mingle with +his dreaded fellow-mortals, his every want being provided for by the +immense fortune inherited from his father and an uncle. + +When a young man, as a pupil of Dr. Black, he had become imbued with the +enthusiasm of his teacher, continuing Black's investigations as to the +properties of carbonic-acid gas when free and in combination. One of his +first investigations was reported in 1766, when he communicated to +the Royal Society his experiments for ascertaining the properties of +carbonic-acid and hydrogen gas, in which he first showed the possibility +of weighing permanently elastic fluids, although Torricelli had before +this shown the relative weights of a column of air and a column of +mercury. Other important experiments were continued by Cavendish, and +in 1784 he announced his discovery of the composition of water, thus +robbing it of its time-honored position as an "element." But his +claim to priority in this discovery was at once disputed by his +fellow-countryman James Watt and by the Frenchman Lavoisier. Lavoisier's +claim was soon disallowed even by his own countrymen, but for many +years a bitter controversy was carried on by the partisans of Watt and +Cavendish. The two principals, however, seem never to have entered +into this controversy with anything like the same ardor as some of their +successors, as they remained on the best of terms.(1) It is certain, at +any rate, that Cavendish announced his discovery officially before Watt +claimed that the announcement had been previously made by him, "and, +whether right or wrong, the honor of scientific discoveries seems to be +accorded naturally to the man who first publishes a demonstration of his +discovery." Englishmen very generally admit the justness of Cavendish's +claim, although the French scientist Arago, after reviewing the evidence +carefully in 1833, decided in favor of Watt. + +It appears that something like a year before Cavendish made known his +complete demonstration of the composition of water, Watt communicated +to the Royal Society a suggestion that water was composed of +"dephlogisticated air (oxygen) and phlogiston (hydrogen) deprived of +part of its latent heat." Cavendish knew of the suggestion, but in his +experiments refuted the idea that the hydrogen lost any of its latent +heat. Furthermore, Watt merely suggested the possible composition +without proving it, although his idea was practically correct, if we can +rightly interpret the vagaries of the nomenclature then in use. But +had Watt taken the steps to demonstrate his theory, the great "Water +Controversy" would have been avoided. Cavendish's report of his +discovery to the Royal Society covers something like forty pages of +printed matter. In this he shows how, by passing an electric spark +through a closed jar containing a mixture of hydrogen gas and oxygen, +water is invariably formed, apparently by the union of the two gases. +The experiment was first tried with hydrogen and common air, the oxygen +of the air uniting with the hydrogen to form water, leaving the nitrogen +of the air still to be accounted for. With pure oxygen and hydrogen, +however, Cavendish found that pure water was formed, leaving slight +traces of any other, substance which might not be interpreted as being +Chemical impurities. There was only one possible explanation of this +phenomenon--that hydrogen and oxygen, when combined, form water. + +"By experiments with the globe it appeared," wrote Cavendish, "that when +inflammable and common air are exploded in a proper proportion, almost +all the inflammable air, and near one-fifth the common air, lose their +elasticity and are condensed into dew. And by this experiment it appears +that this dew is plain water, and consequently that almost all the +inflammable air is turned into pure water. + +"In order to examine the nature of the matter condensed on firing a +mixture of dephlogisticated and inflammable air, I took a glass +globe, holding 8800 grain measures, furnished with a brass cock and an +apparatus for firing by electricity. This globe was well exhausted by +an air-pump, and then filled with a mixture of inflammable and +dephlogisticated air by shutting the cock, fastening the bent glass tube +into its mouth, and letting up the end of it into a glass jar inverted +into water and containing a mixture of 19,500 grain measures of +dephlogisticated air, and 37,000 of inflammable air; so that, upon +opening the cock, some of this mixed air rushed through the bent tube +and filled the globe. The cock was then shut and the included air fired +by electricity, by means of which almost all of it lost its elasticity +(was condensed into water vapors). The cock was then again opened so as +to let in more of the same air to supply the place of that destroyed by +the explosion, which was again fired, and the operation continued till +almost the whole of the mixture was let into the globe and exploded. +By this means, though the globe held not more than a sixth part of the +mixture, almost the whole of it was exploded therein without any fresh +exhaustion of the globe." + +At first this condensed matter was "acid to the taste and contained +two grains of nitre," but Cavendish, suspecting that this was due to +impurities, tried another experiment that proved conclusively that his +opinions were correct. "I therefore made another experiment," he says, +"with some more of the same air from plants in which the proportion of +inflammable air was greater, so that the burnt air was almost completely +phlogisticated, its standard being one-tenth. The condensed liquor was +then not at all acid, but seemed pure water." + +From these experiments he concludes "that when a mixture of inflammable +and dephlogisticated air is exploded, in such proportions that the burnt +air is not much phlogisticated, the condensed liquor contains a little +acid which is always of the nitrous kind, whatever substance the +dephlogisticated air is procured from; but if the proportion be such +that the burnt air is almost entirely phlogisticated, the condensed +liquor is not at all acid, but seems pure water, without any addition +whatever."(2) + +These same experiments, which were undertaken to discover the +composition of water, led him to discover also the composition of nitric +acid. He had observed that, in the combustion of hydrogen gas with +common air, the water was slightly tinged with acid, but that this +was not the case when pure oxygen gas was used. Acting upon this +observation, he devised an experiment to determine the nature of this +acid. He constructed an apparatus whereby an electric spark was passed +through a vessel containing common air. After this process had been +carried on for several weeks a small amount of liquid was formed. This +liquid combined with a solution of potash to form common nitre, which +"detonated with charcoal, sparkled when paper impregnated with it was +burned, and gave out nitrous fumes when sulphuric acid was poured on +it." In other words, the liquid was shown to be nitric acid. Now, since +nothing but pure air had been used in the initial experiment, and since +air is composed of nitrogen and oxygen, there seemed no room to doubt +that nitric acid is a combination of nitrogen and oxygen. + +This discovery of the nature of nitric acid seems to have been about the +last work of importance that Cavendish did in the field of chemistry, +although almost to the hour of his death he was constantly occupied with +scientific observations. Even in the last moments of his life this habit +asserted itself, according to Lord Brougham. "He died on March 10, 1810, +after a short illness, probably the first, as well as the last, which he +ever suffered. His habit of curious observation continued to the end. +He was desirous of marking the progress of the disease and the gradual +extinction of the vital powers. With these ends in view, that he might +not be disturbed, he desired to be left alone. His servant, returning +sooner than he had wished, was ordered again to leave the chamber of +death, and when he came back a second time he found his master had +expired."(3) + + +JOSEPH PRIESTLEY + +While the opulent but diffident Cavendish was making his important +discoveries, another Englishman, a poor country preacher named Joseph +Priestley (1733-1804) was not only rivalling him, but, if anything, +outstripping him in the pursuit of chemical discoveries. In 1761 this +young minister was given a position as tutor in a nonconformist academy +at Warrington, and here, for six years, he was able to pursue his +studies in chemistry and electricity. In 1766, while on a visit to +London, he met Benjamin Franklin, at whose suggestion he published his +History of Electricity. From this time on he made steady progress in +scientific investigations, keeping up his ecclesiastical duties at the +same time. In 1780 he removed to Birmingham, having there for associates +such scientists as James Watt, Boulton, and Erasmus Darwin. + +Eleven years later, on the anniversary of the fall of the Bastile in +Paris, a fanatical mob, knowing Priestley's sympathies with the +French revolutionists, attacked his house and chapel, burning both and +destroying a great number of valuable papers and scientific instruments. +Priestley and his family escaped violence by flight, but his most +cherished possessions were destroyed; and three years later he quitted +England forever, removing to the United States, whose struggle for +liberty he had championed. The last ten years of his life were spent +at Northumberland, Pennsylvania, where he continued his scientific +researches. + +Early in his scientific career Priestley began investigations upon the +"fixed air" of Dr. Black, and, oddly enough, he was stimulated to this +by the same thing that had influenced Black--that is, his residence in +the immediate neighborhood of a brewery. It was during the course of a +series of experiments on this and other gases that he made his greatest +discovery, that of oxygen, or "dephlogisticated air," as he called +it. The story of this important discovery is probably best told in +Priestley's own words: + +"There are, I believe, very few maxims in philosophy that have laid +firmer hold upon the mind than that air, meaning atmospheric air, is a +simple elementary substance, indestructible and unalterable, at least as +much so as water is supposed to be. In the course of my inquiries I +was, however, soon satisfied that atmospheric air is not an unalterable +thing; for that, according to my first hypothesis, the phlogiston with +which it becomes loaded from bodies burning in it, and the animals +breathing it, and various other chemical processes, so far alters +and depraves it as to render it altogether unfit for inflammation, +respiration, and other purposes to which it is subservient; and I had +discovered that agitation in the water, the process of vegetation, and +probably other natural processes, restore it to its original purity.... + +"Having procured a lens of twelve inches diameter and twenty inches +local distance, I proceeded with the greatest alacrity, by the help of +it, to discover what kind of air a great variety of substances would +yield, putting them into the vessel, which I filled with quicksilver, +and kept inverted in a basin of the same .... With this apparatus, after +a variety of experiments.... on the 1st of August, 1774, I endeavored +to extract air from mercurius calcinatus per se; and I presently found +that, by means of this lens, air was expelled from it very readily. +Having got about three or four times as much as the bulk of my +materials, I admitted water to it, and found that it was not imbibed +by it. But what surprised me more than I can express was that a candle +burned in this air with a remarkably vigorous flame, very much like that +enlarged flame with which a candle burns in nitrous oxide, exposed to +iron or liver of sulphur; but as I had got nothing like this remarkable +appearance from any kind of air besides this particular modification of +vitrous air, and I knew no vitrous acid was used in the preparation of +mercurius calcinatus, I was utterly at a loss to account for it."(4) + + +The "new air" was, of course, oxygen. Priestley at once proceeded to +examine it by a long series of careful experiments, in which, as will +be seen, he discovered most of the remarkable qualities of this gas. +Continuing his description of these experiments, he says: + +"The flame of the candle, besides being larger, burned with more +splendor and heat than in that species of nitrous air; and a piece of +red-hot wood sparkled in it, exactly like paper dipped in a solution of +nitre, and it consumed very fast; an experiment that I had never thought +of trying with dephlogisticated nitrous air. + +"... I had so little suspicion of the air from the mercurius calcinatus, +etc., being wholesome, that I had not even thought of applying it to +the test of nitrous air; but thinking (as my reader must imagine I +frequently must have done) on the candle burning in it after long +agitation in water, it occurred to me at last to make the experiment; +and, putting one measure of nitrous air to two measures of this air, I +found not only that it was diminished, but that it was diminished quite +as much as common air, and that the redness of the mixture was likewise +equal to a similar mixture of nitrous and common air.... The next day I +was more surprised than ever I had been before with finding that, after +the above-mentioned mixture of nitrous air and the air from mercurius +calcinatus had stood all night,... a candle burned in it, even better +than in common air." + +A little later Priestley discovered that "dephlogisticated air... is a +principal element in the composition of acids, and may be extracted by +means of heat from many substances which contain them.... It is likewise +produced by the action of light upon green vegetables; and this seems to +be the chief means employed to preserve the purity of the atmosphere." + +This recognition of the important part played by oxygen in the +atmosphere led Priestley to make some experiments upon mice and insects, +and finally upon himself, by inhalations of the pure gas. "The feeling +in my lungs," he said, "was not sensibly different from that of common +air, but I fancied that my breathing felt peculiarly light and easy for +some time afterwards. Who can tell but that in time this pure air may +become a fashionable article in luxury?... Perhaps we may from these +experiments see that though pure dephlogisticated air might be useful as +a medicine, it might not be so proper for us in the usual healthy state +of the body." + +This suggestion as to the possible usefulness of oxygen as a medicine +was prophetic. A century later the use of oxygen had become a matter of +routine practice with many physicians. Even in Priestley's own time such +men as Dr. John Hunter expressed their belief in its efficacy in certain +conditions, as we shall see, but its value in medicine was not fully +appreciated until several generations later. + +Several years after discovering oxygen Priestley thus summarized its +properties: "It is this ingredient in the atmospheric air that enables +it to support combustion and animal life. By means of it most intense +heat may be produced, and in the purest of it animals will live nearly +five times as long as in an equal quantity of atmospheric air. In +respiration, part of this air, passing the membranes of the lungs, +unites with the blood and imparts to it its florid color, while the +remainder, uniting with phlogiston exhaled from venous blood, forms +mixed air. It is dephlogisticated air combined with water that enables +fishes to live in it."(5) + + +KARL WILHELM SCHEELE + +The discovery of oxygen was the last but most important blow to the +tottering phlogiston theory, though Priestley himself would not admit +it. But before considering the final steps in the overthrow of Stahl's +famous theory and the establishment of modern chemistry, we must review +the work of another great chemist, Karl Wilhelm Scheele (1742-1786), of +Sweden, who discovered oxygen quite independently, although later than +Priestley. In the matter of brilliant discoveries in a brief space of +time Scheele probably eclipsed all his great contemporaries. He had a +veritable genius for interpreting chemical reactions and discovering +new substances, in this respect rivalling Priestley himself. Unlike +Priestley, however, he planned all his experiments along the lines of +definite theories from the beginning, the results obtained being the +logical outcome of a predetermined plan. + +Scheele was the son of a merchant of Stralsund, Pomerania, which then +belonged to Sweden. As a boy in school he showed so little aptitude for +the study of languages that he was apprenticed to an apothecary at the +age of fourteen. In this work he became at once greatly interested, and, +when not attending to his duties in the dispensary, he was busy day and +night making experiments or studying books on chemistry. In 1775, still +employed as an apothecary, he moved to Stockholm, and soon after he sent +to Bergman, the leading chemist of Sweden, his first discovery--that of +tartaric acid, which he had isolated from cream of tartar. This was the +beginning of his career of discovery, and from that time on until his +death he sent forth accounts of new discoveries almost uninterruptedly. +Meanwhile he was performing the duties of an ordinary apothecary, and +struggling against poverty. His treatise upon Air and Fire appeared +in 1777. In this remarkable book he tells of his discovery of +oxygen--"empyreal" or "fire-air," as he calls it--which he seems to +have made independently and without ever having heard of the previous +discovery by Priestley. In this book, also, he shows that air is +composed chiefly of oxygen and nitrogen gas. + +Early in his experimental career Scheele undertook the solution of +the composition of black oxide of manganese, a substance that had long +puzzled the chemists. He not only succeeded in this, but incidentally in +the course of this series of experiments he discovered oxygen, baryta, +and chlorine, the last of far greater importance, at least commercially, +than the real object of his search. In speaking of the experiment in +which the discovery was made he says: + +"When marine (hydrochloric) acid stood over manganese in the cold it +acquired a dark reddish-brown color. As manganese does not give any +colorless solution without uniting with phlogiston (probably meaning +hydrogen), it follows that marine acid can dissolve it without this +principle. But such a solution has a blue or red color. The color is +here more brown than red, the reason being that the very finest portions +of the manganese, which do not sink so easily, swim in the red solution; +for without these fine particles the solution is red, and red mixed with +black is brown. The manganese has here attached itself so loosely to +acidum salis that the water can precipitate it, and this precipitate +behaves like ordinary manganese. When, now, the mixture of manganese and +spiritus salis was set to digest, there arose an effervescence and smell +of aqua regis."(6) + +The "effervescence" he refers to was chlorine, which he proceeded to +confine in a suitable vessel and examine more fully. He described it as +having a "quite characteristically suffocating smell," which was very +offensive. He very soon noted the decolorizing or bleaching effects of +this now product, finding that it decolorized flowers, vegetables, and +many other substances. + +Commercially this discovery of chlorine was of enormous importance and +the practical application of this new chemical in bleaching cloth soon +supplanted the old process of crofting--that is, bleaching by spreading +the cloth upon the grass. But although Scheele first pointed out the +bleaching quality of his newly discovered gas, it was the French savant, +Berthollet, who, acting upon Scheele's discovery that the new gas would +decolorize vegetables and flowers, was led to suspect that this property +might be turned to account in destroying the color of cloth. In 1785 he +read a paper before the Academy of Sciences of Paris, in which he showed +that bleaching by chlorine was entirely satisfactory, the color but +not the substance of the cloth being affected. He had experimented +previously and found that the chlorine gas was soluble in water and +could thus be made practically available for bleaching purposes. In 1786 +James Watt examined specimens of the bleached cloth made by Berthollet, +and upon his return to England first instituted the process of practical +bleaching. His process, however, was not entirely satisfactory, and, +after undergoing various modifications and improvements, it was finally +made thoroughly practicable by Mr. Tennant, who hit upon a compound of +chlorine and lime--the chloride of lime--which was a comparatively cheap +chemical product, and answered the purpose better even than chlorine +itself. + +To appreciate how momentous this discovery was to cloth manufacturers, +it should be remembered that the old process of bleaching consumed an +entire summer for the whitening of a single piece of linen; the new +process reduced the period to a few hours. To be sure, lime had been +used with fair success previous to Tennant's discovery, but successful +and practical bleaching by a solution of chloride of lime was first made +possible by him and through Scheele's discovery of chlorine. + +Until the time of Scheele the great subject of organic chemistry had +remained practically unexplored, but under the touch of his marvellous +inventive genius new methods of isolating and studying animal and +vegetable products were introduced, and a large number of acids and +other organic compounds prepared that had been hitherto unknown. His +explanations of chemical phenomena were based on the phlogiston theory, +in which, like Priestley, he always, believed. Although in error in +this respect, he was, nevertheless, able to make his discoveries with +extremely accurate interpretations. A brief epitome of the list of some +of his more important discoveries conveys some idea, of his fertility of +mind as well as his industry. In 1780 he discovered lactic acid,(7) and +showed that it was the substance that caused the acidity of sour +milk; and in the same year he discovered mucic acid. Next followed the +discovery of tungstic acid, and in 1783 he added to his list of useful +discoveries that of glycerine. Then in rapid succession came his +announcements of the new vegetable products citric, malic, oxalic, and +gallic acids. Scheele not only made the discoveries, but told the +world how he had made them--how any chemist might have made them if +he chose--for he never considered that he had really discovered any +substance until he had made it, decomposed it, and made it again. + +His experiments on Prussian blue are most interesting, not only because +of the enormous amount of work involved and the skill he displayed in +his experiments, but because all the time the chemist was handling, +smelling, and even tasting a compound of one of the most deadly poisons, +ignorant of the fact that the substance was a dangerous one to handle. +His escape from injury seems almost miraculous; for his experiments, +which were most elaborate, extended over a considerable period of time, +during which he seems to have handled this chemical with impunity. + +While only forty years of age and just at the zenith of his fame, +Scheele was stricken by a fatal illness, probably induced by his +ceaseless labor and exposure. It is gratifying to know, however, that +during the last eight or nine years of his life he had been less bound +down by pecuniary difficulties than before, as Bergman had obtained for +him an annual grant from the Academy. But it was characteristic of the +man that, while devoting one-sixth of the amount of this grant to his +personal wants, the remaining five-sixths was devoted to the expense of +his experiments. + + +LAVOISIER AND THE FOUNDATION OF MODERN CHEMISTRY + +The time was ripe for formulating the correct theory of chemical +composition: it needed but the master hand to mould the materials into +the proper shape. The discoveries in chemistry during the eighteenth +century had been far-reaching and revolutionary in character. A brief +review of these discoveries shows how completely they had subverted +the old ideas of chemical elements and chemical compounds. Of the four +substances earth, air, fire, and water, for many centuries believed +to be elementary bodies, not one has stood the test of the +eighteenth-century chemists. Earth had long since ceased to be regarded +as an element, and water and air had suffered the same fate in this +century. And now at last fire itself, the last of the four "elements" +and the keystone to the phlogiston arch, was shown to be nothing more +than one of the manifestations of the new element, oxygen, and not +"phlogiston" or any other intangible substance. + +In this epoch of chemical discoveries England had produced such mental +giants and pioneers in science as Black, Priestley, and Cavendish; +Sweden had given the world Scheele and Bergman, whose work, added to +that of their English confreres, had laid the broad base of chemistry +as a science; but it was for France to produce a man who gave the +final touches to the broad but rough workmanship of its foundation, +and establish it as the science of modern chemistry. It was for Antoine +Laurent Lavoisier (1743-1794) to gather together, interpret correctly, +rename, and classify the wealth of facts that his immediate predecessors +and contemporaries had given to the world. + +The attitude of the mother-countries towards these illustrious sons is +an interesting piece of history. Sweden honored and rewarded Scheele +and Bergman for their efforts; England received the intellectuality of +Cavendish with less appreciation than the Continent, and a fanatical mob +drove Priestley out of the country; while France, by sending Lavoisier +to the guillotine, demonstrated how dangerous it was, at that time +at least, for an intelligent Frenchman to serve his fellowman and his +country well. + +"The revolution brought about by Lavoisier in science," says Hoefer, +"coincides by a singular act of destiny with another revolution, much +greater indeed, going on then in the political and social world. Both +happened on the same soil, at the same epoch, among the same people; +and both marked the commencement of a new era in their respective +spheres."(8) + +Lavoisier was born in Paris, and being the son of an opulent family, +was educated under the instruction of the best teachers of the day. With +Lacaille he studied mathematics and astronomy; with Jussieu, botany; +and, finally, chemistry under Rouelle. His first work of importance was +a paper on the practical illumination of the streets of Paris, for which +a prize had been offered by M. de Sartine, the chief of police. This +prize was not awarded to Lavoisier, but his suggestions were of such +importance that the king directed that a gold medal be bestowed upon the +young author at the public sitting of the Academy in April, 1776. Two +years later, at the age of thirty-five, Lavoisier was admitted a member +of the Academy. + +In this same year he began to devote himself almost exclusively to +chemical inquiries, and established a laboratory in his home, fitted +with all manner of costly apparatus and chemicals. Here he was in +constant communication with the great men of science of Paris, to all of +whom his doors were thrown open. One of his first undertakings in this +laboratory was to demonstrate that water could not be converted into +earth by repeated distillations, as was generally advocated; and to show +also that there was no foundation to the existing belief that it was +possible to convert water into a gas so "elastic" as to pass through +the pores of a vessel. He demonstrated the fallaciousness of both these +theories in 1768-1769 by elaborate experiments, a single investigation +of this series occupying one hundred and one days. + +In 1771 he gave the first blow to the phlogiston theory by his +experiments on the calcination of metals. It will be recalled that one +basis for the belief in phlogiston was the fact that when a metal was +calcined it was converted into an ash, giving up its "phlogiston" in the +process. To restore the metal, it was necessary to add some substance +such as wheat or charcoal to the ash. Lavoisier, in examining this +process of restoration, found that there was always evolved a great +quantity of "air," which he supposed to be "fixed air" or carbonic +acid--the same that escapes in effervescence of alkalies and calcareous +earths, and in the fermentation of liquors. He then examined the process +of calcination, whereby the phlogiston of the metal was supposed to +have been drawn off. But far from finding that phlogiston or any other +substance had been driven off, he found that something had been taken +on: that the metal "absorbed air," and that the increased weight of the +metal corresponded to the amount of air "absorbed." Meanwhile he +was within grasp of two great discoveries, that of oxygen and of the +composition of the air, which Priestley made some two years later. + +The next important inquiry of this great Frenchman was as to the +composition of diamonds. With the great lens of Tschirnhausen belonging +to the Academy he succeeded in burning up several diamonds, regardless +of expense, which, thanks to his inheritance, he could ignore. In this +process he found that a gas was given off which precipitated lime from +water, and proved to be carbonic acid. Observing this, and experimenting +with other substances known to give off carbonic acid in the same +manner, he was evidently impressed with the now well-known fact that +diamond and charcoal are chemically the same. But if he did really +believe it, he was cautious in expressing his belief fully. "We should +never have expected," he says, "to find any relation between charcoal +and diamond, and it would be unreasonable to push this analogy too far; +it only exists because both substances seem to be properly ranged in the +class of combustible bodies, and because they are of all these bodies +the most fixed when kept from contact with air." + +As we have seen, Priestley, in 1774, had discovered oxygen, or +"dephlogisticated air." Four years later Lavoisier first advanced his +theory that this element discovered by Priestley was the universal +acidifying or oxygenating principle, which, when combined with charcoal +or carbon, formed carbonic acid; when combined with sulphur, formed +sulphuric (or vitriolic) acid; with nitrogen, formed nitric acid, +etc., and when combined with the metals formed oxides, or calcides. +Furthermore, he postulated the theory that combustion was not due to any +such illusive thing as "phlogiston," since this did not exist, and it +seemed to him that the phenomena of combustion heretofore attributed to +phlogiston could be explained by the action of the new element oxygen +and heat. This was the final blow to the phlogiston theory, which, +although it had been tottering for some time, had not been completely +overthrown. + +In 1787 Lavoisier, in conjunction with Guyon de Morveau, Berthollet, +and Fourcroy, introduced the reform in chemical nomenclature which until +then had remained practically unchanged since alchemical days. Such +expressions as "dephlogisticated" and "phlogisticated" would obviously +have little meaning to a generation who were no longer to believe in +the existence of phlogiston. It was appropriate that a revolution in +chemical thought should be accompanied by a corresponding revolution in +chemical names, and to Lavoisier belongs chiefly the credit of bringing +about this revolution. In his Elements of Chemistry he made use of this +new nomenclature, and it seemed so clearly an improvement over the +old that the scientific world hastened to adopt it. In this connection +Lavoisier says: "We have, therefore, laid aside the expression metallic +calx altogether, and have substituted in its place the word oxide. By +this it may be seen that the language we have adopted is both copious +and expressive. The first or lowest degree of oxygenation in bodies +converts them into oxides; a second degree of additional oxygenation +constitutes the class of acids of which the specific names drawn from +their particular bases terminate in ous, as in the nitrous and the +sulphurous acids. The third degree of oxygenation changes these into the +species of acids distinguished by the termination in ic, as the nitric +and sulphuric acids; and, lastly, we can express a fourth or higher +degree of oxygenation by adding the word oxygenated to the name of the +acid, as has already been done with oxygenated muriatic acid."(9) + +This new work when given to the world was not merely an epoch-making +book; it was revolutionary. It not only discarded phlogiston altogether, +but set forth that metals are simple elements, not compounds of "earth" +and "phlogiston." It upheld Cavendish's demonstration that water itself, +like air, is a compound of oxygen with another element. In short, it was +scientific chemistry, in the modern acceptance of the term. + +Lavoisier's observations on combustion are at once important and +interesting: "Combustion," he says, "... is the decomposition of oxygen +produced by a combustible body. The oxygen which forms the base of this +gas is absorbed by and enters into combination with the burning body, +while the caloric and light are set free. Every combustion necessarily +supposes oxygenation; whereas, on the contrary, every oxygenation +does not necessarily imply concomitant combustion; because combustion +properly so called cannot take place without disengagement of caloric +and light. Before combustion can take place, it is necessary that the +base of oxygen gas should have greater affinity to the combustible body +than it has to caloric; and this elective attraction, to use Bergman's +expression, can only take place at a certain degree of temperature which +is different for each combustible substance; hence the necessity of +giving the first motion or beginning to every combustion by the approach +of a heated body. This necessity of heating any body we mean to burn +depends upon certain considerations which have not hitherto been +attended to by any natural philosopher, for which reason I shall enlarge +a little upon the subject in this place: + +"Nature is at present in a state of equilibrium, which cannot have been +attained until all the spontaneous combustions or oxygenations possible +in an ordinary degree of temperature had taken place.... To illustrate +this abstract view of the matter by example: Let us suppose the usual +temperature of the earth a little changed, and it is raised only to the +degree of boiling water; it is evident that in this case phosphorus, +which is combustible in a considerably lower degree of temperature, +would no longer exist in nature in its pure and simple state, but would +always be procured in its acid or oxygenated state, and its radical +would become one of the substances unknown to chemistry. By gradually +increasing the temperature of the earth, the same circumstance would +successively happen to all the bodies capable of combustion; and, at +the last, every possible combustion having taken place, there would +no longer exist any combustible body whatever, and every substance +susceptible of the operation would be oxygenated and consequently +incombustible. + +"There cannot, therefore, exist, as far as relates to us, any +combustible body but such as are non-combustible at the ordinary +temperature of the earth, or, what is the same thing in other words, +that it is essential to the nature of every combustible body not to +possess the property of combustion unless heated, or raised to a degree +of temperature at which its combustion naturally takes place. When this +degree is once produced, combustion commences, and the caloric which +is disengaged by the decomposition of the oxygen gas keeps up the +temperature which is necessary for continuing combustion. When this is +not the case--that is, when the disengaged caloric is not sufficient +for keeping up the necessary temperature--the combustion ceases. This +circumstance is expressed in the common language by saying that a body +burns ill or with difficulty."(10) + + +It needed the genius of such a man as Lavoisier to complete the +refutation of the false but firmly grounded phlogiston theory, and +against such a book as his Elements of Chemistry the feeble weapons of +the supporters of the phlogiston theory were hurled in vain. + +But while chemists, as a class, had become converts to the new chemistry +before the end of the century, one man, Dr. Priestley, whose work had +done so much to found it, remained unconverted. In this, as in all his +life-work, he showed himself to be a most remarkable man. Davy said of +him, a generation later, that no other person ever discovered so many +new and curious substances as he; yet to the last he was only an amateur +in science, his profession, as we know, being the ministry. There is +hardly another case in history of a man not a specialist in science +accomplishing so much in original research as did this chemist, +physiologist, electrician; the mathematician, logician, and moralist; +the theologian, mental philosopher, and political economist. He took +all knowledge for his field; but how he found time for his numberless +researches and multifarious writings, along with his every-day duties, +must ever remain a mystery to ordinary mortals. + +That this marvellously receptive, flexible mind should have refused +acceptance to the clearly logical doctrines of the new chemistry seems +equally inexplicable. But so it was. To the very last, after all his +friends had capitulated, Priestley kept up the fight. From America he +sent out his last defy to the enemy, in 1800, in a brochure entitled +"The Doctrine of Phlogiston Upheld," etc. In the mind of its author it +was little less than a paean of victory; but all the world beside knew +that it was the swan-song of the doctrine of phlogiston. Despite the +defiance of this single warrior the battle was really lost and won, +and as the century closed "antiphlogistic" chemistry had practical +possession of the field. + + + + +III. CHEMISTRY SINCE THE TIME OF DALTON + +JOHN DALTON AND THE ATOMIC THEORY + +Small beginnings as have great endings--sometimes. As a case in +point, note what came of the small, original effort of a self-trained +back-country Quaker youth named John Dalton, who along towards the close +of the eighteenth century became interested in the weather, and was +led to construct and use a crude water-gauge to test the amount of the +rainfall. The simple experiments thus inaugurated led to no fewer than +two hundred thousand recorded observations regarding the weather, +which formed the basis for some of the most epochal discoveries in +meteorology, as we have seen. But this was only a beginning. The simple +rain-gauge pointed the way to the most important generalization of +the nineteenth century in a field of science with which, to the casual +observer, it might seem to have no alliance whatever. The wonderful +theory of atoms, on which the whole gigantic structure of modern +chemistry is founded, was the logical outgrowth, in the mind of John +Dalton, of those early studies in meteorology. + +The way it happened was this: From studying the rainfall, Dalton turned +naturally to the complementary process of evaporation. He was soon led +to believe that vapor exists, in the atmosphere as an independent gas. +But since two bodies cannot occupy the same space at the same time, +this implies that the various atmospheric gases are really composed of +discrete particles. These ultimate particles are so small that we cannot +see them--cannot, indeed, more than vaguely imagine them--yet each +particle of vapor, for example, is just as much a portion of water as if +it were a drop out of the ocean, or, for that matter, the ocean itself. +But, again, water is a compound substance, for it may be separated, as +Cavendish has shown, into the two elementary substances hydrogen and +oxygen. Hence the atom of water must be composed of two lesser atoms +joined together. Imagine an atom of hydrogen and one of oxygen. Unite +them, and we have an atom of water; sever them, and the water no longer +exists; but whether united or separate the atoms of hydrogen and of +oxygen remain hydrogen and oxygen and nothing else. Differently mixed +together or united, atoms produce different gross substances; but the +elementary atoms never change their chemical nature--their distinct +personality. + +It was about the year 1803 that Dalton first gained a full grasp of the +conception of the chemical atom. At once he saw that the hypothesis, +if true, furnished a marvellous key to secrets of matter hitherto +insoluble--questions relating to the relative proportions of the atoms +themselves. It is known, for example, that a certain bulk of hydrogen +gas unites with a certain bulk of oxygen gas to form water. If it be +true that this combination consists essentially of the union of atoms +one with another (each single atom of hydrogen united to a single atom +of oxygen), then the relative weights of the original masses of hydrogen +and of oxygen must be also the relative weights of each of their +respective atoms. If one pound of hydrogen unites with five and one-half +pounds of oxygen (as, according to Dalton's experiments, it did), then +the weight of the oxygen atom must be five and one-half times that of +the hydrogen atom. Other compounds may plainly be tested in the same +way. Dalton made numerous tests before he published his theory. He found +that hydrogen enters into compounds in smaller proportions than any +other element known to him, and so, for convenience, determined to take +the weight of the hydrogen atom as unity. The atomic weight of oxygen +then becomes (as given in Dalton's first table of 1803) 5.5; that of +water (hydrogen plus oxygen) being of course 6.5. The atomic weights of +about a score of substances are given in Dalton's first paper, which +was read before the Literary and Philosophical Society of Manchester, +October 21, 1803. I wonder if Dalton himself, great and acute intellect +though he had, suspected, when he read that paper, that he was +inaugurating one of the most fertile movements ever entered on in the +whole history of science? + +Be that as it may, it is certain enough that Dalton's contemporaries +were at first little impressed with the novel atomic theory. Just at +this time, as it chanced, a dispute was waging in the field of chemistry +regarding a matter of empirical fact which must necessarily be settled +before such a theory as that of Dalton could even hope for a bearing. +This was the question whether or not chemical elements unite with one +another always in definite proportions. Berthollet, the great co-worker +with Lavoisier, and now the most authoritative of living chemists, +contended that substances combine in almost indefinitely graded +proportions between fixed extremes. He held that solution is really a +form of chemical combination--a position which, if accepted, left no +room for argument. + +But this contention of the master was most actively disputed, in +particular by Louis Joseph Proust, and all chemists of repute were +obliged to take sides with one or the other. For a time the authority of +Berthollet held out against the facts, but at last accumulated evidence +told for Proust and his followers, and towards the close of the first +decade of our century it came to be generally conceded that chemical +elements combine with one another in fixed and definite proportions. + +More than that. As the analysts were led to weigh carefully the +quantities of combining elements, it was observed that the proportions +are not only definite, but that they bear a very curious relation to one +another. If element A combines with two different proportions of element +B to form two compounds, it appears that the weight of the larger +quantity of B is an exact multiple of that of the smaller quantity. This +curious relation was noticed by Dr. Wollaston, one of the most accurate +of observers, and a little later it was confirmed by Johan Jakob +Berzelius, the great Swedish chemist, who was to be a dominating +influence in the chemical world for a generation to come. But this +combination of elements in numerical proportions was exactly what Dalton +had noticed as early as 1802, and what bad led him directly to the +atomic weights. So the confirmation of this essential point by chemists +of such authority gave the strongest confirmation to the atomic theory. + +During these same years the rising authority of the French chemical +world, Joseph Louis Gay-Lussac, was conducting experiments with gases, +which he had undertaken at first in conjunction with Humboldt, but which +later on were conducted independently. In 1809, the next year after +the publication of the first volume of Dalton's New System of Chemical +Philosophy, Gay-Lussac published the results of his observations, and +among other things brought out the remarkable fact that gases, under +the same conditions as to temperature and pressure, combine always in +definite numerical proportions as to volume. Exactly two volumes of +hydrogen, for example, combine with one volume of oxygen to form water. +Moreover, the resulting compound gas always bears a simple relation to +the combining volumes. In the case just cited, the union of two volumes +of hydrogen and one of oxygen results in precisely two volumes of water +vapor. + +Naturally enough, the champions of the atomic theory seized upon +these observations of Gay-Lussac as lending strong support to their +hypothesis--all of them, that is, but the curiously self-reliant and +self-sufficient author of the atomic theory himself, who declined +to accept the observations of the French chemist as valid. Yet the +observations of Gay-Lussac were correct, as countless chemists since +then have demonstrated anew, and his theory of combination by volumes +became one of the foundation-stones of the atomic theory, despite the +opposition of the author of that theory. + +The true explanation of Gay-Lussac's law of combination by volumes was +thought out almost immediately by an Italian savant, Amadeo, Avogadro, +and expressed in terms of the atomic theory. The fact must be, said +Avogadro, that under similar physical conditions every form of gas +contains exactly the same number of ultimate particles in a given +volume. Each of these ultimate physical particles may be composed of two +or more atoms (as in the case of water vapor), but such a compound atom +conducts itself as if it were a simple and indivisible atom, as regards +the amount of space that separates it from its fellows under given +conditions of pressure and temperature. The compound atom, composed +of two or more elementary atoms, Avogadro proposed to distinguish, for +purposes of convenience, by the name molecule. It is to the molecule, +considered as the unit of physical structure, that Avogadro's law +applies. + +This vastly important distinction between atoms and molecules, implied +in the law just expressed, was published in 1811. Four years later, the +famous French physicist Ampere outlined a similar theory, and utilized +the law in his mathematical calculations. And with that the law of +Avogadro dropped out of sight for a full generation. Little suspecting +that it was the very key to the inner mysteries of the atoms for which +they were seeking, the chemists of the time cast it aside, and let it +fade from the memory of their science. + +This, however, was not strange, for of course the law of Avogadro is +based on the atomic theory, and in 1811 the atomic theory was itself +still being weighed in the balance. The law of multiple proportions +found general acceptance as an empirical fact; but many of the leading +lights of chemistry still looked askance at Dalton's explanation of this +law. Thus Wollaston, though from the first he inclined to acceptance of +the Daltonian view, cautiously suggested that it would be well to use +the non-committal word "equivalent" instead of "atom"; and Davy, for +a similar reason, in his book of 1812, speaks only of "proportions," +binding himself to no theory as to what might be the nature of these +proportions. + +At least two great chemists of the time, however, adopted the atomic +view with less reservation. One of these was Thomas Thomson, professor +at Edinburgh, who, in 1807, had given an outline of Dalton's theory in +a widely circulated book, which first brought the theory to the general +attention of the chemical world. The other and even more noted advocate +of the atomic theory was Johan Jakob Berzelius. This great Swedish +chemist at once set to work to put the atomic theory to such tests as +might be applied in the laboratory. He was an analyst of the utmost +skill, and for years he devoted himself to the determination of the +combining weights, "equivalents" or "proportions," of the different +elements. These determinations, in so far as they were accurately made, +were simple expressions of empirical facts, independent of any theory; +but gradually it became more and more plain that these facts all +harmonize with the atomic theory of Dalton. So by common consent the +proportionate combining weights of the elements came to be known as +atomic weights--the name Dalton had given them from the first--and +the tangible conception of the chemical atom as a body of definite +constitution and weight gained steadily in favor. + +From the outset the idea had had the utmost tangibility in the mind of +Dalton. He had all along represented the different atoms by geometrical +symbols--as a circle for oxygen, a circle enclosing a dot for hydrogen, +and the like--and had represented compounds by placing these symbols of +the elements in juxtaposition. Berzelius proposed to improve upon this +method by substituting for the geometrical symbol the initial of the +Latin name of the element represented--O for oxygen, H for hydrogen, and +so on--a numerical coefficient to follow the letter as an indication of +the number of atoms present in any given compound. This simple system +soon gained general acceptance, and with slight modifications it is +still universally employed. Every school-boy now is aware that H2O is +the chemical way of expressing the union of two atoms of hydrogen with +one of oxygen to form a molecule of water. But such a formula would have +had no meaning for the wisest chemist before the day of Berzelius. + +The universal fame of the great Swedish authority served to give general +currency to his symbols and atomic weights, and the new point of view +thus developed led presently to two important discoveries which removed +the last lingering doubts as to the validity of the atomic theory. In +1819 two French physicists, Dulong and Petit, while experimenting with +heat, discovered that the specific heats of solids (that is to say, the +amount of heat required to raise the temperature of a given mass to a +given degree) vary inversely as their atomic weights. In the same year +Eilhard Mitscherlich, a German investigator, observed that compounds +having the same number of atoms to the molecule are disposed to form the +same angles of crystallization--a property which he called isomorphism. + +Here, then, were two utterly novel and independent sets of empirical +facts which harmonize strangely with the supposition that substances are +composed of chemical atoms of a determinate weight. This surely could +not be coincidence--it tells of law. And so as soon as the claims of +Dulong and Petit and of Mitscherlich had been substantiated by other +observers, the laws of the specific heat of atoms, and of isomorphism, +took their place as new levers of chemical science. With the aid of +these new tools an impregnable breastwork of facts was soon piled about +the atomic theory. And John Dalton, the author of that theory, plain, +provincial Quaker, working on to the end in semi-retirement, became +known to all the world and for all time as a master of masters. + + +HUMPHRY DAVY AND ELECTRO-CHEMISTRY + +During those early years of the nineteenth century, when Dalton was +grinding away at chemical fact and theory in his obscure Manchester +laboratory, another Englishman held the attention of the chemical world +with a series of the most brilliant and widely heralded researches. This +was Humphry Davy, a young man who had conic to London in 1801, at the +instance of Count Rumford, to assume the chair of chemical philosophy in +the Royal Institution, which the famous American had just founded. + +Here, under Davy's direction, the largest voltaic battery yet +constructed had been put in operation, and with its aid the brilliant +young experimenter was expected almost to perform miracles. And indeed +he scarcely disappointed the expectation, for with the aid of his +battery he transformed so familiar a substance as common potash into +a metal which was not only so light that it floated on water, but +possessed the seemingly miraculous property of bursting into flames as +soon as it came in contact with that fire-quenching liquid. If this +were not a miracle, it had for the popular eye all the appearance of the +miraculous. + +What Davy really had done was to decompose the potash, which hitherto +had been supposed to be elementary, liberating its oxygen, and thus +isolating its metallic base, which he named potassium. The same +thing was done with soda, and the closely similar metal sodium was +discovered--metals of a unique type, possessed of a strange avidity for +oxygen, and capable of seizing on it even when it is bound up in the +molecules of water. Considered as mere curiosities, these discoveries +were interesting, but aside from that they were of great theoretical +importance, because they showed the compound nature of some familiar +chemicals that had been regarded as elements. Several other elementary +earths met the same fate when subjected to the electrical influence; the +metals barium, calcium, and strontium being thus discovered. Thereafter +Davy always referred to the supposed elementary substances (including +oxygen, hydrogen, and the rest) as "unde-compounded" bodies. These +resist all present efforts to decompose them, but how can one know what +might not happen were they subjected to an influence, perhaps some day +to be discovered, which exceeds the battery in power as the battery +exceeds the blowpipe? + +Another and even more important theoretical result that flowed from +Davy's experiments during this first decade of the century was the +proof that no elementary substances other than hydrogen and oxygen are +produced when pure water is decomposed by the electric current. It was +early noticed by Davy and others that when a strong current is passed +through water, alkalies appear at one pole of the battery and acids at +the other, and this though the water used were absolutely pure. This +seemingly told of the creation of elements--a transmutation but one step +removed from the creation of matter itself--under the influence of the +new "force." It was one of Davy's greatest triumphs to prove, in the +series of experiments recorded in his famous Bakerian lecture of 1806, +that the alleged creation of elements did not take place, the substances +found at the poles of the battery having been dissolved from the walls +of the vessels in which the water experimented upon had been placed. +Thus the same implement which had served to give a certain philosophical +warrant to the fading dreams of alchemy banished those dreams +peremptorily from the domain of present science. + +"As early as 1800," writes Davy, "I had found that when separate +portions of distilled water, filling two glass tubes, connected by moist +bladders, or any moist animal or vegetable substances, were submitted +to the electrical action of the pile of Volta by means of gold wires, +a nitro-muriatic solution of gold appeared in the tube containing the +positive wire, or the wire transmitting the electricity, and a solution +of soda in the opposite tube; but I soon ascertained that the muriatic +acid owed its existence to the animal or vegetable matters employed; +for when the same fibres of cotton were made use of in successive +experiments, and washed after every process in a weak solution of nitric +acid, the water in the apparatus containing them, though acted on for +a great length of time with a very strong power, at last produced no +effects upon nitrate of silver. + +"In cases when I had procured much soda, the glass at its point of +contact with the wire seemed considerably corroded; and I was confirmed +in my idea of referring the production of the alkali principally to +this source, by finding that no fixed saline matter could be obtained +by electrifying distilled water in a single agate cup from two points of +platina with the Voltaic battery. + +"Mr. Sylvester, however, in a paper published in Mr. Nicholson's journal +for last August, states that though no fixed alkali or muriatic acid +appears when a single vessel is employed, yet that they are both formed +when two vessels are used. And to do away with all objections with +regard to vegetable substances or glass, he conducted his process in +a vessel made of baked tobacco-pipe clay inserted in a crucible of +platina. I have no doubt of the correctness of his results; but the +conclusion appears objectionable. He conceives, that he obtained fixed +alkali, because the fluid after being heated and evaporated left a +matter that tinged turmeric brown, which would have happened had it +been lime, a substance that exists in considerable quantities in all +pipe-clay; and even allowing the presence of fixed alkali, the materials +employed for the manufacture of tobacco-pipes are not at all such as to +exclude the combinations of this substance. + +"I resumed the inquiry; I procured small cylindrical cups of agate of +the capacity of about one-quarter of a cubic inch each. They were +boiled for some hours in distilled water, and a piece of very white and +transparent amianthus that had been treated in the same way was made +then to connect together; they were filled with distilled water and +exposed by means of two platina wires to a current of electricity, from +one hundred and fifty pairs of plates of copper and zinc four inches +square, made active by means of solution of alum. After forty-eight +hours the process was examined: Paper tinged with litmus plunged into +the tube containing the transmitting or positive wire was immediately +strongly reddened. Paper colored by turmeric introduced into the other +tube had its color much deepened; the acid matter gave a very slight +degree of turgidness to solution of nitrate of soda. The fluid that +affected turmeric retained this property after being strongly +boiled; and it appeared more vivid as the quantity became reduced by +evaporation; carbonate of ammonia was mixed with it, and the whole +dried and exposed to a strong heat; a minute quantity of white matter +remained, which, as far as my examinations could go, had the properties +of carbonate of soda. I compared it with similar minute portions of +the pure carbonates of potash, and similar minute portions of the pure +carbonates of potash and soda. It was not so deliquescent as the former +of these bodies, and it formed a salt with nitric acid, which, like +nitrate of soda, soon attracted moisture from a damp atmosphere and +became fluid. + +"This result was unexpected, but it was far from convincing me that the +substances which were obtained were generated. In a similar process with +glass tubes, carried on under exactly the same circumstances and for +the same time, I obtained a quantity of alkali which must have been more +than twenty times greater, but no traces of muriatic acid. There was +much probability that the agate contained some minute portion of saline +matter, not easily detected by chemical analysis, either in combination +or intimate cohesion in its pores. To determine this, I repeated this a +second, a third, and a fourth time. In the second experiment turbidness +was still produced by a solution of nitrate of silver in the tube +containing the acid, but it was less distinct; in the third process +it was barely perceptible; and in the fourth process the two fluids +remained perfectly clear after the mixture. The quantity of alkaline +matter diminished in every operation; and in the last process, though +the battery had been kept in great activity for three days, the fluid +possessed, in a very slight degree, only the power of acting on paper +tinged with turmeric; but its alkaline property was very sensible to +litmus paper slightly reddened, which is a much more delicate test; +and after evaporation and the process by carbonate of ammonia, a barely +perceptible quantity of fixed alkali was still left. The acid matter in +the other tube was abundant; its taste was sour; it smelled like water +over which large quantities of nitrous gas have been long kept; it did +not effect solution of muriate of barytes; and a drop of it placed +upon a polished plate of silver left, after evaporation, a black stain, +precisely similar to that produced by extremely diluted nitrous acid. + +"After these results I could no longer doubt that some saline matter +existing in the agate tubes had been the source of the acid matter +capable of precipitating nitrate of silver and much of the alkali. Four +additional repetitions of the process, however, convinced me that there +was likewise some other cause for the presence of this last substance; +for it continued to appear to the last in quantities sufficiently +distinguishable, and apparently equal in every case. I had used every +precaution, I had included the tube in glass vessels out of the reach of +the circulating air; all the acting materials had been repeatedly washed +with distilled water; and no part of them in contact with the fluid had +been touched by the fingers. + +"The only substance that I could now conceive as furnishing the fixed +alkali was the water itself. This water appeared pure by the tests of +nitrate of silver and muriate of barytes; but potash of soda, as is +well known, rises in small quantities in rapid distillation; and the +New River water which I made use of contains animal and vegetable +impurities, which it was easy to conceive might furnish neutral +salts capable of being carried over in vivid ebullition."(1) Further +experiment proved the correctness of this inference, and the last doubt +as to the origin of the puzzling chemical was dispelled. + +Though the presence of the alkalies and acids in the water was +explained, however, their respective migrations to the negative and +positive poles of the battery remained to be accounted for. Davy's +classical explanation assumed that different elements differ among +themselves as to their electrical properties, some being positively, +others negatively, electrified. Electricity and "chemical affinity," he +said, apparently are manifestations of the same force, acting in the one +case on masses, in the other on particles. Electro-positive particles +unite with electro-negative particles to form chemical compounds, in +virtue of the familiar principle that opposite electricities attract +one another. When compounds are decomposed by the battery, this mutual +attraction is overcome by the stronger attraction of the poles of the +battery itself. + +This theory of binary composition of all chemical compounds, through the +union of electro-positive and electro-negative atoms or molecules, +was extended by Berzelius, and made the basis of his famous system of +theoretical chemistry. This theory held that all inorganic compounds, +however complex their composition, are essentially composed of such +binary combinations. For many years this view enjoyed almost undisputed +sway. It received what seemed strong confirmation when Faraday showed +the definite connection between the amount of electricity employed and +the amount of decomposition produced in the so-called electrolyte. But +its claims were really much too comprehensive, as subsequent discoveries +proved. + + +ORGANIC CHEMISTRY AND THE IDEA OF THE MOLECULE + +When Berzelius first promulgated his binary theory he was careful to +restrict its unmodified application to the compounds of the inorganic +world. At that time, and for a long time thereafter, it was supposed +that substances of organic nature had some properties that kept them +aloof from the domain of inorganic chemistry. It was little doubted +that a so-called "vital force" operated here, replacing or modifying the +action of ordinary "chemical affinity." It was, indeed, admitted that +organic compounds are composed of familiar elements--chiefly carbon, +oxygen, hydrogen, and nitrogen; but these elements were supposed to +be united in ways that could not be imitated in the domain of the +non-living. It was regarded almost as an axiom of chemistry that +no organic compound whatever could be put together from its +elements--synthesized--in the laboratory. To effect the synthesis of +even the simplest organic compound, it was thought that the "vital +force" must be in operation. + +Therefore a veritable sensation was created in the chemical world +when, in the year 1828, it was announced that the young German chemist, +Friedrich Wohler, formerly pupil of Berzelius, and already known as a +coming master, had actually synthesized the well-known organic product +urea in his laboratory at Sacrow. The "exception which proves the rule" +is something never heard of in the domain of logical science. Natural +law knows no exceptions. So the synthesis of a single organic compound +sufficed at a blow to break down the chemical barrier which the +imagination of the fathers of the science had erected between animate +and inanimate nature. Thenceforth the philosophical chemist would +regard the plant and animal organisms as chemical laboratories in which +conditions are peculiarly favorable for building up complex compounds of +a few familiar elements, under the operation of universal chemical laws. +The chimera "vital force" could no longer gain recognition in the domain +of chemistry. + +Now a wave of interest in organic chemistry swept over the chemical +world, and soon the study of carbon compounds became as much the fashion +as electrochemistry had been in the, preceding generation. + +Foremost among the workers who rendered this epoch of organic chemistry +memorable were Justus Liebig in Germany and Jean Baptiste Andre Dumas +in France, and their respective pupils, Charles Frederic Gerhardt and +Augustus Laurent. Wohler, too, must be named in the same breath, as also +must Louis Pasteur, who, though somewhat younger than the others, came +upon the scene in time to take chief part in the most important of the +controversies that grew out of their labors. + +Several years earlier than this the way had been paved for the study +of organic substances by Gay-Lussac's discovery, made in 1815, that a +certain compound of carbon and nitrogen, which he named cyanogen, has a +peculiar degree of stability which enables it to retain its identity and +enter into chemical relations after the manner of a simple body. A year +later Ampere discovered that nitrogen and hydrogen, when combined in +certain proportions to form what he called ammonium, have the same +property. Berzelius had seized upon this discovery of the compound +radical, as it was called, because it seemed to lend aid to his +dualistic theory. He conceived the idea that all organic compounds +are binary unions of various compound radicals with an atom of oxygen, +announcing this theory in 1818. Ten years later, Liebig and Wohler +undertook a joint investigation which resulted in proving that compound +radicals are indeed very abundant among organic substances. Thus the +theory of Berzelius seemed to be substantiated, and organic chemistry +came to be defined as the chemistry of compound radicals. + +But even in the day of its seeming triumph the dualistic theory +was destined to receive a rude shock. This came about through the +investigations of Dumas, who proved that in a certain organic substance +an atom of hydrogen may be removed and an atom of chlorine substituted +in its place without destroying the integrity of the original +compound--much as a child might substitute one block for another in +its play-house. Such a substitution would be quite consistent with the +dualistic theory, were it not for the very essential fact that hydrogen +is a powerfully electro-positive element, while chlorine is as strongly +electro-negative. Hence the compound radical which united successively +with these two elements must itself be at one time electro-positive, at +another electro-negative--a seeming inconsistency which threw the entire +Berzelian theory into disfavor. + +In its place there was elaborated, chiefly through the efforts of +Laurent and Gerhardt, a conception of the molecule as a unitary +structure, built up through the aggregation of various atoms, in +accordance with "elective affinities" whose nature is not yet understood +A doctrine of "nuclei" and a doctrine of "types" of molecular structure +were much exploited, and, like the doctrine of compound radicals, became +useful as aids to memory and guides for the analyst, indicating some of +the plans of molecular construction, though by no means penetrating the +mysteries of chemical affinity. They are classifications rather than +explanations of chemical unions. But at least they served an important +purpose in giving definiteness to the idea of a molecular structure +built of atoms as the basis of all substances. Now at last the word +molecule came to have a distinct meaning, as distinct from "atom," in +the minds of the generality of chemists, as it had had for Avogadro a +third of a century before. Avogadro's hypothesis that there are equal +numbers of these molecules in equal volumes of gases, under fixed +conditions, was revived by Gerhardt, and a little later, under the +championship of Cannizzaro, was exalted to the plane of a fixed law. +Thenceforth the conception of the molecule was to be as dominant a +thought in chemistry as the idea of the atom had become in a previous +epoch. + + +CHEMICAL AFFINITY + +Of course the atom itself was in no sense displaced, but Avogadro's law +soon made it plain that the atom had often usurped territory that +did not really belong to it. In many cases the chemists had supposed +themselves dealing with atoms as units where the true unit was the +molecule. In the case of elementary gases, such as hydrogen and oxygen, +for example, the law of equal numbers of molecules in equal spaces made +it clear that the atoms do not exist isolated, as had been supposed. +Since two volumes of hydrogen unite with one volume of oxygen to form +two volumes of water vapor, the simplest mathematics show, in the light +of Avogadro's law, not only that each molecule of water must contain two +hydrogen atoms (a point previously in dispute), but that the original +molecules of hydrogen and oxygen must have been composed in each case of +two atoms---else how could one volume of oxygen supply an atom for every +molecule of two volumes of water? + +What, then, does this imply? Why, that the elementary atom has +an avidity for other atoms, a longing for companionship, an +"affinity"--call it what you will--which is bound to be satisfied if +other atoms are in the neighborhood. Placed solely among atoms of its +own kind, the oxygen atom seizes on a fellow oxygen atom, and in all +their mad dancings these two mates cling together--possibly revolving +about each other in miniature planetary orbits. Precisely the same thing +occurs among the hydrogen atoms. But now suppose the various pairs +of oxygen atoms come near other pairs of hydrogen atoms (under proper +conditions which need not detain us here), then each oxygen atom loses +its attachment for its fellow, and flings itself madly into the circuit +of one of the hydrogen couplets, and--presto!--there are only two +molecules for every three there were before, and free oxygen and +hydrogen have become water. The whole process, stated in chemical +phraseology, is summed up in the statement that under the given +conditions the oxygen atoms had a greater affinity for the hydrogen +atoms than for one another. + +As chemists studied the actions of various kinds of atoms, in regard +to their unions with one another to form molecules, it gradually dawned +upon them that not all elements are satisfied with the same number of +companions. Some elements ask only one, and refuse to take more; while +others link themselves, when occasion offers, with two, three, four, or +more. Thus we saw that oxygen forsook a single atom of its own kind +and linked itself with two atoms of hydrogen. Clearly, then, the oxygen +atom, like a creature with two hands, is able to clutch two other atoms. +But we have no proof that under any circumstances it could hold more +than two. Its affinities seem satisfied when it has two bonds. But, +on the other hand, the atom of nitrogen is able to hold three atoms +of hydrogen, and does so in the molecule of ammonium (NH3); while the +carbon atom can hold four atoms of hydrogen or two atoms of oxygen. + +Evidently, then, one atom is not always equivalent to another atom of +a different kind in combining powers. A recognition of this fact by +Frankland about 1852, and its further investigation by others (notably +A. Kekule and A. S. Couper), led to the introduction of the word +equivalent into chemical terminology in a new sense, and in particular +to an understanding of the affinities or "valency" of different +elements, which proved of the most fundamental importance. Thus it +was shown that, of the four elements that enter most prominently into +organic compounds, hydrogen can link itself with only a single bond to +any other element--it has, so to speak, but a single hand with which +to grasp--while oxygen has capacity for two bonds, nitrogen for +three (possibly for five), and carbon for four. The words monovalent, +divalent, trivalent, tretrava-lent, etc., were coined to express this +most important fact, and the various elements came to be known as +monads, diads, triads, etc. Just why different elements should differ +thus in valency no one as yet knows; it is an empirical fact that they +do. And once the nature of any element has been determined as regards +its valency, a most important insight into the possible behavior of that +element has been secured. Thus a consideration of the fact that hydrogen +is monovalent, while oxygen is divalent, makes it plain that we +must expect to find no more than three compounds of these two +elements--namely, H--O--(written HO by the chemist, and called +hydroxyl); H--O--H (H2O, or water), and H--O--O--H (H2O2, or hydrogen +peroxide). It will be observed that in the first of these compounds the +atom of oxygen stands, so to speak, with one of its hands free, eagerly +reaching out, therefore, for another companion, and hence, in the +language of chemistry, forming an unstable compound. Again, in the third +compound, though all hands are clasped, yet one pair links oxygen with +oxygen; and this also must be an unstable union, since the avidity of an +atom for its own kind is relatively weak. Thus the well-known properties +of hydrogen peroxide are explained, its easy decomposition, and the +eagerness with which it seizes upon the elements of other compounds. + +But the molecule of water, on the other hand, has its atoms arranged +in a state of stable equilibrium, all their affinities being satisfied. +Each hydrogen atom has satisfied its own affinity by clutching the +oxygen atom; and the oxygen atom has both its bonds satisfied by +clutching back at the two hydrogen atoms. Therefore the trio, linked in +this close bond, have no tendency to reach out for any other companion, +nor, indeed, any power to hold another should it thrust itself +upon them. They form a "stable" compound, which under all ordinary +circumstances will retain its identity as a molecule of water, even +though the physical mass of which it is a part changes its condition +from a solid to a gas from ice to vapor. + +But a consideration of this condition of stable equilibrium in the +molecule at once suggests a new question: How can an aggregation of +atoms, having all their affinities satisfied, take any further part in +chemical reactions? Seemingly such a molecule, whatever its physical +properties, must be chemically inert, incapable of any atomic +readjustments. And so in point of fact it is, so long as its component +atoms cling to one another unremittingly. But this, it appears, is +precisely what the atoms are little prone to do. It seems that they are +fickle to the last degree in their individual attachments, and are as +prone to break away from bondage as they are to enter into it. Thus the +oxygen atom which has just flung itself into the circuit of two +hydrogen atoms, the next moment flings itself free again and seeks +new companions. It is for all the world like the incessant change +of partners in a rollicking dance. This incessant dissolution and +reformation of molecules in a substance which as a whole remains +apparently unchanged was first fully appreciated by Ste.-Claire Deville, +and by him named dissociation. It is a process which goes on much more +actively in some compounds than in others, and very much more actively +under some physical conditions (such as increase of temperature) than +under others. But apparently no substances at ordinary temperatures, +and no temperature above the absolute zero, are absolutely free from its +disturbing influence. Hence it is that molecules having all the +valency of their atoms fully satisfied do not lose their chemical +activity--since each atom is momentarily free in the exchange of +partners, and may seize upon different atoms from its former partners, +if those it prefers are at hand. + +While, however, an appreciation of this ceaseless activity of the atom +is essential to a proper understanding of its chemical efficiency, +yet from another point of view the "saturated" molecule--that is, the +molecule whose atoms have their valency all satisfied--may be thought of +as a relatively fixed or stable organism. Even though it may presently +be torn down, it is for the time being a completed structure; and a +consideration of the valency of its atoms gives the best clew that has +hitherto been obtainable as to the character of its architecture. +How important this matter of architecture of the molecule--of space +relations of the atoms--may be--was demonstrated as long ago as 1823, +when Liebig and Wohler proved, to the utter bewilderment of the +chemical world, that two substances may have precisely the same chemical +constitution--the same number and kind of atoms--and yet differ utterly +in physical properties. The word isomerism was coined by Berzelius to +express this anomalous condition of things, which seemed to negative the +most fundamental truths of chemistry. Naming the condition by no means +explained it, but the fact was made clear that something besides the +mere number and kind of atoms is important in the architecture of a +molecule. It became certain that atoms are not thrown together haphazard +to build a molecule, any more than bricks are thrown together at random +to form a house. + +How delicate may be the gradations of architectural design in building +a molecule was well illustrated about 1850, when Pasteur discovered that +some carbon compounds--as certain sugars--can only be distinguished +from one another, when in solution, by the fact of their twisting or +polarizing a ray of light to the left or to the right, respectively. But +no inkling of an explanation of these strange variations of molecular +structure came until the discovery of the law of valency. Then much of +the mystery was cleared away; for it was plain that since each atom in a +molecule can hold to itself only a fixed number of other atoms, complex +molecules must have their atoms linked in definite chains or groups. And +it is equally plain that where the atoms are numerous, the exact plan of +grouping may sometimes be susceptible of change without doing violence +to the law of valency. It is in such cases that isomerism is observed to +occur. + +By paying constant heed to this matter of the affinities, chemists are +able to make diagrammatic pictures of the plan of architecture of any +molecule whose composition is known. In the simple molecule of water +(H2O), for example, the two hydrogen atoms must have released each +other before they could join the oxygen, and the manner of linking must +apparently be that represented in the graphic formula H--O--H. +With molecules composed of a large number of atoms, such graphic +representation of the scheme of linking is of course increasingly +difficult, yet, with the affinities for a guide, it is always possible. +Of course no one supposes that such a formula, written in a single +plane, can possibly represent the true architecture of the molecule: +it is at best suggestive or diagrammatic rather than pictorial. +Nevertheless, it affords hints as to the structure of the molecule such +as the fathers of chemistry would not have thought it possible ever to +attain. + + +PERIODICITY OF ATOMIC WEIGHTS + +These utterly novel studies of molecular architecture may seem at +first sight to take from the atom much of its former prestige as the +all-important personage of the chemical world. Since so much depends +upon the mere position of the atoms, it may appear that comparatively +little depends upon the nature of the atoms themselves. But such a view +is incorrect, for on closer consideration it will appear that at no +time has the atom been seen to renounce its peculiar personality. Within +certain limits the character of a molecule may be altered by changing +the positions of its atoms (just as different buildings may be +constructed of the same bricks), but these limits are sharply defined, +and it would be as impossible to exceed them as it would be to build +a stone building with bricks. From first to last the brick remains a +brick, whatever the style of architecture it helps to construct; it +never becomes a stone. And just as closely does each atom retain its own +peculiar properties, regardless of its surroundings. + +Thus, for example, the carbon atom may take part in the formation at one +time of a diamond, again of a piece of coal, and yet again of a +particle of sugar, of wood fibre, of animal tissue, or of a gas in the +atmosphere; but from first to last--from glass-cutting gem to intangible +gas--there is no demonstrable change whatever in any single property of +the atom itself. So far as we know, its size, its weight, its capacity +for vibration or rotation, and its inherent affinities, remain +absolutely unchanged throughout all these varying fortunes of position +and association. And the same thing is true of every atom of all of +the seventy-odd elementary substances with which the modern chemist is +acquainted. Every one appears always to maintain its unique integrity, +gaining nothing and losing nothing. + +All this being true, it would seem as if the position of the Daltonian +atom as a primordial bit of matter, indestructible and non-transmutable, +had been put to the test by the chemistry of our century, and not found +wanting. Since those early days of the century when the electric battery +performed its miracles and seemingly reached its limitations in the +hands of Davy, many new elementary substances have been discovered, +but no single element has been displaced from its position as an +undecomposable body. Rather have the analyses of the chemist seemed to +make it more and more certain that all elementary atoms are in truth +what John Herschel called them, "manufactured articles"--primordial, +changeless, indestructible. + +And yet, oddly enough, it has chanced that hand in hand with the +experiments leading to such a goal have gone other experiments arid +speculations of exactly the opposite tenor. In each generation there +have been chemists among the leaders of their science who have refused +to admit that the so-called elements are really elements at all in any +final sense, and who have sought eagerly for proof which might warrant +their scepticism. The first bit of evidence tending to support this view +was furnished by an English physician, Dr. William Prout, who in 1815 +called attention to a curious relation to be observed between the atomic +weight of the various elements. Accepting the figures given by the +authorities of the time (notably Thomson and Berzelius), it appeared +that a strikingly large proportion of the atomic weights were exact +multiples of the weight of hydrogen, and that others differed so +slightly that errors of observation might explain the discrepancy. Prout +felt that it could not be accidental, and he could think of no tenable +explanation, unless it be that the atoms of the various alleged elements +are made up of different fixed numbers of hydrogen atoms. Could it be +that the one true element--the one primal matter--is hydrogen, and that +all other forms of matter are but compounds of this original substance? + +Prout advanced this startling idea at first tentatively, in an anonymous +publication; but afterwards he espoused it openly and urged its +tenability. Coming just after Davy's dissociation of some supposed +elements, the idea proved alluring, and for a time gained such +popularity that chemists were disposed to round out the observed atomic +weights of all elements into whole numbers. But presently renewed +determinations of the atomic weights seemed to discountenance this +practice, and Prout's alleged law fell into disrepute. It was revived, +however, about 1840, by Dumas, whose great authority secured it a +respectful hearing, and whose careful redetermination of the weight +of carbon, making it exactly twelve times that of hydrogen, aided the +cause. + +Subsequently Stas, the pupil of Dumas, undertook a long series of +determinations of atomic weights, with the expectation of confirming the +Proutian hypothesis. But his results seemed to disprove the hypothesis, +for the atomic weights of many elements differed from whole numbers by +more, it was thought, than the limits of error of the experiments. It +was noteworthy, however, that the confidence of Dumas was not shaken, +though he was led to modify the hypothesis, and, in accordance with +previous suggestions of Clark and of Marignac, to recognize as the +primordial element, not hydrogen itself, but an atom half the weight, +or even one-fourth the weight, of that of hydrogen, of which primordial +atom the hydrogen atom itself is compounded. But even in this modified +form the hypothesis found great opposition from experimental observers. + +In 1864, however, a novel relation between the weights of the elements +and their other characteristics was called to the attention of chemists +by Professor John A. R. Newlands, of London, who had noticed that if the +elements are arranged serially in the numerical order of their atomic +weights, there is a curious recurrence of similar properties at +intervals of eight elements This so-called "law of octaves" attracted +little immediate attention, but the facts it connotes soon came under +the observation of other chemists, notably of Professors Gustav Hinrichs +in America, Dmitri Mendeleeff in Russia, and Lothar Meyer in Germany. +Mendeleeff gave the discovery fullest expression, explicating it in +1869, under the title of "the periodic law." + +Though this early exposition of what has since been admitted to be a +most important discovery was very fully outlined, the generality of +chemists gave it little heed till a decade or so later, when three new +elements, gallium, scandium, and germanium, were discovered, which, on +being analyzed, were quite unexpectedly found to fit into three gaps +which Mendeleeff had left in his periodic scale. In effect the periodic +law had enabled Mendeleeff to predicate the existence of the new +elements years before they were discovered. Surely a system that leads +to such results is no mere vagary. So very soon the periodic law took +its place as one of the most important generalizations of chemical +science. + +This law of periodicity was put forward as an expression of observed +relations independent of hypothesis; but of course the theoretical +bearings of these facts could not be overlooked. As Professor J. H. +Gladstone has said, it forces upon us "the conviction that the elements +are not separate bodies created without reference to one another, but +that they have been originally fashioned, or have been built up, from +one another, according to some general plan." It is but a short step +from that proposition to the Proutian hypothesis. + + +NEW WEAPONS--SPECTROSCOPE AND CAMERA + +But the atomic weights are not alone in suggesting the compound nature +of the alleged elements. Evidence of a totally different kind has +contributed to the same end, from a source that could hardly have been +imagined when the Proutian hypothesis, was formulated, through the +tradition of a novel weapon to the armamentarium of the chemist--the +spectroscope. The perfection of this instrument, in the hands of two +German scientists, Gustav Robert Kirchhoff and Robert Wilhelm Bunsen, +came about through the investigation, towards the middle of the century, +of the meaning of the dark lines which had been observed in the solar +spectrum by Fraunhofer as early as 1815, and by Wollaston a decade +earlier. It was suspected by Stokes and by Fox Talbot in England, but +first brought to demonstration by Kirchhoff and Bunsen, that these +lines, which were known to occupy definite positions in the spectrum, +are really indicative of particular elementary substances. By means of +the spectroscope, which is essentially a magnifying lens attached to a +prism of glass, it is possible to locate the lines with great accuracy, +and it was soon shown that here was a new means of chemical analysis +of the most exquisite delicacy. It was found, for example, that the +spectroscope could detect the presence of a quantity of sodium so +infinitesimal as the one two-hundred-thousandth of a grain. But what was +even more important, the spectroscope put no limit upon the distance of +location of the substance it tested, provided only that sufficient light +came from it. The experiments it recorded might be performed in the sun, +or in the most distant stars or nebulae; indeed, one of the earliest +feats of the instrument was to wrench from the sun the secret of his +chemical constitution. + +To render the utility of the spectroscope complete, however, it +was necessary to link with it another new chemical agency--namely, +photography. This now familiar process is based on the property of light +to decompose certain unstable compounds of silver, and thus alter their +chemical composition. Davy and Wedgwood barely escaped the discovery of +the value of the photographic method early in the nineteenth century. +Their successors quite overlooked it until about 1826, when Louis J. M. +Daguerre, the French chemist, took the matter in hand, and after many +years of experimentation brought it to relative perfection in 1839, in +which year the famous daguerreotype first brought the matter to popular +attention. In the same year Mr. Fox Talbot read a paper on the subject +before the Royal Society, and soon afterwards the efforts of Herschel +and numerous other natural philosophers contributed to the advancement +of the new method. + +In 1843 Dr. John W. Draper, the famous English-American chemist and +physiologist, showed that by photography the Fraunhofer lines in the +solar spectrum might be mapped with absolute accuracy; also proving that +the silvered film revealed many lines invisible to the unaided eye. The +value of this method of observation was recognized at once, and, as +soon as the spectroscope was perfected, the photographic method, in +conjunction with its use, became invaluable to the chemist. By this +means comparisons of spectra may be made with a degree of accuracy +not otherwise obtainable; and, in case of the stars, whole clusters of +spectra may be placed on record at a single observation. + +As the examination of the sun and stars proceeded, chemists were amazed +or delighted, according to their various preconceptions, to witness the +proof that many familiar terrestrial elements are to be found in the +celestial bodies. But what perhaps surprised them most was to observe +the enormous preponderance in the sidereal bodies of the element +hydrogen. Not only are there vast quantities of this element in the +sun's atmosphere, but some other suns appeared to show hydrogen lines +almost exclusively in their spectra. Presently it appeared that the +stars of which this is true are those white stars, such as Sirius, which +had been conjectured to be the hottest; whereas stars that are only +red-hot, like our sun, show also the vapors of many other elements, +including iron and other metals. + +In 1878 Professor J. Norman Lockyer, in a paper before the Royal +Society, called attention to the possible significance of this series of +observations. He urged that the fact of the sun showing fewer elements +than are observed here on the cool earth, while stars much hotter than +the sun show chiefly one element, and that one hydrogen, the lightest of +known elements, seemed to give color to the possibility that our alleged +elements are really compounds, which at the temperature of the hottest +stars may be decomposed into hydrogen, the latter "element" itself being +also doubtless a compound, which might be resolved under yet more trying +conditions. + +Here, then, was what might be termed direct experimental evidence for +the hypothesis of Prout. Unfortunately, however, it is evidence of a +kind which only a few experts are competent to discuss--so very delicate +a matter is the spectral analysis of the stars. What is still more +unfortunate, the experts do not agree among themselves as to the +validity of Professor Lockyer's conclusions. Some, like Professor +Crookes, have accepted them with acclaim, hailing Lockyer as "the +Darwin of the inorganic world," while others have sought a different +explanation of the facts he brings forward. As yet it cannot be said +that the controversy has been brought to final settlement. Still, it is +hardly to be doubted that now, since the periodic law has seemed to +join hands with the spectroscope, a belief in the compound nature of the +so-called elements is rapidly gaining ground among chemists. More and +more general becomes the belief that the Daltonian atom is really a +compound radical, and that back of the seeming diversity of the alleged +elements is a single form of primordial matter. Indeed, in very recent +months, direct experimental evidence for this view has at last come to +hand, through the study of radio-active substances. In a later chapter +we shall have occasion to inquire how this came about. + + + + +IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH CENTURY + +ALBRECHT VON HALLER + +An epoch in physiology was made in the eighteenth century by the genius +and efforts of Albrecht von Haller (1708-1777), of Berne, who is perhaps +as worthy of the title "The Great" as any philosopher who has been +so christened by his contemporaries since the time of Hippocrates. +Celebrated as a physician, he was proficient in various fields, being +equally famed in his own time as poet, botanist, and statesman, and +dividing his attention between art and science. + +As a child Haller was so sickly that he was unable to amuse himself with +the sports and games common to boys of his age, and so passed most of +his time poring over books. When ten years of age he began writing poems +in Latin and German, and at fifteen entered the University of Tubingen. +At seventeen he wrote learned articles in opposition to certain accepted +doctrines, and at nineteen he received his degree of doctor. Soon after +this he visited England, where his zeal in dissecting brought him under +suspicion of grave-robbery, which suspicion made it expedient for him to +return to the Continent. After studying botany in Basel for some time he +made an extended botanical journey through Switzerland, finally settling +in his native city, Berne, as a practising physician. During this time +he did not neglect either poetry or botany, publishing anonymously a +collection of poems. + +In 1736 he was called to Gottingen as professor of anatomy, surgery, +chemistry, and botany. During his labors in the university he never +neglected his literary work, sometimes living and sleeping for days and +nights together in his library, eating his meals while delving in his +books, and sleeping only when actually compelled to do so by fatigue. +During all this time he was in correspondence with savants from all over +the world, and it is said of him that he never left a letter of any kind +unanswered. + +Haller's greatest contribution to medical science was his famous +doctrine of irritability, which has given him the name of "father of +modern nervous physiology," just as Harvey is called "the father of +the modern physiology of the blood." It has been said of this +famous doctrine of irritability that "it moved all the minds of the +century--and not in the departments of medicine alone--in a way of which +we of the present day have no satisfactory conception, unless we compare +it with our modern Darwinism."(1) + +The principle of general irritability had been laid down by Francis +Glisson (1597-1677) from deductive studies, but Haller proved by +experiments along the line of inductive methods that this irritability +was not common to all "fibre as well as to the fluids of the body," but +something entirely special, and peculiar only to muscular substance. He +distinguished between irritability of muscles and sensibility of nerves. +In 1747 he gave as the three forces that produce muscular movements: +elasticity, or "dead nervous force"; irritability, or "innate nervous +force"; and nervous force in itself. And in 1752 he described one +hundred and ninety experiments for determining what parts of the body +possess "irritability"--that is, the property of contracting when +stimulated. His conclusion that this irritability exists in muscular +substance alone and is quite independent of the nerves proceeding to it +aroused a controversy that was never definitely settled until late in +the nineteenth century, when Haller's theory was found to be entirely +correct. + +It was in pursuit of experiments to establish his theory of irritability +that Haller made his chief discoveries in embryology and development. He +proved that in the process of incubation of the egg the first trace of +the heart of the chick shows itself in the thirty-eighth hour, and that +the first trace of red blood showed in the forty-first hour. By his +investigations upon the lower animals he attempted to confirm the theory +that since the creation of genus every individual is derived from a +preceding individual--the existing theory of preformation, in which +he believed, and which taught that "every individual is fully and +completely preformed in the germ, simply growing from microscopic to +visible proportions, without developing any new parts." + +In physiology, besides his studies of the nervous system, Haller studied +the mechanism of respiration, refuting the teachings of Hamberger +(1697-1755), who maintained that the lungs contract independently. +Haller, however, in common with his contemporaries, failed utterly to +understand the true function of the lungs. The great physiologist's +influence upon practical medicine, while most profound, was largely +indirect. He was a theoretical rather than a practical physician, yet he +is credited with being the first physician to use the watch in counting +the pulse. + + +BATTISTA MORGAGNI AND MORBID ANATOMY + +A great contemporary of Haller was Giovanni Battista Morgagni +(1682-1771), who pursued what Sydenham had neglected, the investigation +in anatomy, thus supplying a necessary counterpart to the great +Englishman's work. Morgagni's investigations were directed chiefly to +the study of morbid anatomy--the study of the structure of diseased +tissue, both during life and post mortem, in contrast to the normal +anatomical structures. This work cannot be said to have originated +with him; for as early as 1679 Bonnet had made similar, although less +extensive, studies; and later many investigators, such as Lancisi and +Haller, had made post-mortem studies. But Morgagni's De sedibus et +causis morborum per anatomen indagatis was the largest, most accurate, +and best-illustrated collection of cases that had ever been brought +together, and marks an epoch in medical science. From the time of the +publication of Morgagni's researches, morbid anatomy became a recognized +branch of the medical science, and the effect of the impetus thus given +it has been steadily increasing since that time. + + +WILLIAM HUNTER + +William Hunter (1718-1783) must always be remembered as one of the +greatest physicians and anatomists of the eighteenth century, and +particularly as the first great teacher of anatomy in England; but his +fame has been somewhat overshadowed by that of his younger brother John. + +Hunter had been intended and educated for the Church, but on the advice +of the surgeon William Cullen he turned his attention to the study of +medicine. His first attempt at teaching was in 1746, when he delivered +a series of lectures on surgery for the Society of Naval Practitioners. +These lectures proved so interesting and instructive that he was at +once invited to give others, and his reputation as a lecturer was soon +established. He was a natural orator and story-teller, and he combined +with these attractive qualities that of thoroughness and clearness in +demonstrations, and although his lectures were two hours long he made +them so full of interest that his pupils seldom tired of listening. +He believed that he could do greater good to the world by "publicly +teaching his art than by practising it," and even during the last few +days of his life, when he was so weak that his friends remonstrated +against it, he continued his teaching, fainting from exhaustion at the +end of his last lecture, which preceded his death by only a few days. + +For many years it was Hunter's ambition to establish a museum where the +study of anatomy, surgery, and medicine might be advanced, and in 1765 +he asked for a grant of a plot of ground for this purpose, offering to +spend seven thousand pounds on its erection besides endowing it with a +professorship of anatomy. Not being able to obtain this grant, however, +he built a house, in which were lecture and dissecting rooms, and his +museum. In this museum were anatomical preparations, coins, minerals, +and natural-history specimens. + +Hunter's weakness was his love of controversy and his resentment of +contradiction. This brought him into strained relations with many of +the leading physicians of his time, notably his own brother John, who +himself was probably not entirely free from blame in the matter. Hunter +is said to have excused his own irritability on the grounds that being +an anatomist, and accustomed to "the passive submission of dead bodies," +contradictions became the more unbearable. Many of the physiological +researches begun by him were carried on and perfected by his more famous +brother, particularly his investigations of the capillaries, but he +added much to the anatomical knowledge of several structures of the +body, notably as to the structure of cartilages and joints. + + +JOHN HUNTER + +In Abbot Islip's chapel in Westminster Abbey, close to the resting-place +of Ben Jonson, rest the remains of John Hunter (1728-1793), famous in +the annals of medicine as among the greatest physiologists and surgeons +that the world has ever produced: a man whose discoveries and inventions +are counted by scores, and whose field of research was only limited by +the outermost boundaries of eighteenth-century science, although his +efforts were directed chiefly along the lines of his profession. + +Until about twenty years of age young Hunter had shown little aptitude +for study, being unusually fond of out-door sports and amusements; but +about that time, realizing that some occupation must be selected, he +asked permission of his brother William to attempt some dissections in +his anatomical school in London. To the surprise of his brother he made +this dissection unusually well; and being given a second, he acquitted +himself with such skill that his brother at once predicted that he would +become a great anatomist. Up to this time he had had no training of +any kind to prepare him for his professional career, and knew little of +Greek or Latin--languages entirely unnecessary for him, as he proved +in all of his life work. Ottley tells the story that, when twitted with +this lack of knowledge of the "dead languages" in after life, he said +of his opponent, "I could teach him that on the dead body which he never +knew in any language, dead or living." + +By his second year in dissection he had become so skilful that he was +given charge of some of the classes in his brother's school; in 1754 he +became a surgeon's pupil in St. George's Hospital, and two years later +house-surgeon. Having by overwork brought on symptoms that seemed to +threaten consumption, he accepted the position of staff-surgeon to an +expedition to Belleisle in 1760, and two years later was serving with +the English army at Portugal. During all this time he was constantly +engaged in scientific researches, many of which, such as his +observations of gun-shot wounds, he put to excellent use in later life. +On returning to England much improved in health in 1763, he entered at +once upon his career as a London surgeon, and from that time forward +his progress was a practically uninterrupted series of successes in his +profession. + +Hunter's work on the study of the lymphatics was of great service to +the medical profession. This important net-work of minute vessels +distributed throughout the body had recently been made the object of +much study, and various students, including Haller, had made extensive +investigations since their discovery by Asellius. But Hunter, in 1758, +was the first to discover the lymphatics in the neck of birds, although +it was his brother William who advanced the theory that the function +of these vessels was that of absorbents. One of John Hunter's pupils, +William Hewson (1739-1774), first gave an account, in 1768, of +the lymphatics in reptiles and fishes, and added to his teacher's +investigations of the lymphatics in birds. These studies of the +lymphatics have been regarded, perhaps with justice, as Hunter's most +valuable contributions to practical medicine. + +In 1767 he met with an accident by which he suffered a rupture of +the tendo Achillis--the large tendon that forms the attachment of the +muscles of the calf to the heel. From observations of this accident, +and subsequent experiments upon dogs, he laid the foundation for the +now simple and effective operation for the cure of club feet and other +deformities involving the tendons. In 1772 he moved into his residence +at Earlscourt, Brompton, where he gathered about him a great menagerie +of animals, birds, reptiles, insects, and fishes, which he used in his +physiological and surgical experiments. Here he performed a countless +number of experiments--more, probably, than "any man engaged in +professional practice has ever conducted." These experiments varied +in nature from observations of the habits of bees and wasps to major +surgical operations performed upon hedgehogs, dogs, leopards, etc. It +is said that for fifteen years he kept a flock of geese for the sole +purpose of studying the process of development in eggs. + +Hunter began his first course of lectures in 1772, being forced to do +this because he had been so repeatedly misquoted, and because he felt +that he could better gauge his own knowledge in this way. Lecturing was +a sore trial to him, as he was extremely diffident, and without writing +out his lectures in advance he was scarcely able to speak at all. In +this he presented a marked contrast to his brother William, who was +a fluent and brilliant speaker. Hunter's lectures were at best simple +readings of the facts as he had written them, the diffident teacher +seldom raising his eyes from his manuscript and rarely stopping +until his complete lecture had been read through. His lectures were, +therefore, instructive rather than interesting, as he used infinite care +in preparing them; but appearing before his classes was so dreaded by +him that he is said to have been in the habit of taking a half-drachm of +laudanum before each lecture to nerve him for the ordeal. One is led to +wonder by what name he shall designate that quality of mind that renders +a bold and fearless surgeon like Hunter, who is undaunted in the face +of hazardous and dangerous operations, a stumbling, halting, and +"frightened" speaker before a little band of, at most, thirty young +medical students. And yet this same thing is not unfrequently seen among +the boldest surgeons. + + +Hunter's Operation for the Cure of Aneurisms + +It should be an object-lesson to those who, ignorantly or otherwise, +preach against the painless vivisection as practised to-day, that by the +sacrifice of a single deer in the cause of science Hunter discovered a +fact in physiology that has been the means of saving thousands of human +lives and thousands of human bodies from needless mutilation. We refer +to the discovery of the "collateral circulation" of the blood, +which led, among other things, to Hunter's successful operation upon +aneurisms. + +Simply stated, every organ or muscle of the body is supplied by one +large artery, whose main trunk distributes the blood into its lesser +branches, and thence through the capillaries. Cutting off this main +artery, it would seem, should cut off entirely the blood-supply to the +particular organ which is supplied by this vessel; and until the time of +Hunter's demonstration this belief was held by most physiologists. But +nature has made a provision for this possible stoppage of blood-supply +from a single source, and has so arranged that some of the small +arterial branches coming from the main supply-trunk are connected with +other arterial branches coming from some other supply-trunk. Under +normal conditions the main arterial trunks supply their respective +organs, the little connecting arterioles playing an insignificant part. +But let the main supply-trunk be cut off or stopped for whatever reason, +and a remarkable thing takes place. The little connecting branches +begin at once to enlarge and draw blood from the neighboring uninjured +supply-trunk, This enlargement continues until at last a new route for +the circulation has been established, the organ no longer depending +on the now defunct original arterial trunk, but getting on as well as +before by this "collateral" circulation that has been established. + +The thorough understanding of this collateral circulation is one of the +most important steps in surgery, for until it was discovered amputations +were thought necessary in such cases as those involving the artery +supplying a leg or arm, since it was supposed that, the artery being +stopped, death of the limb and the subsequent necessity for amputation +were sure to follow. Hunter solved this problem by a single operation +upon a deer, and his practicality as a surgeon led him soon after to +apply this knowledge to a certain class of surgical cases in a most +revolutionary and satisfactory manner. + +What led to Hunter's far-reaching discovery was his investigation as to +the cause of the growth of the antlers of the deer. Wishing to ascertain +just what part the blood-supply on the opposite sides of the neck played +in the process of development, or, perhaps more correctly, to see what +effect cutting off the main blood-supply would have, Hunter had one of +the deer of Richmond Park caught and tied, while he placed a ligature +around one of the carotid arteries--one of the two principal arteries +that supply the head with blood. He observed that shortly after this the +antler (which was only half grown and consequently very vascular) on the +side of the obliterated artery became cold to the touch--from the lack +of warmth-giving blood. There was nothing unexpected in this, and Hunter +thought nothing of it until a few days later, when he found, to his +surprise, that the antler had become as warm as its fellow, and was +apparently increasing in size. Puzzled as to how this could be, and +suspecting that in some way his ligature around the artery had not been +effective, he ordered the deer killed, and on examination was astonished +to find that while his ligature had completely shut off the blood-supply +from the source of that carotid artery, the smaller arteries had become +enlarged so as to supply the antler with blood as well as ever, only by +a different route. + +Hunter soon had a chance to make a practical application of the +knowledge thus acquired. This was a case of popliteal aneurism, +operations for which had heretofore proved pretty uniformly fatal. An +aneurism, as is generally understood, is an enlargement of a certain +part of an artery, this enlargement sometimes becoming of enormous size, +full of palpitating blood, and likely to rupture with fatal results at +any time. If by any means the blood can be allowed to remain quiet for +even a few hours in this aneurism it will form a clot, contract, and +finally be absorbed and disappear without any evil results. The problem +of keeping the blood quiet, with the heart continually driving it +through the vessel, is not a simple one, and in Hunter's time was +considered so insurmountable that some surgeons advocated amputation +of any member having an aneurism, while others cut down upon the tumor +itself and attempted to tie off the artery above and below. The first +of these operations maimed the patient for life, while the second was +likely to prove fatal. + +In pondering over what he had learned about collateral circulation and +the time required for it to become fully established, Hunter conceived +the idea that if the blood-supply was cut off from above the aneurism, +thus temporarily preventing the ceaseless pulsations from the heart, +this blood would coagulate and form a clot before the collateral +circulation could become established or could affect it. The patient +upon whom he performed his now celebrated operation was afflicted with +a popliteal aneurism--that is, the aneurism was located on the large +popliteal artery just behind the knee-joint. Hunter, therefore, tied off +the femoral, or main supplying artery in the thigh, a little distance +above the aneurism. The operation was entirely successful, and in six +weeks' time the patient was able to leave the hospital, and with two +sound limbs. Naturally the simplicity and success of this operation +aroused the attention of Europe, and, alone, would have made the name of +Hunter immortal in the annals of surgery. The operation has ever since +been called the "Hunterian" operation for aneurism, but there is reason +to believe that Dominique Anel (born about 1679) performed a somewhat +similar operation several years earlier. It is probable, however, that +Hunter had never heard of this work of Anel, and that his operation +was the outcome of his own independent reasoning from the facts he had +learned about collateral circulation. Furthermore, Hunter's mode of +operation was a much better one than Anel's, and, while Anel's must +claim priority, the credit of making it widely known will always be +Hunter's. + +The great services of Hunter were recognized both at home and abroad, +and honors and positions of honor and responsibility were given him. In +1776 he was appointed surgeon-extraordinary to the king; in 1783 he +was elected a member of the Royal Society of Medicine and of the Royal +Academy of Surgery at Paris; in 1786 he became deputy surgeon-general +of the army; and in 1790 he was appointed surgeon-general and +inspector-general of hospitals. All these positions he filled with +credit, and he was actively engaged in his tireless pursuit of knowledge +and in discharging his many duties when in October, 1793, he was +stricken while addressing some colleagues, and fell dead in the arms of +a fellow-physician. + + +LAZZARO SPALLANZANI + +Hunter's great rival among contemporary physiologists was the Italian +Lazzaro Spallanzani (1729-1799), one of the most picturesque figures +in the history of science. He was not educated either as a scientist or +physician, devoting, himself at first to philosophy and the languages, +afterwards studying law, and later taking orders. But he was a keen +observer of nature and of a questioning and investigating mind, so that +he is remembered now chiefly for his discoveries and investigations +in the biological sciences. One important demonstration was his +controversion of the theory of abiogenesis, or "spontaneous generation," +as propounded by Needham and Buffon. At the time of Needham's +experiments it had long been observed that when animal or vegetable +matter had lain in water for a little time--long enough for it to begin +to undergo decomposition--the water became filled with microscopic +creatures, the "infusoria animalculis." This would tend to show, either +that the water or the animal or vegetable substance contained the +"germs" of these minute organisms, or else that they were generated +spontaneously. It was known that boiling killed these animalcules, +and Needham agreed, therefore, that if he first heated the meat or +vegetables, and also the water containing them, and then placed them in +hermetically scaled jars--if he did this, and still the animalcules +made their appearance, it would be proof-positive that they had been +generated spontaneously. Accordingly he made numerous experiments, +always with the same results--that after a few days the water was found +to swarm with the microscopic creatures. The thing seemed proven beyond +question--providing, of course, that there had been no slips in the +experiments. + +But Abbe Spallanzani thought that he detected such slips in Needham's +experiment. The possibility of such slips might come in several ways: +the contents of the jar might not have been boiled for a sufficient +length of time to kill all the germs, or the air might not have +been excluded completely by the sealing process. To cover both these +contingencies, Spallanzani first hermetically sealed the glass vessels +and then boiled them for three-quarters of an hour. Under these +circumstances no animalcules ever made their appearance--a conclusive +demonstration that rendered Needham's grounds for his theory at once +untenable.(2) + +Allied to these studies of spontaneous generation were Spallanzani's +experiments and observations on the physiological processes of +generation among higher animals. He experimented with frogs, tortoises, +and dogs; and settled beyond question the function of the ovum and +spermatozoon. Unfortunately he misinterpreted the part played by the +spermatozoa in believing that their surrounding fluid was equally active +in the fertilizing process, and it was not until some forty years later +(1824) that Dumas corrected this error. + + +THE CHEMICAL THEORY OF DIGESTION + +Among the most interesting researches of Spallanzani were his +experiments to prove that digestion, as carried on in the stomach, is a +chemical process. In this he demonstrated, as Rene Reaumur had attempted +to demonstrate, that digestion could be carried on outside the walls of +the stomach as an ordinary chemical reaction, using the gastric juice +as the reagent for performing the experiment. The question as to whether +the stomach acted as a grinding or triturating organ, rather than as a +receptacle for chemical action, had been settled by Reaumur and was +no longer a question of general dispute. Reaumur had demonstrated +conclusively that digestion would take place in the stomach in the same +manner and the same time if the substance to be digested was protected +from the peristalic movements of the stomach and subjected to the action +of the gastric juice only. He did this by introducing the substances to +be digested into the stomach in tubes, and thus protected so that while +the juices of the stomach could act upon them freely they would not be +affected by any movements of the organ. + +Following up these experiments, he attempted to show that digestion +could take place outside the body as well as in it, as it certainly +should if it were a purely chemical process. He collected quantities +of gastric juice, and placing it in suitable vessels containing crushed +grain or flesh, kept the mixture at about the temperature of the body +for several hours. After repeated experiments of this kind, apparently +conducted with great care, Reaumur reached the conclusion that "the +gastric juice has no more effect out of the living body in dissolving +or digesting the food than water, mucilage, milk, or any other bland +fluid."(3) Just why all of these experiments failed to demonstrate a +fact so simple does not appear; but to Spallanzani, at least, they +were by no means conclusive, and he proceeded to elaborate upon the +experiments of Reaumur. He made his experiments in scaled tubes exposed +to a certain degree of heat, and showed conclusively that the chemical +process does go on, even when the food and gastric juice are removed +from their natural environment in the stomach. In this he was opposed +by many physiologists, among them John Hunter, but the truth of his +demonstrations could not be shaken, and in later years we find Hunter +himself completing Spallanzani's experiments by his studies of the +post-mortem action of the gastric juice upon the stomach walls. + +That Spallanzani's and Hunter's theories of the action of the gastric +juice were not at once universally accepted is shown by an essay written +by a learned physician in 1834. In speaking of some of Spallanzani's +demonstrations, he writes: "In some of the experiments, in order to give +the flesh or grains steeped in the gastric juice the same temperature +with the body, the phials were introduced under the armpits. But this is +not a fair mode of ascertaining the effects of the gastric juice out of +the body; for the influence which life may be supposed to have on the +solution of the food would be secured in this case. The affinities +connected with life would extend to substances in contact with any part +of the system: substances placed under the armpits are not placed at +least in the same circumstances with those unconnected with a living +animal." But just how this writer reaches the conclusion that "the +experiments of Reaumur and Spallanzani give no evidence that the gastric +juice has any peculiar influence more than water or any other bland +fluid in digesting the food"(4) is difficult to understand. + +The concluding touches were given to the new theory of digestion by +John Hunter, who, as we have seen, at first opposed Spallanzani, but +who finally became an ardent champion of the chemical theory. Hunter now +carried Spallanzani's experiments further and proved the action of the +digestive fluids after death. For many years anatomists had been puzzled +by pathological lesion of the stomach, found post mortem, when no +symptoms of any disorder of the stomach had been evinced during life. +Hunter rightly conceived that these lesions were caused by the action +of the gastric juice, which, while unable to act upon the living tissue, +continued its action chemically after death, thus digesting the walls +of the stomach in which it had been formed. And, as usual with his +observations, he turned this discovery to practical use in accounting +for certain phenomena of digestion. The following account of the stomach +being digested after death was written by Hunter at the desire of +Sir John Pringle, when he was president of the Royal Society, and the +circumstance which led to this is as follows: "I was opening, in his +presence, the body of a patient of his own, where the stomach was in +part dissolved, which appeared to him very unaccountable, as there had +been no previous symptom that could have led him to suspect any +disease in the stomach. I took that opportunity of giving him my ideas +respecting it, and told him that I had long been making experiments +on digestion, and considered this as one of the facts which proved a +converting power in the gastric juice.... There are a great many powers +in nature which the living principle does not enable the animal matter, +with which it is combined, to resist--viz., the mechanical and most +of the strongest chemical solvents. It renders it, however, capable of +resisting the powers of fermentation, digestion, and perhaps several +others, which are well known to act on the same matter when deprived of +the living principle and entirely to decompose it." + +Hunter concludes his paper with the following paragraph: "These +appearances throw considerable light on the principle of digestion, +and show that it is neither a mechanical power, nor contractions of the +stomach, nor heat, but something secreted in the coats of the stomach, +and thrown into its cavity, which there animalizes the food or +assimilates it to the nature of the blood. The power of this juice is +confined or limited to certain substances, especially of the vegetable +and animal kingdoms; and although this menstruum is capable of acting +independently of the stomach, yet it is indebted to that viscus for its +continuance."(5) + + +THE FUNCTION OF RESPIRATION + +It is a curious commentary on the crude notions of mechanics of previous +generations that it should have been necessary to prove by experiment +that the thin, almost membranous stomach of a mammal has not the power +to pulverize, by mere attrition, the foods that are taken into it. +However, the proof was now for the first time forthcoming, and the +question of the general character of the function of digestion was +forever set at rest. Almost simultaneously with this great advance, +corresponding progress was made in an allied field: the mysteries of +respiration were at last cleared up, thanks to the new knowledge of +chemistry. The solution of the problem followed almost as a matter +of course upon the advances of that science in the latter part of the +century. Hitherto no one since Mayow, of the previous century, whose +flash of insight had been strangely overlooked and forgotten, had even +vaguely surmised the true function of the lungs. The great Boerhaave +had supposed that respiration is chiefly important as an aid to the +circulation of the blood; his great pupil, Haller, had believed to the +day of his death in 1777 that the main purpose of the function is to +form the voice. No genius could hope to fathom the mystery of the lungs +so long as air was supposed to be a simple element, serving a mere +mechanical purpose in the economy of the earth. + +But the discovery of oxygen gave the clew, and very soon all the +chemists were testing the air that came from the lungs--Dr. Priestley, +as usual, being in the van. His initial experiments were made in +1777, and from the outset the problem was as good as solved. Other +experimenters confirmed his results in all their essentials--notably +Scheele and Lavoisier and Spallanzani and Davy. It was clearly +established that there is chemical action in the contact of the air with +the tissue of the lungs; that some of the oxygen of the air disappears, +and that carbonic-acid gas is added to the inspired air. It was shown, +too, that the blood, having come in contact with the air, is changed +from black to red in color. These essentials were not in dispute from +the first. But as to just what chemical changes caused these results +was the subject of controversy. Whether, for example, oxygen is actually +absorbed into the blood, or whether it merely unites with carbon given +off from the blood, was long in dispute. + +Each of the main disputants was biased by his own particular views as +to the moot points of chemistry. Lavoisier, for example, believed oxygen +gas to be composed of a metal oxygen combined with the alleged element +heat; Dr. Priestley thought it a compound of positive electricity and +phlogiston; and Humphry Davy, when he entered the lists a little later, +supposed it to be a compound of oxygen and light. Such mistaken notions +naturally complicated matters and delayed a complete understanding of +the chemical processes of respiration. It was some time, too, before the +idea gained acceptance that the most important chemical changes do not +occur in the lungs themselves, but in the ultimate tissues. Indeed, +the matter was not clearly settled at the close of the century. +Nevertheless, the problem of respiration had been solved in its +essentials. Moreover, the vastly important fact had been established +that a process essentially identical with respiration is necessary to +the existence not only of all creatures supplied with lungs, but to +fishes, insects, and even vegetables--in short, to every kind of living +organism. + + +ERASMUS DARWIN AND VEGETABLE PHYSIOLOGY + +Some interesting experiments regarding vegetable respiration were made +just at the close of the century by Erasmus Darwin, and recorded in his +Botanic Garden as a foot-note to the verse: + +"While spread in air the leaves respiring play." + + +These notes are worth quoting at some length, as they give a clear idea +of the physiological doctrines of the time (1799), while taking advance +ground as to the specific matter in question: + + +"There have been various opinions," Darwin says, "concerning the use of +the leaves of plants in the vegetable economy. Some have contended +that they are perspiratory organs. This does not seem probable from an +experiment of Dr. Hales, Vegetable Statics, p. 30. He, found, by cutting +off branches of trees with apples on them and taking off the leaves, +that an apple exhaled about as much as two leaves the surfaces of which +were nearly equal to the apple; whence it would appear that apples have +as good a claim to be termed perspiratory organs as leaves. Others have +believed them excretory organs of excrementitious juices, but as +the vapor exhaled from vegetables has no taste, this idea is no more +probable than the other; add to this that in most weathers they do not +appear to perspire or exhale at all. + +"The internal surface of the lungs or air-vessels in men is said to +be equal to the external surface of the whole body, or almost fifteen +square feet; on this surface the blood is exposed to the influence of +the respired air through the medium, however, of a thin pellicle; by +this exposure to the air it has its color changed from deep red to +bright scarlet, and acquires something so necessary to the existence of +life that we can live scarcely a minute without this wonderful process. + +"The analogy between the leaves of plants and the lungs or gills of +animals seems to embrace so many circumstances that we can scarcely +withhold our consent to their performing similar offices. + +"1. The great surface of leaves compared to that of the trunk and +branches of trees is such that it would seem to be an organ well adapted +for the purpose of exposing the vegetable juices to the influence of the +air; this, however, we shall see afterwards is probably performed only +by their upper surfaces, yet even in this case the surface of the leaves +in general bear a greater proportion to the surface of the tree than the +lungs of animals to their external surfaces. + +"2. In the lung of animals the blood, after having been exposed to the +air in the extremities of the pulmonary artery, is changed in color +from deep red to bright scarlet, and certainly in some of its essential +properties it is then collected by the pulmonary vein and returned +to the heart. To show a similarity of circumstances in the leaves of +plants, the following experiment was made, June 24, 1781. A stalk with +leaves and seed-vessels of large spurge (Euphorbia helioscopia) had been +several days placed in a decoction of madder (Rubia tinctorum) so that +the lower part of the stem and two of the undermost leaves were immersed +in it. After having washed the immersed leaves in clear water I could +readily discover the color of the madder passing along the middle rib +of each leaf. The red artery was beautifully visible on the under and on +the upper surface of the leaf; but on the upper side many red branches +were seen going from it to the extremities of the leaf, which on the +other side were not visible except by looking through it against the +light. On this under side a system of branching vessels carrying a +pale milky fluid were seen coming from the extremities of the leaf, and +covering the whole under side of it, and joining two large veins, one +on each side of the red artery in the middle rib of the leaf, and along +with it descending to the foot-stalk or petiole. On slitting one of +these leaves with scissors, and having a magnifying-glass ready, the +milky blood was seen oozing out of the returning veins on each side of +the red artery in the middle rib, but none of the red fluid from the +artery. + +"All these appearances were more easily seen in a leaf of Picris treated +in the same manner; for in this milky plant the stems and middle rib of +the leaves are sometimes naturally colored reddish, and hence the color +of the madder seemed to pass farther into the ramifications of their +leaf-arteries, and was there beautifully visible with the returning +branches of milky veins on each side." + + +Darwin now goes on to draw an incorrect inference from his observations: + + +"3. From these experiments," he says, "the upper surface of the leaf +appeared to be the immediate organ of respiration, because the colored +fluid was carried to the extremities of the leaf by vessels most +conspicuous on the upper surface, and there changed into a milky fluid, +which is the blood of the plant, and then returned by concomitant +veins on the under surface, which were seen to ooze when divided with +scissors, and which, in Picris, particularly, render the under surface +of the leaves greatly whiter than the upper one." + + +But in point of fact, as studies of a later generation were to show, it +is the under surface of the leaf that is most abundantly provided +with stomata, or "breathing-pores." From the stand-point of this later +knowledge, it is of interest to follow our author a little farther, +to illustrate yet more fully the possibility of combining correct +observations with a faulty inference. + + +"4. As the upper surface of leaves constitutes the organ of respiration, +on which the sap is exposed in the termination of arteries beneath a +thin pellicle to the action of the atmosphere, these surfaces in many +plants strongly repel moisture, as cabbage leaves, whence the particles +of rain lying over their surfaces without touching them, as observed by +Mr. Melville (Essays Literary and Philosophical: Edinburgh), have the +appearance of globules of quicksilver. And hence leaves with the upper +surfaces on water wither as soon as in the dry air, but continue green +for many days if placed with the under surface on water, as appears +in the experiments of Monsieur Bonnet (Usage des Feuilles). Hence some +aquatic plants, as the water-lily (Nymphoea), have the lower sides +floating on the water, while the upper surfaces remain dry in the air. + +"5. As those insects which have many spiracula, or breathing apertures, +as wasps and flies, are immediately suffocated by pouring oil upon them, +I carefully covered with oil the surfaces of several leaves of phlomis, +of Portugal laurel, and balsams, and though it would not regularly +adhere, I found them all die in a day or two. + +"It must be added that many leaves are furnished with muscles about +their foot-stalks, to turn their surfaces to the air or light, as mimosa +or Hedysarum gyrans. From all these analogies I think there can be no +doubt but that leaves of trees are their lungs, giving out a phlogistic +material to the atmosphere, and absorbing oxygen, or vital air. + +"6. The great use of light to vegetation would appear from this theory +to be by disengaging vital air from the water which they perspire, and +thence to facilitate its union with their blood exposed beneath the +thin surface of their leaves; since when pure air is thus applied it +is probable that it can be more readily absorbed. Hence, in the curious +experiments of Dr. Priestley and Mr. Ingenhouz, some plants purified +less air than others--that is, they perspired less in the sunshine; +and Mr. Scheele found that by putting peas into water which about +half covered them they converted the vital air into fixed air, or +carbonic-acid gas, in the same manner as in animal respiration. + +"7. The circulation in the lungs or leaves of plants is very similar +to that of fish. In fish the blood, after having passed through their +gills, does not return to the heart as from the lungs of air-breathing +animals, but the pulmonary vein taking the structure of an artery after +having received the blood from the gills, which there gains a more +florid color, distributes it to the other parts of their bodies. The +same structure occurs in the livers of fish, whence we see in those +animals two circulations independent of the power of the heart--viz., +that beginning at the termination of the veins of the gills and +branching through the muscles, and that which passes through the liver; +both which are carried on by the action of those respective arteries and +veins."(6) + +Darwin is here a trifle fanciful in forcing the analogy between plants +and animals. The circulatory system of plants is really not quite +so elaborately comparable to that of fishes as he supposed. But the +all-important idea of the uniformity underlying the seeming diversity +of Nature is here exemplified, as elsewhere in the writings of Erasmus +Darwin; and, more specifically, a clear grasp of the essentials of the +function of respiration is fully demonstrated. + + +ZOOLOGY AT THE CLOSE OF THE EIGHTEENTH CENTURY + + +Several causes conspired to make exploration all the fashion during the +closing epoch of the eighteenth century. New aid to the navigator +had been furnished by the perfected compass and quadrant, and by the +invention of the chronometer; medical science had banished scurvy, which +hitherto had been a perpetual menace to the voyager; and, above all, the +restless spirit of the age impelled the venturesome to seek novelty in +fields altogether new. Some started for the pole, others tried for a +northeast or northwest passage to India, yet others sought the great +fictitious antarctic continent told of by tradition. All these of course +failed of their immediate purpose, but they added much to the world's +store of knowledge and its fund of travellers' tales. + +Among all these tales none was more remarkable than those which told of +strange living creatures found in antipodal lands. And here, as did not +happen in every field, the narratives were often substantiated by the +exhibition of specimens that admitted no question. Many a company of +explorers returned more or less laden with such trophies from the +animal and vegetable kingdoms, to the mingled astonishment, delight, and +bewilderment of the closet naturalists. The followers of Linnaeus in the +"golden age of natural history," a few decades before, had increased the +number of known species of fishes to about four hundred, of birds to one +thousand, of insects to three thousand, and of plants to ten thousand. +But now these sudden accessions from new territories doubled the figure +for plants, tripled it for fish and birds, and brought the number of +described insects above twenty thousand. Naturally enough, this wealth +of new material was sorely puzzling to the classifiers. The more +discerning began to see that the artificial system of Linnaeus, +wonderful and useful as it had been, must be advanced upon before the +new material could be satisfactorily disposed of. The way to a more +natural system, based on less arbitrary signs, had been pointed out by +Jussieu in botany, but the zoologists were not prepared to make headway +towards such a system until they should gain a wider understanding of +the organisms with which they had to deal through comprehensive studies +of anatomy. Such studies of individual forms in their relations to the +entire scale of organic beings were pursued in these last decades of +the century, but though two or three most important generalizations were +achieved (notably Kaspar Wolff's conception of the cell as the basis of +organic life, and Goethe's all-important doctrine of metamorphosis of +parts), yet, as a whole, the work of the anatomists of the period was +germinative rather than fruit-bearing. Bichat's volumes, telling of the +recognition of the fundamental tissues of the body, did not begin to +appear till the last year of the century. The announcement by Cuvier of +the doctrine of correlation of parts bears the same date, but in general +the studies of this great naturalist, which in due time were to stamp +him as the successor of Linnaeus, were as yet only fairly begun. + + + + +V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH CENTURY + +CUVIER AND THE CORRELATION OF PARTS + +We have seen that the focal points of the physiological world towards +the close of the eighteenth century were Italy and England, but when +Spallanzani and Hunter passed away the scene shifted to France. The +time was peculiarly propitious, as the recent advances in many lines of +science had brought fresh data for the student of animal life which were +in need of classification, and, as several minds capable of such a task +were in the field, it was natural that great generalizations should have +come to be quite the fashion. Thus it was that Cuvier came forward with +a brand-new classification of the animal kingdom, establishing +four great types of being, which he called vertebrates, mollusks, +articulates, and radiates. Lamarck had shortly before established the +broad distinction between animals with and those without a backbone; +Cuvier's Classification divided the latter--the invertebrates--into +three minor groups. And this division, familiar ever since to all +students of zoology, has only in very recent years been supplanted, and +then not by revolution, but by a further division, which the elaborate +recent studies of lower forms of life seemed to make desirable. + +In the course of those studies of comparative anatomy which led to his +new classification, Cuvier's attention was called constantly to the +peculiar co-ordination of parts in each individual organism. Thus an +animal with sharp talons for catching living prey--as a member of the +cat tribe--has also sharp teeth, adapted for tearing up the flesh of its +victim, and a particular type of stomach, quite different from that of +herbivorous creatures. This adaptation of all the parts of the animal +to one another extends to the most diverse parts of the organism, and +enables the skilled anatomist, from the observation of a single typical +part, to draw inferences as to the structure of the entire animal--a +fact which was of vast aid to Cuvier in his studies of paleontology. It +did not enable Cuvier, nor does it enable any one else, to reconstruct +fully the extinct animal from observation of a single bone, as has +sometimes been asserted, but what it really does establish, in the hands +of an expert, is sufficiently astonishing. + +"While the study of the fossil remains of the greater quadrupeds is more +satisfactory," he writes, "by the clear results which it affords, than +that of the remains of other animals found in a fossil state, it is also +complicated with greater and more numerous difficulties. Fossil shells +are usually found quite entire, and retaining all the characters +requisite for comparing them with the specimens contained in collections +of natural history, or represented in the works of naturalists. Even the +skeletons of fishes are found more or less entire, so that the general +forms of their bodies can, for the most part, be ascertained, +and usually, at least, their generic and specific characters are +determinable, as these are mostly drawn from their solid parts. In +quadrupeds, on the contrary, even when their entire skeletons are +found, there is great difficulty in discovering their distinguishing +characters, as these are chiefly founded upon their hairs and colors and +other marks which have disappeared previous to their incrustation. It is +also very rare to find any fossil skeletons of quadrupeds in any degree +approaching to a complete state, as the strata for the most part only +contain separate bones, scattered confusedly and almost always broken +and reduced to fragments, which are the only means left to naturalists +for ascertaining the species or genera to which they have belonged. + +"Fortunately comparative anatomy, when thoroughly understood, enables +us to surmount all these difficulties, as a careful application of its +principles instructs us in the correspondences and dissimilarities of +the forms of organized bodies of different kinds, by which each may be +rigorously ascertained from almost every fragment of its various parts +and organs. + +"Every organized individual forms an entire system of its own, all the +parts of which naturally correspond, and concur to produce a certain +definite purpose, by reciprocal reaction, or by combining towards the +same end. Hence none of these separate parts can change their forms +without a corresponding change in the other parts of the same animal, +and consequently each of these parts, taken separately, indicates all +the other parts to which it has belonged. Thus, as I have elsewhere +shown, if the viscera of an animal are so organized as only to be fitted +for the digestion of recent flesh, it is also requisite that the jaws +should be so constructed as to fit them for devouring prey; the claws +must be constructed for seizing and tearing it to pieces; the teeth +for cutting and dividing its flesh; the entire system of the limbs, +or organs of motion, for pursuing and overtaking it; and the organs of +sense for discovering it at a distance. Nature must also have endowed +the brain of the animal with instincts sufficient for concealing itself +and for laying plans to catch its necessary victims.... + +"To enable the animal to carry off its prey when seized, a corresponding +force is requisite in the muscles which elevate the head, and this +necessarily gives rise to a determinate form of the vertebrae to which +these muscles are attached and of the occiput into which they are +inserted. In order that the teeth of a carnivorous animal may be able to +cut the flesh, they require to be sharp, more or less so in proportion +to the greater or less quantity of flesh that they have to cut. It is +requisite that their roots should be solid and strong, in proportion to +the quantity and size of the bones which they have to break to pieces. +The whole of these circumstances must necessarily influence the +development and form of all the parts which contribute to move the +jaws...." + +After these observations, it will be easily seen that similar +conclusions may be drawn with respect to the limbs of carnivorous +animals, which require particular conformations to fit them for rapidity +of motion in general; and that similar considerations must influence the +forms and connections of the vertebrae and other bones constituting the +trunk of the body, to fit them for flexibility and readiness of motion +in all directions. The bones also of the nose, of the orbit, and of +the ears require certain forms and structures to fit them for giving +perfection to the senses of smell, sight, and hearing, so necessary to +animals of prey. In short, the shape and structure of the teeth regulate +the forms of the condyle, of the shoulder-blade, and of the claws, +in the same manner as the equation of a curve regulates all its other +properties; and as in regard to any particular curve all its properties +may be ascertained by assuming each separate property as the foundation +of a particular equation, in the same manner a claw, a shoulder-blade, +a condyle, a leg or arm bone, or any other bone separately considered, +enables us to discover the description of teeth to which they have +belonged; and so also reciprocally we may determine the forms of the +other bones from the teeth. Thus commencing our investigations by a +careful survey of any one bone by itself, a person who is sufficiently +master of the laws of organic structure may, as it were, reconstruct the +whole animal to which that bone belonged."(1) + +We have already pointed out that no one is quite able to perform the +necromantic feat suggested in the last sentence; but the exaggeration is +pardonable in the enthusiast to whom the principle meant so much and in +whose hands it extended so far. + +Of course this entire principle, in its broad outlines, is something +with which every student of anatomy had been familiar from the time +when anatomy was first studied, but the full expression of the "law +of co-ordination," as Cuvier called it, had never been explicitly made +before; and, notwithstanding its seeming obviousness, the exposition +which Cuvier made of it in the introduction to his classical work on +comparative anatomy, which was published during the first decade of +the nineteenth century, ranks as a great discovery. It is one of those +generalizations which serve as guideposts to other discoveries. + + +BICHAT AND THE BODILY TISSUES + +Much the same thing may be said of another generalization regarding the +animal body, which the brilliant young French physician Marie Francois +Bichat made in calling attention to the fact that each vertebrate +organism, including man, has really two quite different sets of +organs--one set under volitional control, and serving the end of +locomotion, the other removed from volitional control, and serving the +ends of the "vital processes" of digestion, assimilation, and the like. +He called these sets of organs the animal system and the organic system, +respectively. The division thus pointed out was not quite new, for +Grimaud, professor of physiology in the University of Montpellier, +had earlier made what was substantially the same classification of the +functions into "internal or digestive and external or locomotive"; but +it was Bichat's exposition that gave currency to the idea. + +Far more important, however, was another classification which Bichat put +forward in his work on anatomy, published just at the beginning of the +last century. This was the division of all animal structures into what +Bichat called tissues, and the pointing out that there are really only +a few kinds of these in the body, making up all the diverse organs. Thus +muscular organs form one system; membranous organs another; glandular +organs a third; the vascular mechanism a fourth, and so on. The +distinction is so obvious that it seems rather difficult to conceive +that it could have been overlooked by the earliest anatomists; but, in +point of fact, it is only obvious because now it has been familiarly +taught for almost a century. It had never been given explicit expression +before the time of Bichat, though it is said that Bichat himself was +somewhat indebted for it to his master, Desault, and to the famous +alienist Pinel. + +However that may be, it is certain that all subsequent anatomists have +found Bichat's classification of the tissues of the utmost value in +their studies of the animal functions. Subsequent advances were to +show that the distinction between the various tissues is not really +so fundamental as Bichat supposed, but that takes nothing from the +practical value of the famous classification. + +It was but a step from this scientific classification of tissues to a +similar classification of the diseases affecting them, and this was one +of the greatest steps towards placing medicine on the plane of an exact +science. This subject of these branches completely fascinated Bichat, +and he exclaimed, enthusiastically: "Take away some fevers and nervous +trouble, and all else belongs to the kingdom of pathological anatomy." +But out of this enthusiasm came great results. Bichat practised as he +preached, and, believing that it was only possible to understand disease +by observing the symptoms carefully at the bedside, and, if the disease +terminated fatally, by post-mortem examination, he was so arduous in his +pursuit of knowledge that within a period of less than six months he had +made over six hundred autopsies--a record that has seldom, if ever, +been equalled. Nor were his efforts fruitless, as a single example will +suffice to show. By his examinations he was able to prove that diseases +of the chest, which had formerly been classed under the indefinite name +"peripneumonia," might involve three different structures, the pleural +sac covering the lungs, the lung itself, and the bronchial tubes, the +diseases affecting these organs being known respectively as pleuritis, +pneumonia, and bronchitis, each one differing from the others as to +prognosis and treatment. The advantage of such an exact classification +needs no demonstration. + + +LISTER AND THE PERFECTED MICROSCOPE + +At the same time when these broad macroscopical distinctions were being +drawn there were other workers who were striving to go even deeper into +the intricacies of the animal mechanism with the aid of the microscope. +This undertaking, however, was beset with very great optical +difficulties, and for a long time little advance was made upon the work +of preceding generations. Two great optical barriers, known technically +as spherical and chromatic aberration--the one due to a failure of the +rays of light to fall all in one plane when focalized through a lens, +the other due to the dispersive action of the lens in breaking the +white light into prismatic colors--confronted the makers of microscopic +lenses, and seemed all but insuperable. The making of achromatic lenses +for telescopes had been accomplished, it is true, by Dolland in the +previous century, by the union of lenses of crown glass with those of +flint glass, these two materials having different indices of refraction +and dispersion. But, aside from the mechanical difficulties which arise +when the lens is of the minute dimensions required for use with the +microscope, other perplexities are introduced by the fact that the use +of a wide pencil of light is a desideratum, in order to gain sufficient +illumination when large magnification is to be secured. + +In the attempt to overcome those difficulties, the foremost physical +philosophers of the time came to the aid of the best opticians. Very +early in the century, Dr. (afterwards Sir David) Brewster, the renowned +Scotch physicist, suggested that certain advantages might accrue from +the use of such gems as have high refractive and low dispersive indices, +in place of lenses made of glass. Accordingly lenses were made of +diamond, of sapphire, and so on, and with some measure of success. But +in 1812 a much more important innovation was introduced by Dr. William +Hyde Wollaston, one of the greatest and most versatile, and, since +the death of Cavendish, by far the most eccentric of English natural +philosophers. This was the suggestion to use two plano-convex +lenses, placed at a prescribed distance apart, in lieu of the single +double-convex lens generally used. This combination largely overcame +the spherical aberration, and it gained immediate fame as the "Wollaston +doublet." + +To obviate loss of light in such a doublet from increase of reflecting +surfaces, Dr. Brewster suggested filling the interspace between the two +lenses with a cement having the same index of refraction as the lenses +themselves--an improvement of manifest advantage. An improvement yet +more important was made by Dr. Wollaston himself in the introduction of +the diaphragm to limit the field of vision between the lenses, instead +of in front of the anterior lens. A pair of lenses thus equipped Dr. +Wollaston called the periscopic microscope. Dr. Brewster suggested that +in such a lens the same object might be attained with greater ease by +grinding an equatorial groove about a thick or globular lens and filling +the groove with an opaque cement. This arrangement found much favor, +and came subsequently to be known as a Coddington lens, though Mr. +Coddington laid no claim to being its inventor. + +Sir John Herschel, another of the very great physicists of the time, +also gave attention to the problem of improving the microscope, and in +1821 he introduced what was called an aplanatic combination of lenses, +in which, as the name implies, the spherical aberration was largely +done away with. It was thought that the use of this Herschel aplanatic +combination as an eyepiece, combined with the Wollaston doublet for the +objective, came as near perfection as the compound microscope was likely +soon to come. But in reality the instrument thus constructed, though +doubtless superior to any predecessor, was so defective that for +practical purposes the simple microscope, such as the doublet or the +Coddington, was preferable to the more complicated one. + +Many opticians, indeed, quite despaired of ever being able to make a +satisfactory refracting compound microscope, and some of them had taken +up anew Sir Isaac Newton's suggestion in reference to a reflecting +microscope. In particular, Professor Giovanni Battista Amici, a very +famous mathematician and practical optician of Modena, succeeded in +constructing a reflecting microscope which was said to be superior to +any compound microscope of the time, though the events of the ensuing +years were destined to rob it of all but historical value. For there +were others, fortunately, who did not despair of the possibilities of +the refracting microscope, and their efforts were destined before +long to be crowned with a degree of success not even dreamed of by any +preceding generation. + +The man to whom chief credit is due for directing those final steps +that made the compound microscope a practical implement instead of a +scientific toy was the English amateur optician Joseph Jackson Lister. +Combining mathematical knowledge with mechanical ingenuity, and having +the practical aid of the celebrated optician Tulley, he devised formulae +for the combination of lenses of crown glass with others of flint +glass, so adjusted that the refractive errors of one were corrected +or compensated by the other, with the result of producing lenses of +hitherto unequalled powers of definition; lenses capable of showing an +image highly magnified, yet relatively free from those distortions +and fringes of color that had heretofore been so disastrous to true +interpretation of magnified structures. + +Lister had begun his studies of the lens in 1824, but it was not until +1830 that he contributed to the Royal Society the famous paper detailing +his theories and experiments. Soon after this various continental +opticians who had long been working along similar lines took the matter +up, and their expositions, in particular that of Amici, introduced +the improved compound microscope to the attention of microscopists +everywhere. And it required but the most casual trial to convince the +experienced observers that a new implement of scientific research had +been placed in their hands which carried them a long step nearer +the observation of the intimate physical processes which lie at the +foundation of vital phenomena. For the physiologist this perfection of +the compound microscope had the same significance that the, discovery +of America had for the fifteenth-century geographers--it promised a +veritable world of utterly novel revelations. Nor was the fulfilment of +that promise long delayed. + +Indeed, so numerous and so important were the discoveries now made in +the realm of minute anatomy that the rise of histology to the rank of an +independent science may be said to date from this period. Hitherto, ever +since the discovery of magnifying-glasses, there had been here and there +a man, such as Leuwenhoek or Malpighi, gifted with exceptional vision, +and perhaps unusually happy in his conjectures, who made important +contributions to the knowledge of the minute structure of organic +tissues; but now of a sudden it became possible for the veriest tyro to +confirm or refute the laborious observations of these pioneers, while +the skilled observer could step easily beyond the barriers of vision +that hitherto were quite impassable. And so, naturally enough, the +physiologists of the fourth decade of the nineteenth century rushed +as eagerly into the new realm of the microscope as, for example, their +successors of to-day are exploring the realm of the X-ray. + +Lister himself, who had become an eager interrogator of the instrument +he had perfected, made many important discoveries, the most notable +being his final settlement of the long-mooted question as to the true +form of the red corpuscles of the human blood. In reality, as everybody +knows nowadays, these are biconcave disks, but owing to their peculiar +figure it is easily possible to misinterpret the appearances they +present when seen through a poor lens, and though Dr. Thomas Young and +various other observers had come very near the truth regarding them, +unanimity of opinion was possible only after the verdict of the +perfected microscope was given. + +These blood corpuscles are so infinitesimal in size that something like +five millions of them are found in each cubic millimetre of the blood, +yet they are isolated particles, each having, so to speak, its own +personality. This, of course, had been known to microscopists since the +days of the earliest lenses. It had been noticed, too, by here and +there an observer, that certain of the solid tissues seemed to present +something of a granular texture, as if they, too, in their ultimate +constitution, were made up of particles. And now, as better and better +lenses were constructed, this idea gained ground constantly, though +for a time no one saw its full significance. In the case of vegetable +tissues, indeed, the fact that little particles encased a membranous +covering, and called cells, are the ultimate visible units of structure +had long been known. But it was supposed that animal tissues differed +radically from this construction. The elementary particles of vegetables +"were regarded to a certain extent as individuals which composed the +entire plant, while, on the other hand, no such view was taken of the +elementary parts of animals." + + +ROBERT BROWN AND THE CELL NUCLEUS + +In the year 1833 a further insight into the nature of the ultimate +particles of plants was gained through the observation of the English +microscopist Robert Brown, who, in the course of his microscopic studies +of the epidermis of orchids, discovered in the cells "an opaque spot," +which he named the nucleus. Doubtless the same "spot" had been seen +often enough before by other observers, but Brown was the first to +recognize it as a component part of the vegetable cell and to give it a +name. + + +"I shall conclude my observations on Orchideae," said Brown, "with a +notice of some points of their general structure, which chiefly relate +to the cellular tissue. In each cell of the epidermis of a great part +of this family, especially of those with membranous leaves, a single +circular areola, generally somewhat more opaque than, the membrane of +the cell, is observable. This areola, which is more or less distinctly +granular, is slightly convex, and although it seems to be on the surface +is in reality covered by the outer lamina of the cell. There is no +regularity as to its place in the cell; it is not unfrequently, however, +central or nearly so. + +"As only one areola belongs to each cell, and as in many cases where it +exists in the common cells of the epidermis, it is also visible in the +cutaneous glands or stomata, and in these is always double--one being on +each side of the limb--it is highly probable that the cutaneous gland is +in all cases composed of two cells of peculiar form, the line of union +being the longitudinal axis of the disk or pore. + +"This areola, or nucleus of the cell as perhaps it might be termed, +is not confined to the epidermis, being also found, not only in the +pubescence of the surface, particularly when jointed, as in cypripedium, +but in many cases in the parenchyma or internal cells of the tissue, +especially when these are free from the deposition of granular matter. + +"In the compressed cells of the epidermis the nucleus is in a +corresponding degree flattened; but in the internal tissue it is often +nearly spherical, more or less firmly adhering to one of the walls, +and projecting into the cavity of the cell. In this state it may not +unfrequently be found in the substance of the column and in that of the +perianthium. + +"The nucleus is manifest also in the tissue of the stigma, where in +accordance with the compression of the utriculi, it has an intermediate +form, being neither so much flattened as in the epidermis nor so convex +as it is in the internal tissue of the column. + +"I may here remark that I am acquainted with one case of apparent +exception to the nucleus being solitary in each utriculus or +cell--namely, in Bletia Tankervilliae. In the utriculi of the stigma of +this plant, I have generally, though not always, found a second areola +apparently on the surface, and composed of much larger granules than the +ordinary nucleus, which is formed of very minute granular matter, and +seems to be deep seated. + +"Mr. Bauer has represented the tissue of the stigma, in the species of +Bletia, both before and, as he believes, after impregnation; and in the +latter state the utriculi are marked with from one to three areolae of +similar appearance. + +"The nucleus may even be supposed to exist in the pollen of this family. +In the early stages of its formation, at least a minute areola is of +ten visible in the simple grain, and in each of the constituent parts +of cells of the compound grain. But these areolae may perhaps rather be +considered as merely the points of production of the tubes. + +"This nucleus of the cell is not confined to orchideae, but is equally +manifest in many other monocotyledonous families; and I have even +found it, hitherto however in very few cases, in the epidermis of +dicotyledonous plants; though in this primary division it may perhaps +be said to exist in the early stages of development of the pollen. Among +monocotyledons, the orders in which it is most remarkable are Liliaceae, +Hemerocallideae, Asphodeleae, Irideae, and Commelineae. + +"In some plants belonging to this last-mentioned family, especially +in Tradascantia virginica, and several nearly related species, it is +uncommonly distinct, not in the epidermis and in the jointed hairs of +the filaments, but in the tissue of the stigma, in the cells of the +ovulum even before impregnation, and in all the stages of formation +of the grains of pollen, the evolution of which is so remarkable in +tradascantia. + +"The few indications of the presence of this nucleus, or areola, that I +have hitherto met with in the publications of botanists are chiefly in +some figures of epidermis, in the recent works of Meyen and Purkinje, +and in one case, in M. Adolphe Broigniart's memoir on the structure of +leaves. But so little importance seems to be attached to it that the +appearance is not always referred to in the explanations of the figures +in which it is represented. Mr. Bauer, however, who has also figured +it in the utriculi of the stigma of Bletia Tankervilliae has more +particularly noticed it, and seems to consider it as only visible after +impregnation."(2) + + +SCHLEIDEN AND SCHWANN AND THE CELL THEORY + +That this newly recognized structure must be important in the economy of +the cell was recognized by Brown himself, and by the celebrated German +Meyen, who dealt with it in his work on vegetable physiology, published +not long afterwards; but it remained for another German, the professor +of botany in the University of Jena, Dr. M. J. Schleiden, to bring the +nucleus to popular attention, and to assert its all-importance in the +economy of the cell. + +Schleiden freely acknowledged his indebtedness to Brown for first +knowledge of the nucleus, but he soon carried his studies of that +structure far beyond those of its discoverer. He came to believe that +the nucleus is really the most important portion of the cell, in that +it is the original structure from which the remainder of the cell is +developed. Hence he named it the cytoblast. He outlined his views in +an epochal paper published in Muller's Archives in 1838, under title of +"Beitrage zur Phytogenesis." This paper is in itself of value, yet the +most important outgrowth of Schleiden's observations of the nucleus did +not spring from his own labors, but from those of a friend to whom he +mentioned his discoveries the year previous to their publication. +This friend was Dr. Theodor Schwann, professor of physiology in the +University of Louvain. + +At the moment when these observations were communicated to him Schwann +was puzzling over certain details of animal histology which he could +not clearly explain. His great teacher, Johannes Muller, had called +attention to the strange resemblance to vegetable cells shown by certain +cells of the chorda dorsalis (the embryonic cord from which the spinal +column is developed), and Schwann himself had discovered a corresponding +similarity in the branchial cartilage of a tadpole. Then, too, the +researches of Friedrich Henle had shown that the particles that make up +the epidermis of animals are very cell-like in appearance. Indeed, the +cell-like character of certain animal tissues had come to be matter of +common note among students of minute anatomy. Schwann felt that this +similarity could not be mere coincidence, but he had gained no clew to +further insight until Schleiden called his attention to the nucleus. +Then at once he reasoned that if there really is the correspondence +between vegetable and animal tissues that he suspected, and if the +nucleus is so important in the vegetable cell as Schleiden believed, +the nucleus should also be found in the ultimate particles of animal +tissues. + +Schwann's researches soon showed the entire correctness of this +assumption. A closer study of animal tissues under the microscope +showed, particularly in the case of embryonic tissues, that "opaque +spots" such as Schleiden described are really to be found there +in abundance--forming, indeed, a most characteristic phase of the +structure. The location of these nuclei at comparatively regular +intervals suggested that they are found in definite compartments of the +tissue, as Schleiden had shown to be the case with vegetables; indeed, +the walls that separated such cell-like compartments one from another +were in some cases visible. Particularly was this found to be the case +with embryonic tissues, and the study of these soon convinced Schwann +that his original surmise had been correct, and that all animal tissues +are in their incipiency composed of particles not unlike the ultimate +particles of vegetables in short, of what the botanists termed cells. +Adopting this name, Schwann propounded what soon became famous as his +cell theory, under title of Mikroskopische Untersuchungen uber die +Ubereinstimmung in der Structur und dent Wachsthum der Thiere und +Pflanzen. So expeditious had been his work that this book was published +early in 1839, only a few months after the appearance of Schleiden's +paper. + +As the title suggests, the main idea that actuated Schwann was to unify +vegetable and animal tissues. Accepting cell-structure as the basis of +all vegetable tissues, he sought to show that the same is true of animal +tissues, all the seeming diversities of fibre being but the alteration +and development of what were originally simple cells. And by cell +Schwann meant, as did Schleiden also, what the word ordinarily +implies--a cavity walled in on all sides. He conceived that the ultimate +constituents of all tissues were really such minute cavities, the most +important part of which was the cell wall, with its associated nucleus. +He knew, indeed, that the cell might be filled with fluid contents, but +he regarded these as relatively subordinate in importance to the wall +itself. This, however, did not apply to the nucleus, which was supposed +to lie against the cell wall and in the beginning to generate it. +Subsequently the wall might grow so rapidly as to dissociate itself +from its contents, thus becoming a hollow bubble or true cell; but the +nucleus, as long as it lasted, was supposed to continue in contact +with the cell wall. Schleiden had even supposed the nucleus to be a +constituent part of the wall, sometimes lying enclosed between two +layers of its substance, and Schwann quoted this view with seeming +approval. Schwann believed, however, that in the mature cell the nucleus +ceased to be functional and disappeared. + +The main thesis as to the similarity of development of vegetable and +animal tissues and the cellular nature of the ultimate constitution +of both was supported by a mass of carefully gathered evidence which a +multitude of microscopists at once confirmed, so Schwann's work became +a classic almost from the moment of its publication. Of course various +other workers at once disputed Schwann's claim to priority of discovery, +in particular the English microscopist Valentin, who asserted, not +without some show of justice, that he was working closely along the same +lines. Put so, for that matter, were numerous others, as Henle, Turpin, +Du-mortier, Purkinje, and Muller, all of whom Schwann himself had +quoted. Moreover, there were various physiologists who earlier than +any of these had foreshadowed the cell theory--notably Kaspar Friedrich +Wolff, towards the close of the previous century, and Treviranus about +1807, But, as we have seen in so many other departments of science, it +is one thing to foreshadow a discovery, it is quite another to give +it full expression and make it germinal of other discoveries. And when +Schwann put forward the explicit claim that "there is one universal +principle of development for the elementary parts, of organisms, however +different, and this principle is the formation of cells," he enunciated +a doctrine which was for all practical purposes absolutely new and +opened up a novel field for the microscopist to enter. A most important +era in physiology dates from the publication of his book in 1839. + + +THE CELL THEORY ELABORATED + +That Schwann should have gone to embryonic tissues for the establishment +of his ideas was no doubt due very largely to the influence of the great +Russian Karl Ernst von Baer, who about ten years earlier had published +the first part of his celebrated work on embryology, and whose ideas +were rapidly gaining ground, thanks largely to the advocacy of a few +men, notably Johannes Muller, in Germany, and William B. Carpenter, in +England, and to the fact that the improved microscope had made minute +anatomy popular. Schwann's researches made it plain that the best +field for the study of the animal cell is here, and a host of explorers +entered the field. The result of their observations was, in the main, +to confirm the claims of Schwann as to the universal prevalence of the +cell. The long-current idea that animal tissues grow only as a sort +of deposit from the blood-vessels was now discarded, and the fact of +so-called plantlike growth of animal cells, for which Schwann contended, +was universally accepted. Yet the full measure of the affinity between +the two classes of cells was not for some time generally apprehended. + +Indeed, since the substance that composes the cell walls of plants is +manifestly very different from the limiting membrane of the animal cell, +it was natural, so long as the wall was considered the most essential +part of the structure, that the divergence between the two classes +of cells should seem very pronounced. And for a time this was the +conception of the matter that was uniformly accepted. But as time +went on many observers had their attention called to the peculiar +characteristics of the contents of the cell, and were led to ask +themselves whether these might not be more important than had been +supposed. In particular, Dr. Hugo von Mohl, professor of botany in the +University of Tubingen, in the course of his exhaustive studies of +the vegetable cell, was impressed with the peculiar and characteristic +appearance of the cell contents. He observed universally within the cell +"an opaque, viscid fluid, having granules intermingled in it," which +made up the main substance of the cell, and which particularly impressed +him because under certain conditions it could be seen to be actively in +motion, its parts separated into filamentous streams. + +Von Mohl called attention to the fact that this motion of the cell +contents had been observed as long ago as 1774 by Bonaventura Corti, +and rediscovered in 1807 by Treviranus, and that these observers had +described the phenomenon under the "most unsuitable name of 'rotation +of the cell sap.'" Von Mohl recognized that the streaming substance was +something quite different from sap. He asserted that the nucleus of the +cell lies within this substance and not attached to the cell wall as +Schleiden had contended. He saw, too, that the chlorophyl granules, +and all other of the cell contents, are incorporated with the "opaque, +viscid fluid," and in 1846 he had become so impressed with the +importance of this universal cell substance that he gave it the name +of protoplasm. Yet in so doing he had no intention of subordinating the +cell wall. The fact that Payen, in 1844, had demonstrated that the +cell walls of all vegetables, high or low, are composed largely of one +substance, cellulose, tended to strengthen the position of the cell wall +as the really essential structure, of which the protoplasmic contents +were only subsidiary products. + +Meantime, however, the students of animal histology were more and more +impressed with the seeming preponderance of cell contents over cell +walls in the tissues they studied. They, too, found the cell to be +filled with a viscid, slimy fluid capable of motion. To this Dujardin +gave the name of sarcode. Presently it came to be known, through the +labors of Kolliker, Nageli, Bischoff, and various others, that there are +numerous lower forms of animal life which seem to be composed of this +sarcode, without any cell wall whatever. The same thing seemed to be +true of certain cells of higher organisms, as the blood corpuscles. +Particularly in the case of cells that change their shape markedly, +moving about in consequence of the streaming of their sarcode, did it +seem certain that no cell wall is present, or that, if present, its role +must be insignificant. + +And so histologists came to question whether, after all, the cell +contents rather than the enclosing wall must not be the really essential +structure, and the weight of increasing observations finally left no +escape from the conclusion that such is really the case. But attention +being thus focalized on the cell contents, it was at once apparent +that there is a far closer similarity between the ultimate particles of +vegetables and those of animals than had been supposed. Cellulose and +animal membrane being now regarded as more by-products, the way was +clear for the recognition of the fact that vegetable protoplasm and +animal sarcode are marvellously similar in appearance and general +properties. The closer the observation the more striking seemed this +similarity; and finally, about 1860, it was demonstrated by Heinrich de +Bary and by Max Schultze that the two are to all intents and purposes +identical. Even earlier Remak had reached a similar conclusion, and +applied Von Mohl's word protoplasm to animal cell contents, and now this +application soon became universal. Thenceforth this protoplasm was +to assume the utmost importance in the physiological world, being +recognized as the universal "physical basis of life," vegetable and +animal alike. This amounted to the logical extension and culmination +of Schwann's doctrine as to the similarity of development of the two +animate kingdoms. Yet at the same time it was in effect the banishment +of the cell that Schwann had defined. The word cell was retained, it +is true, but it no longer signified a minute cavity. It now implied, +as Schultze defined it, "a small mass of protoplasm endowed with the +attributes of life." This definition was destined presently to meet with +yet another modification, as we shall see; but the conception of the +protoplasmic mass as the essential ultimate structure, which might or +might not surround itself with a protective covering, was a permanent +addition to physiological knowledge. The earlier idea had, in effect, +declared the shell the most important part of the egg; this developed +view assigned to the yolk its true position. + +In one other important regard the theory of Schleiden and Schwann now +became modified. This referred to the origin of the cell. Schwann had +regarded cell growth as a kind of crystallization, beginning with the +deposit of a nucleus about a granule in the intercellular substance--the +cytoblastema, as Schleiden called it. But Von Mohl, as early as 1835, +had called attention to the formation of new vegetable cells through the +division of a pre-existing cell. Ehrenberg, another high authority of +the time, contended that no such division occurs, and the matter was +still in dispute when Schleiden came forward with his discovery of +so-called free cell-formation within the parent cell, and this for a +long time diverted attention from the process of division which Von Mohl +had described. All manner of schemes of cell-formation were put forward +during the ensuing years by a multitude of observers, and gained +currency notwithstanding Von Mohl's reiterated contention that there +are really but two ways in which the formation of new cells takes +place--namely, "first, through division of older cells; secondly, +through the formation of secondary cells lying free in the cavity of a +cell." + +But gradually the researches of such accurate observers as Unger, +Nageli, Kolliker, Reichart, and Remak tended to confirm the opinion of +Von Mohl that cells spring only from cells, and finally Rudolf Virchow +brought the matter to demonstration about 1860. His Omnis cellula e +cellula became from that time one of the accepted data of physiology. +This was supplemented a little later by Fleming's Omnis nucleus e +nucleo, when still more refined methods of observation had shown that +the part of the cell which always first undergoes change preparatory to +new cell-formation is the all-essential nucleus. Thus the nucleus was +restored to the important position which Schwann and Schleiden had given +it, but with greatly altered significance. Instead of being a structure +generated de novo from non-cellular substance, and disappearing as soon +as its function of cell-formation was accomplished, the nucleus was now +known as the central and permanent feature of every cell, indestructible +while the cell lives, itself the division-product of a pre-existing +nucleus, and the parent, by division of its substance, of other +generations of nuclei. The word cell received a final definition as "a +small mass of protoplasm supplied with a nucleus." + +In this widened and culminating general view of the cell theory it +became clear that every animate organism, animal or vegetable, is but a +cluster of nucleated cells, all of which, in each individual case, are +the direct descendants of a single primordial cell of the ovum. In the +developed individuals of higher organisms the successive generations of +cells become marvellously diversified in form and in specific functions; +there is a wonderful division of labor, special functions being chiefly +relegated to definite groups of cells; but from first to last there is +no function developed that is not present, in a primitive way, in +every cell, however isolated; nor does the developed cell, however +specialized, ever forget altogether any one of its primordial functions +or capacities. All physiology, then, properly interpreted, becomes +merely a study of cellular activities; and the development of the cell +theory takes its place as the great central generalization in physiology +of the nineteenth century. Something of the later developments of this +theory we shall see in another connection. + + +ANIMAL CHEMISTRY + +Just at the time when the microscope was opening up the paths that +were to lead to the wonderful cell theory, another novel line of +interrogation of the living organism was being put forward by a +different set of observers. Two great schools of physiological chemistry +had arisen--one under guidance of Liebig and Wohler, in Germany, the +other dominated by the great French master Jean Baptiste Dumas. Liebig +had at one time contemplated the study of medicine, and Dumas had +achieved distinction in connection with Prevost, at Geneva, in the +field of pure physiology before he turned his attention especially to +chemistry. Both these masters, therefore, and Wohler as well, found +absorbing interest in those phases of chemistry that have to do with the +functions of living tissues; and it was largely through their efforts +and the labors of their followers that the prevalent idea that vital +processes are dominated by unique laws was discarded and physiology was +brought within the recognized province of the chemist. So at about +the time when the microscope had taught that the cell is the really +essential structure of the living organism, the chemists had come to +understand that every function of the organism is really the expression +of a chemical change--that each cell is, in short, a miniature chemical +laboratory. And it was this combined point of view of anatomist and +chemist, this union of hitherto dissociated forces, that made possible +the inroads into the unexplored fields of physiology that were effected +towards the middle of the nineteenth century. + +One of the first subjects reinvestigated and brought to proximal +solution was the long-mooted question of the digestion of foods. +Spallanzani and Hunter had shown in the previous century that digestion +is in some sort a solution of foods; but little advance was made upon +their work until 1824, when Prout detected the presence of hydrochloric +acid in the gastric juice. A decade later Sprott and Boyd detected +the existence of peculiar glands in the gastric mucous membrane; and +Cagniard la Tour and Schwann independently discovered that the really +active principle of the gastric juice is a substance which was named +pepsin, and which was shown by Schwann to be active in the presence of +hydrochloric acid. + +Almost coincidently, in 1836, it was discovered by Purkinje +and Pappenheim that another organ than the stomach--namely, the +pancreas--has a share in digestion, and in the course of the ensuing +decade it came to be known, through the efforts of Eberle, Valentin, +and Claude Bernard, that this organ is all-important in the digestion +of starchy and fatty foods. It was found, too, that the liver and the +intestinal glands have each an important share in the work of preparing +foods for absorption, as also has the saliva--that, in short, a +coalition of forces is necessary for the digestion of all ordinary foods +taken into the stomach. + +And the chemists soon discovered that in each one of the essential +digestive juices there is at least one substance having certain +resemblances to pepsin, though acting on different kinds of food. The +point of resemblance between all these essential digestive agents is +that each has the remarkable property of acting on relatively enormous +quantities of the substance which it can digest without itself being +destroyed or apparently even altered. In virtue of this strange +property, pepsin and the allied substances were spoken of as ferments, +but more recently it is customary to distinguish them from such +organized ferments as yeast by designating them enzymes. The isolation +of these enzymes, and an appreciation of their mode of action, mark a +long step towards the solution of the riddle of digestion, but it must +be added that we are still quite in the dark as to the real ultimate +nature of their strange activity. + +In a comprehensive view, the digestive organs, taken as a whole, are +a gateway between the outside world and the more intimate cells of the +organism. Another equally important gateway is furnished by the lungs, +and here also there was much obscurity about the exact method of +functioning at the time of the revival of physiological chemistry. That +oxygen is consumed and carbonic acid given off during respiration the +chemists of the age of Priestley and Lavoisier had indeed made clear, +but the mistaken notion prevailed that it was in the lungs themselves +that the important burning of fuel occurs, of which carbonic acid is a +chief product. But now that attention had been called to the importance +of the ultimate cell, this misconception could not long hold its ground, +and as early as 1842 Liebig, in the course of his studies of animal +heat, became convinced that it is not in the lungs, but in the ultimate +tissues to which they are tributary, that the true consumption of +fuel takes place. Reviving Lavoisier's idea, with modifications and +additions, Liebig contended, and in the face of opposition finally +demonstrated, that the source of animal heat is really the consumption +of the fuel taken in through the stomach and the lungs. He showed that +all the activities of life are really the product of energy liberated +solely through destructive processes, amounting, broadly speaking, to +combustion occurring in the ultimate cells of the organism. Here is his +argument: + + +LIEBIG ON ANIMAL HEAT + +"The oxygen taken into the system is taken out again in the same forms, +whether in summer or in winter; hence we expire more carbon in cold +weather, and when the barometer is high, than we do in warm weather; and +we must consume more or less carbon in our food in the same proportion; +in Sweden more than in Sicily; and in our more temperate climate a full +eighth more in winter than in summer. + +"Even when we consume equal weights of food in cold and warm countries, +infinite wisdom has so arranged that the articles of food in different +climates are most unequal in the proportion of carbon they contain. The +fruits on which the natives of the South prefer to feed do not in the +fresh state contain more than twelve per cent. of carbon, while the +blubber and train-oil used by the inhabitants of the arctic regions +contain from sixty-six to eighty per cent. of carbon. + +"It is no difficult matter, in warm climates, to study moderation in +eating, and men can bear hunger for a long time under the equator; but +cold and hunger united very soon exhaust the body. + +"The mutual action between the elements of the food and the oxygen +conveyed by the circulation of the blood to every part of the body is +the source of animal heat. + +"All living creatures whose existence depends on the absorption of +oxygen possess within themselves a source of heat independent of +surrounding objects. + +"This truth applies to all animals, and extends besides to the +germination of seeds, to the flowering of plants, and to the maturation +of fruits. It is only in those parts of the body to which arterial +blood, and with it the oxygen absorbed in respiration, is conveyed that +heat is produced. Hair, wool, or feathers do not possess an elevated +temperature. This high temperature of the animal body, or, as it may be +called, disengagement of heat, is uniformly and under all circumstances +the result of the combination of combustible substance with oxygen. + +"In whatever way carbon may combine with oxygen, the act of combination +cannot take place without the disengagement of heat. It is a matter of +indifference whether the combination takes place rapidly or slowly, at a +high or at a low temperature; the amount of heat liberated is a constant +quantity. The carbon of the food, which is converted into carbonic acid +within the body, must give out exactly as much heat as if it had been +directly burned in the air or in oxygen gas; the only difference is that +the amount of heat produced is diffused over unequal times. In oxygen +the combustion is more rapid and the heat more intense; in air it is +slower, the temperature is not so high, but it continues longer. + +"It is obvious that the amount of heat liberated must increase or +diminish with the amount of oxygen introduced in equal times by +respiration. Those animals which respire frequently, and consequently +consume much oxygen, possess a higher temperature than others which, +with a body of equal size to be heated, take into the system less +oxygen. The temperature of a child (102 degrees) is higher than that of +an adult (99.5 degrees). That of birds (104 to 105.4 degrees) is higher +than that of quadrupeds (98.5 to 100.4 degrees), or than that of fishes +or amphibia, whose proper temperature is from 3.7 to 2.6 degrees higher +than that of the medium in which they live. All animals, strictly +speaking, are warm-blooded; but in those only which possess lungs is the +temperature of the body independent of the surrounding medium. + +"The most trustworthy observations prove that in all climates, in the +temperate zones as well as at the equator or the poles, the temperature +of the body in man, and of what are commonly called warm-blooded +animals, is invariably the same; yet how different are the circumstances +in which they live. + +"The animal body is a heated mass, which bears the same relation to +surrounding objects as any other heated mass. It receives heat when the +surrounding objects are hotter, it loses heat when they are colder +than itself. We know that the rapidity of cooling increases with +the difference between the heated body and that of the surrounding +medium--that is, the colder the surrounding medium the shorter the time +required for the cooling of the heated body. How unequal, then, must be +the loss of heat of a man at Palermo, where the actual temperature is +nearly equal to that of the body, and in the polar regions, where the +external temperature is from 70 to 90 degrees lower. + +"Yet notwithstanding this extremely unequal loss of heat, experience +has shown that the blood of an inhabitant of the arctic circle has a +temperature as high as that of the native of the South, who lives in so +different a medium. This fact, when its true significance is perceived, +proves that the heat given off to the surrounding medium is restored +within the body with great rapidity. This compensation takes place more +rapidly in winter than in summer, at the pole than at the equator. + +"Now in different climates the quantity of oxygen introduced into the +system of respiration, as has been already shown, varies according to +the temperature of the external air; the quantity of inspired oxygen +increases with the loss of heat by external cooling, and the quantity +of carbon or hydrogen necessary to combine with this oxygen must be +increased in like ratio. It is evident that the supply of heat lost by +cooling is effected by the mutual action of the elements of the food and +the inspired oxygen, which combine together. To make use of a familiar, +but not on that account a less just illustration, the animal body acts, +in this respect, as a furnace, which we supply with fuel. It signifies +nothing what intermediate forms food may assume, what changes it may +undergo in the body, the last change is uniformly the conversion +of carbon into carbonic acid and of its hydrogen into water; the +unassimilated nitrogen of the food, along with the unburned or +unoxidized carbon, is expelled in the excretions. In order to keep up +in a furnace a constant temperature, we must vary the supply of fuel +according to the external temperature--that is, according to the supply +of oxygen. + +"In the animal body the food is the fuel; with a proper supply of oxygen +we obtain the heat given out during its oxidation or combustion."(3) + + +BLOOD CORPUSCLES, MUSCLES, AND GLANDS + +Further researches showed that the carriers of oxygen, from the time of +its absorption in the lungs till its liberation in the ultimate tissues, +are the red corpuscles, whose function had been supposed to be the +mechanical one of mixing of the blood. It transpired that the red +corpuscles are composed chiefly of a substance which Kuhne first +isolated in crystalline form in 1865, and which was named haemoglobin--a +substance which has a marvellous affinity for oxygen, seizing on it +eagerly at the lungs vet giving it up with equal readiness when coursing +among the remote cells of the body. When freighted with oxygen it +becomes oxyhaemoglobin and is red in color; when freed from its oxygen +it takes a purple hue; hence the widely different appearance of arterial +and venous blood, which so puzzled the early physiologists. + +This proof of the vitally important role played by the red-blood +corpuscles led, naturally, to renewed studies of these infinitesimal +bodies. It was found that they may vary greatly in number at different +periods in the life of the same individual, proving that they may be +both developed and destroyed in the adult organism. Indeed, extended +observations left no reason to doubt that the process of corpuscle +formation and destruction may be a perfectly normal one--that, in +short, every red-blood corpuscle runs its course and dies like any more +elaborate organism. They are formed constantly in the red marrow of +bones, and are destroyed in the liver, where they contribute to the +formation of the coloring matter of the bile. Whether there are other +seats of such manufacture and destruction of the corpuscles is not +yet fully determined. Nor are histologists agreed as to whether the +red-blood corpuscles themselves are to be regarded as true cells, or +merely as fragments of cells budded out from a true cell for a special +purpose; but in either case there is not the slightest doubt that the +chief function of the red corpuscle is to carry oxygen. + +If the oxygen is taken to the ultimate cells before combining with +the combustibles it is to consume, it goes without saying that these +combustibles themselves must be carried there also. Nor could it be in +doubt that the chiefest of these ultimate tissues, as regards, quantity +of fuel required, are the muscles. A general and comprehensive view +of the organism includes, then, digestive apparatus and lungs as the +channels of fuel-supply; blood and lymph channels as the transportation +system; and muscle cells, united into muscle fibres, as the consumption +furnaces, where fuel is burned and energy transformed and rendered +available for the purposes of the organism, supplemented by a set of +excretory organs, through which the waste products--the ashes--are +eliminated from the system. + +But there remain, broadly speaking, two other sets of organs whose size +demonstrates their importance in the economy of the organism, yet +whose functions are not accounted for in this synopsis. These are those +glandlike organs, such as the spleen, which have no ducts and produce no +visible secretions, and the nervous mechanism, whose central organs are +the brain and spinal cord. What offices do these sets of organs perform +in the great labor-specializing aggregation of cells which we call a +living organism? + +As regards the ductless glands, the first clew to their function was +given when the great Frenchman Claude Bernard (the man of whom +his admirers loved to say, "He is not a physiologist merely; he is +physiology itself") discovered what is spoken of as the glycogenic +function of the liver. The liver itself, indeed, is not a ductless +organ, but the quantity of its biliary output seems utterly +disproportionate to its enormous size, particularly when it is +considered that in the case of the human species the liver contains +normally about one-fifth of all the blood in the entire body. Bernard +discovered that the blood undergoes a change of composition in passing +through the liver. The liver cells (the peculiar forms of which had been +described by Purkinje, Henle, and Dutrochet about 1838) have the power +to convert certain of the substances that come to them into a starchlike +compound called glycogen, and to store this substance away till it +is needed by the organism. This capacity of the liver cells is quite +independent of the bile-making power of the same cells; hence the +discovery of this glycogenic function showed that an organ may have +more than one pronounced and important specific function. But its chief +importance was in giving a clew to those intermediate processes between +digestion and final assimilation that are now known to be of such vital +significance in the economy of the organism. + +In the forty odd years that have elapsed since this pioneer observation +of Bernard, numerous facts have come to light showing the extreme +importance of such intermediate alterations of food-supplies in the +blood as that performed by the liver. It has been shown that the +pancreas, the spleen, the thyroid gland, the suprarenal capsules +are absolutely essential, each in its own way, to the health of the +organism, through metabolic changes which they alone seem capable of +performing; and it is suspected that various other tissues, including +even the muscles themselves, have somewhat similar metabolic capacities +in addition to their recognized functions. But so extremely intricate is +the chemistry of the substances involved that in no single case has the +exact nature of the metabolisms wrought by these organs been fully made +out. Each is in its way a chemical laboratory indispensable to the +right conduct of the organism, but the precise nature of its operations +remains inscrutable. The vast importance of the operations of these +intermediate organs is unquestioned. + +A consideration of the functions of that other set of organs known +collectively as the nervous system is reserved for a later chapter. + + + + +VI. THEORIES OF ORGANIC EVOLUTION + +GOETHE AND THE METAMORPHOSIS OF PARTS + +When Coleridge said of Humphry Davy that he might have been the greatest +poet of his time had he not chosen rather to be the greatest chemist, it +is possible that the enthusiasm of the friend outweighed the caution of +the critic. But however that may be, it is beyond dispute that the man +who actually was the greatest poet of that time might easily have taken +the very highest rank as a scientist had not the muse distracted his +attention. Indeed, despite these distractions, Johann Wolfgang von +Goethe achieved successes in the field of pure science that would insure +permanent recognition for his name had he never written a stanza of +poetry. Such is the versatility that marks the highest genius. + +It was in 1790 that Goethe published the work that laid the foundations +of his scientific reputation--the work on the Metamorphoses of Plants, +in which he advanced the novel doctrine that all parts of the flower are +modified or metamorphosed leaves. + +"Every one who observes the growth of plants, even superficially," +wrote Goethe, "will notice that certain external parts of them become +transformed at times and go over into the forms of the contiguous parts, +now completely, now to a greater or less degree. Thus, for example, the +single flower is transformed into a double one when, instead of stamens, +petals are developed, which are either exactly like the other petals of +the corolla in form, and color or else still bear visible signs of their +origin. + +"When we observe that it is possible for a plant in this way to take a +step backward, we shall give so much the more heed to the regular course +of nature and learn the laws of transformation according to which she +produces one part through another, and displays the most varying forms +through the modification of one single organ. + +"Let us first direct our attention to the plant at the moment when it +develops out of the seed-kernel. The first organs of its upward +growth are known by the name of cotyledons; they have also been called +seed-leaves. + +"They often appear shapeless, filled with new matter, and are just as +thick as they are broad. Their vessels are unrecognizable and are hardly +to be distinguished from the mass of the whole; they bear almost no +resemblance to a leaf, and we could easily be misled into regarding them +as special organs. Occasionally, however, they appear as real leaves, +their vessels are capable of the most minute development, their +similarity to the following leaves does not permit us to take them for +special organs, but we recognize them instead to be the first leaves of +the stalk. + +"The cotyledons are mostly double, and there is an observation to be +made here which will appear still more important as we proceed--that +is, that the leaves of the first node are often paired, even when the +following leaves of the stalk stand alternately upon it. Here we see an +approximation and a joining of parts which nature afterwards separates +and places at a distance from one another. It is still more remarkable +when the cotyledons take the form of many little leaves gathered about +an axis, and the stalk which grows gradually from their midst produces +the following leaves arranged around it singly in a whorl. This may be +observed very exactly in the growth of the pinus species. Here a corolla +of needles forms at the same time a calyx, and we shall have occasion to +remember the present case in connection with similar phenomena later. + +"On the other hand, we observe that even the cotyledons which are most +like a leaf when compared with the following leaves of the stalk are +always more undeveloped or less developed. This is chiefly noticeable +in their margin which is extremely simple and shows few traces of +indentation. + +"A few or many of the next following leaves are often already present in +the seed, and lie enclosed between the cotyledons; in their folded state +they are known by the name of plumules. Their form, as compared with the +cotyledons and the following leaves, varies in different plants. Their +chief point of variance, however, from the cotyledons is that they are +flat, delicate, and formed like real leaves generally. They are wholly +green, rest on a visible node, and can no longer deny their relationship +to the following leaves of the stalk, to which, however, they are +usually still inferior, in so far as that their margin is not completely +developed. + +"The further development, however, goes on ceaselessly in the leaf, from +node to node; its midrib is elongated, and more or less additional ribs +stretch out from this towards the sides. The leaves now appear notched, +deeply indented, or composed of several small leaves, in which last case +they seem to form complete little branches. The date-palm furnishes a +striking example of such a successive transformation of the simplest +leaf form. A midrib is elongated through a succession of several +leaves, the single fan-shaped leaf becomes torn and diverted, and a very +complicated leaf is developed, which rivals a branch in form. + +"The transition to inflorescence takes place more or less rapidly. In +the latter case we usually observe that the leaves of the stalk loose +their different external divisions, and, on the other hand, spread out +more or less in their lower parts where they are attached to the stalk. +If the transition takes place rapidly, the stalk, suddenly become +thinner and more elongated since the node of the last-developed leaf, +shoots up and collects several leaves around an axis at its end. + +"That the petals of the calyx are precisely the same organs which have +hitherto appeared as leaves on the stalk, but now stand grouped about a +common centre in an often very different form, can, as it seems to me, +be most clearly demonstrated. Already in connection with the cotyledons +above, we noticed a similar working of nature. The first species, while +they are developing out of the seed-kernel, display a radiate crown of +unmistakable needles; and in the first childhood of these plants we see +already indicated that force of nature whereby when they are older their +flowering and fruit-giving state will be produced. + +"We see this force of nature, which collects several leaves around an +axis, produce a still closer union and make these approximated, modified +leaves still more unrecognizable by joining them together either +wholly or partially. The bell-shaped or so-called one-petalled calices +represent these cloudy connected leaves, which, being more or less +indented from above, or divided, plainly show their origin. + +"We can observe the transition from the calyx to the corolla in more +than one instance, for, although the color of the calyx is still usually +green, and like the color of the leaves of the stalk, it nevertheless +often varies in one or another of its parts--at the tips, the margins, +the back, or even, the inward side--while the outer still remains on +green. + +"The relationship of the corolla to the leaves of the stalk is shown +in more than one way, since on the stalks of some plants appear leaves +which are already more or less colored long before they approach +inflorescence; others are fully colored when near inflorescence. Nature +also goes over at once to the corolla, sometimes by skipping over the +organs of the calyx, and in such a case we likewise have an opportunity +to observe that leaves of the stalk become transformed into petals. Thus +on the stalk of tulips, for instance, there sometimes appears an almost +completely developed and colored petal. Even more remarkable is the +case when such a leaf, half green and half of it belonging to the stalk, +remains attached to the latter, while another colored part is raised +with the corolla, and the leaf is thus torn in two. + +"The relationship between the petals and stamens is very close. In some +instances nature makes the transition regular--e.g., among the Canna +and several plants of the same family. A true, little-modified petal is +drawn together on its upper margin, and produces a pollen sac, while the +rest of the petal takes the place of the stamen. In double flowers +we can observe this transition in all its stages. In several kinds of +roses, within the fully developed and colored petals there appear other +ones which are drawn together in the middle or on the side. This drawing +together is produced by a small weal, which appears as a more or less +complete pollen sac, and in the same proportion the leaf approaches the +simple form of a stamen. + +"The pistil in many cases looks almost like a stamen without anthers, +and the relationship between the formation of the two is much closer +than between the other parts. In retrograde fashion nature often +produces cases where the style and stigma (Narben) become retransformed +into petals--that is, the Ranunculus Asiaticus becomes double by +transforming the stigma and style of the fruit-receptacle into real +petals, while the stamens are often found unchanged immediately behind +the corolla. + +"In the seed receptacles, in spite of their formation, of their special +object, and of their method of being joined together, we cannot fail to +recognize the leaf form. Thus, for instance, the pod would be a simple +leaf folded and grown together on its margin; the siliqua would consist +of more leaves folded over another; the compound receptacles would be +explained as being several leaves which, being united above one centre, +keep their inward parts separate and are joined on their margins. We can +convince ourselves of this by actual sight when such composite capsules +fall apart after becoming ripe, because then every part displays an +opened pod."(1) + + +The theory thus elaborated of the metamorphosis of parts was presently +given greater generality through extension to the animal kingdom, in +the doctrine which Goethe and Oken advanced independently, that the +vertebrate skull is essentially a modified and developed vertebra. These +were conceptions worthy of a poet--impossible, indeed, for any mind that +had not the poetic faculty of correlation. But in this case the poet's +vision was prophetic of a future view of the most prosaic science. +The doctrine of metamorphosis of parts soon came to be regarded as of +fundamental importance. + +But the doctrine had implications that few of its early advocates +realized. If all the parts of a flower--sepal, petal, stamen, +pistil, with their countless deviations of contour and color--are +but modifications of the leaf, such modification implies a marvellous +differentiation and development. To assert that a stamen is a +metamorphosed leaf means, if it means anything, that in the long sweep +of time the leaf has by slow or sudden gradations changed its character +through successive generations, until the offspring, so to speak, of a +true leaf has become a stamen. But if such a metamorphosis as this +is possible--if the seemingly wide gap between leaf and stamen may +be spanned by the modification of a line of organisms--where does the +possibility of modification of organic type find its bounds? Why may +not the modification of parts go on along devious lines until the remote +descendants of an organism are utterly unlike that organism? Why may we +not thus account for the development of various species of beings all +sprung from one parent stock? That, too, is a poet's dream; but is it +only a dream? Goethe thought not. Out of his studies of metamorphosis of +parts there grew in his mind the belief that the multitudinous species +of plants and animals about us have been evolved from fewer and fewer +earlier parent types, like twigs of a giant tree drawing their nurture +from the same primal root. It was a bold and revolutionary thought, and +the world regarded it as but the vagary of a poet. + + +ERASMUS DARWIN + +Just at the time when this thought was taking form in Goethe's brain, +the same idea was germinating in the mind of another philosopher, an +Englishman of international fame, Dr. Erasmus Darwin, who, while he +lived, enjoyed the widest popularity as a poet, the rhymed couplets +of his Botanic Garden being quoted everywhere with admiration. And +posterity repudiating the verse which makes the body of the book, +yet grants permanent value to the book itself, because, forsooth, its +copious explanatory foot-notes furnish an outline of the status of +almost every department of science of the time. + +But even though he lacked the highest art of the versifier, Darwin had, +beyond peradventure, the imagination of a poet coupled with profound +scientific knowledge; and it was his poetic insight, correlating +organisms seemingly diverse in structure and imbuing the lowliest flower +with a vital personality, which led him to suspect that there are no +lines of demarcation in nature. "Can it be," he queries, "that one +form of organism has developed from another; that different species +are really but modified descendants of one parent stock?" The alluring +thought nestled in his mind and was nurtured there, and grew in a fixed +belief, which was given fuller expression in his Zoonomia and in the +posthumous Temple of Nature. + +Here is his rendering of the idea as versified in the Temple of Nature: + + "Organic life beneath the shoreless waves + Was born, and nursed in Ocean's pearly caves; + First forms minute, unseen by spheric glass, + Move on the mud, or pierce the watery mass; + These, as successive generations bloom, + New powers acquire and larger limbs assume; + Whence countless groups of vegetation spring, + And breathing realms of fin, and feet, and wing. + + "Thus the tall Oak, the giant of the wood, + Which bears Britannia's thunders on the flood; + The Whale, unmeasured monster of the main; + The lordly lion, monarch of the plain; + The eagle, soaring in the realms of air, + Whose eye, undazzled, drinks the solar glare; + Imperious man, who rules the bestial crowd, + Of language, reason, and reflection proud, + With brow erect, who scorns this earthy sod, + And styles himself the image of his God-- + Arose from rudiments of form and sense, + An embryon point or microscopic ens!"(2) + + +Here, clearly enough, is the idea of evolution. But in that day there +was little proof forthcoming of its validity that could satisfy any +one but a poet, and when Erasmus Darwin died, in 1802, the idea of +transmutation of species was still but an unsubstantiated dream. + +It was a dream, however, which was not confined to Goethe and Darwin. +Even earlier the idea had come more or less vaguely to another great +dreamer--and worker--of Germany, Immanuel Kant, and to several great +Frenchmen, including De Maillet, Maupertuis, Robinet, and the famous +naturalist Buffon--a man who had the imagination of a poet, though his +message was couched in most artistic prose. Not long after the middle of +the eighteenth century Buffon had put forward the idea of transmutation +of species, and he reiterated it from time to time from then on till +his death in 1788. But the time was not yet ripe for the idea of +transmutation of species to burst its bonds. + +And yet this idea, in a modified or undeveloped form, had taken strange +hold upon the generation that was upon the scene at the close of the +eighteenth century. Vast numbers of hitherto unknown species of animals +had been recently discovered in previously unexplored regions of the +globe, and the wise men were sorely puzzled to account for the disposal +of all of these at the time of the deluge. It simplified matters greatly +to suppose that many existing species had been developed since the +episode of the ark by modification of the original pairs. The remoter +bearings of such a theory were overlooked for the time, and the idea +that American animals and birds, for example, were modified descendants +of Old-World forms--the jaguar of the leopard, the puma of the lion, and +so on--became a current belief with that class of humanity who accept +almost any statement as true that harmonizes with their prejudices +without realizing its implications. + +Thus it is recorded with eclat that the discovery of the close proximity +of America at the northwest with Asia removes all difficulties as to the +origin of the Occidental faunas and floras, since Oriental species +might easily have found their way to America on the ice, and have been +modified as we find them by "the well-known influence of climate." And +the persons who gave expression to this idea never dreamed of its +real significance. In truth, here was the doctrine of evolution in a +nutshell, and, because its ultimate bearings were not clear, it seemed +the most natural of doctrines. But most of the persons who advanced it +would have turned from it aghast could they have realized its import. +As it was, however, only here and there a man like Buffon reasoned +far enough to inquire what might be the limits of such assumed +transmutation; and only here and there a Darwin or a Goethe reached the +conviction that there are no limits. + + +LAMARCK VERSUS CUVIER + +And even Goethe and Darwin had scarcely passed beyond that tentative +stage of conviction in which they held the thought of transmutation of +species as an ancillary belief not ready for full exposition. There was +one of their contemporaries, however, who, holding the same conception, +was moved to give it full explication. This was the friend and disciple +of Buffon, Jean Baptiste de Lamarck. Possessed of the spirit of a poet +and philosopher, this great Frenchman had also the widest range of +technical knowledge, covering the entire field of animate nature. The +first half of his long life was devoted chiefly to botany, in which he +attained high distinction. Then, just at the beginning of the nineteenth +century, he turned to zoology, in particular to the lower forms of +animal life. Studying these lowly organisms, existing and fossil, he +was more and more impressed with the gradations of form everywhere to be +seen; the linking of diverse families through intermediate ones; and +in particular with the predominance of low types of life in the earlier +geological strata. Called upon constantly to classify the various forms +of life in the course of his systematic writings, he found it more +and more difficult to draw sharp lines of demarcation, and at last the +suspicion long harbored grew into a settled conviction that there is +really no such thing as a species of organism in nature; that "species" +is a figment of the human imagination, whereas in nature there are only +individuals. + +That certain sets of individuals are more like one another than like +other sets is of course patent, but this only means, said Lamarck, that +these similar groups have had comparatively recent common ancestors, +while dissimilar sets of beings are more remotely related in +consanguinity. But trace back the lines of descent far enough, and all +will culminate in one original stock. All forms of life whatsoever are +modified descendants of an original organism. From lowest to highest, +then, there is but one race, one species, just as all the multitudinous +branches and twigs from one root are but one tree. For purposes of +convenience of description, we may divide organisms into orders, +families, genera, species, just as we divide a tree into root, trunk, +branches, twigs, leaves; but in the one case, as in the other, the +division is arbitrary and artificial. + +In Philosophie Zoologique (1809), Lamarck first explicitly formulated +his ideas as to the transmutation of species, though he had outlined +them as early as 1801. In this memorable publication not only did he +state his belief more explicitly and in fuller detail than the idea +had been expressed by any predecessor, but he took another long forward +step, carrying him far beyond all his forerunners except Darwin, in +that he made an attempt to explain the way in which the transmutation of +species had been brought about. The changes have been wrought, he said, +through the unceasing efforts of each organism to meet the needs imposed +upon it by its environment. Constant striving means the constant use +of certain organs. Thus a bird running by the seashore is constantly +tempted to wade deeper and deeper in pursuit of food; its incessant +efforts tend to develop its legs, in accordance with the observed +principle that the use of any organ tends to strengthen and develop it. +But such slightly increased development of the legs is transmitted to +the off spring of the bird, which in turn develops its already improved +legs by its individual efforts, and transmits the improved tendency. +Generation after generation this is repeated, until the sum of the +infinitesimal variations, all in the same direction, results in the +production of the long-legged wading-bird. In a similar way, through +individual effort and transmitted tendency, all the diversified organs +of all creatures have been developed--the fin of the fish, the wing of +the bird, the hand of man; nay, more, the fish itself, the bird, the +man, even. Collectively the organs make up the entire organism; and what +is true of the individual organs must be true also of their ensemble, +the living being. + +Whatever might be thought of Lamarck's explanation of the cause of +transmutation--which really was that already suggested by Erasmus +Darwin--the idea of the evolution for which he contended was but the +logical extension of the conception that American animals are the +modified and degenerated descendants of European animals. But people as +a rule are little prone to follow ideas to their logical conclusions, +and in this case the conclusions were so utterly opposed to the proximal +bearings of the idea that the whole thinking world repudiated them with +acclaim. The very persons who had most eagerly accepted the idea of +transmutation of European species into American species, and similar +limited variations through changed environment, because of the +relief thus given the otherwise overcrowded ark, were now foremost in +denouncing such an extension of the doctrine of transmutation as Lamarck +proposed. + +And, for that matter, the leaders of the scientific world were equally +antagonistic to the Lamarckian hypothesis. Cuvier in particular, once +the pupil of Lamarck, but now his colleague, and in authority more than +his peer, stood out against the transmutation doctrine with all his +force. He argued for the absolute fixity of species, bringing to bear +the resources of a mind which, as a mere repository of facts, perhaps +never was excelled. As a final and tangible proof of his position, +he brought forward the bodies of ibises that had been embalmed by the +ancient Egyptians, and showed by comparison that these do not differ in +the slightest particular from the ibises that visit the Nile to-day. + +Cuvier's reasoning has such great historical interest--being the +argument of the greatest opponent of evolution of that day--that we +quote it at some length. + +"The following objections," he says, "have already been started against +my conclusions. Why may not the presently existing races of mammiferous +land quadrupeds be mere modifications or varieties of those ancient +races which we now find in the fossil state, which modifications may +have been produced by change of climate and other local circumstances, +and since raised to the present excessive difference by the operations +of similar causes during a long period of ages? + +"This objection may appear strong to those who believe in the indefinite +possibility of change of form in organized bodies, and think that, +during a succession of ages and by alterations of habitudes, all the +species may change into one another, or one of them give birth to all +the rest. Yet to these persons the following answer may be given from +their own system: If the species have changed by degrees, as they +assume, we ought to find traces of this gradual modification. Thus, +between the palaeotherium and the species of our own day, we should be +able to discover some intermediate forms; and yet no such discovery +has ever been made. Since the bowels of the earth have not preserved +monuments of this strange genealogy, we have no right to conclude that +the ancient and now extinct species were as permanent in their forms +and characters as those which exist at present; or, at least, that the +catastrophe which destroyed them did not leave sufficient time for the +productions of the changes that are alleged to have taken place. + +"In order to reply to those naturalists who acknowledge that the +varieties of animals are restrained by nature within certain limits, +it would be necessary to examine how far these limits extend. This is +a very curious inquiry, and in itself exceedingly interesting under +a variety of relations, but has been hitherto very little attended +to.... + +"Wild animals which subsist upon herbage feel the influence of climate a +little more extensively, because there is added to it the influence +of food, both in regard to its abundance and its quality. Thus the +elephants of one forest are larger than those of another; their tusks +also grow somewhat longer in places where their food may happen to be +more favorable for the production of the substance of ivory. The same +may take place in regard to the horns of stags and reindeer. But let +us examine two elephants, the most dissimilar that can be conceived, +we shall not discover the smallest difference in the number and +articulations of the bones, the structure of the teeth, etc......... + +"Nature appears also to have guarded against the alterations of species +which might proceed from mixture of breeds by influencing the various +species of animals with mutual aversion from one another. Hence all +the cunning and all the force that man is able to exert is necessary +to accomplish such unions, even between species that have the nearest +resemblances. And when the mule breeds that are thus produced by these +forced conjunctions happen to be fruitful, which is seldom the case, +this fecundity never continues beyond a few generations, and would not +probably proceed so far without a continuance of the same cares which +excited it at first. Thus we never see in a wild state intermediate +productions between the hare and the rabbit, between the stag and the +doe, or between the marten and the weasel. But the power of man changes +this established order, and continues to produce all these intermixtures +of which the various species are susceptible, but which they would never +produce if left to themselves. + +"The degrees of these variations are proportional to the intensity of +the causes that produced them--namely, the slavery or subjection +under which those animals are to man. They do not proceed far in +half-domesticated species. In the cat, for example, a softer or harsher +fur, more brilliant or more varied colors, greater or less size--these +form the whole extent of variety in the species; the skeleton of the +cat of Angora differs in no regular and constant circumstances from the +wild-cat of Europe...." + +The most remarkable effects of the influence of man are produced upon +that animal which he has reduced most completely under subjection. Dogs +have been transported by mankind into every part of the world and have +submitted their action to his entire direction. Regulated in their +unions by the pleasure or caprice of their masters, the almost endless +varieties of dogs differ from one another in color, in length, and +abundance of hair, which is sometimes entirely wanting; in their natural +instincts; in size, which varies in measure as one to five, mounting in +some instances to more than a hundredfold in bulk; in the form of their +ears, noses, and tails; in the relative length of their legs; in the +progressive development of the brain, in several of the domesticated +varieties occasioning alterations even in the form of the head, some of +them having long, slender muzzles with a flat forehead, others having +short muzzles with a forehead convex, etc., insomuch that the apparent +difference between a mastiff and a water-spaniel and between a greyhound +and a pugdog are even more striking than between almost any of the wild +species of a genus........ + +It follows from these observations that animals have certain fixed and +natural characters which resist the effects of every kind of influence, +whether proceeding from natural causes or human interference; and we +have not the smallest reason to suspect that time has any more effect on +them than climate. + +"I am aware that some naturalists lay prodigious stress upon the +thousands which they can call into action by a dash of their pens. In +such matters, however, our only way of judging as to the effects which +may be produced by a long period of time is by multiplying, as it were, +such as are produced by a shorter time. With this view I have endeavored +to collect all the ancient documents respecting the forms of animals; +and there are none equal to those furnished by the Egyptians, both in +regard to their antiquity and abundance. They have not only left us +representatives of animals, but even their identical bodies embalmed and +preserved in the catacombs. + +"I have examined, with the greatest attention, the engraved figures of +quadrupeds and birds brought from Egypt to ancient Rome, and all these +figures, one with another, have a perfect resemblance to their intended +objects, such as they still are to-day. + +"From all these established facts, there does not seem to be the +smallest foundation for supposing that the new genera which I have +discovered or established among extraneous fossils, such as the +paleoetherium, anoplotherium, megalonyx, mastodon, pterodactylis, etc., +have ever been the sources of any of our present animals, which only +differ so far as they are influenced by time or climate. Even if it +should prove true, which I am far from believing to be the case, that +the fossil elephants, rhinoceroses, elks, and bears do not differ +further from the existing species of the same genera than the present +races of dogs differ among themselves, this would by no means be a +sufficient reason to conclude that they were of the same species; since +the races or varieties of dogs have been influenced by the trammels +of domesticity, which those other animals never did, and indeed never +could, experience."(3) + + +To Cuvier's argument from the fixity of Egyptian mummified birds and +animals, as above stated, Lamarck replied that this proved nothing +except that the ibis had become perfectly adapted to its Egyptian +surroundings in an early day, historically speaking, and that the +climatic and other conditions of the Nile Valley had not since then +changed. His theory, he alleged, provided for the stability of species +under fixed conditions quite as well as for transmutation under varying +conditions. + +But, needless to say, the popular verdict lay with Cuvier; talent won +for the time against genius, and Lamarck was looked upon as an impious +visionary. His faith never wavered, however. He believed that he had +gained a true insight into the processes of animate nature, and +he reiterated his hypotheses over and over, particularly in the +introduction to his Histoire Naturelle des Animaux sans Vertebres, in +1815, and in his Systeme des Connaissances Positives de l'Homme, in +1820. He lived on till 1829, respected as a naturalist, but almost +unrecognized as a prophet. + + +TENTATIVE ADVANCES + +While the names of Darwin and Goethe, and in particular that of Lamarck, +must always stand out in high relief in this generation as the exponents +of the idea of transmutation of species, there are a few others which +must not be altogether overlooked in this connection. Of these the +most conspicuous is that of Gottfried Reinhold Treviranus, a German +naturalist physician, professor of mathematics in the lyceum at Bremen. + +It was an interesting coincidence that Treviranus should have published +the first volume of his Biologie, oder Philosophie der lebenden Natur, +in which his views on the transmutation of species were expounded, in +1802, the same twelvemonth in which Lamarck's first exposition of the +same doctrine appeared in his Recherches sur l'Organisation des Corps +Vivants. It is singular, too, that Lamarck, in his Hydrogelogie of +the same date, should independently have suggested "biology" as an +appropriate word to express the general science of living things. It is +significant of the tendency of thought of the time that the need of +such a unifying word should have presented itself simultaneously to +independent thinkers in different countries. + +That same memorable year, Lorenz Oken, another philosophical naturalist, +professor in the University of Zurich, published the preliminary +outlines of his Philosophie der Natur, which, as developed through +later publications, outlined a theory of spontaneous generation and of +evolution of species. Thus it appears that this idea was germinating +in the minds of several of the ablest men of the time during the +first decade of our century. But the singular result of their various +explications was to give sudden check to that undercurrent of thought +which for some time had been setting towards this conception. As soon as +it was made clear whither the concession that animals may be changed +by their environment must logically trend, the recoil from the idea +was instantaneous and fervid. Then for a generation Cuvier was almost +absolutely dominant, and his verdict was generally considered final. + +There was, indeed, one naturalist of authority in France who had the +hardihood to stand out against Cuvier and his school, and who was in a +position to gain a hearing, though by no means to divide the following. +This was Etienne Geoffroy Saint-Hilaire, the famous author of the +Philosophie Anatomique, and for many years the colleague of Lamarck +at the Jardin des Plantes. Like Goethe, Geoffroy was pre-eminently an +anatomist, and, like the great German, he had early been impressed with +the resemblances between the analogous organs of different classes of +beings. He conceived the idea that an absolute unity of type prevails +throughout organic nature as regards each set of organs. Out of this +idea grew his gradually formed belief that similarity of structure might +imply identity of origin--that, in short, one species of animal might +have developed from another. + +Geoffroy's grasp of this idea of transmutation was by no means so +complete as that of Lamarck, and he seems never to have fully determined +in his own mind just what might be the limits of such development of +species. Certainly he nowhere includes all organic creatures in one line +of descent, as Lamarck had done; nevertheless, he held tenaciously to +the truth as he saw it, in open opposition to Cuvier, with whom he held +a memorable debate at the Academy of Sciences in 1830--the debate which +so aroused the interest and enthusiasm of Goethe, but which, in the +opinion of nearly every one else, resulted in crushing defeat for +Geoffrey, and brilliant, seemingly final, victory for the advocate of +special creation and the fixity of species. + +With that all ardent controversy over the subject seemed to end, and +for just a quarter of a century to come there was published but a +single argument for transmutation of species which attracted any general +attention whatever. This oasis in a desert generation was a little +book called Vestiges of the Natural History of Creation, which appeared +anonymously in England in 1844, and which passed through numerous +editions, and was the subject of no end of abusive and derisive comment. +This book, the authorship of which remained for forty years a secret, +is now conceded to have been the work of Robert Chambers, the well-known +English author and publisher. The book itself is remarkable as being an +avowed and unequivocal exposition of a general doctrine of evolution, +its view being as radical and comprehensive as that of Lamarck himself. +But it was a resume of earlier efforts rather than a new departure, to +say nothing of its technical shortcomings, which may best be illustrated +by a quotation. + +"The whole question," says Chambers, "stands thus: For the theory of +universal order--that is, order as presiding in both the origin and +administration of the world--we have the testimony of a vast number of +facts in nature, and this one in addition--that whatever is left from +the domain of ignorance, and made undoubted matter of science, forms a +new support to the same doctrine. The opposite view, once predominant, +has been shrinking for ages into lesser space, and now maintains a +footing only in a few departments of nature which happen to be less +liable than others to a clear investigation. The chief of these, if not +almost the only one, is the origin of the organic kingdoms. So long as +this remains obscure, the supernatural will have a certain hold upon +enlightened persons. Should it ever be cleared up in a way that leaves +no doubt of a natural origin of plants and animals, there must be a +complete revolution in the view which is generally taken of the relation +of the Father of our being. + +"This prepares the way for a few remarks on the present state of opinion +with regard to the origin of organic nature. The great difficulty here +is the apparent determinateness of species. These forms of life being +apparently unchangeable, or at least always showing a tendency to return +to the character from which they have diverged, the idea arises that +there can have been no progression from one to another; each must have +taken its special form, independently of other forms, directly from the +appointment of the Creator. The Edinburgh Review writer says, 'they were +created by the hand of God and adapted to the conditions of the period.' +Now it is, in the first place, not certain that species constantly +maintain a fixed character, for we have seen that what were long +considered as determinate species have been transmuted into others. +Passing, however, from this fact, as it is not generally received among +men of science, there remain some great difficulties in connection +with the idea of special creation. First we should have to suppose, as +pointed out in my former volume, a most startling diversity of plan +in the divine workings, a great general plan or system of law in the +leading events of world-making, and a plan of minute, nice operation, +and special attention in some of the mere details of the process. The +discrepancy between the two conceptions is surely overpowering, when we +allow ourselves to see the whole matter in a steady and rational light. +There is, also, the striking fact of an ascertained historical progress +of plants and animals in the order of their organization; marine and +cellular plants and invertebrated animals first, afterwards higher +examples of both. In an arbitrary system we had surely no reason to +expect mammals after reptiles; yet in this order they came. The writer +in the Edinburgh Review speaks of animals as coming in adaptation to +conditions, but this is only true in a limited sense. The groves which +formed the coal-beds might have been a fitting habitation for reptiles, +birds, and mammals, as such groves are at the present day; yet we see +none of the last of these classes and hardly any traces of the two first +at that period of the earth. Where the iguanodon lived the elephant +might have lived, but there was no elephant at that time. The sea of the +Lower Silurian era was capable of supporting fish, but no fish existed. +It hence forcibly appears that theatres of life must have remained +unserviceable, or in the possession of a tenantry inferior to what might +have enjoyed them, for many ages: there surely would have been no such +waste allowed in a system where Omnipotence was working upon the plan +of minute attention to specialities. The fact seems to denote that the +actual procedure of the peopling of the earth was one of a natural kind, +requiring a long space of time for its evolution. In this supposition +the long existence of land without land animals, and more particularly +without the noblest classes and orders, is only analogous to the fact, +not nearly enough present to the minds of a civilized people, that to +this day the bulk of the earth is a waste as far as man is concerned. + +"Another startling objection is in the infinite local variation of +organic forms. Did the vegetable and animal kingdoms consist of a +definite number of species adapted to peculiarities of soil and climate, +and universally distributed, the fact would be in harmony with the +idea of special exertion. But the truth is that various regions exhibit +variations altogether without apparent end or purpose. Professor Henslow +enumerates forty-five distinct flowers or sets of plants upon the +surface of the earth, notwithstanding that many of these would be +equally suitable elsewhere. The animals of different continents are +equally various, few species being the same in any two, though the +general character may conform. The inference at present drawn from this +fact is that there must have been, to use the language of the Rev. Dr. +Pye Smith, 'separate and original creations, perhaps at different and +respectively distinct epochs.' It seems hardly conceivable that rational +men should give an adherence to such a doctrine when we think of what it +involves. In the single fact that it necessitates a special fiat of the +inconceivable Author of this sand-cloud of worlds to produce the flora +of St. Helena, we read its more than sufficient condemnation. It surely +harmonizes far better with our general ideas of nature to suppose that, +just as all else in this far-spread science was formed on the laws +impressed upon it at first by its Author, so also was this. An exception +presented to us in such a light appears admissible only when we succeed +in forbidding our minds to follow out those reasoning processes to +which, by another law of the Almighty, they tend, and for which they are +adapted."(4) + + +Such reasoning as this naturally aroused bitter animadversions, and +cannot have been without effect in creating an undercurrent of thought +in opposition to the main trend of opinion of the time. But the book can +hardly be said to have done more than that. Indeed, some critics +have denied it even this merit. After its publication, as before, +the conception of transmutation of species remained in the popular +estimation, both lay and scientific, an almost forgotten "heresy." + +It is true that here and there a scientist of greater or less repute--as +Von Buch, Meckel, and Von Baer in Germany, Bory Saint-Vincent in +France, Wells, Grant, and Matthew in England, and Leidy in America--had +expressed more or less tentative dissent from the doctrine of +special creation and immutability of species, but their unaggressive +suggestions, usually put forward in obscure publications, and +incidentally, were utterly overlooked and ignored. And so, despite the +scientific advances along many lines at the middle of the century, the +idea of the transmutability of organic races had no such prominence, +either in scientific or unscientific circles, as it had acquired fifty +years before. Special creation held the day, seemingly unopposed. + + +DARWIN AND THE ORIGIN OF SPECIES + +But even at this time the fancied security of the special-creation +hypothesis was by no means real. Though it seemed so invincible, its +real position was that of an apparently impregnable fortress beneath +which, all unbeknown to the garrison, a powder-mine has been dug and +lies ready for explosion. For already there existed in the secluded +work-room of an English naturalist, a manuscript volume and a portfolio +of notes which might have sufficed, if given publicity, to shatter the +entire structure of the special-creation hypothesis. The naturalist who, +by dint of long and patient effort, had constructed this powder-mine of +facts was Charles Robert Darwin, grandson of the author of Zoonomia. + +As long ago as July 1, 1837, young Darwin, then twenty-eight years of +age, had opened a private journal, in which he purposed to record all +facts that came to him which seemed to have any bearing on the moot +point of the doctrine of transmutation of species. Four or five years +earlier, during the course of that famous trip around the world with +Admiral Fitzroy, as naturalist to the Beagle, Darwin had made the +personal observations which first tended to shake his belief of the +fixity of species. In South America, in the Pampean formation, he had +discovered "great fossil animals covered with armor like that on the +existing armadillos," and had been struck with this similarity of type +between ancient and existing faunas of the same region. He was also +greatly impressed by the manner in which closely related species of +animals were observed to replace one another as he proceeded southward +over the continent; and "by the South-American character of most of the +productions of the Galapagos Archipelago, and more especially by the +manner in which they differ slightly on each island of the group, none +of the islands appearing to be very ancient in a geological sense." + +At first the full force of these observations did not strike him; for, +under sway of Lyell's geological conceptions, he tentatively explained +the relative absence of life on one of the Galapagos Islands by +suggesting that perhaps no species had been created since that island +arose. But gradually it dawned upon him that such facts as he had +observed "could only be explained on the supposition that species +gradually become modified." From then on, as he afterwards asserted, the +subject haunted him; hence the journal of 1837. + +It will thus be seen that the idea of the variability of species came to +Charles Darwin as an inference from personal observations in the field, +not as a thought borrowed from books. He had, of course, read the works +of his grandfather much earlier in life, but the arguments of Zoonomia +and The Temple of Nature had not served in the least to weaken his +acceptance of the current belief in fixity of species. Nor had he been +more impressed with the doctrine of Lamarck, so closely similar to that +of his grandfather. Indeed, even after his South-American experience had +aroused him to a new point of view he was still unable to see anything +of value in these earlier attempts at an explanation of the variation +of species. In opening his journal, therefore, he had no preconceived +notion of upholding the views of these or any other makers of +hypotheses, nor at the time had he formulated any hypothesis of his own. +His mind was open and receptive; he was eager only for facts which might +lead him to an understanding of a problem which seemed utterly obscure. +It was something to feel sure that species have varied; but how have +such variations been brought about? + +It was not long before Darwin found a clew which he thought might +lead to the answer he sought. In casting about for facts he had soon +discovered that the most available field for observation lay among +domesticated animals, whose numerous variations within specific lines +are familiar to every one. Thus under domestication creatures so +tangibly different as a mastiff and a terrier have sprung from a +common stock. So have the Shetland pony, the thoroughbred, and the +draught-horse. In short, there is no domesticated animal that has not +developed varieties deviating more or less widely from the parent stock. +Now, how has this been accomplished? Why, clearly, by the preservation, +through selective breeding, of seemingly accidental variations. Thus +one horseman, by constantly selecting animals that "chance" to have +the right build and stamina, finally develops a race of running-horses; +while another horseman, by selecting a different series of progenitors, +has developed a race of slow, heavy draught animals. + +So far, so good; the preservation of "accidental" variations through +selective breeding is plainly a means by which races may be developed +that are very different from their original parent form. But this +is under man's supervision and direction. By what process could such +selection be brought about among creatures in a state of nature? Here +surely was a puzzle, and one that must be solved before another step +could be taken in this direction. + +The key to the solution of this puzzle came into Darwin's mind through +a chance reading of the famous essay on "Population" which Thomas +Robert Malthus had published almost half a century before. This +essay, expositing ideas by no means exclusively original with Malthus, +emphasizes the fact that organisms tend to increase at a geometrical +ratio through successive generations, and hence would overpopulate the +earth if not somehow kept in check. Cogitating this thought, Darwin +gained a new insight into the processes of nature. He saw that in virtue +of this tendency of each race of beings to overpopulate the earth, +the entire organic world, animal and vegetable, must be in a state of +perpetual carnage and strife, individual against individual, fighting +for sustenance and life. + +That idea fully imagined, it becomes plain that a selective influence +is all the time at work in nature, since only a few individuals, +relatively, of each generation can come to maturity, and these few +must, naturally, be those best fitted to battle with the particular +circumstances in the midst of which they are placed. In other words, the +individuals best adapted to their surroundings will, on the average, be +those that grow to maturity and produce offspring. To these +offspring will be transmitted the favorable peculiarities. Thus these +peculiarities will become permanent, and nature will have accomplished +precisely what the human breeder is seen to accomplish. Grant that +organisms in a state of nature vary, however slightly, one from another +(which is indubitable), and that such variations will be transmitted by +a parent to its offspring (which no one then doubted); grant, further, +that there is incessant strife among the various organisms, so that +only a small proportion can come to maturity--grant these things, said +Darwin, and we have an explanation of the preservation of variations +which leads on to the transmutation of species themselves. + +This wonderful coign of vantage Darwin had reached by 1839. Here was the +full outline of his theory; here were the ideas which afterwards came to +be embalmed in familiar speech in the phrases "spontaneous variation," +and the "survival of the fittest," through "natural selection." After +such a discovery any ordinary man would at once have run through the +streets of science, so to speak, screaming "Eureka!" Not so Darwin. He +placed the manuscript outline of his theory in his portfolio, and went +on gathering facts bearing on his discovery. In 1844 he made an abstract +in a manuscript book of the mass of facts by that time accumulated. +He showed it to his friend Hooker, made careful provision for its +publication in the event of his sudden death, then stored it away in +his desk and went ahead with the gathering of more data. This was the +unexploded powder-mine to which I have just referred. + +Twelve years more elapsed--years during which the silent worker gathered +a prodigious mass of facts, answered a multitude of objections that +arose in his own mind, vastly fortified his theory. All this time +the toiler was an invalid, never knowing a day free from illness and +discomfort, obliged to husband his strength, never able to work more +than an hour and a half at a stretch; yet he accomplished what would +have been vast achievements for half a dozen men of robust health. Two +friends among the eminent scientists of the day knew of his labors--Sir +Joseph Hooker, the botanist, and Sir Charles Lyell, the geologist. +Gradually Hooker had come to be more than half a convert to Darwin's +views. Lyell was still sceptical, yet he urged Darwin to publish his +theory without further delay lest he be forestalled. At last the patient +worker decided to comply with this advice, and in 1856 he set to work to +make another and fuller abstract of the mass of data he had gathered. + +And then a strange thing happened. After Darwin had been at work on his +"abstract" about two years, but before he had published a line of it, +there came to him one day a paper in manuscript, sent for his approval +by a naturalist friend named Alfred Russel Wallace, who had been for +some time at work in the East India Archipelago. He read the paper, and, +to his amazement, found that it contained an outline of the same theory +of "natural selection" which he himself had originated and for twenty +years had worked upon. Working independently, on opposite sides of the +globe, Darwin and Wallace had hit upon the same explanation of the cause +of transmutation of species. "Were Wallace's paper an abstract of my +unpublished manuscript of 1844," said Darwin, "it could not better +express my ideas." + +Here was a dilemma. To publish this paper with no word from Darwin would +give Wallace priority, and wrest from Darwin the credit of a discovery +which he had made years before his codiscoverer entered the field. Yet, +on the other hand, could Darwin honorably do otherwise than publish his +friend's paper and himself remain silent? It was a complication well +calculated to try a man's soul. Darwin's was equal to the test. Keenly +alive to the delicacy of the position, he placed the whole matter before +his friends Hooker and Lyell, and left the decision as to a course of +action absolutely to them. Needless to say, these great men did the one +thing which insured full justice to all concerned. They counselled a +joint publication, to include on the one hand Wallace's paper, and on +the other an abstract of Darwin's ideas, in the exact form in which it +had been outlined by the author in a letter to Asa Gray in the previous +year--an abstract which was in Gray's hands before Wallace's paper was +in existence. This joint production, together with a full statement of +the facts of the case, was presented to the Linnaean Society of London +by Hooker and Lyell on the evening of July 1, 1858, this being, by an +odd coincidence, the twenty-first anniversary of the day on which +Darwin had opened his journal to collect facts bearing on the "species +question." Not often before in the history of science has it happened +that a great theory has been nurtured in its author's brain through +infancy and adolescence to its full legal majority before being sent out +into the world. + +Thus the fuse that led to the great powder-mine had been lighted. The +explosion itself came more than a year later, in November, 1859, when +Darwin, after thirteen months of further effort, completed the outline +of his theory, which was at first begun as an abstract for the Linnaean +Society, but which grew to the size of an independent volume despite +his efforts at condensation, and which was given that ever-to-be-famous +title, The Origin of Species by Means of Natural Selection, or the +Preservation of Favored Races in the Struggle for Life. And what an +explosion it was! The joint paper of 1858 had made a momentary flare, +causing the hearers, as Hooker said, to "speak of it with bated breath," +but beyond that it made no sensation. What the result was when the +Origin itself appeared no one of our generation need be told. The rumble +and roar that it made in the intellectual world have not yet altogether +ceased to echo after more than forty years of reverberation. + + +NEW CHAMPIONS + +To the Origin of Species, then, and to its author, Charles Darwin, +must always be ascribed chief credit for that vast revolution in the +fundamental beliefs of our race which has come about since 1859, and +which made the second half of the century memorable. But it must not be +overlooked that no such sudden metamorphosis could have been effected +had it not been for the aid of a few notable lieutenants, who rallied +to the standards of the leader immediately after the publication of the +Origin. Darwin had all along felt the utmost confidence in the ultimate +triumph of his ideas. "Our posterity," he declared, in a letter to +Hooker, "will marvel as much about the current belief (in special +creation) as we do about fossil shells having been thought to be created +as we now see them." But he fully realized that for the present success +of his theory of transmutation the championship of a few leaders of +science was all-essential. He felt that if he could make converts of +Hooker and Lyell and of Thomas Henry Huxley at once, all would be well. + +His success in this regard, as in others, exceeded his expectations. +Hooker was an ardent disciple from reading the proof-sheets before the +book was published; Lyell renounced his former beliefs and fell into +line a few months later; while Huxley, so soon as he had mastered +the central idea of natural selection, marvelled that so simple yet +all-potent a thought had escaped him so long, and then rushed eagerly +into the fray, wielding the keenest dialectic blade that was drawn +during the entire controversy. Then, too, unexpected recruits were found +in Sir John Lubbock and John Tyndall, who carried the war eagerly into +their respective territories; while Herbert Spencer, who had advocated +a doctrine of transmutation on philosophic grounds some years before +Darwin published the key to the mystery--and who himself had barely +escaped independent discovery of that key--lent his masterful influence +to the cause. In America the famous botanist Asa Gray, who had long been +a correspondent of Darwin's but whose advocacy of the new theory had not +been anticipated, became an ardent propagandist; while in Germany Ernst +Heinrich Haeckel, the youthful but already noted zoologist, took up the +fight with equal enthusiasm. + +Against these few doughty champions--with here and there another of less +general renown--was arrayed, at the outset, practically all Christendom. +The interest of the question came home to every person of intelligence, +whatever his calling, and the more deeply as it became more and more +clear how far-reaching are the real bearings of the doctrine of natural +selection. Soon it was seen that should the doctrine of the survival +of the favored races through the struggle for existence win, there must +come with it as radical a change in man's estimate of his own position +as had come in the day when, through the efforts of Copernicus and +Galileo, the world was dethroned from its supposed central position in +the universe. The whole conservative majority of mankind recoiled from +this necessity with horror. And this conservative majority included not +laymen merely, but a vast preponderance of the leaders of science also. + +With the open-minded minority, on the other hand, the theory of +natural selection made its way by leaps and bounds. Its delightful +simplicity--which at first sight made it seem neither new nor +important--coupled with the marvellous comprehensiveness of its +implications, gave it a hold on the imagination, and secured it a +hearing where other theories of transmutation of species had been +utterly scorned. Men who had found Lamarck's conception of change +through voluntary effort ridiculous, and the vaporings of the Vestiges +altogether despicable, men whose scientific cautions held them back +from Spencer's deductive argument, took eager hold of that tangible, +ever-present principle of natural selection, and were led on and on to +its goal. Hour by hour the attitude of the thinking world towards this +new principle changed; never before was so great a revolution wrought so +suddenly. + +Nor was this merely because "the times were ripe" or "men's minds +prepared for evolution." Darwin himself bears witness that this was not +altogether so. All through the years in which he brooded this theory he +sounded his scientific friends, and could find among them not one +who acknowledged a doctrine of transmutation. The reaction from the +stand-point of Lamarck and Erasmus Darwin and Goethe had been complete, +and when Charles Darwin avowed his own conviction he expected always +to have it met with ridicule or contempt. In 1857 there was but one +man speaking with any large degree of authority in the world who openly +avowed a belief in transmutation of species--that man being Herbert +Spencer. But the Origin of Species came, as Huxley has said, like a +flash in the darkness, enabling the benighted voyager to see the way. +The score of years during which its author had waited and worked +had been years well spent. Darwin had become, as he himself says, a +veritable Croesus, "overwhelmed with his riches in facts"--facts of +zoology, of selective artificial breeding, of geographical distribution +of animals, of embryology, of paleontology. He had massed his facts +about his theory, condensed them and recondensed, until his volume of +five hundred pages was an encyclopaedia in scope. During those long +years of musing he had thought out almost every conceivable objection to +his theory, and in his book every such objection was stated with fullest +force and candor, together with such reply as the facts at command +might dictate. It was the force of those twenty years of effort of +a master-mind that made the sudden breach in the breaswtork{sic} of +current thought. + +Once this breach was effected the work of conquest went rapidly on. Day +by day squads of the enemy capitulated and struck their arms. By the +time another score of years had passed the doctrine of evolution had +become the working hypothesis of the scientific world. The revolution +had been effected. + +And from amid the wreckage of opinion and belief stands forth the figure +of Charles Darwin, calm, imperturbable, serene; scatheless to ridicule, +contumely, abuse; unspoiled by ultimate success; unsullied alike by +the strife and the victory--take him for all in all, for character, for +intellect, for what he was and what he did, perhaps the most Socratic +figure of the century. When, in 1882, he died, friend and foe alike +conceded that one of the greatest sons of men had rested from his +labors, and all the world felt it fitting that the remains of Charles +Darwin should be entombed in Westminster Abbey close beside the honored +grave of Isaac Newton. Nor were there many who would dispute the justice +of Huxley's estimate of his accomplishment: "He found a great truth +trodden under foot. Reviled by bigots, and ridiculed by all the world, +he lived long enough to see it, chiefly by his own efforts, irrefragably +established in science, inseparably incorporated with the common +thoughts of men, and only hated and feared by those who would revile but +dare not." + + +THE ORIGIN OF THE FITTEST + +Wide as are the implications of the great truth which Darwin and his +co-workers established, however, it leaves quite untouched the problem +of the origin of those "favored variations" upon which it operates. +That such variations are due to fixed and determinate causes no one +understood better than Darwin; but in his original exposition of his +doctrine he made no assumption as to what these causes are. He accepted +the observed fact of variation--as constantly witnessed, for example, in +the differences between parents and offspring--and went ahead from this +assumption. + +But as soon as the validity of the principle of natural selection came +to be acknowledged speculators began to search for the explanation of +those variations which, for purposes of argument, had been provisionally +called "spontaneous." Herbert Spencer had all along dwelt on this phase +of the subject, expounding the Lamarckian conceptions of the direct +influence of the environment (an idea which had especially appealed +to Buffon and to Geoffroy Saint-Hilaire), and of effort in response to +environment and stimulus as modifying the individual organism, and thus +supplying the basis for the operation of natural selection. Haeckel also +became an advocate of this idea, and presently there arose a so-called +school of neo-Lamarckians, which developed particular strength and +prominence in America under the leadership of Professors A. Hyatt and E. +D. Cope. + +But just as the tide of opinion was turning strongly in this direction, +an utterly unexpected obstacle appeared in the form of the theory of +Professor August Weismann, put forward in 1883, which antagonized the +Lamarckian conception (though not touching the Darwinian, of which +Weismann is a firm upholder) by denying that individual variations, +however acquired by the mature organism, are transmissible. The +flurry which this denial created has not yet altogether subsided, but +subsequent observations seem to show that it was quite disproportionate +to the real merits of the case. Notwithstanding Professor Weismann's +objections, the balance of evidence appears to favor the view that the +Lamarckian factor of acquired variations stands as the complement of the +Darwinian factor of natural selection in effecting the transmutation of +species. + +Even though this partial explanation of what Professor Cope calls the +"origin of the fittest" be accepted, there still remains one great life +problem which the doctrine of evolution does not touch. The origin +of species, genera, orders, and classes of beings through endless +transmutations is in a sense explained; but what of the first term of +this long series? Whence came that primordial organism whose transmuted +descendants make up the existing faunas and floras of the globe? + +There was a time, soon after the doctrine of evolution gained a hearing, +when the answer to that question seemed to some scientists of authority +to have been given by experiment. Recurring to a former belief, and +repeating some earlier experiments, the director of the Museum of +Natural History at Rouen, M. F. A. Pouchet, reached the conclusion that +organic beings are spontaneously generated about us constantly, in the +familiar processes of putrefaction, which were known to be due to the +agency of microscopic bacteria. But in 1862 Louis Pasteur proved that +this seeming spontaneous generation is in reality due to the existence +of germs in the air. Notwithstanding the conclusiveness of these +experiments, the claims of Pouchet were revived in England ten years +later by Professor Bastian; but then the experiments of John Tyndall, +fully corroborating the results of Pasteur, gave a final quietus to the +claim of "spontaneous generation" as hitherto formulated. + +There for the moment the matter rests. But the end is not yet. Fauna +and flora are here, and, thanks to Lamarck and Wallace and Darwin, their +development, through the operation of those "secondary causes" which we +call laws of nature, has been proximally explained. The lowest forms of +life have been linked with the highest in unbroken chains of descent. +Meantime, through the efforts of chemists and biologists, the gap +between the inorganic and the organic worlds, which once seemed almost +infinite, has been constantly narrowed. Already philosophy can throw +a bridge across that gap. But inductive science, which builds its own +bridges, has not yet spanned the chasm, small though it appear. Until +it shall have done so, the bridge of organic evolution is not quite +complete; yet even as it stands to-day it is perhaps the most stupendous +scientific structure of the nineteenth century. + + + + +VII. EIGHTEENTH-CENTURY MEDICINE + +THE SYSTEM OF BOERHAAVE + +At least two pupils of William Harvey distinguished themselves in +medicine, Giorgio Baglivi (1669-1707), who has been called the "Italian +Sydenham," and Hermann Boerhaave (1668-1738). The work of Baglivi was +hardly begun before his early death removed one of the most promising of +the early eighteenth-century physicians. Like Boerhaave, he represents a +type of skilled, practical clinitian rather than the abstract scientist. +One of his contributions to medical literature is the first accurate +description of typhoid, or, as he calls it, mesenteric fever. + +If for nothing else, Boerhaave must always be remembered as the teacher +of Von Haller, but in his own day he was the widest known and the most +popular teacher in the medical world. He was the idol of his pupils +at Leyden, who flocked to his lectures in such numbers that it became +necessary to "tear down the walls of Leyden to accommodate them." His +fame extended not only all over Europe but to Asia, North America, and +even into South America. A letter sent him from China was addressed +to "Boerhaave in Europe." His teachings represent the best medical +knowledge of his day, a high standard of morality, and a keen +appreciation of the value of observation; and it was through such +teachings imparted to his pupils and advanced by them, rather than to +any new discoveries, that his name is important in medical history. His +arrangement and classification of the different branches of medicine +are interesting as representing the attitude of the medical profession +towards these various branches at that time. + + +"In the first place we consider Life; then Health, afterwards Diseases; +and lastly their several Remedies. + +"Health the first general branch of Physic in our Institutions is termed +Physiology, or the Animal Oeconomy; demonstrating the several Parts of +the human Body, with their Mechanism and Actions. + +"The second branch of Physic is called Pathology, treating of Diseases, +their Differences, Causes and Effects, or Symptoms; by which the human +Body is known to vary from its healthy state. + +"The third part of Physic is termed Semiotica, which shows the Signs +distinguishing between sickness and Health, Diseases and their Causes +in the human Body; it also imports the State and Degrees of Health and +Diseases, and presages their future Events. + +"The fourth general branch of Physic is termed Hygiene, or Prophylaxis. + +"The fifth and last part of Physic is called Therapeutica; which +instructs us in the Nature, Preparation and uses of the Materia Medica; +and the methods of applying the same, in order to cure Diseases and +restore lost Health."(1) + +From this we may gather that his general view of medicine was not unlike +that taken at the present time. + +Boerhaave's doctrines were arranged into a "system" by Friedrich +Hoffmann, of Halle (1660-1742), this system having the merit of being +simple and more easily comprehended than many others. In this system +forces were considered inherent in matter, being expressed as mechanical +movements, and determined by mass, number, and weight. Similarly, forces +express themselves in the body by movement, contraction, and relaxation, +etc., and life itself is movement, "particularly movement of the +heart." Life and death are, therefore, mechanical phenomena, health is +determined by regularly recurring movements, and disease by irregularity +of them. The body is simply a large hydraulic machine, controlled by +"the aether" or "sensitive soul," and the chief centre of this soul lies +in the medulla. + +In the practical application of medicines to diseases Hoffman used +simple remedies, frequently with happy results, for whatever the +medical man's theory may be he seldom has the temerity to follow it out +logically, and use the remedies indicated by his theory to the exclusion +of long-established, although perhaps purely empirical, remedies. +Consequently, many vague theorists have been excellent practitioners, +and Hoffman was one of these. Some of the remedies he introduced are +still in use, notably the spirits of ether, or "Hoffman's anodyne." + + +ANIMISTS, VITALISTS, AND ORGANICISTS + +Besides Hoffman's system of medicine, there were numerous others during +the eighteenth century, most of which are of no importance whatever; +but three, at least, that came into existence and disappeared during the +century are worthy of fuller notice. One of these, the Animists, had for +its chief exponent Georg Ernst Stahl of "phlogiston" fame; another, the +Vitalists, was championed by Paul Joseph Barthez (1734-1806); and the +third was the Organicists. This last, while agreeing with the other +two that vital activity cannot be explained by the laws of physics +and chemistry, differed in not believing that life "was due to some +spiritual entity," but rather to the structure of the body itself. + +The Animists taught that the soul performed functions of ordinary life +in man, while the life of lower animals was controlled by ordinary +mechanical principles. Stahl supported this theory ardently, sometimes +violently, at times declaring that there were "no longer any doctors, +only mechanics and chemists." He denied that chemistry had anything to +do with medicine, and, in the main, discarded anatomy as useless to the +medical man. The soul, he thought, was the source of all vital movement; +and the immediate cause of death was not disease but the direct action +of the soul. When through some lesion, or because the machinery of the +body has become unworkable, as in old age, the soul leaves the body +and death is produced. The soul ordinarily selects the channels of the +circulation, and the contractile parts, as the route for influencing +the body. Hence in fever the pulse is quickened, due to the increased +activity of the soul, and convulsions and spasmodic movements in disease +are due, to the, same cause. Stagnation of the blood was supposed to +be a fertile cause of diseases, and such diseases were supposed to +arise mostly from "plethora"--an all-important element in Stahl's +therapeutics. By many this theory is regarded as an attempt on the +part of the pious Stahl to reconcile medicine and theology in a +way satisfactory to both physicians and theologians, but, like many +conciliatory attempts, it was violently opposed by both doctors and +ministers. + +A belief in such a theory would lead naturally to simplicity in +therapeutics, and in this respect at least Stahl was consistent. Since +the soul knew more about the body than any physician could know, Stahl +conceived that it would be a hinderance rather than a help for the +physician to interfere with complicated doses of medicine. As he +advanced in age this view of the administration of drugs grew upon him, +until after rejecting quinine, and finally opium, he at last used only +salt and water in treating his patients. From this last we may judge +that his "system," if not doing much good, was at least doing little +harm. + +The theory of the Vitalists was closely allied to that of the Animists, +and its most important representative, Paul Joseph Barthez, was a +cultured and eager scientist. After an eventful and varied career as +physician, soldier, editor, lawyer, and philosopher in turn, he finally +returned to the field of medicine, was made consulting physician by +Napoleon in 1802, and died in Paris four years later. + +The theory that he championed was based on the assumption that there was +a "vital principle," the nature of which was unknown, but which differed +from the thinking mind, and was the cause of the phenomena of life. This +"vital principle" differed from the soul, and was not exhibited in human +beings alone, but even in animals and plants. This force, or whatever it +might be called, was supposed to be present everywhere in the body, and +all diseases were the results of it. + +The theory of the Organicists, like that of the Animists and Vitalists, +agreed with the other two that vital activity could not be explained by +the laws of physics and chemistry, but, unlike them, it held that it +was a part of the structure of the body itself. Naturally the practical +physicians were more attracted by this tangible doctrine than by vague +theories "which converted diseases into unknown derangements of some +equally unknown 'principle.'" + +It is perhaps straining a point to include this brief description of +these three schools of medicine in the history of the progress of the +science. But, on the whole, they were negatively at least prominent +factors in directing true progress along its proper channel, showing +what courses were not to be pursued. Some one has said that science +usually stumbles into the right course only after stumbling into all +the wrong ones; and if this be only partially true, the wrong ones still +play a prominent if not a very creditable part. Thus the medical systems +of William Cullen (1710-1790), and John Brown (1735-1788), while doing +little towards the actual advancement of scientific medicine, played +so conspicuous a part in so wide a field that the "Brunonian system" at +least must be given some little attention. + +According to Brown's theory, life, diseases, and methods of cure are +explained by the property of "excitability." All exciting powers were +supposed to be stimulating, the apparent debilitating effects of some +being due to a deficiency in the amount of stimulus. Thus "the whole +phenomena of life, health, as well as disease, were supposed to consist +of stimulus and nothing else." This theory created a great stir in the +medical world, and partisans and opponents sprang up everywhere. In +Italy it was enthusiastically supported; in England it was strongly +opposed; while in Scotland riots took place between the opposing +factions. Just why this system should have created any stir, either for +or against it, is not now apparent. + +Like so many of the other "theorists" of his century, Brown's practical +conclusions deduced from his theory (or perhaps in spite of it) were +generally beneficial to medicine, and some of them extremely valuable in +the treatment of diseases. He first advocated the modern stimulant, or +"feeding treatment" of fevers, and first recognized the usefulness of +animal soups and beef-tea in certain diseases. + + +THE SYSTEM OF HAHNEMANN + +Just at the close of the century there came into prominence the school +of homoeopathy, which was destined to influence the practice of medicine +very materially and to outlive all the other eighteenth-century schools. +It was founded by Christian Samuel Friedrich Hahnemann (1755-1843), a +most remarkable man, who, after propounding a theory in his younger days +which was at least as reasonable as most of the existing theories, had +the misfortune to outlive his usefulness and lay his doctrine open to +ridicule by the unreasonable teachings of his dotage. + +Hahnemann rejected all the teachings of morbid anatomy and pathology +as useless in practice, and propounded his famous "similia similibus +curantur"--that all diseases were to be cured by medicine which in +health produced symptoms dynamically similar to the disease under +treatment. If a certain medicine produced a headache when given to a +healthy person, then this medicine was indicated in case of headaches, +etc. At the present time such a theory seems crude enough, but in the +latter part of the eighteenth century almost any theory was as good as +the ones propounded by Animists, Vitalists, and other such schools. It +certainly had the very commendable feature of introducing simplicity +in the use of drugs in place of the complicated prescriptions then in +vogue. Had Hahnemann stopped at this point he could not have been +held up to the indefensible ridicule that was brought upon him, with +considerable justice, by his later theories. But he lived onto propound +his extraordinary theory of "potentiality"--that medicines gained +strength by being diluted--and his even more extraordinary theory +that all chronic diseases are caused either by the itch, syphilis, or +fig-wart disease, or are brought on by medicines. + +At the time that his theory of potentialities was promulgated, the +medical world had gone mad in its administration of huge doses of +compound mixtures of drugs, and any reaction against this was surely +an improvement. In short, no medicine at all was much better than the +heaping doses used in common practice; and hence one advantage, at +least, of Hahnemann's methods. Stated briefly, his theory was that if a +tincture be reduced to one-fiftieth in strength, and this again reduced +to one-fiftieth, and this process repeated up to thirty such dilutions, +the potency of such a medicine will be increased by each dilution, +Hahnemann himself preferring the weakest, or, as he would call it, the +strongest dilution. The absurdity of such a theory is apparent when it +is understood that long before any drug has been raised to its thirtieth +dilution it has been so reduced in quantity that it cannot be weighed, +measured, or recognized as being present in the solution at all by +any means known to chemists. It is but just to modern followers of +homoeopathy to say that while most of them advocate small dosage, they +do not necessarily follow the teachings of Hahnemann in this respect, +believing that the theory of the dose "has nothing more to do with the +original law of cure than the psora (itch) theory has; and that it was +one of the later creations of Hahnemann's mind." + +Hahnemann's theory that all chronic diseases are derived from either +itch, syphilis, or fig-wart disease is no longer advocated by his +followers, because it is so easily disproved, particularly in the case +of itch. Hahnemann taught that fully three-quarters of all diseases were +caused by "itch struck in," and yet it had been demonstrated long before +his day, and can be demonstrated any time, that itch is simply a local +skin disease caused by a small parasite. + + +JENNER AND VACCINATION + +All advances in science have a bearing, near or remote, on the welfare +of our race; but it remains to credit to the closing decade of the +eighteenth century a discovery which, in its power of direct and +immediate benefit to humanity, surpasses any other discovery of this or +any previous epoch. Needless to say, I refer to Jenner's discovery +of the method of preventing smallpox by inoculation with the virus of +cow-pox. It detracts nothing from the merit of this discovery to say +that the preventive power of accidental inoculation had long been +rumored among the peasantry of England. Such vague, unavailing +half-knowledge is often the forerunner of fruitful discovery. + +To all intents and purposes Jenner's discovery was original and unique. +Nor, considered as a perfect method, was it in any sense an accident. It +was a triumph of experimental science. The discoverer was no novice in +scientific investigation, but a trained observer, who had served a long +apprenticeship in scientific observation under no less a scientist than +the celebrated John Hunter. At the age of twenty-one Jenner had gone to +London to pursue his medical studies, and soon after he proved himself +so worthy a pupil that for two years he remained a member of Hunter's +household as his favorite pupil. His taste for science and natural +history soon attracted the attention of Sir Joseph Banks, who intrusted +him with the preparation of the zoological specimens brought back by +Captain Cook's expedition in 1771. He performed this task so well that +he was offered the position of naturalist to the second expedition, but +declined it, preferring to take up the practice of his profession in his +native town of Berkeley. + +His many accomplishments and genial personality soon made him a favorite +both as a physician and in society. He was a good singer, a fair +violinist and flute-player, and a very successful writer of prose and +verse. But with all his professional and social duties he still kept up +his scientific investigations, among other things making some careful +observations on the hibernation of hedgehogs at the instigation of +Hunter, the results of which were laid before the Royal Society. He also +made quite extensive investigations as to the geological formations and +fossils found in his neighborhood. + +Even during his student days with Hunter he had been much interested in +the belief, current in the rural districts of Gloucestershire, of the +antagonism between cow-pox and small-pox, a person having suffered +from cow-pox being immuned to small-pox. At various times Jenner had +mentioned the subject to Hunter, and he was constantly making inquiries +of his fellow-practitioners as to their observations and opinions on the +subject. Hunter was too fully engrossed in other pursuits to give the +matter much serious attention, however, and Jenner's brothers of the +profession gave scant credence to the rumors, although such rumors were +common enough. + +At this time the practice of inoculation for preventing small-pox, or +rather averting the severer forms of the disease, was widely practised. +It was customary, when there was a mild case of the disease, to take +some of the virus from the patient and inoculate persons who had never +had the disease, producing a similar attack in them. Unfortunately there +were many objections to this practice. The inoculated patient frequently +developed a virulent form of the disease and died; or if he recovered, +even after a mild attack, he was likely to be "pitted" and disfigured. +But, perhaps worst of all, a patient so inoculated became the source of +infection to others, and it sometimes happened that disastrous epidemics +were thus brought about. The case was a most perplexing one, for the +awful scourge of small-pox hung perpetually over the head of every +person who had not already suffered and recovered from it. The practice +of inoculation was introduced into England by Lady Mary Wortley Montague +(1690-1762), who had seen it practised in the East, and who announced +her intention of "introducing it into England in spite of the doctors." + +From the fact that certain persons, usually milkmaids, who had suffered +from cow-pox seemed to be immuned to small-pox, it would seem a very +simple process of deduction to discover that cow-pox inoculation was the +solution of the problem of preventing the disease. But there was another +form of disease which, while closely resembling cow-pox and quite +generally confounded with it, did not produce immunity. The confusion of +these two forms of the disease had constantly misled investigations as +to the possibility of either of them immunizing against smallpox, and +the confusion of these two diseases for a time led Jenner to question +the possibility of doing so. After careful investigations, however, he +reached the conclusion that there was a difference in the effects of the +two diseases, only one of which produced immunity from small-pox. + +"There is a disease to which the horse, from his state of domestication, +is frequently subject," wrote Jenner, in his famous paper on +vaccination. "The farriers call it the grease. It is an inflammation and +swelling in the heel, accompanied at its commencement with small cracks +or fissures, from which issues a limpid fluid possessing properties of a +very peculiar kind. This fluid seems capable of generating a disease +in the human body (after it has undergone the modification I shall +presently speak of) which bears so strong a resemblance to small-pox +that I think it highly probable it may be the source of that disease. + +"In this dairy country a great number of cows are kept, and the office +of milking is performed indiscriminately by men and maid servants. One +of the former having been appointed to apply dressings to the heels of +a horse affected with the malady I have mentioned, and not paying due +attention to cleanliness, incautiously bears his part in milking the +cows with some particles of the infectious matter adhering to his +fingers. When this is the case it frequently happens that a disease is +communicated to the cows, and from the cows to the dairy-maids, which +spreads through the farm until most of the cattle and domestics feel its +unpleasant consequences. This disease has obtained the name of Cow-Pox. +It appears on the nipples of the cows in the form of irregular pustules. +At their first appearance they are commonly of a palish blue, or rather +of a color somewhat approaching to livid, and are surrounded by an +inflammation. These pustules, unless a timely remedy be applied, +frequently degenerate into phagedenic ulcers, which prove extremely +troublesome. The animals become indisposed, and the secretion of milk is +much lessened. Inflamed spots now begin to appear on different parts +of the hands of the domestics employed in milking, and sometimes on the +wrists, which run on to suppuration, first assuming the appearance of +the small vesications produced by a burn. Most commonly they appear +about the joints of the fingers and at their extremities; but whatever +parts are affected, if the situation will admit the superficial +suppurations put on a circular form with their edges more elevated than +their centre and of a color distinctly approaching to blue. Absorption +takes place, and tumors appear in each axilla. The system becomes +affected, the pulse is quickened; shiverings, succeeded by heat, general +lassitude, and pains about the loins and limbs, with vomiting, come on. +The head is painful, and the patient is now and then even affected +with delirium. These symptoms, varying in their degrees of violence, +generally continue from one day to three or four, leaving ulcerated +sores about the hands which, from the sensibility of the parts, are very +troublesome and commonly heal slowly, frequently becoming phagedenic, +like those from which they sprang. During the progress of the disease +the lips, nostrils, eyelids, and other parts of the body are sometimes +affected with sores; but these evidently arise from their being +heedlessly rubbed or scratched by the patient's infected fingers. No +eruptions on the skin have followed the decline of the feverish symptoms +in any instance that has come under my inspection, one only excepted, +and in this case a very few appeared on the arms: they were very +minute, of a vivid red color, and soon died away without advancing to +maturation, so that I cannot determine whether they had any connection +with the preceding symptoms. + +"Thus the disease makes its progress from the horse (as I conceive) to +the nipple of the cow, and from the cow to the human subject. + +"Morbid matter of various kinds, when absorbed into the system, may +produce effects in some degree similar; but what renders the cow-pox +virus so extremely singular is that the person that has been thus +affected is forever after secure from the infection of small-pox, +neither exposure to the variolous effluvia nor the insertion of the +matter into the skin producing this distemper."(2) + + +In 1796 Jenner made his first inoculation with cowpox matter, and two +months later the same subject was inoculated with small-pox matter. But, +as Jenner had predicted, no attack of small-pox followed. Although fully +convinced by this experiment that the case was conclusively proven, he +continued his investigations, waiting two years before publishing his +discovery. Then, fortified by indisputable proofs, he gave it to the +world. The immediate effects of his announcement have probably never +been equalled in the history of scientific discovery, unless, perhaps, +in the single instance of the discovery of anaesthesia. In Geneva and +Holland clergymen advocated the practice of vaccination from their +pulpits; in some of the Latin countries religious processions were +formed for receiving vaccination; Jenner's birthday was celebrated as +a feast in Germany; and the first child vaccinated in Russia was named +"Vaccinov" and educated at public expense. In six years the discovery +had penetrated to the most remote corners of civilization; it had even +reached some savage nations. And in a few years small-pox had fallen +from the position of the most dreaded of all diseases to that of being +practically the only disease for which a sure and easy preventive was +known. + +Honors were showered upon Jenner from the Old and the New World, and +even Napoleon, the bitter hater of the English, was among the others who +honored his name. On one occasion Jenner applied to the Emperor for the +release of certain Englishmen detained in France. The petition was about +to be rejected when the name of the petitioner was mentioned. "Ah," said +Napoleon, "we can refuse nothing to that name!" + +It is difficult for us of to-day clearly to conceive the greatness of +Jenner's triumph, for we can only vaguely realize what a ruthless and +ever-present scourge smallpox had been to all previous generations of +men since history began. Despite all efforts to check it by medication +and by direct inoculation, it swept now and then over the earth as an +all-devastating pestilence, and year by year it claimed one-tenth of +all the beings in Christendom by death as its average quota of victims. +"From small-pox and love but few remain free," ran the old saw. A pitted +face was almost as much a matter of course a hundred years ago as a +smooth one is to-day. + +Little wonder, then, that the world gave eager acceptance to Jenner's +discovery. No urging was needed to induce the majority to give it trial; +passengers on a burning ship do not hold aloof from the life-boats. Rich +and poor, high and low, sought succor in vaccination and blessed the +name of their deliverer. Of all the great names that were before the +world in the closing days of the century, there was perhaps no other one +at once so widely known and so uniformly reverenced as that of the great +English physician Edward Jenner. Surely there was no other one that +should be recalled with greater gratitude by posterity. + + + + +VIII. NINETEENTH-CENTURY MEDICINE + +PHYSICAL DIAGNOSIS + +Although Napoleon Bonaparte, First Consul, was not lacking in +self-appreciation, he probably did not realize that in selecting a +physician for his own needs he was markedly influencing the progress +of medical science as a whole. Yet so strangely are cause and effect +adjusted in human affairs that this simple act of the First Consul had +that very unexpected effect. For the man chosen was the envoy of a new +method in medical practice, and the fame which came to him through being +physician to the First Consul, and subsequently to the Emperor, enabled +him to promulgate the method in a way otherwise impracticable. Hence the +indirect but telling value to medical science of Napoleon's selection. + +The physician in question was Jean Nicolas de Corvisart. His novel +method was nothing more startling than the now-familiar procedure of +tapping the chest of a patient to elicit sounds indicative of diseased +tissues within. Every one has seen this done commonly enough in our day, +but at the beginning of the century Corvisart, and perhaps some of his +pupils, were probably the only physicians in the world who resorted to +this simple and useful procedure. Hence Napoleon's surprise when, on +calling in Corvisart, after becoming somewhat dissatisfied with +his other physicians Pinel and Portal, his physical condition was +interrogated in this strange manner. With characteristic shrewdness +Bonaparte saw the utility of the method, and the physician who thus +attempted to substitute scientific method for guess-work in the +diagnosis of disease at once found favor in his eyes and was installed +as his regular medical adviser. + +For fifteen years before this Corvisart had practised percussion, as +the chest-tapping method is called, without succeeding in convincing the +profession of its value. The method itself, it should be added, had not +originated with Corvisart, nor did the French physician for a moment +claim it as his own. The true originator of the practice was the German +physician Avenbrugger, who published a book about it as early as 1761. +This book had even been translated into French, then the language of +international communication everywhere, by Roziere de la Chassagne, of +Montpellier, in 1770; but no one other than Corvisart appears to +have paid any attention to either original or translation. It was far +otherwise, however, when Corvisart translated Avenbrugger's work anew, +with important additions of his own, in 1808. + +"I know very well how little reputation is allotted to translator and +commentators," writes Corvisart, "and I might easily have elevated +myself to the rank of an author if I had elaborated anew the doctrine +of Avenbrugger and published an independent work on percussion. In this +way, however, I should have sacrificed the name of Avenbrugger to my own +vanity, a thing which I am unwilling to do. It is he, and the beautiful +invention which of right belongs to him, that I desire to recall to +life."(1) + +By this time a reaction had set in against the metaphysical methods in +medicine that had previously been so alluring; the scientific spirit of +the time was making itself felt in medical practice; and this, combined +with Corvisart's fame, brought the method of percussion into immediate +and well-deserved popularity. Thus was laid the foundation for +the method of so-called physical diagnosis, which is one of the +corner-stones of modern medicine. + +The method of physical diagnosis as practised in our day was by no means +completed, however, with the work of Corvisart. Percussion alone tells +much less than half the story that may be elicited from the organs of +the chest by proper interrogation. The remainder of the story can +only be learned by applying the ear itself to the chest, directly or +indirectly. Simple as this seems, no one thought of practising it for +some years after Corvisart had shown the value of percussion. + +Then, in 1815, another Paris physician, Rene Theophile Hyacinthe +Laennec, discovered, almost by accident, that the sound of the +heart-beat could be heard surprisingly through a cylinder of paper held +to the ear and against the patient's chest. Acting on the hint thus +received, Laennec substituted a hollow cylinder of wood for the paper, +and found himself provided with an instrument through which not merely +heart sounds but murmurs of the lungs in respiration could be heard with +almost startling distinctness. + +The possibility of associating the varying chest sounds with diseased +conditions of the organs within appealed to the fertile mind of Laennec +as opening new vistas in therapeutics, which he determined to enter to +the fullest extent practicable. His connection with the hospitals of +Paris gave him full opportunity in this direction, and his labors of +the next few years served not merely to establish the value of the new +method as an aid to diagnosis, but laid the foundation also for the +science of morbid anatomy. In 1819 Laennec published the results of his +labors in a work called Traite d'Auscultation Mediate,(2) a work +which forms one of the landmarks of scientific medicine. By mediate +auscultation is meant, of course, the interrogation of the chest with +the aid of the little instrument already referred to, an instrument +which its originator thought hardly worth naming until various barbarous +appellations were applied to it by others, after which Laennec decided +to call it the stethoscope, a name which it has ever since retained. + +In subsequent years the form of the stethoscope, as usually employed, +was modified and its value augmented by a binauricular attachment, +and in very recent years a further improvement has been made through +application of the principle of the telephone; but the essentials of +auscultation with the stethoscope were established in much detail by +Laennec, and the honor must always be his of thus taking one of the +longest single steps by which practical medicine has in our century +acquired the right to be considered a rational science. Laennec's +efforts cost him his life, for he died in 1826 of a lung disease +acquired in the course of his hospital practice; but even before this +his fame was universal, and the value of his method had been recognized +all over the world. Not long after, in 1828, yet another French +physician, Piorry, perfected the method of percussion by introducing +the custom of tapping, not the chest directly, but the finger or a small +metal or hard-rubber plate held against the chest-mediate percussion, in +short. This perfected the methods of physical diagnosis of diseases of +the chest in all essentials; and from that day till this percussion +and auscultation have held an unquestioned place in the regular +armamentarium of the physician. + +Coupled with the new method of physical diagnosis in the effort to +substitute knowledge for guess-work came the studies of the experimental +physiologists--in particular, Marshall Hall in England and Francois +Magendie in France; and the joint efforts of these various workers +led presently to the abandonment of those severe and often irrational +depletive methods--blood-letting and the like--that had previously +dominated medical practice. To this end also the "statistical method," +introduced by Louis and his followers, largely contributed; and by the +close of the first third of our century the idea was gaining ground that +the province of therapeutics is to aid nature in combating disease, and +that this may often be accomplished better by simple means than by +the heroic measures hitherto thought necessary. In a word, scientific +empiricism was beginning to gain a hearing in medicine as against the +metaphysical preconceptions of the earlier generations. + + +PARASITIC DISEASES + +I have just adverted to the fact that Napoleon Bonaparte, as First +Consul and as Emperor, was the victim of a malady which caused him to +seek the advice of the most distinguished physicians of Paris. It is a +little shocking to modern sensibilities to read that these physicians, +except Corvisart, diagnosed the distinguished patient's malady as "gale +repercutee"--that is to say, in idiomatic English, the itch "struck in." +It is hardly necessary to say that no physician of today would make +so inconsiderate a diagnosis in the case of a royal patient. If by +any chance a distinguished patient were afflicted with the itch, the +sagacious physician would carefully hide the fact behind circumlocutions +and proceed to eradicate the disease with all despatch. That the +physicians of Napoleon did otherwise is evidence that at the beginning +of the century the disease in question enjoyed a very different status. +At that time itch, instead of being a most plebeian malady, was, so to +say, a court disease. It enjoyed a circulation, in high circles and in +low, that modern therapeutics has quite denied it; and the physicians +of the time gave it a fictitious added importance by ascribing to its +influence the existence of almost any obscure malady that came under +their observation. Long after Napoleon's time gale continued to hold +this proud distinction. For example, the imaginative Dr. Hahnemann did +not hesitate to affirm, as a positive maxim, that three-fourths of all +the ills that flesh is heir to were in reality nothing but various forms +of "gale repercutee." + +All of which goes to show how easy it may be for a masked pretender to +impose on credulous humanity, for nothing is more clearly established in +modern knowledge than the fact that "gale repercutee" was simply a name +to hide a profound ignorance; no such disease exists or ever did exist. +Gale itself is a sufficiently tangible reality, to be sure, but it is a +purely local disease of the skin, due to a perfectly definite cause, +and the dire internal conditions formerly ascribed to it have really no +causal connection with it whatever. This definite cause, as every one +nowadays knows, is nothing more or less than a microscopic insect which +has found lodgment on the skin, and has burrowed and made itself at home +there. Kill that insect and the disease is no more; hence it has come to +be an axiom with the modern physician that the itch is one of the three +or four diseases that he positively is able to cure, and that very +speedily. But it was far otherwise with the physicians of the first +third of our century, because to them the cause of the disease was an +absolute mystery. + +It is true that here and there a physician had claimed to find an insect +lodged in the skin of a sufferer from itch, and two or three times the +claim had been made that this was the cause of the malady, but such +views were quite ignored by the general profession, and in 1833 it was +stated in an authoritative medical treatise that the "cause of gale is +absolutely unknown." But even at this time, as it curiously happened, +there were certain ignorant laymen who had attained to a bit of medical +knowledge that was withheld from the inner circles of the profession. As +the peasantry of England before Jenner had known of the curative value +of cow-pox over small-pox, so the peasant women of Poland had learned +that the annoying skin disease from which they suffered was caused by +an almost invisible insect, and, furthermore, had acquired the trick of +dislodging the pestiferous little creature with the point of a needle. +From them a youth of the country, F. Renucci by name, learned the open +secret. He conveyed it to Paris when he went there to study medicine, +and in 1834 demonstrated it to his master Alibert. This physician, at +first sceptical, soon was convinced, and gave out the discovery to the +medical world with an authority that led to early acceptance. + +Now the importance of all this, in the present connection, is not at all +that it gave the clew to the method of cure of a single disease. What +makes the discovery epochal is the fact that it dropped a brand-new +idea into the medical ranks--an idea destined, in the long-run, to +prove itself a veritable bomb--the idea, namely, that a minute and quite +unsuspected animal parasite may be the cause of a well-known, widely +prevalent, and important human disease. Of course the full force of this +idea could only be appreciated in the light of later knowledge; but even +at the time of its coming it sufficed to give a great impetus to that +new medical knowledge, based on microscopical studies, which had but +recently been made accessible by the inventions of the lens-makers. The +new knowledge clarified one very turbid medical pool and pointed the way +to the clarification of many others. + +Almost at the same time that the Polish medical student was +demonstrating the itch mite in Paris, it chanced, curiously enough, +that another medical student, this time an Englishman, made an analogous +discovery of perhaps even greater importance. Indeed, this English +discovery in its initial stages slightly antedated the other, for it +was in 1833 that the student in question, James Paget, interne in St. +Bartholomew's Hospital, London, while dissecting the muscular tissues of +a human subject, found little specks of extraneous matter, which, +when taken to the professor of comparative anatomy, Richard Owen, were +ascertained, with the aid of the microscope, to be the cocoon of a +minute and hitherto unknown insect. Owen named the insect Trichina +spiralis. After the discovery was published it transpired that similar +specks had been observed by several earlier investigators, but no one +had previously suspected or, at any rate, demonstrated their nature. Nor +was the full story of the trichina made out for a long time after Owen's +discovery. It was not till 1847 that the American anatomist Dr. Joseph +Leidy found the cysts of trichina in the tissues of pork; and another +decade or so elapsed after that before German workers, chief among whom +were Leuckart, Virchow, and Zenker, proved that the parasite gets into +the human system through ingestion of infected pork, and that it causes +a definite set of symptoms of disease which hitherto had been mistaken +for rheumatism, typhoid fever, and other maladies. Then the medical +world was agog for a time over the subject of trichinosis; government +inspection of pork was established in some parts of Germany; American +pork was excluded altogether from France; and the whole subject thus +came prominently to public attention. But important as the trichina +parasite proved on its own account in the end, its greatest importance, +after all, was in the share it played in directing attention at the +time of its discovery in 1833 to the subject of microscopic parasites in +general. + +The decade that followed that discovery was a time of great activity in +the study of microscopic organisms and microscopic tissues, and such +men as Ehrenberg and Henle and Bory Saint-Vincent and Kolliker and +Rokitansky and Remak and Dujardin were widening the bounds of knowledge +of this new subject with details that cannot be more than referred to +here. But the crowning achievement of the period in this direction was +the discovery made by the German, J. L. Schoenlein, in 1839, that a very +common and most distressing disease of the scalp, known as favus, +is really due to the presence and growth on the scalp of a vegetable +organism of microscopic size. Thus it was made clear that not merely +animal but also vegetable organisms of obscure, microscopic species have +causal relations to the diseases with which mankind is afflicted. This +knowledge of the parasites was another long step in the direction of +scientific medical knowledge; but the heights to which this knowledge +led were not to be scaled, or even recognized, until another generation +of workers had entered the field. + + +PAINLESS SURGERY + +Meantime, in quite another field of medicine, events were developing +which led presently to a revelation of greater immediate importance to +humanity than any other discovery that had come in the century, +perhaps in any field of science whatever. This was the discovery of +the pain-dispelling power of the vapor of sulphuric ether inhaled by a +patient undergoing a surgical operation. This discovery came solely out +of America, and it stands curiously isolated, since apparently no minds +in any other country were trending towards it even vaguely. Davy, in +England, had indeed originated the method of medication by inhalation, +and earned out some most interesting experiments fifty years earlier, +and it was doubtless his experiments with nitrous oxide gas that gave +the clew to one of the American investigators; but this was the sole +contribution of preceding generations to the subject, and since the +beginning of the century, when Davy turned his attention to other +matters, no one had made the slightest advance along the same line until +an American dentist renewed the investigation. + +In view of the sequel, Davy's experiments merit full attention. Here is +his own account of them, as written in 1799: + + +"Immediately after a journey of one hundred and twenty-six miles, +in which I had no sleep the preceding night, being much exhausted, I +respired seven quarts of nitrous oxide gas for near three minutes. It +produced the usual pleasurable effects and slight muscular motion. I +continued exhilarated for some minutes afterwards, but in half an hour +found myself neither more nor less exhausted than before the experiment. +I had a great propensity to sleep. + +"To ascertain with certainty whether the more extensive action of +nitrous oxide compatible with life was capable of producing debility, I +resolved to breathe the gas for such a time, and in such quantities, +as to produce excitement equal in duration and superior in intensity to +that occasioned by high intoxication from opium or alcohol. + +"To habituate myself to the excitement, and to carry it on gradually, +on December 26th I was enclosed in an air-tight breathing-box, of the +capacity of about nine and one-half cubic feet, in the presence of Dr. +Kinglake. After I had taken a situation in which I could by means of a +curved thermometer inserted under the arm, and a stop-watch, ascertain +the alterations in my pulse and animal heat, twenty quarts of nitrous +oxide were thrown into the box. + +"For three minutes I experienced no alteration in my sensations, though +immediately after the introduction of the nitrous oxide the smell and +taste of it were very evident. In four minutes I began to feel a slight +glow in the cheeks and a generally diffused warmth over the chest, +though the temperature of the box was not quite 50 degrees.... In +twenty-five minutes the animal heat was 100 degrees, pulse 124. In +thirty minutes twenty quarts more of gas were introduced. + +"My sensations were now pleasant; I had a generally diffused warmth +without the slightest moisture of the skin, a sense of exhilaration +similar to that produced by a small dose of wine, and a disposition to +muscular motion and to merriment. + +"In three-quarters of an hour the pulse was 104 and the animal heat not +99.5 degrees, the temperature of the chamber 64 degrees. The pleasurable +feelings continued to increase, the pulse became fuller and slower, till +in about an hour it was 88, when the animal heat was 99 degrees. Twenty +quarts more of air were admitted. I had now a great disposition to +laugh, luminous points seemed frequently to pass before my eyes, my +hearing was certainly more acute, and I felt a pleasant lightness and +power of exertion in my muscles. In a short time the symptoms became +stationary; breathing was rather oppressed, and on account of the great +desire for action rest was painful. + +"I now came out of the box, having been in precisely an hour and a +quarter. The moment after I began to respire twenty quarts of unmingled +nitrous oxide. A thrilling extending from the chest to the extremities +was almost immediately produced. I felt a sense of tangible extension +highly pleasurable in every limb; my visible impressions were dazzling +and apparently magnified, I heard distinctly every sound in the room, +and was perfectly aware of my situation. By degrees, as the pleasurable +sensations increased, I lost all connection with external things; +trains of vivid visible images rapidly passed through my mind and +were connected with words in such a manner as to produce perceptions +perfectly novel. + +"I existed in a world of newly connected and newly modified ideas. I +theorized; I imagined that I made discoveries. When I was awakened from +this semi-delirious trance by Dr. Kinglake, who took the bag from my +mouth, indignation and pride were the first feelings produced by the +sight of persons about me. My emotions were enthusiastic and sublime; +and for a minute I walked about the room perfectly regardless of what +was said to me. As I recovered my former state of mind, I felt an +inclination to communicate the discoveries I had made during the +experiment. I endeavored to recall the ideas--they were feeble and +indistinct; one collection of terms, however, presented itself, and, +with most intense belief and prophetic manner, I exclaimed to Dr. +Kinglake, 'Nothing exists but thoughts!--the universe is composed of +impressions, ideas, pleasures, and pains.' "(3) + + +From this account we see that Davy has anaesthetized himself to a point +where consciousness of surroundings was lost, but not past the stage +of exhilaration. Had Dr. Kinglake allowed the inhaling-bag to remain in +Davy's mouth for a few moments longer complete insensibility would have +followed. As it was, Davy appears to have realized that sensibility was +dulled, for he adds this illuminative suggestion: "As nitrous oxide in +its extensive operation appears capable of destroying physical pain, it +may probably be used with advantage during surgical operations in which +no great effusion of blood takes place."(4) + +Unfortunately no one took advantage of this suggestion at the time, +and Davy himself became interested in other fields of science and never +returned to his physiological studies, thus barely missing one of the +greatest discoveries in the entire field of science. In the generation +that followed no one seems to have thought of putting Davy's suggestion +to the test, and the surgeons of Europe had acknowledged with one accord +that all hope of finding a means to render operations painless must be +utterly abandoned--that the surgeon's knife must ever remain a synonym +for slow and indescribable torture. By an odd coincidence it chanced +that Sir Benjamin Brodie, the acknowledged leader of English surgeons, +had publicly expressed this as his deliberate though regretted opinion +at a time when the quest which he considered futile had already led to +the most brilliant success in America, and while the announcement of +the discovery, which then had no transatlantic cable to convey it, was +actually on its way to the Old World. + +The American dentist just referred to, who was, with one exception to +be noted presently, the first man in the world to conceive that the +administration of a definite drug might render a surgical operation +painless and to give the belief application was Dr. Horace Wells, of +Hartford, Connecticut. The drug with which he experimented was nitrous +oxide--the same that Davy had used; the operation that he rendered +painless was no more important than the extraction of a tooth--yet it +sufficed to mark a principle; the year of the experiment was 1844. + +The experiments of Dr. Wells, however, though important, were not +sufficiently demonstrative to bring the matter prominently to the +attention of the medical world. The drug with which he experimented +proved not always reliable, and he himself seems ultimately to have +given the matter up, or at least to have relaxed his efforts. +But meantime a friend, to whom he had communicated his belief and +expectations, took the matter up, and with unremitting zeal carried +forward experiments that were destined to lead to more tangible results. +This friend was another dentist, Dr. W. T. G. Morton, of Boston, then a +young man full of youthful energy and enthusiasm. He seems to have +felt that the drug with which Wells had experimented was not the +most practicable one for the purpose, and so for several months +he experimented with other allied drugs, until finally he hit upon +sulphuric ether, and with this was able to make experiments upon +animals, and then upon patients in the dental chair, that seemed to him +absolutely demonstrative. + +Full of eager enthusiasm, and absolutely confident of his results, he at +once went to Dr. J. C. Warren, one of the foremost surgeons of Boston, +and asked permission to test his discovery decisively on one of the +patients at the Boston Hospital during a severe operation. The request +was granted; the test was made on October 16, 1846, in the presence of +several of the foremost surgeons of the city and of a body of medical +students. The patient slept quietly while the surgeon's knife was plied, +and awoke to astonished comprehension that the ordeal was over. The +impossible, the miraculous, had been accomplished.(5) + +Swiftly as steam could carry it--slowly enough we should think it +to-day--the news was heralded to all the world. It was received in +Europe with incredulity, which vanished before repeated experiments. +Surgeons were loath to believe that ether, a drug that had long held +a place in the subordinate armamentarium of the physician, could +accomplish such a miracle. But scepticism vanished before the tests +which any surgeon might make, and which surgeons all over the world did +make within the next few weeks. Then there came a lingering outcry from +a few surgeons, notably some of the Parisians, that the shock of pain +was beneficial to the patient, hence that anaesthesia--as Dr. Oliver +Wendell Holmes had christened the new method--was a procedure not to +be advised. Then, too, there came a hue-and-cry from many a pulpit that +pain was God-given, and hence, on moral grounds, to be clung to rather +than renounced. But the outcry of the antediluvians of both hospital +and pulpit quickly received its quietus; for soon it was clear that the +patient who did not suffer the shock of pain during an operation rallied +better than the one who did so suffer, while all humanity outside the +pulpit cried shame to the spirit that would doom mankind to suffer +needless agony. And so within a few months after that initial operation +at the Boston Hospital in 1846, ether had made good its conquest of +pain throughout the civilized world. Only by the most active use of the +imagination can we of this present day realize the full meaning of that +victory. + +It remains to be added that in the subsequent bickerings over the +discovery--such bickerings as follow every great advance--two other +names came into prominent notice as sharers in the glory of the new +method. Both these were Americans--the one, Dr. Charles T. Jackson, of +Boston; the other, Dr. Crawford W. Long, of Alabama. As to Dr. Jackson, +it is sufficient to say that he seems to have had some vague inkling +of the peculiar properties of ether before Morton's discovery. He even +suggested the use of this drug to Morton, not knowing that Morton had +already tried it; but this is the full measure of his association with +the discovery. Hence it is clear that Jackson's claim to equal share +with Morton in the discovery was unwarranted, not to say absurd. + +Dr. Long's association with the matter was far different and altogether +honorable. By one of those coincidences so common in the history +of discovery, he was experimenting with ether as a pain-destroyer +simultaneously with Morton, though neither so much as knew of the +existence of the other. While a medical student he had once inhaled +ether for the intoxicant effects, as other medical students were wont to +do, and when partially under influence of the drug he had noticed that a +chance blow to his shins was painless. This gave him the idea that ether +might be used in surgical operations; and in subsequent years, in the +course of his practice in a small Georgia town, he put the idea into +successful execution. There appears to be no doubt whatever that he +performed successful minor operations under ether some two or three +years before Morton's final demonstration; hence that the merit of first +using the drug, or indeed any drug, in this way belongs to him. But, +unfortunately, Dr. Long did not quite trust the evidence of his own +experiments. Just at that time the medical journals were full of +accounts of experiments in which painless operations were said to be +performed through practice of hypnotism, and Dr. Long feared that his +own success might be due to an incidental hypnotic influence rather than +to the drug. Hence he delayed announcing his apparent discovery until +he should have opportunity for further tests--and opportunities did not +come every day to the country practitioner. And while he waited, Morton +anticipated him, and the discovery was made known to the world without +his aid. It was a true scientific caution that actuated Dr. Long to this +delay, but the caution cost him the credit, which might otherwise have +been his, of giving to the world one of the greatest blessings--dare we +not, perhaps, say the very greatest?--that science has ever conferred +upon humanity. + +A few months after the use of ether became general, the Scotch surgeon +Sir J. Y. Simpson(6) discovered that another drug, chloroform, could be +administered with similar effects; that it would, indeed, in many cases +produce anaesthesia more advantageously even than ether. From that day +till this surgeons have been more or less divided in opinion as to +the relative merits of the two drugs; but this fact, of course, has no +bearing whatever upon the merit of the first discovery of the method of +anaesthesia. Even had some other drug subsequently quite banished ether, +the honor of the discovery of the beneficent method of anaesthesia would +have been in no wise invalidated. And despite all cavillings, it is +unequivocally established that the man who gave that method to the world +was William T. G. Morton. + + +PASTEUR AND THE GERM THEORY OF DISEASE + +The discovery of the anaesthetic power of drugs was destined presently, +in addition to its direct beneficences, to aid greatly in the progress +of scientific medicine, by facilitating those experimental studies +of animals from which, before the day of anaesthesia, many humane +physicians were withheld, and which in recent years have led to +discoveries of such inestimable value to humanity. But for the moment +this possibility was quite overshadowed by the direct benefits of +anaesthesia, and the long strides that were taken in scientific medicine +during the first fifteen years after Morton's discovery were mainly +independent of such aid. These steps were taken, indeed, in a field +that at first glance might seem to have a very slight connection with +medicine. Moreover, the chief worker in the field was not himself a +physician. He was a chemist, and the work in which he was now engaged +was the study of alcoholic fermentation in vinous liquors. Yet these +studies paved the way for the most important advances that medicine has +made in any century towards the plane of true science; and to this man +more than to any other single individual--it might almost be said more +than to all other individuals--was due this wonderful advance. It is +almost superfluous to add that the name of this marvellous chemist was +Louis Pasteur. + +The studies of fermentation which Pasteur entered upon in 1854 were +aimed at the solution of a controversy that had been waging in the +scientific world with varying degrees of activity for a quarter of a +century. Back in the thirties, in the day of the early enthusiasm over +the perfected microscope, there had arisen a new interest in the minute +forms of life which Leeuwenhoek and some of the other early workers with +the lens had first described, and which now were shown to be of almost +universal prevalence. These minute organisms had been studied more or +less by a host of observers, but in particular by the Frenchman Cagniard +Latour and the German of cell-theory fame, Theodor Schwann. These men, +working independently, had reached the conclusion, about 1837, that +the micro-organisms play a vastly more important role in the economy +of nature than any one previously had supposed. They held, for example, +that the minute specks which largely make up the substance of yeast are +living vegetable organisms, and that the growth of these organisms is +the cause of the important and familiar process of fermentation. They +even came to hold, at least tentatively, the opinion that the somewhat +similar micro-organisms to be found in all putrefying matter, animal or +vegetable, had a causal relation to the process of putrefaction. + +This view, particularly as to the nature of putrefaction, was expressed +even more outspokenly a little later by the French botanist Turpin. +Views so supported naturally gained a following; it was equally natural +that so radical an innovation should be antagonized. In this case it +chanced that one of the most dominating scientific minds of the time, +that of Liebig, took a firm and aggressive stand against the new +doctrine. In 1839 he promulgated his famous doctrine of fermentation, +in which he stood out firmly against any "vitalistic" explanation of the +phenomena, alleging that the presence of micro-organisms in fermenting +and putrefying substances was merely incidental, and in no sense causal. +This opinion of the great German chemist was in a measure substantiated +by experiments of his compatriot Helmholtz, whose earlier experiments +confirmed, but later ones contradicted, the observations of Schwann, and +this combined authority gave the vitalistic conception a blow from which +it had not rallied at the time when Pasteur entered the field. Indeed, +it was currently regarded as settled that the early students of the +subject had vastly over-estimated the importance of micro-organisms. + +And so it came as a new revelation to the generality of scientists +of the time, when, in 1857 and the succeeding half-decade, Pasteur +published the results of his researches, in which the question had been +put to a series of altogether new tests, and brought to unequivocal +demonstration. + +He proved that the micro-organisms do all that his most imaginative +predecessors had suspected, and more. Without them, he proved, there +would be no fermentation, no putrefaction--no decay of any tissues, +except by the slow process of oxidation. It is the microscopic +yeast-plant which, by seizing on certain atoms of the molecule, +liberates the remaining atoms in the form of carbonic-acid and alcohol, +thus effecting fermentation; it is another microscopic plant--a +bacterium, as Devaine had christened it--which in a similar way effects +the destruction of organic molecules, producing the condition which we +call putrefaction. Pasteur showed, to the amazement of biologists, that +there are certain forms of these bacteria which secure the oxygen which +all organic life requires, not from the air, but by breaking up unstable +molecules in which oxygen is combined; that putrefaction, in short, has +its foundation in the activities of these so-called anaerobic bacteria. + +In a word, Pasteur showed that all the many familiar processes of the +decay of organic tissues are, in effect, forms of fermentation, and +would not take place at all except for the presence of the living +micro-organisms. A piece of meat, for example, suspended in an +atmosphere free from germs, will dry up gradually, without the slightest +sign of putrefaction, regardless of the temperature or other conditions +to which it may have been subjected. Let us witness one or two series of +these experiments as presented by Pasteur himself in one of his numerous +papers before the Academy of Sciences. + + +EXPERIMENTS WITH GRAPE SUGAR + +"In the course of the discussion which took place before the Academy +upon the subject of the generation of ferments properly so-called, there +was a good deal said about that of wine, the oldest fermentation known. +On this account I decided to disprove the theory of M. Fremy by a +decisive experiment bearing solely upon the juice of grapes. + +"I prepared forty flasks of a capacity of from two hundred and fifty to +three hundred cubic centimetres and filled them half full with filtered +grape-must, perfectly clear, and which, as is the case of all acidulated +liquids that have been boiled for a few seconds, remains uncontaminated +although the curved neck of the flask containing them remain constantly +open during several months or years. + +"In a small quantity of water I washed a part of a bunch of grapes, the +grapes and the stalks together, and the stalks separately. This +washing was easily done by means of a small badger's-hair brush. The +washing-water collected the dust upon the surface of the grapes and the +stalks, and it was easily shown under the microscope that this water +held in suspension a multitude of minute organisms closely resembling +either fungoid spores, or those of alcoholic Yeast, or those of +Mycoderma vini, etc. This being done, ten of the forty flasks were +preserved for reference; in ten of the remainder, through the straight +tube attached to each, some drops of the washing-water were introduced; +in a third series of ten flasks a few drops of the same liquid were +placed after it had been boiled; and, finally, in the ten remaining +flasks were placed some drops of grape-juice taken from the inside of a +perfect fruit. In order to carry out this experiment, the straight tube +of each flask was drawn out into a fine and firm point in the lamp, and +then curved. This fine and closed point was filed round near the end and +inserted into the grape while resting upon some hard substance. When +the point was felt to touch the support of the grape it was by a slight +pressure broken off at the point file mark. Then, if care had been taken +to create a slight vacuum in the flask, a drop of the juice of the grape +got into it, the filed point was withdrawn, and the aperture immediately +closed in the alcohol lamp. This decreased pressure of the atmosphere in +the flask was obtained by the following means: After warming the sides +of the flask either in the hands or in the lamp-flame, thus causing a +small quantity of air to be driven out of the end of the curved neck, +this end was closed in the lamp. After the flask was cooled, there was +a tendency to suck in the drop of grape-juice in the manner just +described. + +"The drop of grape-juice which enters into the flask by this suction +ordinarily remains in the curved part of the tube, so that to mix it +with the must it was necessary to incline the flask so as to bring +the must into contact with the juice and then replace the flask in its +normal position. The four series of comparative experiments produced the +following results: + +"The first ten flasks containing the grape-must boiled in pure air did +not show the production of any organism. The grape-must could possibly +remain in them for an indefinite number of years. Those in the second +series, containing the water in which the grapes had been washed +separately and together, showed without exception an alcoholic +fermentation which in several cases began to appear at the end of +forty-eight hours when the experiment took place at ordinary summer +temperature. At the same time that the yeast appeared, in the form of +white traces, which little by little united themselves in the form of a +deposit on the sides of all the flasks, there were seen to form little +flakes of Mycellium, often as a single fungoid growth or in combination, +these fungoid growths being quite independent of the must or of any +alcoholic yeast. Often, also, the Mycoderma vini appeared after some +days upon the surface of the liquid. The Vibria and the lactic ferments +properly so called did not appear on account of the nature of the +liquid. + +"The third series of flasks, the washing-water in which had been +previously boiled, remained unchanged, as in the first series. Those of +the fourth series, in which was the juice of the interior of the grapes, +remained equally free from change, although I was not always able, on +account of the delicacy of the experiment, to eliminate every chance of +error. These experiments cannot leave the least doubt in the mind as to +the following facts: + +"Grape-must, after heating, never ferments on contact with the air, when +the air has been deprived of the germs which it ordinarily holds in a +state of suspension. + +"The boiled grape-must ferments when there is introduced into it a very +small quantity of water in which the surface of the grapes or their +stalks have been washed. + +"The grape-must does not ferment when this washing-water has been boiled +and afterwards cooled. + +"The grape-must does not ferment when there is added to it a small +quantity of the juice of the inside of the grape. + +"The yeast, therefore, which causes the fermentation of the grapes in +the vintage-tub comes from the outside and not from the inside of the +grapes. Thus is destroyed the hypothesis of MM. Trecol and Fremy, who +surmised that the albuminous matter transformed itself into yeast +on account of the vital germs which were natural to it. With greater +reason, therefore, there is no longer any question of the theory of +Liebig of the transformation of albuminoid matter into ferments on +account of the oxidation." + + +FOREIGN ORGANISMS AND THE WORT OF BEER + +"The method which I have just followed," Pasteur continues, "in order +to show that there exists a correlation between the diseases of beer and +certain microscopic organisms leaves no room for doubt, it seems to me, +in regard to the principles I am expounding. + +"Every time that the microscope reveals in the leaven, and especially in +the active yeast, the production of organisms foreign to the alcoholic +yeast properly so called, the flavor of the beer leaves something to be +desired, much or little, according to the abundance and the character of +these little germs. Moreover, when a finished beer of good quality loses +after a time its agreeable flavor and becomes sour, it can be easily +shown that the alcoholic yeast deposited in the bottles or the casks, +although originally pure, at least in appearance, is found to be +contaminated gradually with these filiform or other ferments. All +this can be deduced from the facts already given, but some critics may +perhaps declare that these foreign ferments are the consequences of the +diseased condition, itself produced by unknown causes. + +"Although this gratuitous hypothesis may be difficult to uphold, I will +endeavor to corroborate the preceding observations by a clearer method +of investigation. This consists in showing that the beer never has any +unpleasant taste in all cases when the alcoholic ferment properly so +called is not mixed with foreign ferments; that it is the same in +the case of wort, and that wort, liable to changes as it is, can be +preserved unaltered if it is kept from those microscopic parasites which +find in it a suitable nourishment and a field for growth. + +"The employment of this second method has, moreover, the advantage of +proving with certainty the proposition that I advanced at first--namely, +that the germs of these organisms are derived from the dust of the +atmosphere, carried about and deposited upon all objects, or scattered +over the utensils and the materials used in a brewery-materials +naturally charged with microscopic germs, and which the various +operations in the store-rooms and the malt-house may multiply +indefinitely. + +"Let us take a glass flask with a long neck of from two hundred and +fifty to three hundred cubic centimetres capacity, and place in it some +wort, with or without hops, and then in the flame of a lamp draw out the +neck of the flask to a fine point, afterwards heating the liquid until +the steam comes out of the end of the neck. It can then be allowed to +cool without any other precautions; but for additional safety there +can be introduced into the little point a small wad of asbestos at the +moment that the flame is withdrawn from beneath the flask. Before thus +placing the asbestos it also can be passed through the flame, as well as +after it has been put into the end of the tube. The air which then first +re-enters the flask will thus come into contact with the heated glass +and the heated liquid, so as to destroy the vitality of any dust germs +that may exist in the air. The air itself will re-enter very gradually, +and slowly enough to enable any dust to be taken up by the drop of water +which the air forces up the curvature of the tube. Ultimately the tube +will be dry, but the re-entering of the air will be so slow that the +particles of dust will fall upon the sides of the tube. The experiments +show that with this kind of vessel, allowing free communication with the +air, and the dust not being allowed to enter, the dust will not enter +at all events for a period of ten or twelve years, which has been the +longest period devoted to these trials; and the liquid, if it were +naturally limpid, will not be in the least polluted neither on its +surface nor in its mass, although the outside of the flask may become +thickly coated with dust. This is a most irrefutable proof of the +impossibility of dust getting inside the flask. + +"The wort thus prepared remains uncontaminated indefinitely, in spite +of its susceptibility to change when exposed to the air under conditions +which allow it to gather the dusty particles which float in the +atmosphere. It is the same in the case of urine, beef-tea, and +grape-must, and generally with all those putrefactable and fermentable +liquids which have the property when heated to boiling-point of +destroying the vitality of dust germs."(7) + + +There was nothing in these studies bearing directly upon the question +of animal diseases, yet before they were finished they had stimulated +progress in more than one field of pathology. At the very outset +they sufficed to start afresh the inquiry as to the role played by +micro-organisms in disease. In particular they led the French physician +Devaine to return to some interrupted studies which he had made ten +years before in reference to the animal disease called anthrax, or +splenic fever, a disease that cost the farmers of Europe millions of +francs annually through loss of sheep and cattle. In 1850 Devaine had +seen multitudes of bacteria in the blood of animals who had died of +anthrax, but he did not at that time think of them as having a causal +relation to the disease. Now, however, in 1863, stimulated by Pasteur's +new revelations regarding the power of bacteria, he returned to the +subject, and soon became convinced, through experiments by means of +inoculation, that the microscopic organisms he had discovered were the +veritable and the sole cause of the infectious disease anthrax. + +The publication of this belief in 1863 aroused a furor of controversy. +That a microscopic vegetable could cause a virulent systemic disease +was an idea altogether too startling to be accepted in a day, and the +generality of biologists and physicians demanded more convincing proofs +than Devaine as yet was able to offer. + +Naturally a host of other investigators all over the world entered the +field. Foremost among these was the German Dr. Robert Koch, who soon +corroborated all that Devaine had observed, and carried the experiments +further in the direction of the cultivation of successive generations of +the bacteria in artificial media, inoculations being made from such +pure cultures of the eighth generation, with the astonishing result that +animals thus inoculated succumbed to the disease. + +Such experiments seem demonstrative, yet the world was unconvinced, +and in 1876, while the controversy was still at its height, Pasteur +was prevailed upon to take the matter in hand. The great chemist was +becoming more and more exclusively a biologist as the years passed, and +in recent years his famous studies of the silk-worm diseases, which he +proved due to bacterial infection, and of the question of spontaneous +generation, had given him unequalled resources in microscopical +technique. And so when, with the aid of his laboratory associates +Duclaux and Chamberland and Roux, he took up the mooted anthrax question +the scientific world awaited the issue with bated breath. And when, in +1877, Pasteur was ready to report on his studies of anthrax, he came +forward with such a wealth of demonstrative experiments--experiments +the rigid accuracy of which no one would for a moment think of +questioning--going to prove the bacterial origin of anthrax, that +scepticism was at last quieted for all time to come. + +Henceforth no one could doubt that the contagious disease anthrax is due +exclusively to the introduction into an animal's system of a specific +germ--a microscopic plant--which develops there. And no logical mind +could have a reasonable doubt that what is proved true of one infectious +disease would some day be proved true also of other, perhaps of all, +forms of infectious maladies. + +Hitherto the cause of contagion, by which certain maladies spread from +individual to individual, had been a total mystery, quite unillumined +by the vague terms "miasm," "humor," "virus," and the like cloaks of +ignorance. Here and there a prophet of science, as Schwann and Henle, +had guessed the secret; but guessing, in science, is far enough from +knowing. Now, for the first time, the world KNEW, and medicine had taken +another gigantic stride towards the heights of exact science. + + +LISTER AND ANTISEPTIC SURGERY + +Meantime, in a different though allied field of medicine there had +been a complementary growth that led to immediate results of even more +practical importance. I mean the theory and practice of antisepsis in +surgery. This advance, like the other, came as a direct outgrowth of +Pasteur's fermentation studies of alcoholic beverages, though not at +the hands of Pasteur himself. Struck by the boundless implications of +Pasteur's revelations regarding the bacteria, Dr. Joseph Lister (the +present Lord Lister), then of Glasgow, set about as early as 1860 to +make a wonderful application of these ideas. If putrefaction is always +due to bacterial development, he argued, this must apply as well to +living as to dead tissues; hence the putrefactive changes which occur +in wounds and after operations on the human subject, from which +blood-poisoning so often follows, might be absolutely prevented if the +injured surfaces could be kept free from access of the germs of decay. + +In the hope of accomplishing this result, Lister began experimenting +with drugs that might kill the bacteria without injury to the patient, +and with means to prevent further access of germs once a wound was freed +from them. How well he succeeded all the world knows; how bitterly +he was antagonized for about a score of years, most of the world has +already forgotten. As early as 1867 Lister was able to publish results +pointing towards success in his great project; yet so incredulous were +surgeons in general that even some years later the leading surgeons +on the Continent had not so much as heard of his efforts. In 1870 the +soldiers of Paris died, as of old, of hospital gangrene; and when, +in 1871, the French surgeon Alphonse Guerin, stimulated by Pasteur's +studies, conceived the idea of dressing wounds with cotton in the hope +of keeping germs from entering them, he was quite unaware that a +British contemporary had preceded him by a full decade in this effort at +prevention and had made long strides towards complete success. Lister's +priority, however, and the superiority of his method, were freely +admitted by the French Academy of Sciences, which in 1881 officially +crowned his achievement, as the Royal Society of London had done the +year before. + +By this time, to be sure, as everybody knows, Lister's new methods had +made their way everywhere, revolutionizing the practice of surgery and +practically banishing from the earth maladies that hitherto had been the +terror of the surgeon and the opprobrium of his art. And these bedside +studies, conducted in the end by thousands of men who had no knowledge +of microscopy, had a large share in establishing the general belief in +the causal relation that micro-organisms bear to disease, which by about +the year 1880 had taken possession of the medical world. But they did +more; they brought into equal prominence the idea that, the cause of +a diseased condition being known, it maybe possible as never before to +grapple with and eradicate that condition. + + +PREVENTIVE INOCULATION + +The controversy over spontaneous generation, which, thanks to Pasteur +and Tyndall, had just been brought to a termination, made it clear that +no bacterium need be feared where an antecedent bacterium had not +found lodgment; Listerism in surgery had now shown how much might be +accomplished towards preventing the access of germs to abraded surfaces +of the body and destroying those that already had found lodgment there. +As yet, however, there was no inkling of a way in which a corresponding +onslaught might be made upon those other germs which find their way into +the animal organism by way of the mouth and the nostrils, and which, as +was now clear, are the cause of those contagious diseases which, first +and last, claim so large a proportion of mankind for their victims. +How such means might be found now became the anxious thought of every +imaginative physician, of every working microbiologist. + +As it happened, the world was not kept long in suspense. Almost before +the proposition had taken shape in the minds of the other leaders, +Pasteur had found a solution. Guided by the empirical success of Jenner, +he, like many others, had long practised inoculation experiments, and on +February 9, 1880, he announced to the French Academy of Sciences that he +had found a method of so reducing the virulence of a disease germ that +when introduced into the system of a susceptible animal it produced only +a mild form of the disease, which, however, sufficed to protect against +the usual virulent form exactly as vaccinia protects against small-pox. +The particular disease experimented with was that infectious malady of +poultry known familiarly as "chicken cholera." In October of the same +year Pasteur announced the method by which this "attenuation of the +virus," as he termed it, had been brought about--by cultivation of the +disease germs in artificial media, exposed to the air, and he did not +hesitate to assert his belief that the method would prove "susceptible +of generalization"--that is to say, of application to other diseases +than the particular one in question. + +Within a few months he made good this prophecy, for in February, +1881, he announced to the Academy that with the aid, as before, of his +associates MM. Chamberland and Roux, he had produced an attenuated virus +of the anthrax microbe by the use of which, as he affirmed with great +confidence, he could protect sheep, and presumably cattle, against that +fatal malady. "In some recent publications," said Pasteur, "I announced +the first case of the attenuation of a virus by experimental methods +only. Formed of a special microbe of an extreme minuteness, this virus +may be multiplied by artificial culture outside the animal body. These +cultures, left alone without any possible external contamination, +undergo, in the course of time, modifications of their virulency to a +greater or less extent. The oxygen of the atmosphere is said to be +the chief cause of these attenuations--that is, this lessening of the +facilities of multiplication of the microbe; for it is evident that the +difference of virulence is in some way associated with differences of +development in the parasitic economy. + +"There is no need to insist upon the interesting character of these +results and the deductions to be made therefrom. To seek to lessen the +virulence by rational means would be to establish, upon an experimental +basis, the hope of preparing from an active virus, easily cultivated +either in the human or animal body, a vaccine-virus of restrained +development capable of preventing the fatal effects of the former. +Therefore, we have applied all our energies to investigate the possible +generalizing action of atmospheric oxygen in the attenuation of virus. + +"The anthrax virus, being one that has been most carefully studied, +seemed to be the first that should attract our attention. Every time, +however, we encountered a difficulty. Between the microbe of chicken +cholera and the microbe of anthrax there exists an essential difference +which does not allow the new experiment to be verified by the old. +The microbes of chicken cholera do not, in effect, seem to resolve +themselves, in their culture, into veritable germs. The latter are +merely cells, or articulations always ready to multiply by division, +except when the particular conditions in which they become true germs +are known. + +"The yeast of beer is a striking example of these cellular productions, +being able to multiply themselves indefinitely without the apparition +of their original spores. There exist many mucedines (Mucedinae?) of +tubular mushrooms, which in certain conditions of culture produce +a chain of more or less spherical cells called Conidae. The latter, +detached from their branches, are able to reproduce themselves in the +form of cells, without the appearance, at least with a change in the +conditions of culture, of the spores of their respective mucedines. +These vegetable organisms can be compared to plants which are cultivated +by slipping, and to produce which it is not necessary to have the fruits +or the seeds of the mother plant. + +"The anthrax bacterium, in its artificial cultivation, behaves very +differently. Its mycelian filaments, if one may so describe them, have +been produced scarcely for twenty-four or forty-eight hours when they +are seen to transform themselves, those especially which are in free +contact with the air, into very refringent corpuscles, capable of +gradually isolating themselves into true germs of slight organization. +Moreover, observation shows that these germs, formed so quickly in the +culture, do not undergo, after exposure for a time to atmospheric air, +any change either in their vitality or their virulence. I was able to +present to the Academy a tube containing some spores of anthrax bacteria +produced four years ago, on March 21, 1887. Each year the germination +of these little corpuscles has been tried, and each year the germination +has been accomplished with the same facility and the same rapidity as at +first. Each year also the virulence of the new cultures has been tested, +and they have not shown any visible falling off. Therefore, how can we +experiment with the action of the air upon the anthrax virus with any +expectation of making it less virulent? + +"The crucial difficulty lies perhaps entirely in this rapid reproduction +of the bacteria germs which we have just related. In its form of a +filament, and in its multiplication by division, is not this organism at +all points comparable with the microbe of the chicken cholera? + +"That a germ, properly so called, that a seed, does not suffer any +modification on account of the air is easily conceived; but it is +conceivable not less easily that if there should be any change it would +occur by preference in the case of a mycelian fragment. It is thus that +a slip which may have been abandoned in the soil in contact with the air +does not take long to lose all vitality, while under similar conditions +a seed is preserved in readiness to reproduce the plant. If these views +have any foundation, we are led to think that in order to prove the +action of the air upon the anthrax bacteria it will be indispensable to +submit to this action the mycelian development of the minute organism +under conditions where there cannot be the least admixture of +corpuscular germs. Hence the problem of submitting the bacteria to the +action of oxygen comes back to the question of presenting entirely +the formation of spores. The question being put in this way, we are +beginning to recognize that it is capable of being solved. + +"We can, in fact, prevent the appearance of spores in the artificial +cultures of the anthrax parasite by various artifices. At the lowest +temperature at which this parasite can be cultivated--that is to say, +about +16 degrees Centigrade--the bacterium does not produce germs--at +any rate, for a very long time. The shapes of the minute microbe at this +lowest limit of its development are irregular, in the form of balls and +pears--in a word, they are monstrosities--but they are without spores. +In the last regard also it is the same at the highest temperatures at +which the parasite can be cultivated, temperatures which vary slightly +according to the means employed. In neutral chicken bouillon the +bacteria cannot be cultivated above 45 degrees. Culture, however, is +easy and abundant at 42 to 43 degrees, but equally without any formation +of spores. Consequently a culture of mycelian bacteria can be kept +entirely free from germs while in contact with the open air at a +temperature of from 42 to 43 degrees Centigrade. Now appear the three +remarkable results. After about one month of waiting the culture +dies--that is to say, if put into a fresh bouillon it becomes absolutely +sterile. + +"So much for the life and nutrition of this organism. In respect to its +virulence, it is an extraordinary fact that it disappears entirely after +eight days' culture at 42 to 43 degrees Centigrade, or, at any rate, the +cultures are innocuous for the guinea-pig, the rabbit, and the sheep, +the three kinds of animals most apt to contract anthrax. We are thus +able to obtain, not only the attenuation of the virulence, but also its +complete suppression by a simple method of cultivation. Moreover, we see +also the possibility of preserving and cultivating the terrible microbe +in an inoffensive state. What is it that happens in these eight days at +43 degrees that suffices to take away the virulence of the bacteria? Let +us remember that the microbe of chicken cholera dies in contact with the +air, in a period somewhat protracted, it is true, but after successive +attenuations. Are we justified in thinking that it ought to be the same +in regard to the microbe of anthrax? This hypothesis is confirmed +by experiment. Before the disappearance of its virulence the anthrax +microbe passes through various degrees of attenuation, and, moreover, +as is also the case with the microbe of chicken cholera, each of these +attenuated states of virulence can be obtained by cultivation. Moreover, +since, according to one of our recent Communications, anthrax is +not recurrent, each of our attenuated anthrax microbes is, for the +better-developed microbe, a vaccine--that is to say, a virus producing a +less-malignant malady. What, therefore, is easier than to find in these +a virus that will infect with anthrax sheep, cows, and horses, without +killing them, and ultimately capable of warding off the mortal malady? +We have practised this experiment with great success upon sheep, and +when the season comes for the assembling of the flocks at Beauce we +shall try the experiment on a larger scale. + +"Already M. Toussaint has announced that sheep can be saved by +preventive inoculations; but when this able observer shall have +published his results; on the subject of which we have made such +exhaustive studies, as yet unpublished, we shall be able to see the +whole difference which exists between the two methods--the uncertainty +of the one and the certainty of the other. That which we announce has, +moreover, the very great advantage of resting upon the existence of +a poison vaccine cultivable at will, and which can be increased +indefinitely in the space of a few hours without having recourse to +infected blood."(8) + + +This announcement was immediately challenged in a way that brought it +to the attention of the entire world. The president of an agricultural +society, realizing the enormous importance of the subject, proposed to +Pasteur that his alleged discovery should be submitted to a decisive +public test. He proposed to furnish a drove of fifty sheep half of which +were to be inoculated with the attenuated virus of Pasteur. Subsequently +all the sheep were to be inoculated with virulent virus, all being kept +together in one pen under precisely the same conditions. The "protected" +sheep were to remain healthy; the unprotected ones to die of anthrax; +so read the terms of the proposition. Pasteur accepted the challenge; +he even permitted a change in the programme by which two goats were +substituted for two of the sheep, and ten cattle added, stipulating, +however, that since his experiments had not yet been extended to cattle +these should not be regarded as falling rigidly within the terms of the +test. + +It was a test to try the soul of any man, for all the world looked on +askance, prepared to deride the maker of so preposterous a claim as soon +as his claim should be proved baseless. Not even the fame of Pasteur +could make the public at large, lay or scientific, believe in the +possibility of what he proposed to accomplish. There was time for all +the world to be informed of the procedure, for the first "preventive" +inoculation--or vaccination, as Pasteur termed it--was made on May 5th, +the second on May 17th, and another interval of two weeks must elapse +before the final inoculations with the unattenuated virus. Twenty-four +sheep, one goat, and five cattle were submitted to the preliminary +vaccinations. Then, on May 31 st, all sixty of the animals were +inoculated, a protected and unprotected one alternately, with an +extremely virulent culture of anthrax microbes that had been in +Pasteur's laboratory since 1877. This accomplished, the animals were +left together in one enclosure to await the issue. + +Two days later, June 2d, at the appointed hour of rendezvous, a vast +crowd, composed of veterinary surgeons, newspaper correspondents, and +farmers from far and near, gathered to witness the closing scenes of +this scientific tourney. What they saw was one of the most dramatic +scenes in the history of peaceful science--a scene which, as Pasteur +declared afterwards, "amazed the assembly." Scattered about the +enclosure, dead, dying, or manifestly sick unto death, lay the +unprotected animals, one and all, while each and every "protected" +animal stalked unconcernedly about with every appearance of perfect +health. Twenty of the sheep and the one goat were already dead; two +other sheep expired under the eyes of the spectators; the remaining +victims lingered but a few hours longer. Thus in a manner theatrical +enough, not to say tragic, was proclaimed the unequivocal victory of +science. Naturally enough, the unbelievers struck their colors and +surrendered without terms; the principle of protective vaccination, +with a virus experimentally prepared in the laboratory, was established +beyond the reach of controversy. + +That memorable scientific battle marked the beginning of a new era +in medicine. It was a foregone conclusion that the principle thus +established would be still further generalized; that it would be +applied to human maladies; that in all probability it would grapple +successfully, sooner or later, with many infectious diseases. That +expectation has advanced rapidly towards realization. Pasteur himself +made the application to the human subject in the disease hydrophobia in +1885, since which time that hitherto most fatal of maladies has largely +lost its terrors. Thousands of persons bitten by mad dogs have been +snatched from the fatal consequences of that mishap by this method at +the Pasteur Institute in Paris, and at the similar institutes, built on +the model of this parent one, that have been established all over the +world in regions as widely separated as New York and Nha-Trang. + + +SERUM-THERAPY + +In the production of the rabies vaccine Pasteur and his associates +developed a method of attenuation of a virus quite different from that +which had been employed in the case of the vaccines of chicken cholera +and of anthrax. The rabies virus was inoculated into the system of +guinea-pigs or rabbits and, in effect, cultivated in the systems of +these animals. The spinal cord of these infected animals was found to +be rich in the virus, which rapidly became attenuated when the cord was +dried in the air. The preventive virus, of varying strengths, was made +by maceration of these cords at varying stages of desiccation. This +cultivation of a virus within the animal organism suggested, no doubt, +by the familiar Jennerian method of securing small-pox vaccine, was at +the same time a step in the direction of a new therapeutic procedure +which was destined presently to become of all-absorbing importance--the +method, namely, of so-called serum-therapy, or the treatment of a +disease with the blood serum of an animal that has been subjected to +protective inoculation against that disease. + +The possibility of such a method was suggested by the familiar +observation, made by Pasteur and numerous other workers, that animals +of different species differ widely in their susceptibility to various +maladies, and that the virus of a given disease may become more and more +virulent when passed through the systems of successive individuals +of one species, and, contrariwise, less and less virulent when passed +through the systems of successive individuals of another species. These +facts suggested the theory that the blood of resistant animals might +contain something directly antagonistic to the virus, and the hope that +this something might be transferred with curative effect to the blood +of an infected susceptible animal. Numerous experimenters all over the +world made investigations along the line of this alluring possibility, +the leaders perhaps being Drs. Behring and Kitasato, closely followed by +Dr. Roux and his associates of the Pasteur Institute of Paris. Definite +results were announced by Behring in 1892 regarding two important +diseases--tetanus and diphtheria--but the method did not come into +general notice until 1894, when Dr. Roux read an epoch-making paper on +the subject at the Congress of Hygiene at Buda-Pesth. + +In this paper Dr. Roux, after adverting to the labors of Behring, +Ehrlich, Boer, Kossel, and Wasserman, described in detail the methods +that had been developed at the Pasteur Institute for the development of +the curative serum, to which Behring had given the since-familiar name +antitoxine. The method consists, first, of the cultivation, for some +months, of the diphtheria bacillus (called the Klebs-Loeffler bacillus, +in honor of its discoverers) in an artificial bouillon, for the +development of a powerful toxine capable of giving the disease in a +virulent form. + +This toxine, after certain details of mechanical treatment, is injected +in small but increasing doses into the system of an animal, care being +taken to graduate the amount so that the animal does not succumb to the +disease. After a certain course of this treatment it is found that a +portion of blood serum of the animal so treated will act in a curative +way if injected into the blood of another animal, or a human patient, +suffering with diphtheria. In other words, according to theory, an +antitoxine has been developed in the system of the animal subjected to +the progressive inoculations of the diphtheria toxine. In Dr. Roux's +experience the animal best suited for the purpose is the horse, though +almost any of the domesticated animals will serve the purpose. + +But Dr. Roux's paper did not stop with the description of laboratory +methods. It told also of the practical application of the serum to +the treatment of numerous cases of diphtheria in the hospitals of +Paris--applications that had met with a gratifying measure of success. +He made it clear that a means had been found of coping successfully with +what had been one of the most virulent and intractable of the diseases +of childhood. Hence it was not strange that his paper made a sensation +in all circles, medical and lay alike. + +Physicians from all over the world flocked to Paris to learn the details +of the open secret, and within a few months the new serum-therapy had +an acknowledged standing with the medical profession everywhere. What it +had accomplished was regarded as but an earnest of what the new +method might accomplish presently when applied to the other infectious +diseases. + +Efforts at such applications were immediately begun in numberless +directions--had, indeed, been under way in many a laboratory for some +years before. It is too early yet to speak of the results in detail. But +enough has been done to show that this method also is susceptible of the +widest generalization. It is not easy at the present stage to sift that +which is tentative from that which will be permanent; but so great an +authority as Behring does not hesitate to affirm that today we possess, +in addition to the diphtheria antitoxine, equally specific antitoxines +of tetanus, cholera, typhus fever, pneumonia, and tuberculosis--a set +of diseases which in the aggregate account for a startling proportion +of the general death-rate. Then it is known that Dr. Yersin, with the +collaboration of his former colleagues of the Pasteur Institute, has +developed, and has used with success, an antitoxine from the microbe of +the plague which recently ravaged China. + +Dr. Calmette, another graduate of the Pasteur Institute, has extended +the range of the serum-therapy to include the prevention and treatment +of poisoning by venoms, and has developed an antitoxine that has already +given immunity from the lethal effects of snake bites to thousands of +persons in India and Australia. + +Just how much of present promise is tentative, just what are the limits +of the methods--these are questions for the future to decide. But, in +any event, there seems little question that the serum treatment will +stand as the culminating achievement in therapeutics of our century. +It is the logical outgrowth of those experimental studies with the +microscope begun by our predecessors of the thirties, and it represents +the present culmination of the rigidly experimental method which has +brought medicine from a level of fanciful empiricism to the plane of a +rational experimental science. + + + + +IX. THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY + +BRAIN AND MIND + +A little over a hundred years ago a reform movement was afoot in the +world in the interests of the insane. As was fitting, the movement +showed itself first in America, where these unfortunates were humanely +cared for at a time when their treatment elsewhere was worse than +brutal; but England and France quickly fell into line. The leader on +this side of the water was the famous Philadelphian, Dr. Benjamin Rush, +"the Sydenham of America"; in England, Dr. William Tuke inaugurated the +movement; and in France, Dr. Philippe Pinel, single-handed, led the way. +Moved by a common spirit, though acting quite independently, these +men raised a revolt against the traditional custom which, spurning the +insane as demon-haunted outcasts, had condemned these unfortunates to +dungeons, chains, and the lash. Hitherto few people had thought it other +than the natural course of events that the "maniac" should be thrust +into a dungeon, and perhaps chained to the wall with the aid of an iron +band riveted permanently about his neck or waist. Many an unfortunate, +thus manacled, was held to the narrow limits of his chain for +years together in a cell to which full daylight never penetrated; +sometimes--iron being expensive--the chain was so short that the +wretched victim could not rise to the upright posture or even shift his +position upon his squalid pallet of straw. + +In America, indeed, there being no Middle Age precedents to crystallize +into established customs, the treatment accorded the insane had seldom +or never sunk to this level. Partly for this reason, perhaps, the work +of Dr. Rush at the Philadelphia Hospital, in 1784, by means of which the +insane came to be humanely treated, even to the extent of banishing the +lash, has been but little noted, while the work of the European leaders, +though belonging to later decades, has been made famous. And perhaps +this is not as unjust as it seems, for the step which Rush took, from +relatively bad to good, was a far easier one to take than the leap from +atrocities to good treatment which the European reformers were obliged +to compass. In Paris, for example, Pinel was obliged to ask permission +of the authorities even to make the attempt at liberating the insane +from their chains, and, notwithstanding his recognized position as a +leader of science, he gained but grudging assent, and was regarded as +being himself little better than a lunatic for making so manifestly +unwise and hopeless an attempt. Once the attempt had been made, however, +and carried to a successful issue, the amelioration wrought in the +condition of the insane was so patent that the fame of Pinel's work at +the Bicetre and the Salpetriere went abroad apace. It required, indeed, +many years to complete it in Paris, and a lifetime of effort on the +part of Pinel's pupil Esquirol and others to extend the reform to the +provinces; but the epochal turning-point had been reached with Pinel's +labors of the closing years of the eighteenth century. + +The significance of this wise and humane reform, in the present +connection, is the fact that these studies of the insane gave emphasis +to the novel idea, which by-and-by became accepted as beyond question, +that "demoniacal possession" is in reality no more than the outward +expression of a diseased condition of the brain. This realization made +it clear, as never before, how intimately the mind and the body are +linked one to the other. And so it chanced that, in striking the +shackles from the insane, Pinel and his confreres struck a blow also, +unwittingly, at time-honored philosophical traditions. The liberation +of the insane from their dungeons was an augury of the liberation of +psychology from the musty recesses of metaphysics. Hitherto psychology, +in so far as it existed at all, was but the subjective study of +individual minds; in future it must become objective as well, taking +into account also the relations which the mind bears to the body, and in +particular to the brain and nervous system. + +The necessity for this collocation was advocated quite as earnestly, and +even more directly, by another worker of this period, whose studies were +allied to those of alienists, and who, even more actively than they, +focalized his attention upon the brain and its functions. This earliest +of specialists in brain studies was a German by birth but Parisian +by adoption, Dr. Franz Joseph Gall, originator of the since-notorious +system of phrenology. The merited disrepute into which this system has +fallen through the exposition of peripatetic charlatans should not +make us forget that Dr. Gall himself was apparently a highly educated +physician, a careful student of the brain and mind according to the best +light of his time, and, withal, an earnest and honest believer in the +validity of the system he had originated. The system itself, taken as a +whole, was hopelessly faulty, yet it was not without its latent germ +of truth, as later studies were to show. How firmly its author himself +believed in it is evidenced by the paper which he contributed to the +French Academy of Sciences in 1808. The paper itself was referred to a +committee of which Pinel and Cuvier were members. The verdict of this +committee was adverse, and justly so; yet the system condemned had at +least one merit which its detractors failed to realize. It popularized +the conception that the brain is the organ of mind. Moreover, by its +insistence it rallied about it a band of scientific supporters, chief of +whom was Dr. Kaspar Spurzlieim, a man of no mean abilities, who became +the propagandist of phrenology in England and in America. Of course such +advocacy and popularity stimulated opposition as well, and out of the +disputations thus arising there grew presently a general interest in the +brain as the organ of mind, quite aside from any preconceptions whatever +as to the doctrines of Gall and Spurzheim. + +Prominent among the unprejudiced class of workers who now appeared was +the brilliant young Frenchman Louis Antoine Desmoulins, who studied +first under the tutorage of the famous Magendie, and published jointly +with him a classical work on the nervous system of vertebrates in +1825. Desmoulins made at least one discovery of epochal importance. He +observed that the brains of persons dying in old age were lighter than +the average and gave visible evidence of atrophy, and he reasoned that +such decay is a normal accompaniment of senility. No one nowadays would +question the accuracy of this observation, but the scientific world +was not quite ready for it in 1825; for when Desmoulins announced his +discovery to the French Academy, that august and somewhat patriarchal +body was moved to quite unscientific wrath, and forbade the young +iconoclast the privilege of further hearings. From which it is evident +that the partially liberated spirit of the new psychology had by no +means freed itself altogether, at the close of the first quarter of +the nineteenth century, from the metaphysical cobwebs of its long +incarceration. + + +FUNCTIONS OF THE NERVES + +While studies of the brain were thus being inaugurated, the nervous +system, which is the channel of communication between the brain and the +outside world, was being interrogated with even more tangible results. +The inaugural discovery was made in 1811 by Dr. (afterwards Sir Charles) +Bell,(1) the famous English surgeon and experimental physiologist. +It consisted of the observation that the anterior roots of the spinal +nerves are given over to the function of conveying motor impulses from +the brain outward, whereas the posterior roots convey solely sensory +impulses to the brain from without. Hitherto it had been supposed that +all nerves have a similar function, and the peculiar distribution of the +spinal nerves had been an unsolved puzzle. + +Bell's discovery was epochal; but its full significance was not +appreciated for a decade, nor, indeed, was its validity at first +admitted. In Paris, in particular, then the court of final appeal in +all matters scientific, the alleged discovery was looked at askance, or +quite ignored. But in 1823 the subject was taken up by the recognized +leader of French physiology--Francois Magendie--in the course of his +comprehensive experimental studies of the nervous system, and Bell's +conclusions were subjected to the most rigid experimental tests +and found altogether valid. Bell himself, meanwhile, had turned his +attention to the cranial nerves, and had proved that these also are +divisible into two sets--sensory and motor. Sometimes, indeed, the two +sets of filaments are combined into one nerve cord, but if traced to +their origin these are found to arise from different brain centres. Thus +it was clear that a hitherto unrecognized duality of function pertains +to the entire extra-cranial nervous system. Any impulse sent from the +periphery to the brain must be conveyed along a perfectly definite +channel; the response from the brain, sent out to the peripheral +muscles, must traverse an equally definite and altogether different +course. If either channel is interrupted--as by the section of its +particular nerve tract--the corresponding message is denied transmission +as effectually as an electric current is stopped by the section of the +transmitting wire. + +Experimenters everywhere soon confirmed the observations of Bell and +Magendie, and, as always happens after a great discovery, a fresh +impulse was given to investigations in allied fields. Nevertheless, a +full decade elapsed before another discovery of comparable importance +was made. Then Marshall Hall, the most famous of English physicians +of his day, made his classical observations on the phenomena +that henceforth were to be known as reflex action. In 1832, while +experimenting one day with a decapitated newt, he observed that the +headless creature's limbs would contract in direct response to certain +stimuli. Such a response could no longer be secured if the spinal +nerves supplying a part were severed. Hence it was clear that responsive +centres exist in the spinal cord capable of receiving a sensory message +and of transmitting a motor impulse in reply--a function hitherto +supposed to be reserved for the brain. Further studies went to show that +such phenomena of reflex action on the part of centres lying outside the +range of consciousness, both in the spinal cord and in the brain itself, +are extremely common; that, in short, they enter constantly into the +activities of every living organism and have a most important share in +the sum total of vital movements. Hence, Hall's discovery must always +stand as one of the great mile-stones of the advance of neurological +science. + +Hall gave an admirably clear and interesting account of his experiments +and conclusions in a paper before the Royal Society, "On the Reflex +Functions of the Medulla Oblongata and the Medulla Spinalis," from +which, as published in the Transactions of the society for 1833, we may +quote at some length: + +"In the entire animal, sensation and voluntary motion, functions of +the cerebrum, combine with the functions of the medulla oblongata and +medulla spinalis, and may therefore render it difficult or impossible to +determine those which are peculiar to each; if, in an animal deprived +of the brain, the spinal marrow or the nerves supplying the muscles be +stimulated, those muscles, whether voluntary or respiratory, are equally +thrown into contraction, and, it may be added, equally in the complete +and in the mutilated animal; and, in the case of the nerves, equally in +limbs connected with and detached from the spinal marrow. + +"The operation of all these various causes may be designated centric, as +taking place AT, or at least in a direction FROM, central parts of the +nervous system. But there is another function the phenomena of which +are of a totally different order and obey totally different laws, being +excited by causes in a situation which is EXCENTRIC in the nervous +system--that is, distant from the nervous centres. This mode of action +has not, I think, been hitherto distinctly understood by physiologists. + +"Many of the phenomena of this principle of action, as they occur in +the limbs, have certainly been observed. But, in the first place, this +function is by no means confined to the limbs; for, while it imparts +to each muscle its appropriate tone, and to each system of muscles its +appropriate equilibrium or balance, it performs the still more important +office of presiding over the orifices and terminations of each of the +internal canals in the animal economy, giving them their due form +and action; and, in the second place, in the instances in which the +phenomena of this function have been noticed, they have been confounded, +as I have stated, with those of sensation and volition; or, if they +have been distinguished from these, they have been too indefinitely +denominated instinctive, or automatic. I have been compelled, therefore, +to adopt some new designation for them, and I shall now give the reasons +for my choice of that which is given in the title of this paper--'Reflex +Functions.' + +"This property is characterized by being EXCITED in its action and +REFLEX in its course: in every instance in which it is exerted an +impression made upon the extremities of certain nerves is conveyed to +the medulla oblongata or the medulla spinalis, and is reflected along +the nerves to parts adjacent to, or remote from, that which has received +the impression. + +"It is by this reflex character that the function to which I have +alluded is to be distinguished from every other. There are, in the +animal economy, four modes of muscular action, of muscular contraction. +The first is that designated VOLUNTARY: volition, originated in the +cerebrum and spontaneous in its acts, extends its influence along the +spinal marrow and the motor nerves in a DIRECT LINE to the voluntary +muscles. The SECOND is that of RESPIRATION: like volition, the motive +influence in respiration passes in a DIRECT LINE from one point of the +nervous system to certain muscles; but as voluntary motion seems to +originate in the cerebrum, so the respiratory motions originate in +the medulla oblongata: like the voluntary motions, the motions of +respirations are spontaneous; they continue, at least, after the eighth +pair of nerves have been divided. The THIRD kind of muscular action +in the animal economy is that termed involuntary: it depends upon the +principle of irritability and requires the IMMEDIATE application of +a stimulus to the nervo-muscular fibre itself. These three kinds of +muscular motion are well known to physiologists; and I believe they are +all which have been hitherto pointed out. There is, however, a FOURTH, +which subsists, in part, after the voluntary and respiratory motions +have ceased, by the removal of the cerebrum and medulla oblongata, and +which is attached to the medulla spinalis, ceasing itself when this +is removed, and leaving the irritability undiminished. In this kind of +muscular motion the motive influence does not originate in any central +part of the nervous system, but from a distance from that centre; it is +neither spontaneous in its action nor direct in its course; it is, on +the contrary, EXCITED by the application of appropriate stimuli, which +are not, however, applied immediately to the muscular or nervo-muscular +fibre, but to certain membraneous parts, whence the impression is +carried through the medulla, REFLECTED and reconducted to the part +impressed, or conducted to a part remote from it in which muscular +contraction is effected. + +"The first three modes of muscular action are known only by actual +movements of muscular contractions. But the reflex function exists as +a continuous muscular action, as a power presiding over organs not +actually in a state of motion, preserving in some, as the glottis, an +open, in others, as the sphincters, a closed form, and in the limbs a +due degree of equilibrium or balanced muscular action--a function not, I +think, hitherto recognized by physiologists. + +"The three kinds of muscular motion hitherto known may be distinguished +in another way. The muscles of voluntary motion and of respiration may +be excited by stimulating the nerves which supply them, in any part of +their course, whether at their source as a part of the medulla oblongata +or the medulla spinalis or exterior to the spinal canal: the muscles of +involuntary motion are chiefly excited by the actual contact of stimuli. +In the case of the reflex function alone the muscles are excited by a +stimulus acting mediately and indirectly in a curved and reflex course, +along superficial subcutaneous or submucous nerves proceeding from the +medulla. The first three of these causes of muscular motion may act on +detached limbs or muscles. The last requires the connection with the +medulla to be preserved entire. + +"All the kinds of muscular motion may be unduly excited, but the reflex +function is peculiar in being excitable in two modes of action, not +previously subsisting in the animal economy, as in the case of sneezing, +coughing, vomiting, etc. The reflex function also admits of being +permanently diminished or augmented and of taking on some other morbid +forms, of which I shall treat hereafter. + +"Before I proceed to the details of the experiments upon which this +disposition rests, it may be well to point out several instances in +illustration of the various sources of and the modes of muscular action +which have been enumerated. None can be more familiar than the act of +swallowing. Yet how complicated is the act! The apprehension of the food +by the teeth and tongue, etc., is voluntary, and cannot, therefore, take +place in an animal from which the cerebrum is removed. The transition of +food over the glottis and along the middle and lower part of the pharynx +depends upon the reflex action: it can take place in animals from which +the cerebrum has been removed or the ninth pair of nerves divided; but +it requires the connection with the medulla oblongata to be preserved +entirely; and the actual contact of some substance which may act as a +stimulus: it is attended by the accurate closure of the glottis and by +the contraction of the pharynx. The completion of the act of deglutition +is dependent upon the stimulus immediately impressed upon the muscular +fibre of the oesophagus, and is the result of excited irritability. + +"However plain these observations may have made the fact that there is +a function of the nervous muscular system distinct from sensation, from +the voluntary and respiratory motions, and from irritability, it is +right, in every such inquiry as the present, that the statements and +reasonings should be made with the experiment, as it were, actually +before us. It has already been remarked that the voluntary and +respiratory motions are spontaneous, not necessarily requiring the +agency of a stimulus. If, then, an animal can be placed in such +circumstances that such motions will certainly not take place, the power +of moving remaining, it may be concluded that volition and the motive +influence of respiration are annihilated. Now this is effected by +removing the cerebrum and the medulla oblongata. These facts are fully +proved by the experiments of Legallois and M. Flourens, and by several +which I proceed to detail, for the sake of the opportunity afforded by +doing so of stating the arguments most clearly. + +"I divided the spinal marrow of a very lively snake between the second +and third vertebrae. The movements of the animal were immediately before +extremely vigorous and unintermitted. From the moment of the division +of the spinal marrow it lay perfectly tranquil and motionless, with the +exception of occasional gaspings and slight movements of the head. +It became quite evident that this state of quiescence would continue +indefinitely were the animal secured from all external impressions. + +"Being now stimulated, the body began to move with great activity, and +continued to do so for a considerable time, each change of position or +situation bringing some fresh part of the surface of the animal into +contact with the table or other objects and renewing the application of +stimulants. + +"At length the animal became again quiescent; and being carefully +protected from all external impressions it moved no more, but died in +the precise position and form which it had last assumed. + +"It requires a little manoeuvre to perform this experiment successfully: +the motions of the animal must be watched and slowly and cautiously +arrested by opposing some soft substance, as a glove or cotton wool; +they are by this means gradually lulled into quiescence. The slightest +touch with a hard substance, the slightest stimulus, will, on the other +hand, renew the movements on the animal in an active form. But that this +phenomenon does not depend upon sensation is further fully proved by the +facts that the position last assumed, and the stimuli, may be such as +would be attended by extreme or continued pain, if the sensibility were +undestroyed: in one case the animal remained partially suspended over +the acute edge of the table; in others the infliction of punctures and +the application of a lighted taper did not prevent the animal, still +possessed of active powers of motion, from passing into a state of +complete and permanent quiescence." + + +In summing up this long paper Hall concludes with this sentence: "The +reflex function appears in a word to be the COMPLEMENT of the functions +of the nervous system hitherto known."(2) + +All these considerations as to nerve currents and nerve tracts becoming +stock knowledge of science, it was natural that interest should +become stimulated as to the exact character of these nerve tracts in +themselves, and all the more natural in that the perfected microscope +was just now claiming all fields for its own. A troop of observers soon +entered upon the study of the nerves, and the leader here, as in so +many other lines of microscopical research, was no other than Theodor +Schwann. Through his efforts, and with the invaluable aid of such other +workers as Remak, Purkinje, Henle, Muller, and the rest, all the mystery +as to the general characteristics of nerve tracts was cleared away. It +came to be known that in its essentials a nerve tract is a tenuous fibre +or thread of protoplasm stretching between two terminal points in the +organism, one of such termini being usually a cell of the brain +or spinal cord, the other a distribution-point at or near the +periphery--for example, in a muscle or in the skin. Such a fibril may +have about it a protective covering, which is known as the sheath of +Schwann; but the fibril itself is the essential nerve tract; and in +many cases, as Remak presently discovered, the sheath is dispensed with, +particularly in case of the nerves of the so-called sympathetic system. + +This sympathetic system of ganglia and nerves, by-the-bye, had long been +a puzzle to the physiologists. Its ganglia, the seeming centre of +the system, usually minute in size and never very large, are found +everywhere through the organism, but in particular are gathered into a +long double chain which lies within the body cavity, outside the spinal +column, and represents the sole nervous system of the non-vertebrated +organisms. Fibrils from these ganglia were seen to join the cranial and +spinal nerve fibrils and to accompany them everywhere, but what special +function they subserved was long a mere matter of conjecture and led to +many absurd speculations. Fact was not substituted for conjecture +until about the year 1851, when the great Frenchman Claude Bernard +conclusively proved that at least one chief function of the sympathetic +fibrils is to cause contraction of the walls of the arterioles of the +system, thus regulating the blood-supply of any given part. Ten years +earlier Henle had demonstrated the existence of annular bands of muscle +fibres in the arterioles, hitherto a much-mooted question, and several +tentative explanations of the action of these fibres had been made, +particularly by the brothers Weber, by Stilling, who, as early as 1840, +had ventured to speak of "vaso-motor" nerves, and by Schiff, who was +hard upon the same track at the time of Bernard's discovery. But a clear +light was not thrown on the subject until Bernard's experiments were +made in 1851. The experiments were soon after confirmed and extended +by Brown-Sequard, Waller, Budge, and numerous others, and henceforth +physiologists felt that they understood how the blood-supply of any +given part is regulated by the nervous system. + +In reality, however, they had learned only half the story, as Bernard +himself proved only a few years later by opening up a new and quite +unsuspected chapter. While experimenting in 1858 he discovered that +there are certain nerves supplying the heart which, if stimulated, +cause that organ to relax and cease beating. As the heart is essentially +nothing more than an aggregation of muscles, this phenomenon was utterly +puzzling and without precedent in the experience of physiologists. An +impulse travelling along a motor nerve had been supposed to be able to +cause a muscular contraction and to do nothing else; yet here such an +impulse had exactly the opposite effect. The only tenable explanation +seemed to be that this particular impulse must arrest or inhibit the +action of the impulses that ordinarily cause the heart muscles to +contract. But the idea of such inhibition of one impulse by another was +utterly novel and at first difficult to comprehend. Gradually, however, +the idea took its place in the current knowledge of nerve physiology, +and in time it came to be understood that what happens in the case of +the heart nerve-supply is only a particular case under a very general, +indeed universal, form of nervous action. Growing out of Bernard's +initial discovery came the final understanding that the entire nervous +system is a mechanism of centres subordinate and centres superior, the +action of the one of which may be counteracted and annulled in effect +by the action of the other. This applies not merely to such physical +processes as heart-beats and arterial contraction and relaxing, but +to the most intricate functionings which have their counterpart in +psychical processes as well. Thus the observation of the inhibition of +the heart's action by a nervous impulse furnished the point of departure +for studies that led to a better understanding of the modus operandi of +the mind's activities than had ever previously been attained by the most +subtle of psychologists. + + +PSYCHO-PHYSICS + +The work of the nerve physiologists had thus an important bearing on +questions of the mind. But there was another company of workers of +this period who made an even more direct assault upon the "citadel of +thought." A remarkable school of workers had been developed in Germany, +the leaders being men who, having more or less of innate metaphysical +bias as a national birthright, had also the instincts of the empirical +scientist, and whose educational equipment included a profound knowledge +not alone of physiology and psychology, but of physics and mathematics +as well. These men undertook the novel task of interrogating the +relations of body and mind from the standpoint of physics. They sought +to apply the vernier and the balance, as far as might be, to the +intangible processes of mind. + +The movement had its precursory stages in the early part of the century, +notably in the mathematical psychology of Herbart, but its first +definite output to attract general attention came from the master-hand +of Hermann Helmholtz in 1851. It consisted of the accurate measurement +of the speed of transit of a nervous impulse along a nerve tract. To +make such measurement had been regarded as impossible, it being supposed +that the flight of the nervous impulse was practically instantaneous. +But Helmholtz readily demonstrated the contrary, showing that the +nerve cord is a relatively sluggish message-bearer. According to his +experiments, first performed upon the frog, the nervous "current" +travels less than one hundred feet per second. Other experiments +performed soon afterwards by Helmholtz himself, and by various +followers, chief among whom was Du Bois-Reymond, modified somewhat the +exact figures at first obtained, but did not change the general bearings +of the early results. Thus the nervous impulse was shown to be something +far different, as regards speed of transit, at any rate, from the +electric current to which it had been so often likened. An electric +current would flash halfway round the globe while a nervous impulse +could travel the length of the human body--from a man's foot to his +brain. + +The tendency to bridge the gulf that hitherto had separated the physical +from the psychical world was further evidenced in the following decade +by Helmholtz's remarkable but highly technical study of the sensations +of sound and of color in connection with their physical causes, in the +course of which he revived the doctrine of color vision which that other +great physiologist and physicist, Thomas Young, had advanced half +a century before. The same tendency was further evidenced by the +appearance, in 1852, of Dr. Hermann Lotze's famous Medizinische +Psychologie, oder Physiologie der Seele, with its challenge of the old +myth of a "vital force." But the most definite expression of the new +movement was signalized in 1860, when Gustav Fechner published his +classical work called Psychophysik. That title introduced a new word +into the vocabulary of science. Fechner explained it by saying, "I mean +by psychophysics an exact theory of the relation between spirit and +body, and, in a general way, between the physical and the psychic +worlds." The title became famous and the brunt of many a controversy. +So also did another phrase which Fechner introduced in the course of +his book--the phrase "physiological psychology." In making that happy +collocation of words Fechner virtually christened a new science. + + +FECHNER EXPOUNDS WEBER'S LAW + +The chief purport of this classical book of the German +psycho-physiologist was the elaboration and explication of experiments +based on a method introduced more than twenty years earlier by his +countryman E. H. Weber, but which hitherto had failed to attract the +attention it deserved. The method consisted of the measurement and +analysis of the definite relation existing between external stimuli +of varying degrees of intensity (various sounds, for example) and the +mental states they induce. Weber's experiments grew out of the familiar +observation that the nicety of our discriminations of various sounds, +weights, or visual images depends upon the magnitude of each particular +cause of a sensation in its relation with other similar causes. Thus, +for example, we cannot see the stars in the daytime, though they shine +as brightly then as at night. Again, we seldom notice the ticking of a +clock in the daytime, though it may become almost painfully audible in +the silence of the night. Yet again, the difference between an ounce +weight and a two-ounce weight is clearly enough appreciable when we +lift the two, but one cannot discriminate in the same way between a +five-pound weight and a weight of one ounce over five pounds. + +This last example, and similar ones for the other senses, gave Weber +the clew to his novel experiments. Reflection upon every-day experiences +made it clear to him that whenever we consider two visual sensations, or +two auditory sensations, or two sensations of weight, in comparison +one with another, there is always a limit to the keenness of our +discrimination, and that this degree of keenness varies, as in the case +of the weights just cited, with the magnitude of the exciting cause. + +Weber determined to see whether these common experiences could be +brought within the pale of a general law. His method consisted of making +long series of experiments aimed at the determination, in each case, of +what came to be spoken of as the least observable difference between the +stimuli. Thus if one holds an ounce weight in each hand, and has tiny +weights added to one of them, grain by grain, one does not at first +perceive a difference; but presently, on the addition of a certain +grain, he does become aware of the difference. Noting now how many +grains have been added to produce this effect, we have the weight which +represents the least appreciable difference when the standard is one +ounce. + +Now repeat the experiment, but let the weights be each of five pounds. +Clearly in this case we shall be obliged to add not grains, but drachms, +before a difference between the two heavy weights is perceived. But +whatever the exact amount added, that amount represents the stimulus +producing a just-perceivable sensation of difference when the standard +is five pounds. And so on for indefinite series of weights of varying +magnitudes. Now came Weber's curious discovery. Not only did he find +that in repeated experiments with the same pair of weights the measure +of "just-{p}erceivable difference" remained approximately fixed, but +he found, further, that a remarkable fixed relation exists between +the stimuli of different magnitude. If, for example, he had found it +necessary, in the case of the ounce weights, to add one-fiftieth of an +ounce to the one before a difference was detected, he found also, in the +case of the five-pound weights, that one-fiftieth of five pounds must be +added before producing the same result. And so of all other weights; the +amount added to produce the stimulus of "least-appreciable difference" +always bore the same mathematical relation to the magnitude of the +weight used, be that magnitude great or small. + +Weber found that the same thing holds good for the stimuli of the +sensations of sight and of hearing, the differential stimulus bearing +always a fixed ratio to the total magnitude of the stimuli. Here, then, +was the law he had sought. + +Weber's results were definite enough and striking enough, yet they +failed to attract any considerable measure of attention until they were +revived and extended by Fechner and brought before the world in the +famous work on psycho-physics. Then they precipitated a veritable +melee. Fechner had not alone verified the earlier results (with certain +limitations not essential to the present consideration), but had +invented new methods of making similar tests, and had reduced the whole +question to mathematical treatment. He pronounced Weber's discovery +the fundamental law of psycho-physics. In honor of the discoverer, +he christened it Weber's Law. He clothed the law in words and in +mathematical formulae, and, so to say, launched it full tilt at the +heads of the psychological world. It made a fine commotion, be assured, +for it was the first widely heralded bulletin of the new psychology +in its march upon the strongholds of the time-honored metaphysics. The +accomplishments of the microscopists and the nerve physiologists had +been but preliminary--mere border skirmishes of uncertain import. But +here was proof that the iconoclastic movement meant to invade the very +heart of the sacred territory of mind--a territory from which tangible +objective fact had been supposed to be forever barred. + + +PHYSIOLOGICAL PSYCHOLOGY + +Hardly had the alarm been sounded, however, before a new movement was +made. While Fechner's book was fresh from the press, steps were being +taken to extend the methods of the physicist in yet another way to +the intimate processes of the mind. As Helmholtz had shown the rate of +nervous impulsion along the nerve tract to be measurable, it was +now sought to measure also the time required for the central nervous +mechanism to perform its work of receiving a message and sending out +a response. This was coming down to the very threshold of mind. The +attempt was first made by Professor Donders in 1861, but definitive +results were only obtained after many years of experiment on the part +of a host of observers. The chief of these, and the man who has stood +in the forefront of the new movement and has been its recognized leader +throughout the remainder of the century, is Dr. Wilhelm Wundt, of +Leipzig. + +The task was not easy, but, in the long run, it was accomplished. Not +alone was it shown that the nerve centre requires a measurable time for +its operations, but much was learned as to conditions that modify this +time. Thus it was found that different persons vary in the rate of their +central nervous activity--which explained the "personal equation" that +the astronomer Bessel had noted a half-century before. It was found, +too, that the rate of activity varies also for the same person under +different conditions, becoming retarded, for example, under influence of +fatigue, or in case of certain diseases of the brain. All details aside, +the essential fact emerges, as an experimental demonstration, that the +intellectual processes--sensation, apperception, volition--are linked +irrevocably with the activities of the central nervous tissues, and +that these activities, like all other physical processes, have a time +element. To that old school of psychologists, who scarcely cared more +for the human head than for the heels--being interested only in the +mind--such a linking of mind and body as was thus demonstrated was +naturally disquieting. But whatever the inferences, there was no +escaping the facts. + +Of course this new movement has not been confined to Germany. Indeed, +it had long had exponents elsewhere. Thus in England, a full century +earlier, Dr. Hartley had championed the theory of the close and +indissoluble dependence of the mind upon the brain, and formulated +a famous vibration theory of association that still merits careful +consideration. Then, too, in France, at the beginning of the century, +there was Dr. Cabanis with his tangible, if crudely phrased, doctrine +that the brain digests impressions and secretes thought as the stomach +digests food and the liver secretes bile. Moreover, Herbert Spencer's +Principles of Psychology, with its avowed co-ordination of mind and body +and its vitalizing theory of evolution, appeared in 1855, half a +decade before the work of Fechner. But these influences, though of vast +educational value, were theoretical rather than demonstrative, and the +fact remains that the experimental work which first attempted to gauge +mental operations by physical principles was mainly done in Germany. +Wundt's Physiological Psychology, with its full preliminary descriptions +of the anatomy of the nervous system, gave tangible expression to the +growth of the new movement in 1874; and four years later, with the +opening of his laboratory of physiological psychology at the University +of Leipzig, the new psychology may be said to have gained a permanent +foothold and to have forced itself into official recognition. From then +on its conquest of the world was but a matter of time. + +It should be noted, however, that there is one other method of strictly +experimental examination of the mental field, latterly much in vogue, +which had a different origin. This is the scientific investigation of +the phenomena of hypnotism. This subject was rescued from the hands of +charlatans, rechristened, and subjected to accurate investigation by +Dr. James Braid, of Manchester, as early as 1841. But his results, after +attracting momentary attention, fell from view, and, despite desultory +efforts, the subject was not again accorded a general hearing from +the scientific world until 1878, when Dr. Charcot took it up at +the Salpetriere, in Paris, followed soon afterwards by Dr. Rudolf +Heidenhain, of Breslau, and a host of other experimenters. The value +of the method in the study of mental states was soon apparent. Most +of Braid's experiments were repeated, and in the main his results were +confirmed. His explanation of hypnotism, or artificial somnambulism, +as a self-induced state, independent of any occult or supersensible +influence, soon gained general credence. His belief that the initial +stages are due to fatigue of nervous centres, usually from excessive +stimulation, has not been supplanted, though supplemented by notions +growing out of the new knowledge as to subconscious mentality in +general, and the inhibitory influence of one centre over another in the +central nervous mechanism. + + +THE BRAIN AS THE ORGAN OF MIND + +These studies of the psychologists and pathologists bring the relations +of mind and body into sharp relief. But even more definite in this +regard was the work of the brain physiologists. Chief of these, during +the middle period of the century, was the man who is sometimes spoken of +as the "father of brain physiology," Marie Jean Pierre Flourens, of the +Jardin des Plantes of Paris, the pupil and worthy successor of Magendie. +His experiments in nerve physiology were begun in the first quarter of +the century, but his local experiments upon the brain itself were +not culminated until about 1842. At this time the old dispute over +phrenology had broken out afresh, and the studies of Flourens were +aimed, in part at least, at the strictly scientific investigation of +this troublesome topic. + +In the course of these studies Flourens discovered that in the medulla +oblongata, the part of the brain which connects that organ with the +spinal cord, there is a centre of minute size which cannot be injured in +the least without causing the instant death of the animal operated upon. +It may be added that it is this spot which is reached by the needle of +the garroter in Spanish executions, and that the same centre also is +destroyed when a criminal is "successfully" hanged, this time by the +forced intrusion of a process of the second cervical vertebra. Flourens +named this spot the "vital knot." Its extreme importance, as is now +understood, is due to the fact that it is the centre of nerves that +supply the heart; but this simple explanation, annulling the conception +of a specific "life centre," was not at once apparent. + +Other experiments of Flourens seemed to show that the cerebellum is the +seat of the centres that co-ordinate muscular activities, and that the +higher intellectual faculties are relegated to the cerebrum. But beyond +this, as regards localization, experiment faltered. Negative results, as +regards specific faculties, were obtained from all localized irritations +of the cerebrum, and Flourens was forced to conclude that the cerebral +lobe, while being undoubtedly the seat of higher intellection, performs +its functions with its entire structure. This conclusion, which +incidentally gave a quietus to phrenology, was accepted generally, and +became the stock doctrine of cerebral physiology for a generation. + +It will be seen, however, that these studies of Flourens had a double +bearing. They denied localization of cerebral functions, but they +demonstrated the localization of certain nervous processes in other +portions of the brain. On the whole, then, they spoke positively for the +principle of localization of function in the brain, for which a certain +number of students contended; while their evidence against cerebral +localization was only negative. There was here and there an observer who +felt that this negative testimony was not conclusive. In particular, +the German anatomist Meynert, who had studied the disposition of nerve +tracts in the cerebrum, was led to believe that the anterior portions of +the cerebrum must have motor functions in preponderance; the posterior +positions, sensory functions. Somewhat similar conclusions were reached +also by Dr. Hughlings-Jackson, in England, from his studies of epilepsy. +But no positive evidence was forthcoming until 1861, when Dr. Paul Broca +brought before the Academy of Medicine in Paris a case of brain lesion +which he regarded as having most important bearings on the question of +cerebral localization. + +The case was that of a patient at the Bicetre, who for twenty years had +been deprived of the power of speech, seemingly through loss of memory +of words. In 1861 this patient died, and an autopsy revealed that a +certain convolution of the left frontal lobe of his cerebrum had been +totally destroyed by disease, the remainder of his brain being intact. +Broca felt that this observation pointed strongly to a localization +of the memory of words in a definite area of the brain. Moreover, it +transpired that the case was not without precedent. As long ago as +1825 Dr. Boillard had been led, through pathological studies, to locate +definitely a centre for the articulation of words in the frontal lobe, +and here and there other observers had made tentatives in the same +direction. Boillard had even followed the matter up with pertinacity, +but the world was not ready to listen to him. Now, however, in the +half-decade that followed Broca's announcements, interest rose to +fever-beat, and through the efforts of Broca, Boillard, and numerous +others it was proved that a veritable centre having a strange +domination over the memory of articulate words has its seat in the third +convolution of the frontal lobe of the cerebrum, usually in the +left hemisphere. That part of the brain has since been known to the +English-speaking world as the convolution of Broca, a name which, +strangely enough, the discoverer's compatriots have been slow to accept. + +This discovery very naturally reopened the entire subject of brain +localization. It was but a short step to the inference that there must +be other definite centres worth the seeking, and various observers set +about searching for them. In 1867 a clew was gained by Eckhard, who, +repeating a forgotten experiment by Haller and Zinn of the previous +century, removed portions of the brain cortex of animals, with the +result of producing convulsions. But the really vital departure was +made in 1870 by the German investigators Fritsch and Hitzig, who, by +stimulating definite areas of the cortex of animals with a galvanic +current, produced contraction of definite sets of muscles of the +opposite side of the body. These most important experiments, received at +first with incredulity, were repeated and extended in 1873 by Dr. David +Ferrier, of London, and soon afterwards by a small army of independent +workers everywhere, prominent among whom were Franck and Pitres in +France, Munck and Goltz in Germany, and Horsley and Schafer in England. +The detailed results, naturally enough, were not at first all in +harmony. Some observers, as Goltz, even denied the validity of the +conclusions in toto. But a consensus of opinion, based on multitudes of +experiments, soon placed the broad general facts for which Fritsch and +Hitzig contended beyond controversy. It was found, indeed, that the +cerebral centres of motor activities have not quite the finality at +first ascribed to them by some observers, since it may often happen +that after the destruction of a centre, with attending loss of function, +there may be a gradual restoration of the lost function, proving that +other centres have acquired the capacity to take the place of the one +destroyed. There are limits to this capacity for substitution, however, +and with this qualification the definiteness of the localization of +motor functions in the cerebral cortex has become an accepted part of +brain physiology. + +Nor is such localization confined to motor centres. Later experiments, +particularly of Ferrier and of Munck, proved that the centres of vision +are equally restricted in their location, this time in the posterior +lobes of the brain, and that hearing has likewise its local habitation. +Indeed, there is every reason to believe that each form of primary +sensation is based on impressions which mainly come to a definitely +localized goal in the brain. But all this, be it understood, has no +reference to the higher forms of intellection. All experiment has proved +futile to localize these functions, except indeed to the extent of +corroborating the familiar fact of their dependence upon the brain, and, +somewhat problematically, upon the anterior lobes of the cerebrum in +particular. But this is precisely what should be expected, for the +clearer insight into the nature of mental processes makes it plain that +in the main these alleged "faculties" are not in themselves localized. +Thus, for example, the "faculty" of language is associated irrevocably +with centres of vision, of hearing, and of muscular activity, to go +no further, and only becomes possible through the association of these +widely separated centres. The destruction of Broca's centre, as was +early discovered, does not altogether deprive a patient of his knowledge +of language. He may be totally unable to speak (though as to this there +are all degrees of variation), and yet may comprehend what is said +to him, and be able to read, think, and even write correctly. Thus it +appears that Broca's centre is peculiarly bound up with the capacity for +articulate speech, but is far enough from being the seat of the faculty +of language in its entirety. + +In a similar way, most of the supposed isolated "faculties" of higher +intellection appear, upon clearer analysis, as complex aggregations of +primary sensations, and hence necessarily dependent upon numerous and +scattered centres. Some "faculties," as memory and volition, may be +said in a sense to be primordial endowments of every nerve cell--even +of every body cell. Indeed, an ultimate analysis relegates all +intellection, in its primordial adumbrations, to every particle of +living matter. But such refinements of analysis, after all, cannot hide +the fact that certain forms of higher intellection involve a pretty +definite collocation and elaboration of special sensations. Such +specialization, indeed, seems a necessary accompaniment of mental +evolution. That every such specialized function has its localized +centres of co-ordination, of some such significance as the demonstrated +centres of articulate speech, can hardly be in doubt--though this, be it +understood, is an induction, not as yet a demonstration. In other +words, there is every reason to believe that numerous "centres," in +this restricted sense, exist in the brain that have as yet eluded the +investigator. Indeed, the current conception regards the entire cerebral +cortex as chiefly composed of centres of ultimate co-ordination of +impressions, which in their cruder form are received by more primitive +nervous tissues--the basal ganglia, the cerebellum and medulla, and the +spinal cord. + +This, of course, is equivalent to postulating the cerebral cortex as +the exclusive seat of higher intellection. This proposition, however, +to which a safe induction seems to lead, is far afield from the +substantiation of the old conception of brain localization, which +was based on faulty psychology and equally faulty inductions from few +premises. The details of Gall's system, as propounded by generations of +his mostly unworthy followers, lie quite beyond the pale of scientific +discussion. Yet, as I have said, a germ of truth was there--the idea +of specialization of cerebral functions--and modern investigators have +rescued that central conception from the phrenological rubbish heap in +which its discoverer unfortunately left it buried. + + +THE MINUTE STRUCTURE OF THE BRAIN + +The common ground of all these various lines of investigations of +pathologist, anatomist, physiologist, physicist, and psychologist is, +clearly, the central nervous system--the spinal cord and the brain. +The importance of these structures as the foci of nervous and mental +activities has been recognized more and more with each new accretion +of knowledge, and the efforts to fathom the secrets of their intimate +structure has been unceasing. For the earlier students, only the +crude methods of gross dissections and microscopical inspection were +available. These could reveal something, but of course the inner secrets +were for the keener insight of the microscopist alone. And even for him +the task of investigation was far from facile, for the central nervous +tissues are the most delicate and fragile, and on many accounts the most +difficult of manipulation of any in the body. + +Special methods, therefore, were needed for this essay, and brain +histology has progressed by fitful impulses, each forward jet marking +the introduction of some ingenious improvement of mechanical technique, +which placed a new weapon in the hands of the investigators. + +The very beginning was made in 1824 by Rolando, who first thought of +cutting chemically hardened pieces of brain tissues into thin sections +for microscopical examination--the basal structure upon which almost all +the later advances have been conducted. Muller presently discovered that +bichromate of potassium in solution makes the best of fluids for the +preliminary preservation and hardening of the tissues. Stilling, in +1842, perfected the method by introducing the custom of cutting a series +of consecutive sections of the same tissue, in order to trace nerve +tracts and establish spacial relations. Then from time to time +mechanical ingenuity added fresh details of improvement. It was found +that pieces of hardened tissue of extreme delicacy can be made +better subject to manipulation by being impregnated with collodion or +celloidine and embedded in paraffine. Latterly it has become usual +to cut sections also from fresh tissues, unchanged by chemicals, by +freezing them suddenly with vaporized ether or, better, carbonic acid. +By these methods, and with the aid of perfected microtomes, the worker +of recent periods avails himself of sections of brain tissues of a +tenuousness which the early investigators could not approach. + +But more important even than the cutting of thin sections is the +process of making the different parts of the section visible, one tissue +differentiated from another. The thin section, as the early workers +examined it, was practically colorless, and even the crudest details of +its structure were made out with extreme difficulty. Remak did, indeed, +manage to discover that the brain tissue is cellular, as early as 1833, +and Ehrenberg in the same year saw that it is also fibrillar, but beyond +this no great advance was made until 1858, when a sudden impulse was +received from a new process introduced by Gerlach. The process itself +was most simple, consisting essentially of nothing more than the +treatment of a microscopical section with a solution of carmine. But the +result was wonderful, for when such a section was placed under the lens +it no longer appeared homogeneous. Sprinkled through its substance were +seen irregular bodies that had taken on a beautiful color, while the +matrix in which they were embedded remained unstained. In a word, the +central nerve cell had sprung suddenly into clear view. + +A most interesting body it proved, this nerve cell, or ganglion cell, +as it came to be called. It was seen to be exceedingly minute in size, +requiring high powers of the microscope to make it visible. It exists in +almost infinite numbers, not, however, scattered at random through the +brain and spinal cord. On the contrary, it is confined to those portions +of the central nervous masses which to the naked eye appear gray in +color, being altogether wanting in the white substance which makes up +the chief mass of the brain. Even in the gray matter, though sometimes +thickly distributed, the ganglion cells are never in actual contact one +with another; they always lie embedded in intercellular tissues, which +came to be known, following Virchow, as the neuroglia. + +Each ganglion cell was seen to be irregular in contour, and to have +jutting out from it two sets of minute fibres, one set relatively short, +indefinitely numerous, and branching in every direction; the other set +limited in number, sometimes even single, and starting out directly from +the cell as if bent on a longer journey. The numerous filaments came to +be known as protoplasmic processes; the other fibre was named, after its +discoverer, the axis cylinder of Deiters. It was a natural inference, +though not clearly demonstrable in the sections, that these filamentous +processes are the connecting links between the different nerve cells and +also the channels of communication between nerve cells and the periphery +of the body. The white substance of brain and cord, apparently, is made +up of such connecting fibres, thus bringing the different ganglion cells +everywhere into communication one with another. + +In the attempt to trace the connecting nerve tracts through this +white substance by either macroscopical or microscopical methods, most +important aid is given by a method originated by Waller in 1852. Earlier +than that, in 1839, Nasse had discovered that a severed nerve cord +degenerates in its peripheral portions. Waller discovered that every +nerve fibre, sensory or motor, has a nerve cell to or from which it +leads, which dominates its nutrition, so that it can only retain its +vitality while its connection with that cell is intact. Such cells he +named trophic centres. Certain cells of the anterior part of the spinal +cord, for example, are the trophic centres of the spinal motor nerves. +Other trophic centres, governing nerve tracts in the spinal cord itself, +are in the various regions of the brain. It occurred to Waller that +by destroying such centres, or by severing the connection at various +regions between a nervous tract and its trophic centre, sharply +defined tracts could be made to degenerate, and their location could +subsequently be accurately defined, as the degenerated tissues take on +a changed aspect, both to macroscopical and microscopical observation. +Recognition of this principle thus gave the experimenter a new weapon +of great efficiency in tracing nervous connections. Moreover, the same +principle has wide application in case of the human subject in disease, +such as the lesion of nerve tracts or the destruction of centres by +localized tumors, by embolisms, or by traumatisms. + +All these various methods of anatomical examination combine to make the +conclusion almost unavoidable that the central ganglion cells are the +veritable "centres" of nervous activity to which so many other lines of +research have pointed. The conclusion was strengthened by experiments +of the students of motor localization, which showed that the veritable +centres of their discovery lie, demonstrably, in the gray cortex of the +brain, not in the white matter. But the full proof came from pathology. +At the hands of a multitude of observers it was shown that in certain +well-known diseases of the spinal cord, with resulting paralysis, it is +the ganglion cells themselves that are found to be destroyed. Similarly, +in the case of sufferers from chronic insanities, with marked dementia, +the ganglion cells of the cortex of the brain are found to have +undergone degeneration. The brains of paretics in particular show such +degeneration, in striking correspondence with their mental decadence. +The position of the ganglion cell as the ultimate centre of nervous +activities was thus placed beyond dispute. + +Meantime, general acceptance being given the histological scheme of +Gerlach, according to which the mass of the white substance of the +brain is a mesh-work of intercellular fibrils, a proximal idea seemed +attainable of the way in which the ganglionic activities are correlated, +and, through association, built up, so to speak, into the higher mental +processes. Such a conception accorded beautifully with the ideas of +the associationists, who had now become dominant in psychology. But +one standing puzzle attended this otherwise satisfactory correlation +of anatomical observations and psychic analyses. It was this: Since, +according to the histologist, the intercellular fibres, along which +impulses are conveyed, connect each brain cell, directly or indirectly, +with every other brain cell in an endless mesh-work, how is it possible +that various sets of cells may at times be shut off from one another? +Such isolation must take place, for all normal ideation depends for +its integrity quite as much upon the shutting-out of the great mass of +associations as upon the inclusion of certain other associations. For +example, a student in solving a mathematical problem must for the moment +become quite oblivious to the special associations that have to do with +geography, natural history, and the like. But does histology give any +clew to the way in which such isolation may be effected? + +Attempts were made to find an answer through consideration of the very +peculiar character of the blood-supply in the brain. Here, as nowhere +else, the terminal twigs of the arteries are arranged in closed systems, +not anastomosing freely with neighboring systems. Clearly, then, a +restricted area of the brain may, through the controlling influence of +the vasomotor nerves, be flushed with arterial blood while neighboring +parts remain relatively anaemic. And since vital activities +unquestionably depend in part upon the supply of arterial blood, this +peculiar arrangement of the vascular mechanism may very properly be +supposed to aid in the localized activities of the central nervous +ganglia. But this explanation left much to be desired--in particular +when it is recalled that all higher intellection must in all probability +involve multitudes of widely scattered centres. + +No better explanation was forthcoming, however, until the year 1889, +when of a sudden the mystery was cleared away by a fresh discovery. +Not long before this the Italian histologist Dr. Camille Golgi had +discovered a method of impregnating hardened brain tissues with a +solution of nitrate of silver, with the result of staining the nerve +cells and their processes almost infinitely better than was possible by +the methods of Gerlach, or by any of the multiform methods that other +workers had introduced. Now for the first time it became possible to +trace the cellular prolongations definitely to their termini, for the +finer fibrils had not been rendered visible by any previous method +of treatment. Golgi himself proved that the set of fibrils known as +protoplasmic prolongations terminate by free extremities, and have no +direct connection with any cell save the one from which they spring. +He showed also that the axis cylinders give off multitudes of lateral +branches not hitherto suspected. But here he paused, missing the real +import of the discovery of which he was hard on the track. It remained +for the Spanish histologist Dr. S. Ramon y Cajal to follow up the +investigation by means of an improved application of Golgi's method of +staining, and to demonstrate that the axis cylinders, together with +all their collateral branches, though sometimes extending to a great +distance, yet finally terminate, like the other cell prolongations, in +arborescent fibrils having free extremities. In a word, it was shown +that each central nerve cell, with its fibrillar offshoots, is an +isolated entity. Instead of being in physical connection with a +multitude of other nerve cells, it has no direct physical connection +with any other nerve cell whatever. + +When Dr. Cajal announced his discovery, in 1889, his revolutionary +claims not unnaturally amazed the mass of histologists. There were some +few of them, however, who were not quite unprepared for the revelation; +in particular His, who had half suspected the independence of the cells, +because they seemed to develop from dissociated centres; and Forel, +who based a similar suspicion on the fact that he had never been able +actually to trace a fibre from one cell to another. These observers +then came readily to repeat Cajal's experiments. So also did the veteran +histologist Kolliker, and soon afterwards all the leaders everywhere. +The result was a practically unanimous confirmation of the Spanish +histologist's claims, and within a few months after his announcements +the old theory of union of nerve cells into an endless mesh-work was +completely discarded, and the theory of isolated nerve elements--the +theory of neurons, as it came to be called--was fully established in its +place. + +As to how these isolated nerve cells functionate, Dr. Cajal gave the +clew from the very first, and his explanation has met with universal +approval. + +In the modified view, the nerve cell retains its old position as the +storehouse of nervous energy. Each of the filaments jutting out from the +cell is held, as before, to be indeed a transmitter of impulses, but a +transmitter that operates intermittently, like a telephone wire that is +not always "connected," and, like that wire, the nerve fibril operates +by contact and not by continuity. Under proper stimulation the ends of +the fibrils reach out, come in contact with other end fibrils of other +cells, and conduct their destined impulse. Again they retract, and +communication ceases for the time between those particular cells. +Meantime, by a different arrangement of the various conductors, +different sets of cells are placed in communication, different +associations of nervous impulses induced, different trains of thought +engendered. Each fibril when retracted becomes a non-conductor, but when +extended and in contact with another fibril, or with the body of another +cell, it conducts its message as readily as a continuous filament could +do--precisely as in the case of an electric wire. + +This conception, founded on a most tangible anatomical basis, enables +us to answer the question as to how ideas are isolated, and also, as Dr. +Cajal points out, throws new light on many other mental processes. +One can imagine, for example, by keeping in mind the flexible nerve +prolongations, how new trains of thought may be engendered through novel +associations of cells; how facility of thought or of action in certain +directions is acquired through the habitual making of certain nerve-cell +connections; how certain bits of knowledge may escape our memory and +refuse to be found for a time because of a temporary incapacity of the +nerve cells to make the proper connections, and so on indefinitely. + +If one likens each nerve cell to a central telephone office, each of +its filamentous prolongations to a telephone wire, one can imagine a +striking analogy between the modus operandi of nervous processes and +of the telephone system. The utility of new connections at the central +office, the uselessness of the mechanism when the connections cannot +be made, the "wires in use" that retard your message, perhaps even the +crossing of wires, bringing you a jangle of sounds far different from +what you desire--all these and a multiplicity of other things that will +suggest themselves to every user of the telephone may be imagined as +being almost ludicrously paralleled in the operations of the nervous +mechanism. And that parallel, startling as it may seem, is not a mere +futile imagining. It is sustained and rendered plausible by a sound +substratum of knowledge of the anatomical conditions under which the +central nervous mechanism exists, and in default of which, as pathology +demonstrates with no less certitude, its functionings are futile to +produce the normal manifestations of higher intellection. + + + + +X. THE NEW SCIENCE OF ORIENTAL ARCHAEOLOGY + +HOW THE "RIDDLE OF THE SPHINX" WAS READ + +Conspicuously placed in the great hall of Egyptian antiquities in the +British Museum is a wonderful piece of sculpture known as the Rosetta +Stone. I doubt if any other piece in the entire exhibit attracts so much +attention from the casual visitor as this slab of black basalt on its +telescope-like pedestal. The hall itself, despite its profusion of +strangely sculptured treasures, is never crowded, but before this stone +you may almost always find some one standing, gazing with more or less +of discernment at the strange characters that are graven neatly across +its upturned, glass-protected face. A glance at this graven surface +suffices to show that three sets of inscriptions are recorded there. +The upper one, occupying about one-fourth of the surface, is a pictured +scroll, made up of chains of those strange outlines of serpents, hawks, +lions, and so on, which are recognized, even by the least initiated, +as hieroglyphics. The middle inscription, made up of lines, angles, +and half-pictures, one might surmise to be a sort of abbreviated +or short-hand hieroglyphic. The third or lower inscription is +Greek--obviously a thing of words. If the screeds above be also made of +words, only the elect have any way of proving the fact. + +Fortunately, however, even the least scholarly observer is left in +no doubt as to the real import of the thing he sees, for an obliging +English label tells us that these three inscriptions are renderings of +the same message, and that this message is a "decree of the priests +of Memphis conferring divine honors on Ptolemy V. (Epiphenes), King of +Egypt, B.C. 195." The label goes on to state that the upper inscription +(of which, unfortunately, only part of the last dozen lines or so +remains, the slab being broken) is in "the Egyptian language, in +hieroglyphics, or writing of the priests"; the second inscription "in +the same language is in Demotic, or the writing of the people"; and +the third "the Greek language and character." Following this is a brief +biography of the Rosetta Stone itself, as follows: "The stone was found +by the French in 1798 among the ruins of Fort Saint Julien, near the +Rosetta mouth of the Nile. It passed into the hands of the British by +the treaty of Alexandria, and was deposited in the British Museum in +the year 1801." There is a whole volume of history in that brief +inscription--and a bitter sting thrown in, if the reader chance to be +a Frenchman. Yet the facts involved could scarcely be suggested more +modestly. They are recorded much more bluntly in a graven inscription +on the side of the stone, which reads: "Captured in Egypt by the British +Army, 1801." No Frenchman could read those words without a veritable +sinking of the heart. + +The value of the Rosetta Stone depended on the fact that it gave +promise, even when casually inspected, of furnishing a key to the +centuries-old mystery of the hieroglyphics. For two thousand years the +secret of these strange markings had been forgotten. Nowhere in the +world--quite as little in Egypt as elsewhere--had any man the slightest +clew to their meaning; there were those who even doubted whether these +droll picturings really had any specific meaning, questioning whether +they were not rather vague symbols of esoteric religious import and +nothing more. And it was the Rosetta Stone that gave the answer to +these doubters and restored to the world a lost language and a forgotten +literature. + +The trustees of the museum recognized at once that the problem of the +Rosetta Stone was one on which the scientists of the world might well +exhaust their ingenuity, and promptly published to the world a carefully +lithographed copy of the entire inscription, so that foreign scholarship +had equal opportunity with the British to try at the riddle. It was an +Englishman, however, who first gained a clew to the solution. This was +none other than the extraordinary Dr. Thomas Young, the demonstrator of +the vibratory nature of light. + +Young's specific discoveries were these: (1) That many of the pictures +of the hieroglyphics stand for the names of the objects actually +delineated; (2) that other pictures are sometimes only symbolic; (3) +that plural numbers are represented by repetition; (4) that numerals are +represented by dashes; (5) that hieroglyphics may read either from +the right or from the left, but always from the direction in which the +animal and human figures face; (6) that proper names are surrounded by +a graven oval ring, making what he called a cartouche; (7) that the +cartouches of the preserved portion of the Rosetta Stone stand for the +name of Ptolemy alone; (8) that the presence of a female figure after +such cartouches in other inscriptions always denotes the female sex; (9) +that within the cartouches the hieroglyphic symbols have a positively +phonetic value, either alphabetic or syllabic; and (10) that several +different characters may have the same phonetic value. + +Just what these phonetic values are Young pointed out in the case of +fourteen characters representing nine sounds, six of which are accepted +to-day as correctly representing the letters to which he ascribed them, +and the three others as being correct regarding their essential or +consonant element. It is clear, therefore, that he was on the right +track thus far, and on the very verge of complete discovery. But, +unfortunately, he failed to take the next step, which would have been to +realize that the same phonetic values which were given to the alphabetic +characters within the cartouches were often ascribed to them also when +used in the general text of an inscription; in other words, that the +use of an alphabet was not confined to proper names. This was the great +secret which Young missed and which his French successor, Jean Francois +Champollion, working on the foundation that Young had laid, was enabled +to ferret out. + +Young's initial studies of the Rosetta Stone were made in 1814; his +later publication bore date of 1819. Champollion's first announcement of +results came in 1822; his second and more important one in 1824. By this +time, through study of the cartouches of other inscriptions, Champollion +had made out almost the complete alphabet, and the "riddle of the +Sphinx" was practically solved. He proved that the Egyptians had +developed a relatively complete alphabet (mostly neglecting the vowels, +as early Semitic alphabets did also) centuries before the Phoenicians +were heard of in history. What relation this alphabet bore to the +Phoenician we shall have occasion to ask in another connection; for the +moment it suffices to know that those strange pictures of the Egyptian +scroll are really letters. + +Even this statement, however, must be in a measure modified. These +pictures are letters and something more. Some of them are purely +alphabetical in character and some are symbolic in another way. +Some characters represent syllables. Others stand sometimes as mere +representatives of sounds, and again, in a more extended sense, as +representations of things, such as all hieroglyphics doubtless were +in the beginning. In a word, this is an alphabet, but not a perfected +alphabet, such as modern nations are accustomed to; hence the enormous +complications and difficulties it presented to the early investigators. + +Champollion did not live to clear up all these mysteries. His work was +taken up and extended by his pupil Rossellini, and in particular by Dr. +Richard Lepsius in Germany, followed by M. Bernouf, and by Samuel +Birch of the British Museum, and more recently by such well-known +Egyptologists as MM. Maspero and Mariette and Chabas, in France, Dr. +Brugsch, in Germany, and Dr. E. Wallis Budge, the present head of the +Department of Oriental Antiquities at the British Museum. But the +task of later investigators has been largely one of exhumation and +translation of records rather than of finding methods. + + +TREASURES FROM NINEVEH + +The most casual wanderer in the British Museum can hardly fail to notice +two pairs of massive sculptures, in the one case winged bulls, in the +other winged lions, both human-headed, which guard the entrance to the +Egyptian hall, close to the Rosetta Stone. Each pair of these weird +creatures once guarded an entrance to the palace of a king in the famous +city of Nineveh. As one stands before them his mind is carried back over +some twenty-seven intervening centuries, to the days when the "Cedar of +Lebanon" was "fair in his greatness" and the scourge of Israel. + +The very Sculptures before us, for example, were perhaps seen by Jonah +when he made that famous voyage to Nineveh some seven or eight hundred +years B.C. A little later the Babylonian and the Mede revolted against +Assyrian tyranny and descended upon the fair city of Nineveh, and almost +literally levelled it to the ground. But these great sculptures, among +other things, escaped destruction, and at once hidden and preserved by +the accumulating debris of the centuries, they stood there age after +age, their very existence quite forgotten. When Xenophon marched past +their site with the ill-starred expedition of the ten thousand, in the +year 400 B.C., he saw only a mound which seemed to mark the site of some +ancient ruin; but the Greek did not suspect that he looked upon the site +of that city which only two centuries before had been the mistress of +the world. + +So ephemeral is fame! And yet the moral scarcely holds in the sequel; +for we of to-day, in this new, undreamed-of Western world, behold these +mementos of Assyrian greatness fresh from their twenty-five hundred +years of entombment, and with them records which restore to us the +history of that long-forgotten people in such detail as it was not known +to any previous generation since the fall of Nineveh. For two thousand +five hundred years no one saw these treasures or knew that they existed. +One hundred generations of men came and went without once pronouncing +the name of kings Shalmaneser or Asumazirpal or Asurbanipal. And to-day, +after these centuries of oblivion, these names are restored to +history, and, thanks to the character of their monuments, are assured a +permanency of fame that can almost defy time itself. It would be nothing +strange, but rather in keeping with their previous mutations of fortune, +if the names of Asurnazirpal and Asurbanipal should be familiar as +household words to future generations that have forgotten the existence +of an Alexander, a Caesar, and a Napoleon. For when Macaulay's +prospective New Zealander explores the ruins of the British Museum +the records of the ancient Assyrians will presumably still be there +unscathed, to tell their story as they have told it to our generation, +though every manuscript and printed book may have gone the way of +fragile textures. + +But the past of the Assyrian sculptures is quite necromantic enough +without conjuring for them a necromantic future. The story of their +restoration is like a brilliant romance of history. Prior to the middle +of this century the inquiring student could learn in an hour or so all +that was known in fact and in fable of the renowned city of Nineveh. He +had but to read a few chapters of the Bible and a few pages of Diodorus +to exhaust the important literature on the subject. If he turned also to +the pages of Herodotus and Xenophon, of Justin and Aelian, these served +chiefly to confirm the suspicion that the Greeks themselves knew almost +nothing more of the history of their famed Oriental forerunners. The +current fables told of a first King Ninus and his wonderful queen +Semiramis; of Sennacherib the conqueror; of the effeminate Sardanapalus, +who neglected the warlike ways of his ancestors but perished gloriously +at the last, with Nineveh itself, in a self-imposed holocaust. And that +was all. How much of this was history, how much myth, no man could say; +and for all any one suspected to the contrary, no man could ever know. +And to-day the contemporary records of the city are before us in such +profusion as no other nation of antiquity, save Egypt alone, can at all +rival. Whole libraries of Assyrian books are at hand that were written +in the seventh century before our era. These, be it understood, are the +original books themselves, not copies. The author of that remote time +appeals to us directly, hand to eye, without intermediary transcriber. +And there is not a line of any Hebrew or Greek manuscript of a like age +that has been preserved to us; there is little enough that can match +these ancient books by a thousand years. When one reads Moses or +Isaiah, Homer, Hesiod, or Herodotus, he is but following the +transcription--often unquestionably faulty and probably never in all +parts perfect--of successive copyists of later generations. The oldest +known copy of the Bible, for example, dates probably from the fourth +century A.D., a thousand years or more after the last Assyrian records +were made and read and buried and forgotten. + +There was at least one king of Assyria--namely, Asurbanipal, whose +palace boasted a library of some ten thousand volumes--a library, if you +please, in which the books were numbered and shelved systematically, and +classified and cared for by an official librarian. If you would see some +of the documents of this marvellous library you have but to step past +the winged lions of Asurnazirpal and enter the Assyrian hall just around +the corner from the Rosetta Stone. Indeed, the great slabs of stone from +which the lions themselves are carved are in a sense books, inasmuch as +there are written records inscribed on their surface. A glance reveals +the strange characters in which these records are written, graven neatly +in straight lines across the stone, and looking to casual inspection +like nothing so much as random flights of arrow-heads. The resemblance +is so striking that this is sometimes called the arrow-head character, +though it is more generally known as the wedge or cuneiform character. +The inscriptions on the flanks of the lions are, however, only makeshift +books. But the veritable books are no farther away than the next room +beyond the hall of Asurnazirpal. They occupy part of a series of cases +placed down the centre of this room. Perhaps it is not too much to speak +of this collection as the most extraordinary set of documents of all the +rare treasures of the British Museum, for it includes not books alone, +but public and private letters, business announcements, marriage +contracts--in a word, all the species of written records that enter into +the every-day life of an intelligent and cultured community. + +But by what miracle have such documents been preserved through all these +centuries? A glance makes the secret evident. It is simply a case of +time-defying materials. Each one of these Assyrian documents appears to +be, and in reality is, nothing more or less than an inscribed fragment +of brick, having much the color and texture of a weathered terra-cotta +tile of modern manufacture. These slabs are usually oval or oblong in +shape, and from two or three to six or eight inches in length and +an inch or so in thickness. Each of them was originally a portion of +brick-clay, on which the scribe indented the flights of arrowheads +with some sharp-cornered instrument, after which the document was made +permanent by baking. They are somewhat fragile, of course, as all bricks +are, and many of them have been more or less crumbled in the destruction +of the palace at Nineveh; but to the ravages of mere time they are as +nearly invulnerable as almost anything in nature. Hence it is that these +records of a remote civilization have been preserved to us, while the +similar records of such later civilizations as the Grecian have utterly +perished, much as the flint implements of the cave-dweller come to +us unchanged, while the iron implements of a far more recent age have +crumbled away. + + +HOW THE RECORDS WERE READ + +After all, then, granted the choice of materials, there is nothing so +very extraordinary in the mere fact of preservation of these ancient +records. To be sure, it is vastly to the credit of nineteenth-century +enterprise to have searched them out and brought them back to light. +But the real marvel in connection with them is the fact that +nineteenth-century scholarship should have given us, not the material +documents themselves, but a knowledge of their actual contents. The +flight of arrow-heads on wall or slab or tiny brick have surely a +meaning; but how shall we guess that meaning? These must be words; but +what words? The hieroglyphics of the Egyptians were mysterious enough +in all conscience; yet, after all, their symbols have a certain +suggestiveness, whereas there is nothing that seems to promise a mental +leverage in the unbroken succession of these cuneiform dashes. Yet the +Assyrian scholar of to-day can interpret these strange records almost +as readily and as surely as the classical scholar interprets a +Greek manuscript. And this evidences one of the greatest triumphs of +nineteenth-century scholarship, for within almost two thousand years no +man has lived, prior to our century, to whom these strange inscriptions +would not have been as meaningless as they are to the most casual +stroller who looks on them with vague wonderment here in the museum +to-day. For the Assyrian language, like the Egyptian, was veritably a +dead language; not, like Greek and Latin, merely passed from practical +every-day use to the closet of the scholar, but utterly and absolutely +forgotten by all the world. Such being the case, it is nothing less than +marvellous that it should have been restored. + +It is but fair to add that this restoration probably never would have +been effected, with Assyrian or with Egyptian, had the language in dying +left no cognate successor; for the powers of modern linguistry, though +great, are not actually miraculous. But, fortunately, a language once +developed is not blotted out in toto; it merely outlives its usefulness +and is gradually supplanted, its successor retaining many traces of its +origin. So, just as Latin, for example, has its living representatives +in Italian and the other Romance tongues, the language of Assyria is +represented by cognate Semitic languages. As it chances, however, these +have been of aid rather in the later stages of Assyrian study than at +the very outset; and the first clew to the message of the cuneiform +writing came through a slightly different channel. + +Curiously enough, it was a trilingual inscription that gave the clew, as +in the case of the Rosetta Stone, though with very striking difference +withal. The trilingual inscription now in question, instead of being +a small, portable monument, covers the surface of a massive bluff at +Behistun in western Persia. Moreover, all three of its inscriptions +are in cuneiform characters, and all three are in languages that at +the beginning of our century were absolutely unknown. This inscription +itself, as a striking monument of unknown import, had been seen by +successive generations. Tradition ascribed it, as we learn from Ctesias, +through Diodorus, to the fabled Assyrian queen Semiramis. Tradition +was quite at fault in this; but it is only recently that knowledge has +availed to set it right. The inscription, as is now known, was really +written about the year 515 B.C., at the instance of Darius I., King of +Persia, some of whose deeds it recounts in the three chief languages of +his widely scattered subjects. + +The man who at actual risk of life and limb copied this wonderful +inscription, and through interpreting it became the veritable "father of +Assyriology," was the English general Sir Henry Rawlinson. His feat was +another British triumph over the same rivals who had competed for +the Rosetta Stone; for some French explorers had been sent by their +government, some years earlier, expressly to copy this strange record, +and had reported that it was impossible to reach the inscription. But +British courage did not find it so, and in 1835 Rawlinson scaled the +dangerous height and made a paper cast of about half the inscription. +Diplomatic duties called him away from the task for some years, but +in 1848 he returned to it and completed the copy of all parts of the +inscription that have escaped the ravages of time. And now the material +was in hand for a new science, which General Rawlinson himself soon, +assisted by a host of others, proceeded to elaborate. + +The key to the value of this unique inscription lies in the fact that +its third language is ancient Persian. It appears that the ancient +Persians had adopted the cuneiform character from their western +neighbors, the Assyrians, but in so doing had made one of those +essential modifications and improvements which are scarcely possible to +accomplish except in the transition from one race to another. Instead +of building with the arrow-head a multitude of syllabic characters, +including many homophones, as had been and continued to be the custom +with the Assyrians, the Persians selected a few of these characters and +ascribed to them phonetic values that were almost purely alphabetic. In +a word, while retaining the wedge as the basal stroke of their script, +they developed an alphabet, making the last wonderful analysis of +phonetic sounds which even to this day has escaped the Chinese, which +the Egyptians had only partially effected, and which the Phoenicians +were accredited by the Greeks with having introduced to the Western +world. In addition to this all-essential step, the Persians had +introduced the minor but highly convenient custom of separating the +words of a sentence from one another by a particular mark, differing +in this regard not only from the Assyrians and Egyptians, but from the +early Greek scribes as well. + +Thanks to these simplifications, the old Persian language had been +practically restored about the beginning of the nineteenth century, +through the efforts of the German Grotefend, and further advances in +it were made just at this time by Renouf, in France, and by Lassen, in +Germany, as well as by Rawlinson himself, who largely solved the problem +of the Persian alphabet independently. So the Persian portion of the +Behistun inscription could be at least partially deciphered. This +in itself, however, would have been no very great aid towards the +restoration of the languages of the other portions had it not chanced, +fortunately, that the inscription is sprinkled with proper names. Now +proper names, generally speaking, are not translated from one language +to another, but transliterated as nearly as the genius of the language +will permit. It was the fact that the Greek word Ptolemaics was +transliterated on the Rosetta Stone that gave the first clew to the +sounds of the Egyptian characters. Had the upper part of the Rosetta +Stone been preserved, on which, originally, there were several other +names, Young would not have halted where he did in his decipherment. + +But fortune, which had been at once so kind and so tantalizing in the +case of the Rosetta Stone, had dealt more gently with the Behistun +inscriptions; for no fewer than ninety proper names were preserved +in the Persian portion and duplicated, in another character, in the +Assyrian inscription. A study of these gave a clew to the sounds of the +Assyrian characters. The decipherment of this character, however, even +with this aid, proved enormously difficult, for it was soon evident that +here it was no longer a question of a nearly perfect alphabet of a few +characters, but of a syllabary of several hundred characters, including +many homophones, or different forms for representing the same sound. +But with the Persian translation for a guide on the one hand, and the +Semitic languages, to which family the Assyrian belonged, on the other, +the appalling task was gradually accomplished, the leading investigators +being General Rawlinson, Professor Hincks, and Mr. Fox-Talbot, in +England, Professor Jules Oppert, in Paris, and Professor Julian +Schrader, in Germany, though a host of other scholars soon entered the +field. + +This great linguistic feat was accomplished about the middle of the +nineteenth century. But so great a feat was it that many scholars of the +highest standing, including Joseph Erneste Renan, in France, and Sir G. +Cornewall Lewis, in England, declined at first to accept the results, +contending that the Assyriologists had merely deceived themselves by +creating an arbitrary language. The matter was put to a test in 1855 +at the suggestion of Mr. Fox-Talbot, when four scholars, one being Mr. +Talbot himself and the others General Rawlinson, Professor Hincks, +and Professor Oppert, laid before the Royal Asiatic Society their +independent interpretations of a hitherto untranslated Assyrian text. A +committee of the society, including England's greatest historian of the +century, George Grote, broke the seals of the four translations, and +reported that they found them unequivocally in accord as regards their +main purport, and even surprisingly uniform as regards the phraseology +of certain passages--in short, as closely similar as translations from +the obscure texts of any difficult language ever are. This decision gave +the work of the Assyriologists official status, and the reliability of +their method has never since been in question. Henceforth Assyriology +was an established science. + + + + +APPENDIX + + REFERENCE-LIST + + CHAPTER I. MODERN DEVELOPMENT OF THE PHYSICAL SCIENCES + + (1) Robert Boyle, Philosophical Works (3 vols.). London, 1738. + + CHAPTER II. THE BEGINNINGS OF MODERN CHEMISTRY + + (1) For a complete account of the controversy called the "Water + Controversy," see The Life of the Hon. Henry Cavendish, by George + Wilson, M.D., F.R.S.E. London, 1850. + + (2) Henry Cavendish, in Phil. Trans. for 1784, P. 119. + + (3) Lives of the Philosophers of the Time of George III., by Henry, Lord + Brougham, F.R.S., p. 106. London, 1855. + + (4) Experiments and Observations on Different Kinds of Air, by Joseph + Priestley (3 vols.). Birmingham, 790, vol. II, pp. 103-107. + + (5) Lectures on Experimental Philosophy, by Joseph Priestley, lecture + IV., pp. 18, ig. J. Johnson, London, 1794. + + (6) Translated from Scheele's Om Brunsten, eller Magnesia, och dess + Egenakaper. Stockholm, 1774, and published as Alembic Club Reprints, No. + 13, 1897, p. 6. + + (7) According to some writers this was discovered by Berzelius. + + (8) Histoire de la Chimie, par Ferdinand Hoefer. Paris, 1869, Vol. CL, + p. 289. + + (9) Elements of Chemistry, by Anton Laurent Lavoisier, translated by + Robert Kerr, p. 8. London and Edinburgh, 1790. + + (10) Ibid., pp. 414-416. + + CHAPTER III. CHEMISTRY SINCE THE TIME OF DALTON + + (1) Sir Humphry Davy, in Phil. Trans., Vol. VIII. + + CHAPTER IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH CENTURY + + (1) Baas, History of Medicine, p. 692. + + (2) Based on Thomas H. Huxley's Presidential Address to the British + Association for the Advancement of Science, 1870. + + (3) Essays on Digestion, by James Carson. London, 1834, p. 6. + + (4) Ibid., p. 7. + + (5) John Hunter, On the Digestion of the Stomach after Death, first + edition, pp. 183-188. + + (6) Erasmus Darwin, The Botanic Garden, pp. 448-453. London, 1799. + + CHAPTER V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH CENTURY + + (1) Baron de Cuvier's Theory of the Earth. New York, 1818, p. 123. + + (2) On the Organs and Mode of Fecundation of Orchidex and Asclepiadea, + by Robert Brown, Esq., in Miscellaneous Botanical Works. London, 1866, + Vol. I., pp. 511-514. + + (3) Justin Liebig, Animal Chemistry. London, 1843, p. 17f. + + CHAPTER VI. THEORIES OF ORGANIC EVOLUTION + + (1) "Essay on the Metamorphoses of Plants," by Goethe, translated + for the present work from Grundriss einer Geschichte der + Naturwissenschaften, by Friederich Dannemann (2 vols.). Leipzig, 1896, + Vol. I., p. 194. + + (2) The Temple of Nature, or The Origin of Society, by Erasmus Darwin, + edition published in 1807, p. 35. + + (3) Baron de Cuvier, Theory of the Earth. New York, 1818, p.74. (This + was the introduction to Cuvier's great work.) + + (4) Robert Chambers, Explanations: a sequel to Vestiges of Creation. + London, Churchill, 1845, pp. 148-153. + + CHAPTER VII. EIGHTEENTH-CENTURY MEDICINE + + (1) Condensed from Dr. Boerhaave's Academical Lectures on the Theory of + Physic. London, 1751, pp. 77, 78. Boerhaave's lectures were published as + Aphorismi de cognoscendis et curandis Morbis, Leyden, 1709. On this + book Van Swieten wrote commentaries filling five volumes. Another very + celebrated work of Boerhaave is his Institutiones et Experimenta + Chemic, Paris, 1724, the germs of this being given as a lecture on his + appointment to the chair of chemistry in the University of Leyden in + 1718. + + (2) An Inquiry into the Causes and Effects of the Variola Vaccine, etc., + by Edward Jenner, M.D., F.R.S., etc. London, 1799, pp. 2-7. He wrote + several other papers, most of which were communications to the Royal + Society. His last publication was, On the Influence of Artificial + Eruptions in Certain Diseases (London, 1822), a subject to which he had + given much time and study. + + CHAPTER VIII. NINETEENTH-CENTURY MEDICINE + + (1) In the introduction to Corvisart's translation of Avenbrugger's + work. Paris, 1808. + + (2) Laennec, Traite d'Auscultation Mediate. Paris, 1819. This was + Laennec's chief work, and was soon translated into several different + languages. Before publishing this he had written also, Propositions sur + la doctrine midicale d'Hippocrate, Paris, 1804, and Memoires sur les + vers visiculaires, in the same year. + + (3) Researches, Chemical and Philosophical, chiefly concerning Nitrous + Oxide or Dephlogisticated Nitrous Air and its Respiration, by Humphry + Davy. London, 1800, pp. 479-556. + + (4) Ibid. + + (5) For accounts of the discovery of anaesthesia, see Report of the + Board of Trustees of the Massachusetts General Hospital, Boston, 1888. + Also, The Ether Controversy: Vindication of the Hospital Reports of + 1848, by N. L Bowditch, Boston, 1848. An excellent account is given in + Littell's Living Age, for March, 1848, written by R. H. Dana, Jr. There + are also two Congressional Reports on the question of the discovery of + etherization, one for 1848, the other for 11852. + + (6) Simpson made public this discovery of the anaesthetic properties + of chloroform in a paper read before the Medico-Chirurgical Society of + Edinburgh, in March, 1847, about three months after he had first seen + a surgical operation performed upon a patient to whom ether had been + administered. + + (7) Louis Pasteur, Studies on Fermentation. London, 1870. + + (8) Louis Pasteur, in Comptes Rendus des Sciences de L'Academie des + Sciences, vol. XCII., 1881, pp. 429-435. + + CHAPTER IX. THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY + + (1) Bell's communications were made to the Royal Society, but his + studies and his discoveries in the field of anatomy of the nervous + system were collected and published, in 1824, as An Exposition of the + Natural System of Nerves of the Human Body: being a Republication of the + Papers delivered to the Royal Society on the Subject of the Nerves. + + (2) Marshall Hall, M.D., F.R.S.L., On the Reflex Functions of the + Medulla Oblongata and the Medulla Spinalis, in Phil. Trans. of Royal + Soc., vol. XXXIII., 1833. + + + + + + +End of the Project Gutenberg EBook of A History of Science, Volume 4(of 5), by +Henry Smith Williams + +*** END OF THIS PROJECT GUTENBERG EBOOK HISTORY OF SCIENCE, V4 *** + +***** This file should be named 1708.txt or 1708.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/1/7/0/1708/ + +Produced by Charles Keller + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. Special rules, +set forth in the General Terms of Use part of this license, apply to +copying and distributing Project Gutenberg-tm electronic works to +protect the PROJECT GUTENBERG-tm concept and trademark. 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WILLIAMS, M.D. + +IN FIVE VOLUMES +VOLUME IV. + +MODERN DEVELOPMENT OF THE +CHEMICAL AND BIOLOGICAL SCIENCES + + + + +A HISTORY OF SCIENCE + +BOOK IV + +MODERN DEVELOPMENT OF THE CHEMICAL AND BIOLOGICAL SCIENCES + +AS regards chronology, the epoch covered in the present volume is +identical with that viewed in the preceding one. But now as +regards subject matter we pass on to those diverse phases of the +physical world which are the field of the chemist, and to those +yet more intricate processes which have to do with living +organisms. So radical are the changes here that we seem to be +entering new worlds; and yet, here as before, there are +intimations of the new discoveries away back in the Greek days. +The solution of the problem of respiration will remind us that +Anaxagoras half guessed the secret; and in those diversified +studies which tell us of the Daltonian atom in its wonderful +transmutations, we shall be reminded again of the Clazomenian +philosopher and his successor Democritus. + +Yet we should press the analogy much too far were we to intimate +that the Greek of the elder day or any thinker of a more recent +period had penetrated, even in the vaguest way, all of the +mysteries that the nineteenth century has revealed in the fields +of chemistry and biology. At the very most the insight of those +great Greeks and of the wonderful seventeenth-century +philosophers who so often seemed on the verge of our later +discoveries did no more than vaguely anticipate their successors +of this later century. To gain an accurate, really specific +knowledge of the properties of elementary bodies was reserved for +the chemists of a recent epoch. The vague Greek questionings as +to organic evolution were world-wide from the precise inductions +of a Darwin. If the mediaeval Arabian endeavored to dull the +knife of the surgeon with the use of drugs, his results hardly +merit to be termed even an anticipation of modern anaesthesia. +And when we speak of preventive medicine--of bacteriology in all +its phases--we have to do with a marvellous field of which no +previous generation of men had even the slightest inkling. + +All in all, then, those that lie before us are perhaps the most +wonderful and the most fascinating of all the fields of science. +As the chapters of the preceding book carried us out into a +macrocosm of inconceivable magnitude, our present studies are to +reveal a microcosm of equally inconceivable smallness. As the +studies of the physicist attempted to reveal the very nature of +matter and of energy, we have now to seek the solution of the yet +more inscrutable problems of life and of mind. + + + +I. THE PHLOGISTON THEORY IN CHEMISTRY + +The development of the science of chemistry from the "science" of +alchemy is a striking example of the complete revolution in the +attitude of observers in the field of science. As has been +pointed out in a preceding chapter, the alchemist, having a +preconceived idea of how things should be, made all his +experiments to prove his preconceived theory; while the chemist +reverses this attitude of mind and bases his conceptions on the +results of his laboratory experiments. In short, chemistry is +what alchemy never could be, an inductive science. But this +transition from one point of view to an exactly opposite one was +necessarily a very slow process. Ideas that have held undisputed +sway over the minds of succeeding generations for hundreds of +years cannot be overthrown in a moment, unless the agent of such +an overthrow be so obvious that it cannot be challenged. The +rudimentary chemistry that overthrew alchemy had nothing so +obvious and palpable. + +The great first step was the substitution of the one principle, +phlogiston, for the three principles, salt, sulphur, and mercury. +We have seen how the experiment of burning or calcining such a +metal as lead "destroyed" the lead as such, leaving an entirely +different substance in its place, and how the original metal +could be restored by the addition of wheat to the calcined +product. To the alchemist this was "mortification" and +"revivification" of the metal. For, as pointed out by +Paracelsus, "anything that could be killed by man could also be +revivified by him, although this was not possible to the things +killed by God." The burning of such substances as wood, wax, +oil, etc., was also looked upon as the same "killing" process, +and the fact that the alchemist was unable to revivify them was +regarded as simply the lack of skill on his part, and in no wise +affecting the theory itself. + +But the iconoclastic spirit, if not the acceptance of all the +teachings, of the great Paracelsus had been gradually taking root +among the better class of alchemists, and about the middle of the +seventeenth century Robert Boyle (1626-1691) called attention to +the possibility of making a wrong deduction from the phenomenon +of the calcination of the metals, because of a very important +factor, the action of the air, which was generally overlooked. +And he urged his colleagues of the laboratories to give greater +heed to certain other phenomena that might pass unnoticed in the +ordinary calcinating process. In his work, The Sceptical Chemist, +he showed the reasons for doubting the threefold constitution of +matter; and in his General History of the Air advanced some novel +and carefully studied theories as to the composition of the +atmosphere. This was an important step, and although Boyle is not +directly responsible for the phlogiston theory, it is probable +that his experiments on the atmosphere influenced considerably +the real founders, Becker and Stahl. + +Boyle gave very definitely his idea of how he thought air might +be composed. "I conjecture that the atmospherical air consists of +three different kinds of corpuscles," he says; "the first, those +numberless particles which, in the form of vapors or dry +exhalations, ascend from the earth, water, minerals, vegetables, +animals, etc.; in a word, whatever substances are elevated by the +celestial or subterraneal heat, and thence diffused into the +atmosphere. The second may be yet more subtle, and consist of +those exceedingly minute atoms, the magnetical effluvia of the +earth, with other innumerable particles sent out from the bodies +of the celestial luminaries, and causing, by their influence, the +idea of light in us. The third sort is its characteristic and +essential property, I mean permanently elastic parts. Various +hypotheses may be framed relating to the structure of these later +particles of the air. They might be resembled to the springs of +watches, coiled up and endeavoring to restore themselves; to +wool, which, being compressed, has an elastic force; to slender +wires of different substances, consistencies, lengths, and +thickness; in greater curls or less, near to, or remote from each +other, etc., yet all continuing springy, expansible, and +compressible. Lastly, they may also be compared to the thin +shavings of different kinds of wood, various in their lengths, +breadth, and thickness. And this, perhaps, will seem the most +eligible hypothesis, because it, in some measure, illustrates the +production of the elastic particles we are considering. For no +art or curious instruments are required to make these shavings +whose curls are in no wise uniform, but seemingly casual; and +what is more remarkable, bodies that before seemed unelastic, as +beams and blocks, will afford them."[1] + +Although this explanation of the composition of the air is most +crude, it had the effect of directing attention to the fact that +the atmosphere is not "mere nothingness," but a "something" with +a definite composition, and this served as a good foundation for +future investigations. To be sure, Boyle was neither the first +nor the only chemist who had suspected that the air was a mixture +of gases, and not a simple one, and that only certain of these +gases take part in the process of calcination. Jean Rey, a +French physician, and John Mayow, an Englishman, had preformed +experiments which showed conclusively that the air was not a +simple substance; but Boyle's work was better known, and in its +effect probably more important. But with all Boyle's explanations +of the composition of air, he still believed that there was an +inexplicable something, a "vital substance," which he was unable +to fathom, and which later became the basis of Stahl's phlogiston +theory. Commenting on this mysterious substance, Boyle says: +"The, difficulty we find in keeping flame and fire alive, though +but for a little time, without air, renders it suspicious that +there be dispersed through the rest of the atmosphere some odd +substance, either of a solar, astral, or other foreign nature; on +account of which the air is so necessary to the substance of +flame!" It was this idea that attracted the attention of George +Ernst Stahl (1660-1734), a professor of medicine in the +University of Halle, who later founded his new theory upon it. +Stahl's theory was a development of an earlier chemist, Johann +Joachim Becker (1635-1682), in whose footsteps he followed and +whose experiments he carried further. + +In many experiments Stahl had been struck with the fact that +certain substances, while differing widely, from one another in +many respects, were alike in combustibility. From this he argued +that all combustible substances must contain a common principle, +and this principle he named phlogiston. This phlogiston he +believed to be intimately associated in combination with other +substances in nature, and in that condition not perceivable by +the senses; but it was supposed to escape as a substance burned, +and become apparent to the senses as fire or flame. In other +words, phlogiston was something imprisoned in a combustible +structure (itself forming part of the structure), and only +liberated when this structure was destroyed. Fire, or flame, was +FREE phlogiston, while the imprisoned phlogiston was called +COMBINED PHLOGISTON, or combined fire. The peculiar quality of +this strange substance was that it disliked freedom and was +always striving to conceal itself in some combustible substance. +Boyle's tentative suggestion that heat was simply motion was +apparently not accepted by Stahl, or perhaps it was unknown to +him. + +According to the phlogistic theory, the part remaining after a +substance was burned was simply the original substance deprived +of phlogiston. To restore the original combustible substance, it +was necessary to heat the residue of the combustion with +something that burned easily, so that the freed phlogiston might +again combine with the ashes. This was explained by the +supposition that the more combustible a substance was the more +phlogiston it contained, and since free phlogiston sought always +to combine with some suitable substance, it was only necessary to +mix the phlogisticating agents, such as charcoal, phosphorus, +oils, fats, etc., with the ashes of the original substance, and +heat the mixture, the phlogiston thus freed uniting at once with +the ashes. This theory fitted very nicely as applied to the +calcined lead revivified by the grains of wheat, although with +some other products of calcination it did not seem to apply at +all. + +It will be seen from this that the phlogistic theory was a step +towards chemistry and away from alchemy. It led away from the +idea of a "spirit" in metals that could not be seen, felt, or +appreciated by any of the senses, and substituted for it a +principle which, although a falsely conceived one, was still much +more tangible than the "spirit," since it could be seen and felt +as free phlogiston and weighed and measured as combined +phlogiston. The definiteness of the statement that a metal, for +example, was composed of phlogiston and an element was much less +enigmatic, even if wrong, than the statement of the alchemist +that "metals are produced by the spiritual action of the three +principles, salt, mercury, sulphur"--particularly when it is +explained that salt, mercury, and sulphur were really not what +their names implied, and that there was no universally accepted +belief as to what they really were. + +The metals, which are now regarded as elementary bodies, were +considered compounds by the phlogistians, and they believed that +the calcining of a metal was a process of simplification. They +noted, however, that the remains of calcination weighed more than +the original product, and the natural inference from this would +be that the metal must have taken in some substance rather than +have given off anything. But the phlogistians had not learned +the all-important significance of weights, and their explanation +of variation in weight was either that such gain or loss was an +unimportant "accident" at best, or that phlogiston, being light, +tended to lighten any substance containing it, so that driving it +out of the metal by calcination naturally left the residue +heavier. + +At first the phlogiston theory seemed to explain in an +indisputable way all the known chemical phenomena. Gradually, +however, as experiments multiplied, it became evident that the +plain theory as stated by Stahl and his followers failed to +explain satisfactorily certain laboratory reactions. To meet +these new conditions, certain modifications were introduced from +time to time, giving the theory a flexibility that would allow it +to cover all cases. But as the number of inexplicable experiments +continued to increase, and new modifications to the theory became +necessary, it was found that some of these modifications were +directly contradictory to others, and thus the simple theory +became too cumbersome from the number of its modifications. Its +supporters disagreed among themselves, first as to the +explanation of certain phenomena that did not seem to accord with +the phlogistic theory, and a little later as to the theory +itself. But as yet there was no satisfactory substitute for this +theory, which, even if unsatisfactory, seemed better than +anything that had gone before or could be suggested. + +But the good effects of the era of experimental research, to +which the theory of Stahl had given such an impetus, were showing +in the attitude of the experimenters. The works of some of the +older writers, such as Boyle and Hooke, were again sought out in +their dusty corners and consulted, and their surmises as to the +possible mixture of various gases in the air were more carefully +considered. Still the phlogiston theory was firmly grounded in +the minds of the philosophers, who can hardly be censured for +adhering to it, at least until some satisfactory substitute was +offered. The foundation for such a theory was finally laid, as +we shall see presently, by the work of Black, Priestley, +Cavendish, and Lavoisier, in the eighteenth century, but the +phlogiston theory cannot be said to have finally succumbed until +the opening years of the nineteenth century. + + + +II. THE BEGINNINGS OF MODERN CHEMISTRY + +THE "PNEUMATIC" CHEMISTS + +Modern chemistry may be said to have its beginning with the work +of Stephen Hales (1677-1761), who early in the eighteenth century +began his important study of the elasticity of air. Departing +from the point of view of most of the scientists of the time, be +considered air to be "a fine elastic fluid, with particles of +very different nature floating in it" ; and he showed that these +"particles" could be separated. He pointed out, also, that +various gases, or "airs," as he called them, were contained in +many solid substances. The importance of his work, however, lies +in the fact that his general studies were along lines leading +away from the accepted doctrines of the time, and that they gave +the impetus to the investigation of the properties of gases by +such chemists as Black, Priestley, Cavendish, and Lavoisier, +whose specific discoveries are the foundation-stones of modern +chemistry. + + +JOSEPH BLACK + +The careful studies of Hales were continued by his younger +confrere, Dr. Joseph Black (1728-1799), whose experiments in the +weights of gases and other chemicals were first steps in +quantitative chemistry. But even more important than his +discoveries of chemical properties in general was his discovery +of the properties of carbonic-acid gas. + +Black had been educated for the medical profession in the +University of Glasgow, being a friend and pupil of the famous Dr. +William Cullen. But his liking was for the chemical laboratory +rather than for the practice of medicine. Within three years +after completing his medical course, and when only twenty-three +years of age, he made the discovery of the properties of carbonic +acid, which he called by the name of "fixed air." After +discovering this gas, Black made a long series of experiments, by +which he was able to show how widely it was distributed +throughout nature. Thus, in 1757, be discovered that the bubbles +given off in the process of brewing, where there was vegetable +fermentation, were composed of it. To prove this, he collected +the contents of these bubbles in a bottle containing lime-water. +When this bottle was shaken violently, so that the lime-water and +the carbonic acid became thoroughly mixed, an insoluble white +powder was precipitated from the solution, the carbonic acid +having combined chemically with the lime to form the insoluble +calcium carbonate, or chalk. This experiment suggested another. +Fixing a piece of burning charcoal in the end of a bellows, he +arranged a tube so that the gas coming from the charcoal would +pass through the lime-water, and, as in the case of the bubbles +from the brewer's vat, he found that the white precipitate was +thrown down; in short, that carbonic acid was given off in +combustion. Shortly after, Black discovered that by blowing +through a glass tube inserted into lime-water, chalk was +precipitated, thus proving that carbonic acid was being +constantly thrown off in respiration. + +The effect of Black's discoveries was revolutionary, and the +attitude of mind of the chemists towards gases, or "airs," was +changed from that time forward. Most of the chemists, however, +attempted to harmonize the new facts with the older theories--to +explain all the phenomena on the basis of the phlogiston theory, +which was still dominant. But while many of Black's discoveries +could not be made to harmonize with that theory, they did not +directly overthrow it. It required the additional discoveries of +some of Black's fellow-scientists to complete its downfall, as we +shall see. + + +HENRY CAVENDISH + +This work of Black's was followed by the equally important work +of his former pupil, Henry Cavendish (1731-1810), whose discovery +of the composition of many substances, notably of nitric acid and +of water, was of great importance, adding another link to the +important chain of evidence against the phlogiston theory. +Cavendish is one of the most eccentric figures in the history of +science, being widely known in his own time for his immense +wealth and brilliant intellect, and also for his peculiarities +and his morbid sensibility, which made him dread society, and +probably did much in determining his career. Fortunately for him, +and incidentally for the cause of science, he was able to pursue +laboratory investigations without being obliged to mingle with +his dreaded fellow-mortals, his every want being provided for by +the immense fortune inherited from his father and an uncle. + +When a young man, as a pupil of Dr. Black, he had become imbued +with the enthusiasm of his teacher, continuing Black's +investigations as to the properties of carbonic-acid gas when +free and in combination. One of his first investigations was +reported in 1766, when he communicated to the Royal Society his +experiments for ascertaining the properties of carbonic-acid and +hydrogen gas, in which he first showed the possibility of +weighing permanently elastic fluids, although Torricelli had +before this shown the relative weights of a column of air and a +column of mercury. Other important experiments were continued by +Cavendish, and in 1784 he announced his discovery of the +composition of water, thus robbing it of its time-honored +position as an "element." But his claim to priority in this +discovery was at once disputed by his fellow-countryman James +Watt and by the Frenchman Lavoisier. Lavoisier's claim was soon +disallowed even by his own countrymen, but for many years a +bitter controversy was carried on by the partisans of Watt and +Cavendish. The two principals, however, seem. never to have +entered into this controversy with anything like the same ardor +as some of their successors, as they remained on the best of +terms.[1] It is certain, at any rate, that Cavendish announced +his discovery officially before Watt claimed that the +announcement had been previously made by him, "and, whether right +or wrong, the honor of scientific discoveries seems to be +accorded naturally to the man who first publishes a demonstration +of his discovery." Englishmen very generally admit the justness +of Cavendish's claim, although the French scientist Arago, after +reviewing the evidence carefully in 1833, decided in favor of +Watt. + +It appears that something like a year before Cavendish made known +his complete demonstration of the composition of water, Watt +communicated to the Royal Society a suggestion that water was +composed of "dephlogisticated air (oxygen) and phlogiston +(hydrogen) deprived of part of its latent heat." Cavendish knew +of the suggestion, but in his experiments refuted the idea that +the hydrogen lost any of its latent heat. Furthermore, Watt +merely suggested the possible composition without proving it, +although his idea was practically correct, if we can rightly +interpret the vagaries of the nomenclature then in use. But had +Watt taken the steps to demonstrate his theory, the great "Water +Controversy" would have been avoided. Cavendish's report of his +discovery to the Royal Society covers something like forty pages +of printed matter. In this he shows how, by passing an electric +spark through a closed jar containing a mixture of hydrogen gas +and oxygen, water is invariably formed, apparently by the union +of the two gases. The experiment was first tried with hydrogen +and common air, the oxygen of the air uniting with the hydrogen +to form water, leaving the nitrogen of the air still to be +accounted for. With pure oxygen and hydrogen, however, Cavendish +found that pure water was formed, leaving slight traces of any +other, substance which might not be interpreted as being Chemical +impurities. There was only one possible explanation of this +phenomenon--that hydrogen and oxygen, when combined, form water. + +"By experiments with the globe it appeared," wrote Cavendish, +"that when inflammable and common air are exploded in a proper +proportion, almost all the inflammable air, and near one-fifth +the common air, lose their elasticity and are condensed into dew. +And by this experiment it appears that this dew is plain water, +and consequently that almost all the inflammable air is turned +into pure water. + +"In order to examine the nature of the matter condensed on firing +a mixture of dephlogisticated and inflammable air, I took a glass +globe, holding 8800 grain measures, furnished with a brass cock +and an apparatus for firing by electricity. This globe was well +exhausted by an air-pump, and then filled with a mixture of +inflammable and dephlogisticated air by shutting the cock, +fastening the bent glass tube into its mouth, and letting up the +end of it into a glass jar inverted into water and containing a +mixture of 19,500 grain measures of dephlogisticated air, and +37,000 of inflammable air; so that, upon opening the cock, some +of this mixed air rushed through the bent tube and filled the +globe. The cock was then shut and the included air fired by +electricity, by means of which almost all of it lost its +elasticity (was condensed into water vapors). The cock was then +again opened so as to let in more of the same air to supply the +place of that destroyed by the explosion, which was again fired, +and the operation continued till almost the whole of the mixture +was let into the globe and exploded. By this means, though the +globe held not more than a sixth part of the mixture, almost the +whole of it was exploded therein without any fresh exhaustion of +the globe." + +At first this condensed matter was "acid to the taste and +contained two grains of nitre," but Cavendish, suspecting that +this was due to impurities, tried another experiment that proved +conclusively that his opinions were correct. "I therefore made +another experiment," he says, "with some more of the same air +from plants in which the proportion of inflammable air was +greater, so that the burnt air was almost completely +phlogisticated, its standard being one-tenth. The condensed +liquor was then not at all acid, but seemed pure water." + +From these experiments he concludes "that when a mixture of +inflammable and dephlogisticated air is exploded, in such +proportions that the burnt air is not much phlogisticated, the +condensed liquor contains a little acid which is always of the +nitrous kind, whatever substance the dephlogisticated air is +procured from; but if the proportion be such that the burnt air +is almost entirely phlogisticated, the condensed liquor is not at +all acid, but seems pure water, without any addition +whatever."[2] + +These same experiments, which were undertaken to discover the +composition of water, led him to discover also the composition of +nitric acid. He had observed that, in the combustion of hydrogen +gas with common air, the water was slightly tinged with acid, but +that this was not the case when pure oxygen gas was used. Acting +upon this observation, he devised an experiment to determine the +nature of this acid. He constructed an apparatus whereby an +electric spark was passed through a vessel containing common air. +After this process had been carried on for several weeks a small +amount of liquid was formed. This liquid combined with a solution +of potash to form common nitre, which "detonated with charcoal, +sparkled when paper impregnated with it was burned, and gave out +nitrous fumes when sulphuric acid was poured on it." In other +words, the liquid was shown to be nitric acid. Now, since nothing +but pure air had been used in the initial experiment, and since +air is composed of nitrogen and oxygen, there seemed no room to +doubt that nitric acid is a combination of nitrogen and oxygen. + +This discovery of the nature of nitric acid seems to have been +about the last work of importance that Cavendish did in the field +of chemistry, although almost to the hour of his death he was +constantly occupied with scientific observations. Even in the +last moments of his life this habit asserted itself, according to +Lord Brougham. "He died on March 10, 1810, after a short +illness, probably the first, as well as the last, which he ever +suffered. His habit of curious observation continued to the end. +He was desirous of marking the progress of the disease and the +gradual extinction of the vital powers. With these ends in view, +that he might not be disturbed, he desired to be left alone. His +servant, returning sooner than he had wished, was ordered again +to leave the chamber of death, and when be came back a second +time he found his master had expired.[3] + + +JOSEPH PRIESTLEY + +While the opulent but diffident Cavendish was making his +important discoveries, another Englishman, a poor country +preacher named Joseph Priestley (1733-1804) was not only +rivalling him, but, if anything, outstripping him in the pursuit +of chemical discoveries. In 1761 this young minister was given a +position as tutor in a nonconformist academy at Warrington, and +here, for six years, he was able to pursue his studies in +chemistry and electricity. In 1766, while on a visit to London, +he met Benjamin Franklin, at whose suggestion he published his +History of Electricity. From this time on he made steady +progress in scientific investigations, keeping up his +ecclesiastical duties at the same time. In 1780 he removed to +Birmingham, having there for associates such scientists as James +Watt, Boulton, and Erasmus Darwin. + +Eleven years later, on the anniversary of the fall of the Bastile +in Paris, a fanatical mob, knowing Priestley's sympathies with +the French revolutionists, attacked his house and chapel, burning +both and destroying a great number of valuable papers and +scientific instruments. Priestley and his family escaped violence +by flight, but his most cherished possessions were destroyed; and +three years later he quitted England forever, removing to the +United States, whose struggle for liberty he had championed. The +last ten years of his life were spent at Northumberland, +Pennsylvania, where he continued his scientific researches. + +Early in his scientific career Priestley began investigations +upon the "fixed air" of Dr. Black, and, oddly enough, he was +stimulated to this by the same thing that had influenced +Black--that is, his residence in the immediate neighborhood of a +brewery. It was during the course of a series of experiments on +this and other gases that he made his greatest discovery, that of +oxygen, or "dephlogisticated air," as he called it. The story of +this important discovery is probably best told in Priestley's own +words: + +"There are, I believe, very few maxims in philosophy that have +laid firmer hold upon the mind than that air, meaning atmospheric +air, is a simple elementary substance, indestructible and +unalterable, at least as much so as water is supposed to be. In +the course of my inquiries I was, however, soon satisfied that +atmospheric air is not an unalterable thing; for that, according +to my first hypothesis, the phlogiston with which it becomes +loaded from bodies burning in it, and the animals breathing it, +and various other chemical processes, so far alters and depraves +it as to render it altogether unfit for inflammation, +respiration, and other purposes to which it is subservient; and I +had discovered that agitation in the water, the process of +vegetation, and probably other natural processes, restore it to +its original purity.... + +"Having procured a lens of twelve inches diameter and twenty +inches local distance, I proceeded with the greatest alacrity, by +the help of it, to discover what kind of air a great variety of +substances would yield, putting them into the vessel, which I +filled with quicksilver, and kept inverted in a basin of the same +.... With this apparatus, after a variety of experiments .... on +the 1st of August, 1774, I endeavored to extract air from +mercurius calcinatus per se; and I presently found that, by means +of this lens, air was expelled from it very readily. Having got +about three or four times as much as the bulk of my materials, I +admitted water to it, and found that it was not imbibed by it. +But what surprised me more than I can express was that a candle +burned in this air with a remarkably vigorous flame, very much +like that enlarged flame with which a candle burns in nitrous +oxide, exposed to iron or liver of sulphur; but as I had got +nothing like this remarkable appearance from any kind of air +besides this particular modification of vitrous air, and I knew +no vitrous acid was used in the preparation of mercurius +calcinatus, I was utterly at a loss to account for it."[4] + + +The "new air" was, of course, oxygen. Priestley at once +proceeded to examine it by a long series of careful experiments, +in which, as will be seen, he discovered most of the remarkable +qualities of this gas. Continuing his description of these +experiments, he says: + +"The flame of the candle, besides being larger, burned with more +splendor and heat than in that species of nitrous air; and a +piece of red-hot wood sparkled in it, exactly like paper dipped +in a solution of nitre, and it consumed very fast; an experiment +that I had never thought of trying with dephlogisticated nitrous +air. + +". . . I had so little suspicion of the air from the mercurius +calcinatus, etc., being wholesome, that I had not even thought of +applying it to the test of nitrous air; but thinking (as my +reader must imagine I frequently must have done) on the candle +burning in it after long agitation in water, it occurred to me at +last to make the experiment; and, putting one measure of nitrous +air to two measures of this air, I found not only that it was +diminished, but that it was diminished quite as much as common +air, and that the redness of the mixture was likewise equal to a +similar mixture of nitrous and common air.... The next day I was +more surprised than ever I had been before with finding that, +after the above-mentioned mixture of nitrous air and the air from +mercurius calcinatus had stood all night, . . . a candle burned +in it, even better than in common air." + +A little later Priestley discovered that "dephlogisticated air . +. . is a principal element in the composition of acids, and may +be extracted by means of heat from many substances which contain +them.... It is likewise produced by the action of light upon +green vegetables; and this seems to be the chief means employed +to preserve the purity of the atmosphere." + +This recognition of the important part played by oxygen in the +atmosphere led Priestley to make some experiments upon mice and +insects, and finally upon himself, by inhalations of the pure +gas. "The feeling in my lungs," he said, "was not sensibly +different from that of common air, but I fancied that my +breathing felt peculiarly light and easy for some time +afterwards. Who can tell but that in time this pure air may +become a fashionable article in luxury? . . . Perhaps we may from +these experiments see that though pure dephlogisticated air might +be useful as a medicine, it might not be so proper for us in the +usual healthy state of the body." + +This suggestion as to the possible usefulness of oxygen as a +medicine was prophetic. A century later the use of oxygen had +become a matter of routine practice with many physicians. Even in +Priestley's own time such men as Dr. John Hunter expressed their +belief in its efficacy in certain conditions, as we shall see, +but its value in medicine was not fully appreciated until several +generations later. + +Several years after discovering oxygen Priestley thus summarized +its properties: "It is this ingredient in the atmospheric air +that enables it to support combustion and animal life. By means +of it most intense heat may be produced, and in the purest of it +animals will live nearly five times as long as in an equal +quantity of atmospheric air. In respiration, part of this air, +passing the membranes of the lungs, unites with the blood and +imparts to it its florid color, while the remainder, uniting with +phlogiston exhaled from venous blood, forms mixed air. It is +dephlogisticated air combined with water that enables fishes to +live in it."[5] + + +KARL WILHELM SCHEELE + +The discovery of oxygen was the last but most important blow to +the tottering phlogiston theory, though Priestley himself would +not admit it. But before considering the final steps in the +overthrow of Stahl's famous theory and the establishment of +modern chemistry, we must review the work of another great +chemist, Karl Wilhelm Scheele (1742-1786), of Sweden, who +discovered oxygen quite independently, although later than +Priestley. In the matter of brilliant discoveries in a brief +space of time Scheele probably eclipsed all his great +contemporaries. He had a veritable genius for interpreting +chemical reactions and discovering new substances, in this +respect rivalling Priestley himself. Unlike Priestley, however, +he planned all his experiments along the lines of definite +theories from the beginning, the results obtained being the +logical outcome of a predetermined plan. + +Scheele was the son of a merchant of Stralsund, Pomerania, which +then belonged to Sweden. As a boy in school he showed so little +aptitude for the study of languages that he was apprenticed to an +apothecary at the age of fourteen. In this work he became at +once greatly interested, and, when not attending to his duties in +the dispensary, he was busy day and night making experiments or +studying books on chemistry. In 1775, still employed as an +apothecary, he moved to Stockholm, and soon after he sent to +Bergman, the leading chemist of Sweden, his first discovery--that +of tartaric acid, which he had isolated from cream of tartar. +This was the beginning of his career of discovery, and from that +time on until his death he sent forth accounts of new discoveries +almost uninterruptedly. Meanwhile he was performing the duties of +an ordinary apothecary, and struggling against poverty. His +treatise upon Air and Fire appeared in 1777. In this remarkable +book he tells of his discovery of oxygen--"empyreal" or +"fire-air," as he calls it--which he seems to have made +independently and without ever having heard of the previous +discovery by Priestley. In this book, also, he shows that air is +composed chiefly of oxygen and nitrogen gas. + +Early in his experimental career Scheele undertook the solution +of the composition of black oxide of manganese, a substance that +had long puzzled the chemists. He not only succeeded in this, +but incidentally in the course of this series of experiments he +discovered oxygen, baryta, and chlorine, the last of far greater +importance, at least commercially, than the real object of his +search. In speaking of the experiment in which the discovery was +made he says: + +"When marine (hydrochloric) acid stood over manganese in the cold +it acquired a dark reddish-brown color. As manganese does not +give any colorless solution without uniting with phlogiston +[probably meaning hydrogen], it follows that marine acid can +dissolve it without this principle. But such a solution has a +blue or red color. The color is here more brown than red, the +reason being that the very finest portions of the manganese, +which do not sink so easily, swim in the red solution; for +without these fine particles the solution is red, and red mixed +with black is brown. The manganese has here attached itself so +loosely to acidum salis that the water can precipitate it, and +this precipitate behaves like ordinary manganese. When, now, the +mixture of manganese and spiritus salis was set to digest, there +arose an effervescence and smell of aqua regis."[6] + +The "effervescence" he refers to was chlorine, which he proceeded +to confine in a suitable vessel and examine more fully. He +described it as having a "quite characteristically suffocating +smell," which was very offensive. He very soon noted the +decolorizing or bleaching effects of this now product, finding +that it decolorized flowers, vegetables, and many other +substances. + +Commercially this discovery of chlorine was of enormous +importance, and the practical application of this new chemical in +bleaching cloth soon supplanted the, old process of +crofting--that is, bleaching by spreading the cloth upon the +grass. But although Scheele first pointed out the bleaching +quality of his newly discovered gas, it was the French savant, +Berthollet, who, acting upon Scheele's discovery that the new gas +would decolorize vegetables and flowers, was led to suspect that +this property might be turned to account in destroying the color +of cloth. In 1785 he read a paper before the Academy of Sciences +of Paris, in which he showed that bleaching by chlorine was +entirely satisfactory, the color but not the substance of the +cloth being affected. He had experimented previously and found +that the chlorine gas was soluble in water and could thus be made +practically available for bleaching purposes. In 1786 James Watt +examined specimens of the bleached cloth made by Berthollet, and +upon his return to England first instituted the process of +practical bleaching. His process, however, was not entirely +satisfactory, and, after undergoing various modifications and +improvements, it was finally made thoroughly practicable by Mr. +Tennant, who hit upon a compound of chlorine and lime--the +chloride of lime--which was a comparatively cheap chemical +product, and answered the purpose better even than chlorine +itself. + +To appreciate how momentous this discovery was to cloth +manufacturers, it should be remembered that the old process of +bleaching consumed an entire summer for the whitening of a single +piece of linen; the new process reduced the period to a few +hours. To be sure, lime had been used with fair success previous +to Tennant's discovery, but successful and practical bleaching by +a solution of chloride of lime was first made possible by him and +through Scheele's discovery of chlorine. + +Until the time of Scheele the great subject of organic chemistry +had remained practically unexplored, but under the touch of his +marvellous inventive genius new methods of isolating and studying +animal and vegetable products were introduced, and a large number +of acids and other organic compounds prepared that had been +hitherto unknown. His explanations of chemical phenomena were +based on the phlogiston theory, in which, like Priestley, he +always, believed. Although in error in this respect, he was, +nevertheless, able to make his discoveries with extremely +accurate interpretations. A brief epitome of the list of some of +his more important discoveries conveys some idea, of his +fertility of mind as well as his industry. In 1780 he discovered +lactic acid,[7] and showed that it was the substance that caused +the acidity of sour milk; and in the same year he discovered +mucic acid. Next followed the discovery of tungstic acid, and in +1783 he added to his list of useful discoveries that of +glycerine. Then in rapid succession came his announcements of the +new vegetable products citric, malic, oxalic, and gallic acids. +Scheele not only made the discoveries, but told the world how he +had made them--how any chemist might have made them if he +chose--for he never considered that he had really discovered any +substance until he had made it, decomposed it, and made it again. + +His experiments on Prussian blue are most interesting, not only +because of the enormous amount of work involved and the skill he +displayed in his experiments, but because all the time the +chemist was handling, smelling, and even tasting a compound of +one of the most deadly poisons, ignorant of the fact that the +substance was a dangerous one to handle. His escape from injury +seems almost miraculous; for his experiments, which were most +elaborate, extended over a considerable period of time, during +which he seems to have handled this chemical with impunity. + +While only forty years of age and just at the zenith of his fame, +Scheele was stricken by a fatal illness, probably induced by his +ceaseless labor and exposure. It is gratifying to know, however, +that during the last eight or nine years of his life he had been +less bound down by pecuniary difficulties than before, as Bergman +had obtained for him an annual grant from the Academy. But it +was characteristic of the man that, while devoting one-sixth of +the amount of this grant to his personal wants, the remaining +five-sixths was devoted to the expense of his experiments. + + +LAVOISIER AND THE FOUNDATION OF MODERN CHEMISTRY + +The time was ripe for formulating the correct theory of chemical +composition: it needed but the master hand to mould the materials +into the proper shape. The discoveries in chemistry during the +eighteenth century had been far-reaching and revolutionary in +character. A brief review of these discoveries shows how +completely they had subverted the old ideas of chemical elements +and chemical compounds. Of the four substances earth, air, fire, +and water, for many centuries believed to be elementary bodies, +not one has stood the test of the eighteenth-century chemists. +Earth had long since ceased to be regarded as an element, and +water and air had suffered the same fate in this century. And +now at last fire itself, the last of the four "elements" and the +keystone to the phlogiston arch, was shown to be nothing more +than one of the manifestations of the new element, oxygen, and +not "phlogiston" or any other intangible substance. + +In this epoch of chemical discoveries England had produced such +mental giants and pioneers in science as Black, Priestley, and +Cavendish; Sweden had given the world Scheele and Bergman, whose +work, added to that of their English confreres, had laid the +broad base of chemistry as a science; but it was for France to +produce a man who gave the final touches to the broad but rough +workmanship of its foundation, and establish it as the science of +modern chemistry. It was for Antoine Laurent Lavoisier +(1743-1794) to gather together, interpret correctly, rename, and +classify the wealth of facts that his immediate predecessors and +contemporaries had given to the world. + +The attitude of the mother-countries towards these illustrious +sons is an interesting piece of history. Sweden honored and +rewarded Scheele and Bergman for their efforts; England received +the intellectuality of Cavendish with less appreciation than the +Continent, and a fanatical mob drove Priestley out of the +country; while France, by sending Lavoisier to the guillotine, +demonstrated how dangerous it was, at that time at least, for an +intelligent Frenchman to serve his fellowman and his country +well. + +"The revolution brought about by Lavoisier in science," says +Hoefer, "coincides by a singular act of destiny with another +revolution, much greater indeed, going on then in the political +and social world. Both happened on the same soil, at the same +epoch, among the same people; and both marked the commencement of +a new era in their respective spheres."[8] + +Lavoisier was born in Paris, and being the son of an opulent +family, was educated under the instruction of the best teachers +of the day. With Lacaille he studied mathematics and astronomy; +with Jussieu, botany; and, finally, chemistry under Rouelle. His +first work of importance was a paper on the practical +illumination of the streets of Paris, for which a prize had been +offered by M. de Sartine, the chief of police. This prize was not +awarded to Lavoisier, but his suggestions were of such importance +that the king directed that a gold medal be bestowed upon the +young author at the public sitting of the Academy in April, 1776. +Two years later, at the age of thirty-five, Lavoisier was +admitted a member of the Academy. + +In this same year he began to devote himself almost exclusively +to chemical inquiries, and established a laboratory in his home, +fitted with all manner of costly apparatus and chemicals. Here he +was in constant communication with the great men of science of +Paris, to all of whom his doors were thrown open. One of his +first undertakings in this laboratory was to demonstrate that +water could not be converted into earth by repeated +distillations, as was generally advocated; and to show also that +there was no foundation to the existing belief that it was +possible to convert water into a gas so "elastic" as to pass +through the pores of a vessel. He demonstrated the fallaciousness +of both these theories in 1768-1769 by elaborate experiments, a +single investigation of this series occupying one hundred and one +days. + +In 1771 he gave the first blow to the phlogiston theory by his +experiments on the calcination of metals. It will be recalled +that one basis for the belief in phlogiston was the fact that +when a metal was calcined it was converted into an ash, giving up +its "phlogiston" in the process. To restore the metal, it was +necessary to add some substance such as wheat or charcoal to the +ash. Lavoisier, in examining this process of restoration, found +that there was always evolved a great quantity of "air," which he +supposed to be "fixed air" or carbonic acid--the same that +escapes in effervescence of alkalies and calcareous earths, and +in the fermentation of liquors. He then examined the process of +calcination, whereby the phlogiston of the metal was supposed to +have been drawn off. But far from finding that phlogiston or any +other substance had been driven off, he found that something had +been taken on: that the metal "absorbed air," and that the +increased weight of the metal corresponded to the amount of air +"absorbed." Meanwhile he was within grasp of two great +discoveries, that of oxygen and of the composition of the air, +which Priestley made some two years later. + +The next important inquiry of this great Frenchman was as to the +composition of diamonds. With the great lens of Tschirnhausen +belonging to the Academy he succeeded in burning up several +diamonds, regardless of expense, which, thanks to his +inheritance, he could ignore. In this process he found that a gas +was given off which precipitated lime from water, and proved to +be carbonic acid. Observing this, and experimenting with other +substances known to give off carbonic acid in the same manner, he +was evidently impressed with the now well-known fact that diamond +and charcoal are chemically the same. But if he did really +believe it, he was cautious in expressing his belief fully. "We +should never have expected," he says, "to find any relation +between charcoal and diamond, and it would be unreasonable to +push this analogy too far; it only exists because both substances +seem to be properly ranged in the class of combustible bodies, +and because they are of all these bodies the most fixed when kept +from contact with air." + +As we have seen, Priestley, in 1774, had discovered oxygen, or +"dephlogisticated air." Four years later Lavoisier first +advanced his theory that this element discovered by Priestley was +the universal acidifying or oxygenating principle, which, when +combined with charcoal or carbon, formed carbonic acid; when +combined with sulphur, formed sulphuric (or vitriolic) acid; with +nitrogen, formed nitric acid, etc., and when combined with the +metals formed oxides, or calcides. Furthermore, he postulated the +theory that combustion was not due to any such illusive thing as +"phlogiston," since this did not exist, and it seemed to him that +the phenomena of combustion heretofore attributed to phlogiston +could be explained by the action of the new element oxygen and +heat. This was the final blow to the phlogiston theory, which, +although it had been tottering for some time, had not been +completely overthrown. + +In 1787 Lavoisier, in conjunction with Guyon de Morveau, +Berthollet, and Fourcroy, introduced the reform in chemical +nomenclature which until then had remained practically unchanged +since alchemical days. Such expressions as "dephlogisticated" and +"phlogisticated" would obviously have little meaning to a +generation who were no longer to believe in the existence of +phlogiston. It was appropriate that a revolution in chemical +thought should be accompanied by a corresponding revolution in +chemical names, and to Lavoisier belongs chiefly the credit of +bringing about this revolution. In his Elements of Chemistry he +made use of this new nomenclature, and it seemed so clearly an +improvement over the old that the scientific world hastened to +adopt it. In this connection Lavoisier says: "We have, +therefore, laid aside the expression metallic calx altogether, +and have substituted in its place the word oxide. By this it may +be seen that the language we have adopted is both copious and +expressive. The first or lowest degree of oxygenation in bodies +converts them into oxides; a second degree of additional +oxygenation constitutes the class of acids of which the specific +names drawn from their particular bases terminate in ous, as in +the nitrous and the sulphurous acids. The third degree of +oxygenation changes these into the species of acids distinguished +by the termination in ic, as the nitric and sulphuric acids; and, +lastly, we can express a fourth or higher degree of oxygenation +by adding the word oxygenated to the name of the acid, as has +already been done with oxygenated muriatic acid."[9] + +This new work when given to the world was not merely an +epoch-making book; it was revolutionary. It not only discarded +phlogiston altogether, but set forth that metals are simple +elements, not compounds of "earth" and "phlogiston." It upheld +Cavendish's demonstration that water itself, like air, is a +compound of oxygen with another element. In short, it was +scientific chemistry, in the modern acceptance of the term. + +Lavoisier's observations on combustion are at once important and +interesting: "Combustion," he says, ". . . is the decomposition +of oxygen produced by a combustible body. The oxygen which forms +the base of this gas is absorbed by and enters into combination +with the burning body, while the caloric and light are set free. +Every combustion necessarily supposes oxygenation; whereas, on +the contrary, every oxygenation does not necessarily imply +concomitant combustion; because combustion properly so called +cannot take place without disengagement of caloric and light. +Before combustion can take place, it is necessary that the base +of oxygen gas should have greater affinity to the combustible +body than it has to caloric; and this elective attraction, to use +Bergman's expression, can only take place at a certain degree of +temperature which is different for each combustible substance; +hence the necessity of giving the first motion or beginning to +every combustion by the approach of a heated body. This necessity +of heating any body we mean to burn depends upon certain +considerations which have not hitherto been attended to by any +natural philosopher, for which reason I shall enlarge a little +upon the subject in this place: + +"Nature is at present in a state of equilibrium, which cannot +have been attained until all the spontaneous combustions or +oxygenations possible in an ordinary degree of temperature had +taken place.... To illustrate this abstract view of the matter by +example: Let us suppose the usual temperature of the earth a +little changed, and it is raised only to the degree of boiling +water; it is evident that in this case phosphorus, which is +combustible in a considerably lower degree of temperature, would +no longer exist in nature in its pure and simple state, but would +always be procured in its acid or oxygenated state, and its +radical would become one of the substances unknown to chemistry. +By gradually increasing the temperature of the earth, the same +circumstance would successively happen to all the bodies capable +of combustion; and, at the last, every possible combustion having +taken place, there would no longer exist any combustible body +whatever, and every substance susceptible of the operation would +be oxygenated and consequently incombustible. + +"There cannot, therefore, exist, as far as relates to us, any +combustible body but such as are non-combustible at the ordinary +temperature of the earth, or, what is the same thing in other +words, that it is essential to the nature of every combustible +body not to possess the property of combustion unless heated, or +raised to a degree of temperature at which its combustion +naturally takes place. When this degree is once produced, +combustion commences, and the caloric which is disengaged by the +decomposition of the oxygen gas keeps up the temperature which is +necessary for continuing combustion. When this is not the +case--that is, when the disengaged caloric is not sufficient for +keeping up the necessary temperature--the combustion ceases. This +circumstance is expressed in the common language by saying that a +body burns ill or with difficulty."[10] + + +It needed the genius of such a man as Lavoisier to complete the +refutation of the false but firmly grounded phlogiston theory, +and against such a book as his Elements of Chemistry the feeble +weapons of the supporters of the phlogiston theory were hurled in +vain. + +But while chemists, as a class, had become converts to the new +chemistry before the end of the century, one man, Dr. Priestley, +whose work had done so much to found it, remained unconverted. +In this, as in all his life-work, he showed himself to be a most +remarkable man. Davy said of him, a generation later, that no +other person ever discovered so many new and curious substances +as he; yet to the last he was only an amateur in science, his +profession, as we know, being the ministry. There is hardly +another case in history of a man not a specialist in science +accomplishing so much in original research as did this chemist, +physiologist, electrician; the mathematician, logician, and +moralist; the theologian, mental philosopher, and political +economist. He took all knowledge for his field; but how he found +time for his numberless researches and multifarious writings, +along with his every-day duties, must ever remain a mystery to +ordinary mortals. + +That this marvellously receptive, flexible mind should have +refused acceptance to the clearly logical doctrines of the new +chemistry seems equally inexplicable. But so it was. To the +very last, after all his friends had capitulated, Priestley kept +up the fight. From America he sent out his last defy to the +enemy, in 1800, in a brochure entitled "The Doctrine of +Phlogiston Upheld," etc. In the mind of its author it was little +less than a paean of victory; but all the world beside knew that +it was the swan-song of the doctrine of phlogiston. Despite the +defiance of this single warrior the battle was really lost and +won, and as the century closed "antiphlogistic" chemistry had +practical possession of the field. + + + +III. CHEMISTRY SINCE THE TIME OF DALTON + +JOHN DALTON AND THE ATOMIC THEORY + +Small beginnings as have great endings--sometimes. As a case in +point, note what came of the small, original effort of a +self-trained back-country Quaker youth named John Dalton, who +along towards the close of the eighteenth century became +interested in the weather, and was led to construct and use a +crude water-gauge to test the amount of the rainfall. The simple +experiments thus inaugurated led to no fewer than two hundred +thousand recorded observations regarding the weather, which +formed the basis for some of the most epochal discoveries in +meteorology, as we have seen. But this was only a beginning. The +simple rain-gauge pointed the way to the most important +generalization of the nineteenth century in a field of science +with which, to the casual observer, it might seem to have no +alliance whatever. The wonderful theory of atoms, on which the +whole gigantic structure of modern chemistry is founded, was the +logical outgrowth, in the mind of John Dalton, of those early +studies in meteorology. + +The way it happened was this: From studying the rainfall, Dalton +turned naturally to the complementary process of evaporation. He +was soon led to believe that vapor exists, in the atmosphere as +an independent gas. But since two bodies cannot occupy the same +space at the same time, this implies that the various atmospheric +gases are really composed of discrete particles. These ultimate +particles are so small that we cannot see them--cannot, indeed, +more than vaguely imagine them--yet each particle of vapor, for +example, is just as much a portion of water as if it were a drop +out of the ocean, or, for that matter, the ocean itself. But, +again, water is a compound substance, for it may be separated, as +Cavendish has shown, into the two elementary substances hydrogen +and oxygen. Hence the atom of water must be composed of two +lesser atoms joined together. Imagine an atom of hydrogen and one +of oxygen. Unite them, and we have an atom of water; sever them, +and the water no longer exists; but whether united or separate +the atoms of hydrogen and of oxygen remain hydrogen and oxygen +and nothing else. Differently mixed together or united, atoms +produce different gross substances; but the elementary atoms +never change their chemical nature--their distinct personality. + +It was about the year 1803 that Dalton first gained a full grasp +of the conception of the chemical atom. At once he saw that the +hypothesis, if true, furnished a marvellous key to secrets of +matter hitherto insoluble--questions relating to the relative +proportions of the atoms themselves. It is known, for example, +that a certain bulk of hydrogen gas unites with a certain bulk of +oxygen gas to form water. If it be true that this combination +consists essentially of the union of atoms one with another (each +single atom of hydrogen united to a single atom of oxygen), then +the relative weights of the original masses of hydrogen and of +oxygen must be also the relative weights of each of their +respective atoms. If one pound of hydrogen unites with five and +one-half pounds of oxygen (as, according to Dalton's experiments, +it did), then the weight of the oxygen atom must be five and +one-half times that of the hydrogen atom. Other compounds may +plainly be tested in the same way. Dalton made numerous tests +before he published his theory. He found that hydrogen enters +into compounds in smaller proportions than any other element +known to him, and so, for convenience, determined to take the +weight of the hydrogen atom as unity. The atomic weight of +oxygen then becomes (as given in Dalton's first table of 1803) +5.5; that of water (hydrogen plus oxygen) being of course 6.5. +The atomic weights of about a score of substances are given in +Dalton's first paper, which was read before the Literary and +Philosophical Society of Manchester, October 21, 1803. I wonder +if Dalton himself, great and acute intellect though he had, +suspected, when he read that paper, that he was inaugurating one +of the most fertile movements ever entered on in the whole +history of science? + +Be that as it may, it is certain enough that Dalton's +contemporaries were at first little impressed with the novel +atomic theory. Just at this time, as it chanced, a dispute was +waging in the field of chemistry regarding a matter of empirical +fact which must necessarily be settled before such a theory as +that of Dalton could even hope for a bearing. This was the +question whether or not chemical elements unite with one another +always in definite proportions. Berthollet, the great co-worker +with Lavoisier, and now the most authoritative of living +chemists, contended that substances combine in almost +indefinitely graded proportions between fixed extremes. He held +that solution is really a form of chemical combination--a +position which, if accepted, left no room for argument. + +But this contention of the master was most actively disputed, in +particular by Louis Joseph Proust, and all chemists of repute +were obliged to take sides with one or the other. For a time the +authority of Berthollet held out against the facts, but at last +accumulated evidence told for Proust and his followers, and +towards the close of the first decade of our century it came to +be generally conceded that chemical elements combine with one +another in fixed and definite proportions. + +More than that. As the analysts were led to weigh carefully the +quantities of combining elements, it was observed that the +proportions are not only definite, but that they bear a very +curious relation to one another. If element A combines with two +different proportions of element B to form two compounds, it +appears that the weight of the larger quantity of B is an exact +multiple of that of the smaller quantity. This curious relation +was noticed by Dr. Wollaston, one of the most accurate of +observers, and a little later it was confirmed by Johan Jakob +Berzelius, the great Swedish chemist, who was to be a dominating +influence in the chemical world for a generation to come. But +this combination of elements in numerical proportions was exactly +what Dalton had noticed as early as 1802, and what bad led him +directly to the atomic weights. So the confirmation of this +essential point by chemists of such authority gave the strongest +confirmation to the atomic theory. + +During these same years the rising authority of the French +chemical world, Joseph Louis Gay-Lussac, was conducting +experiments with gases, which he had undertaken at first in +conjunction with Humboldt, but which later on were conducted +independently. In 1809, the next year after the publication of +the first volume of Dalton's New System of Chemical Philosophy, +Gay-Lussac published the results of his observations, and among +other things brought out the remarkable fact that gases, under +the same conditions as to temperature and pressure, combine +always in definite numerical proportions as to volume. Exactly +two volumes of hydrogen, for example, combine with one volume of +oxygen to form water. Moreover, the resulting compound gas +always bears a simple relation to the combining volumes. In the +case just cited, the union of two volumes of hydrogen and one of +oxygen results in precisely two volumes of water vapor. + +Naturally enough, the champions of the atomic theory seized upon +these observations of Gay-Lussac as lending strong support to +their hypothesis--all of them, that is, but the curiously +self-reliant and self-sufficient author of the atomic theory +himself, who declined to accept the observations of the French +chemist as valid. Yet the observations of Gay-Lussac were +correct, as countless chemists since then have demonstrated anew, +and his theory of combination by volumes became one of the +foundation-stones of the atomic theory, despite the opposition of +the author of that theory. + +The true explanation of Gay-Lussac's law of combination by +volumes was thought out almost immediately by an Italian savant, +Amadeo, Avogadro, and expressed in terms of the atomic theory. +The fact must be, said Avogadro, that under similar physical +conditions every form of gas contains exactly the same number of +ultimate particles in a given volume. Each of these ultimate +physical particles may be composed of two or more atoms (as in +the case of water vapor), but such a compound atom conducts +itself as if it were a simple and indivisible atom, as regards +the amount of space that separates it from its fellows under +given conditions of pressure and temperature. The compound atom, +composed of two or more elementary atoms, Avogadro proposed to +distinguish, for purposes of convenience, by the name molecule. +It is to the molecule, considered as the unit of physical +structure, that Avogadro's law applies. + +This vastly important distinction between atoms and molecules, +implied in the law just expressed, was published in 1811. Four +years later, the famous French physicist Ampere outlined a +similar theory, and utilized the law in his mathematical +calculations. And with that the law of Avogadro dropped out of +sight for a full generation. Little suspecting that it was the +very key to the inner mysteries of the atoms for which they were +seeking, the chemists of the time cast it aside, and let it fade +from the memory of their science. + +This, however, was not strange, for of course the law of Avogadro +is based on the atomic theory, and in 1811 the atomic theory was +itself still being weighed in the balance. The law of multiple +proportions found general acceptance as an empirical fact; but +many of the leading lights of chemistry still looked askance at +Dalton's explanation of this law. Thus Wollaston, though from the +first he inclined to acceptance of the Daltonian view, cautiously +suggested that it would be well to use the non-committal word +"equivalent" instead of "atom"; and Davy, for a similar reason, +in his book of 1812, speaks only of "proportions," binding +himself to no theory as to what might be the nature of these +proportions. + +At least two great chemists of the time, however, adopted the +atomic view with less reservation. One of these was Thomas +Thomson, professor at Edinburgh, who, in 1807, had given an +outline of Dalton's theory in a widely circulated book, which +first brought the theory to the general attention of the chemical +world. The other and even more noted advocate of the atomic +theory was Johan Jakob Berzelius. This great Swedish chemist at +once set to work to put the atomic theory to such tests as might +be applied in the laboratory. He was an analyst of the utmost +skill, and for years be devoted himself to the determination of +the combining weights, "equivalents" or "proportions," of the +different elements. These determinations, in so far as they were +accurately made, were simple expressions of empirical facts, +independent of any theory; but gradually it became more and more +plain that these facts all harmonize with the atomic theory of +Dalton. So by common consent the proportionate combining weights +of the elements came to be known as atomic weights--the name +Dalton had given them from the first--and the tangible conception +of the chemical atom as a body of definite constitution and +weight gained steadily in favor. + +From the outset the idea had had the utmost tangibility in the +mind of Dalton. He had all along represented the different atoms +by geometrical symbols--as a circle for oxygen, a circle +enclosing a dot for hydrogen, and the like--and had represented +compounds by placing these symbols of the elements in +juxtaposition. Berzelius proposed to improve upon this method by +substituting for the geometrical symbol the initial of the Latin +name of the element represented--O for oxygen, H for hydrogen, +and so on--a numerical coefficient to follow the letter as an +indication of the number of atoms present in any given compound. +This simple system soon gained general acceptance, and with +slight modifications it is still universally employed. Every +school-boy now is aware that H2O is the chemical way of +expressing the union of two atoms of hydrogen with one of oxygen +to form a molecule of water. But such a formula would have had +no meaning for the wisest chemist before the day of Berzelius. + +The universal fame of the great Swedish authority served to give +general currency to his symbols and atomic weights, and the new +point of view thus developed led presently to two important +discoveries which removed the last lingering doubts as to the +validity of the atomic theory. In 1819 two French physicists, +Dulong and Petit, while experimenting with heat, discovered that +the specific heats of solids (that is to say, the amount of heat +required to raise the temperature of a given mass to a given +degree) vary inversely as their atomic weights. In the same year +Eilhard Mitscherlich, a German investigator, observed that +compounds having the same number of atoms to the molecule are +disposed to form the same angles of crystallization--a property +which he called isomorphism. + +Here, then, were two utterly novel and independent sets of +empirical facts which harmonize strangely with the supposition +that substances are composed of chemical atoms of a determinate +weight. This surely could not be coincidence--it tells of law. +And so as soon as the claims of Dulong and Petit and of +Mitscherlich had been substantiated by other observers, the laws +of the specific heat of atoms, and of isomorphism, took their +place as new levers of chemical science. With the aid of these +new tools an impregnable breastwork of facts was soon piled about +the atomic theory. And John Dalton, the author of that theory, +plain, provincial Quaker, working on to the end in +semi-retirement, became known to all the world and for all time +as a master of masters. + + +HUMPHRY DAVY AND ELECTRO-CHEMISTRY + +During those early years of the nineteenth century, when Dalton +was grinding away at chemical fact and theory in his obscure +Manchester laboratory, another Englishman held the attention of +the chemical world with a series of the most brilliant and widely +heralded researches. This was Humphry Davy, a young man who had +conic to London in 1801, at the instance of Count Rumford, to +assume the chair of chemical philosophy in the Royal Institution, +which the famous American had just founded. + +Here, under Davy's direction, the largest voltaic battery yet +constructed had been put in operation, and with its aid the +brilliant young experimenter was expected almost to perform +miracles. And indeed he scarcely disappointed the expectation, +for with the aid of his battery he transformed so familiar a +substance as common potash into a metal which was not only so +light that it floated on water, but possessed the seemingly +miraculous property of bursting into flames as soon as it came in +contact with that fire-quenching liquid. If this were not a +miracle, it had for the popular eye all the appearance of the +miraculous. + +What Davy really had done was to decompose the potash, which +hitherto had been supposed to be elementary, liberating its +oxygen, and thus isolating its metallic base, which he named +potassium. The same thing was done with soda, and the closely +similar metal sodium was discovered--metals of a unique type, +possessed of a strange avidity for oxygen, and capable of seizing +on it even when it is bound up in the molecules of water. +Considered as mere curiosities, these discoveries were +interesting, but aside from that they were of great theoretical +importance, because they showed the compound nature of some +familiar chemicals that had been regarded as elements. Several +other elementary earths met the same fate when subjected to the +electrical influence; the metals barium, calcium, and strontium +being thus discovered. Thereafter Davy always referred to the +supposed elementary substances (including oxygen, hydrogen, and +the rest) as "unde-compounded" bodies. These resist all present +efforts to decompose them, but how can one know what might not +happen were they subjected to an influence, perhaps some day to +be discovered, which exceeds the battery in power as the battery +exceeds the blowpipe? + +Another and even more important theoretical result that flowed +from Davy's experiments during this first decade of the century +was the proof that no elementary substances other than hydrogen +and oxygen are produced when pure water is decomposed by the +electric current. It was early noticed by Davy and others that +when a strong current is passed through water, alkalies appear at +one pole of the battery and acids at the other, and this though +the water used were absolutely pure. This seemingly told of the +creation of elements--a transmutation but one step removed from +the creation of matter itself--under the influence of the new +"force." It was one of Davy's greatest triumphs to prove, in the +series of experiments recorded in his famous Bakerian lecture of +1806, that the alleged creation of elements did not take place, +the substances found at the poles of the battery having been +dissolved from the walls of the vessels in which the water +experimented upon had been placed. Thus the same implement which +had served to give a certain philosophical warrant to the fading +dreams of alchemy banished those dreams peremptorily from the +domain of present science. + +"As early as 1800," writes Davy, "I had found that when separate +portions of distilled water, filling two glass tubes, connected +by moist bladders, or any moist animal or vegetable substances, +were submitted to the electrical action of the pile of Volta by +means of gold wires, a nitro-muriatic solution of gold appeared +in the tube containing the positive wire, or the wire +transmitting the electricity, and a solution of soda in the +opposite tube; but I soon ascertained that the muriatic acid owed +its existence to the animal or vegetable matters employed; for +when the same fibres of cotton were made use of in successive +experiments, and washed after every process in a weak solution of +nitric acid, the water in the apparatus containing them, though +acted on for a great length of time with a very strong power, at +last produced no effects upon nitrate of silver. + +"In cases when I had procured much soda, the glass at its point +of contact with the wire seemed considerably corroded; and I was +confirmed in my idea of referring the production of the alkali +principally to this source, by finding that no fixed saline +matter could be obtained by electrifying distilled water in a +single agate cup from two points of platina with the Voltaic +battery. + +"Mr. Sylvester, however, in a paper published in Mr. Nicholson's +journal for last August, states that though no fixed alkali or +muriatic acid appears when a single vessel is employed, yet that +they are both formed when two vessels are used. And to do away +with all objections with regard to vegetable substances or glass, +he conducted his process in a vessel made of baked tobacco-pipe +clay inserted in a crucible of platina. I have no doubt of the +correctness of his results; but the conclusion appears +objectionable. He conceives, that he obtained fixed alkali, +because the fluid after being heated and evaporated left a matter +that tinged turmeric brown, which would have happened had it been +lime, a substance that exists in considerable quantities in all +pipe-clay; and even allowing the presence of fixed alkali, the +materials employed for the manufacture of tobacco-pipes are not +at all such as to exclude the combinations of this substance. + +"I resumed the inquiry; I procured small cylindrical cups of +agate of the capacity of about one-quarter of a cubic inch each. +They were boiled for some hours in distilled water, and a piece +of very white and transparent amianthus that had been treated in +the same way was made then to connect together; they were filled +with distilled water and exposed by means of two platina wires to +a current of electricity, from one hundred and fifty pairs of +plates of copper and zinc four inches square, made active by +means of solution of alum. After forty-eight hours the process +was examined: Paper tinged with litmus plunged into the tube +containing the transmitting or positive wire was immediately +strongly reddened. Paper colored by turmeric introduced into the +other tube had its color much deepened; the acid matter gave a +very slight degree of turgidness to solution of nitrate of soda. +The fluid that affected turmeric retained this property after +being strongly boiled; and it appeared more vivid as the quantity +became reduced by evaporation; carbonate of ammonia was mixed +with it, and the whole dried and exposed to a strong heat; a +minute quantity of white matter remained, which, as far as my +examinations could go, had the properties of carbonate of soda. I +compared it with similar minute portions of the pure carbonates +of potash, and similar minute portions of the pure carbonates of +potash and soda. It was not so deliquescent as the former of +these bodies, and it formed a salt with nitric acid, which, like +nitrate of soda, soon attracted moisture from a damp atmosphere +and became fluid. + +"This result was unexpected, but it was far from convincing me +that the substances which were obtained were generated. In a +similar process with glass tubes, carried on under exactly the +same circumstances and for the same time, I obtained a quantity +of alkali which must have been more than twenty times greater, +but no traces of muriatic acid. There was much probability that +the agate contained some minute portion of saline matter, not +easily detected by chemical analysis, either in combination or +intimate cohesion in its pores. To determine this, I repeated +this a second, a third, and a fourth time. In the second +experiment turbidness was still produced by a solution of nitrate +of silver in the tube containing the acid, but it was less +distinct; in the third process it was barely perceptible; and in +the fourth process the two fluids remained perfectly clear after +the mixture. The quantity of alkaline matter diminished in every +operation; and in the last process, though the battery had been +kept in great activity for three days, the fluid possessed, in a +very slight degree, only the power of acting on paper tinged with +turmeric; but its alkaline property was very sensible to litmus +paper slightly reddened, which is a much more delicate test; and +after evaporation and the process by carbonate of ammonia, a +barely perceptible quantity of fixed alkali was still left. The +acid matter in the other tube was abundant; its taste was sour; +it smelled like water over which large quantities of nitrous gas +have been long kept; it did not effect solution of muriate of +barytes; and a drop of it placed upon a polished plate of silver +left, after evaporation, a black stain, precisely similar to that +produced by extremely diluted nitrous acid. + +"After these results I could no longer doubt that some saline +matter existing in the agate tubes had been the source of the +acid matter capable of precipitating nitrate of silver and much +of the alkali. Four additional repetitions of the process, +however, convinced me that there was likewise some other cause +for the presence of this last substance; for it continued to +appear to the last in quantities sufficiently distinguishable, +and apparently equal in every case. I had used every precaution, +I had included the tube in glass vessels out of the reach of the +circulating air; all the acting materials had been repeatedly +washed with distilled water; and no part of them in contact with +the fluid had been touched by the fingers. + +"The only substance that I could now conceive as furnishing the +fixed alkali was the water itself. This water appeared pure by +the tests of nitrate of silver and muriate of barytes; but potash +of soda, as is well known, rises in small quantities in rapid +distillation; and the New River water which I made use of +contains animal and vegetable impurities, which it was easy to +conceive might furnish neutral salts capable of being carried +over in vivid ebullition."[1] Further experiment proved the +correctness of this inference, and the last doubt as to the +origin of the puzzling chemical was dispelled. + +Though the presence of the alkalies and acids in the water was +explained, however, their respective migrations to the negative +and positive poles of the battery remained to be accounted for. +Davy's classical explanation assumed that different elements +differ among themselves as to their electrical properties, some +being positively, others negatively, electrified. Electricity +and "chemical affinity," he said, apparently are manifestations +of the same force, acting in the one case on masses, in the other +on particles. Electro-positive particles unite with +electro-negative particles to form chemical compounds, in virtue +of the familiar principle that opposite electricities attract one +another. When compounds are decomposed by the battery, this +mutual attraction is overcome by the stronger attraction of the +poles of the battery itself. + +This theory of binary composition of all chemical compounds, +through the union of electro-positive and electro-negative atoms +or molecules, was extended by Berzelius, and made the basis of +his famous system of theoretical chemistry. This theory held +that all inorganic compounds, however complex their composition, +are essentially composed of such binary combinations. For many +years this view enjoyed almost undisputed sway. It received what +seemed strong confirmation when Faraday showed the definite +connection between the amount of electricity employed and the +amount of decomposition produced in the so-called electrolyte. +But its claims were really much too comprehensive, as subsequent +discoveries proved. + + +ORGANIC CHEMISTRY AND THE IDEA OF THE MOLECULE + +When Berzelius first promulgated his binary theory he was careful +to restrict its unmodified application to the compounds of the +inorganic world. At that time, and for a long time thereafter, +it was supposed that substances of organic nature had some +properties that kept them aloof from the domain of inorganic +chemistry. It was little doubted that a so-called "vital force" +operated here, replacing or modifying the action of ordinary +"chemical affinity." It was, indeed, admitted that organic +compounds are composed of familiar elements--chiefly carbon, +oxygen, hydrogen, and nitrogen; but these elements were supposed +to be united in ways that could not be imitated in the domain of +the non-living. It was regarded almost as an axiom of chemistry +that no organic compound whatever could be put together from its +elements--synthesized--in the laboratory. To effect the synthesis +of even the simplest organic compound, it was thought that the +"vital force" must be in operation. + +Therefore a veritable sensation was created in the chemical world +when, in the year 1828, it was announced that the young German +chemist, Friedrich Wohler, formerly pupil of Berzelius, and +already known as a coming master, had actually synthesized the +well-known organic product urea in his laboratory at Sacrow. The +"exception which proves the rule" is something never heard of in +the domain of logical science. Natural law knows no exceptions. +So the synthesis of a single organic compound sufficed at a blow +to break down the chemical barrier which the imagination of the +fathers of the science had erected between animate and inanimate +nature. Thenceforth the philosophical chemist would regard the +plant and animal organisms as chemical laboratories in which +conditions are peculiarly favorable for building up complex +compounds of a few familiar elements, under the operation of +universal chemical laws. The chimera "vital force" could no +longer gain recognition in the domain of chemistry. + +Now a wave of interest in organic chemistry swept over the +chemical world, and soon the study of carbon compounds became as +much the fashion as electrochemistry had been in the, preceding +generation. + +Foremost among the workers who rendered this epoch of organic +chemistry memorable were Justus Liebig in Germany and Jean +Baptiste Andre Dumas in France, and their respective pupils, +Charles Frederic Gerhardt and Augustus Laurent. Wohler, too, +must be named in the same breath, as also must Louis Pasteur, +who, though somewhat younger than the others, came upon the scene +in time to take chief part in the most important of the +controversies that grew out of their labors. + +Several years earlier than this the way had been paved for the +study of organic substances by Gay-Lussac's discovery, made in +1815, that a certain compound of carbon and nitrogen, which he +named cyanogen, has a peculiar degree of stability which enables +it to retain its identity and enter into chemical relations after +the manner of a simple body. A year later Ampere discovered that +nitrogen and hydrogen, when combined in certain proportions to +form what he called ammonium, have the same property. Berzelius +had seized upon this discovery of the compound radical, as it was +called, because it seemed to lend aid to his dualistic theory. He +conceived the idea that all organic compounds are binary unions +of various compound radicals with an atom of oxygen, announcing +this theory in 1818. Ten years later, Liebig and Wohler undertook +a joint investigation which resulted in proving that compound +radicals are indeed very abundant among organic substances. Thus +the theory of Berzelius seemed to be substantiated, and organic +chemistry came to be defined as the chemistry of compound +radicals. + +But even in the day of its seeming triumph the dualistic theory +was destined to receive a rude shock. This came about through +the investigations of Dumas, who proved that in a certain organic +substance an atom of hydrogen may be removed and an atom of +chlorine substituted in its place without destroying the +integrity of the original compound--much as a child might +substitute one block for another in its play-house. Such a +substitution would be quite consistent with the dualistic theory, +were it not for the very essential fact that hydrogen is a +powerfully electro-positive element, while chlorine is as +strongly electro-negative. Hence the compound radical which +united successively with these two elements must itself be at one +time electro-positive, at another electro-negative--a seeming +inconsistency which threw the entire Berzelian theory into +disfavor. + +In its place there was elaborated, chiefly through the efforts of +Laurent and Gerhardt, a conception of the molecule as a unitary +structure, built up through the aggregation of various atoms, in +accordance with "elective affinities" whose nature is not yet +understood A doctrine of "nuclei" and a doctrine of "types" of +molecular structure were much exploited, and, like the doctrine +of compound radicals, became useful as aids to memory and guides +for the analyst, indicating some of the plans of molecular +construction, though by no means penetrating the mysteries of +chemical affinity. They are classifications rather than +explanations of chemical unions. But at least they served an +important purpose in giving definiteness to the idea of a +molecular structure built of atoms as the basis of all +substances. Now at last the word molecule came to have a distinct +meaning, as distinct from "atom," in the minds of the generality +of chemists, as it had had for Avogadro a third of a century +before. Avogadro's hypothesis that there are equal numbers of +these molecules in equal volumes of gases, under fixed +conditions, was revived by Gerhardt, and a little later, under +the championship of Cannizzaro, was exalted to the plane of a +fixed law. Thenceforth the conception of the molecule was to be +as dominant a thought in chemistry as the idea of the atom had +become in a previous epoch. + + +CHEMICAL AFFINITY + +Of course the atom itself was in no sense displaced, but +Avogadro's law soon made it plain that the atom had often usurped +territory that did not really belong to it. In many cases the +chemists had supposed themselves dealing with atoms as units +where the true unit was the molecule. In the case of elementary +gases, such as hydrogen and oxygen, for example, the law of equal +numbers of molecules in equal spaces made it clear that the atoms +do not exist isolated, as had been supposed. Since two volumes +of hydrogen unite with one volume of oxygen to form two volumes +of water vapor, the simplest mathematics show, in the light of +Avogadro's law, not only that each molecule of water must contain +two hydrogen atoms (a point previously in dispute), but that the +original molecules of hydrogen and oxygen must have been composed +in each case of two atoms---else how could one volume of oxygen +supply an atom for every molecule of two volumes of water? + +What, then, does this imply? Why, that the elementary atom has +an avidity for other atoms, a longing for companionship, an +"affinity"--call it what you will--which is bound to be satisfied +if other atoms are in the neighborhood. Placed solely among +atoms of its own kind, the oxygen atom seizes on a fellow oxygen +atom, and in all their mad dancings these two mates cling +together--possibly revolving about each other in miniature +planetary orbits. Precisely the same thing occurs among the +hydrogen atoms. But now suppose the various pairs of oxygen atoms +come near other pairs of hydrogen atoms (under proper conditions +which need not detain us here), then each oxygen atom loses its +attachment for its fellow, and flings itself madly into the +circuit of one of the hydrogen couplets, and--presto!--there are +only two molecules for every three there were before, and free +oxygen and hydrogen have become water. The whole process, stated +in chemical phraseology, is summed up in the statement that under +the given conditions the oxygen atoms had a greater affinity for +the hydrogen atoms than for one another. + +As chemists studied the actions of various kinds of atoms, in +regard to their unions with one another to form molecules, it +gradually dawned upon them that not all elements are satisfied +with the same number of companions. Some elements ask only one, +and refuse to take more; while others link themselves, when +occasion offers, with two, three, four, or more. Thus we saw that +oxygen forsook a single atom of its own kind and linked itself +with two atoms of hydrogen. Clearly, then, the oxygen atom, like +a creature with two hands, is able to clutch two other atoms. +But we have no proof that under any circumstances it could hold +more than two. Its affinities seem satisfied when it has two +bonds. But, on the other hand, the atom of nitrogen is able to +hold three atoms of hydrogen, and does so in the molecule of +ammonium (NH3); while the carbon atom can hold four atoms of +hydrogen or two atoms of oxygen. + +Evidently, then, one atom is not always equivalent to another +atom of a different kind in combining powers. A recognition of +this fact by Frankland about 1852, and its further investigation +by others (notably A. Kekule and A. S. Couper), led to the +introduction of the word equivalent into chemical terminology in +a new sense, and in particular to an understanding of the +affinities or "valency" of different elements, which proved of +the most fundamental importance. Thus it was shown that, of the +four elements that enter most prominently into organic compounds, +hydrogen can link itself with only a single bond to any other +element--it has, so to speak, but a single hand with which to +grasp--while oxygen has capacity for two bonds, nitrogen for +three (possibly for five), and carbon for four. The words +monovalent, divalent, trivalent, tretrava-lent, etc., were coined +to express this most important fact, and the various elements +came to be known as monads, diads, triads, etc. Just why +different elements should differ thus in valency no one as yet +knows; it is an empirical fact that they do. And once the nature +of any element has been determined as regards its valency, a most +important insight into the possible behavior of that element has +been secured. Thus a consideration of the fact that hydrogen is +monovalent, while oxygen is divalent, makes it plain that we must +expect to find no more than three compounds of these two +elements--namely, H--O--(written HO by the chemist, and called +hydroxyl); H--O--H (H2O, or water), and H--O--O--H (H2O2, or +hydrogen peroxide). It will be observed that in the first of +these compounds the atom of oxygen stands, so to speak, with one +of its hands free, eagerly reaching out, therefore, for another +companion, and hence, in the language of chemistry, forming an +unstable compound. Again, in the third compound, though all hands +are clasped, yet one pair links oxygen with oxygen; and this also +must be an unstable union, since the avidity of an atom for its +own kind is relatively weak. Thus the well-known properties of +hydrogen peroxide are explained, its easy decomposition, and the +eagerness with which it seizes upon the elements of other +compounds. + +But the molecule of water, on the other hand, has its atoms +arranged in a state of stable equilibrium, all their affinities +being satisfied. Each hydrogen atom has satisfied its own +affinity by clutching the oxygen atom; and the oxygen atom has +both its bonds satisfied by clutching back at the two hydrogen +atoms. Therefore the trio, linked in this close bond, have no +tendency to reach out for any other companion, nor, indeed, any +power to hold another should it thrust itself upon them. They +form a "stable" compound, which under all ordinary circumstances +will retain its identity as a molecule of water, even though the +physical mass of which it is a part changes its condition from a +solid to a gas from ice to vapor. + +But a consideration of this condition of stable equilibrium in +the molecule at once suggests a new question: How can an +aggregation of atoms, having all their affinities satisfied, take +any further part in chemical reactions? Seemingly such a +molecule, whatever its physical properties, must be chemically +inert, incapable of any atomic readjustments. And so in point of +fact it is, so long as its component atoms cling to one another +unremittingly. But this, it appears, is precisely what the atoms +are little prone to do. It seems that they are fickle to the last +degree in their individual attachments, and are as prone to break +away from bondage as they are to enter into it. Thus the oxygen +atom which has just flung itself into the circuit of two hydrogen +atoms, the next moment flings itself free again and seeks new +companions. It is for all the world like the incessant change of +partners in a rollicking dance. This incessant dissolution and +reformation of molecules in a substance which as a whole remains +apparently unchanged was first fully appreciated by Ste.-Claire +Deville, and by him named dissociation. It is a process which +goes on much more actively in some compounds than in others, and +very much more actively under some physical conditions (such as +increase of temperature) than under others. But apparently no +substances at ordinary temperatures, and no temperature above the +absolute zero, are absolutely free from its disturbing influence. +Hence it is that molecules having all the valency of their atoms +fully satisfied do not lose their chemical activity--since each +atom is momentarily free in the exchange of partners, and may +seize upon different atoms from its former partners, if those it +prefers are at hand. + +While, however, an appreciation of this ceaseless activity of the +atom is essential to a proper understanding of its chemical +efficiency, yet from another point of view the "saturated" +molecule--that is, the molecule whose atoms have their valency +all satisfied--may be thought of as a relatively fixed or stable +organism. Even though it may presently be torn down, it is for +the time being a completed structure; and a consideration of the +valency of its atoms gives the best clew that has hitherto been +obtainable as to the character of its architecture. How +important this matter of architecture of the molecule--of space +relations of the atoms--may be was demonstrated as long ago as +1823, when Liebig and Wohler proved, to the utter bewilderment of +the chemical world, that two substances may have precisely the +same chemical constitution--the same number and kind of +atoms--and yet differ utterly in physical properties. The word +isomerism was coined by Berzelius to express this anomalous +condition of things, which seemed to negative the most +fundamental truths of chemistry. Naming the condition by no +means explained it, but the fact was made clear that something +besides the mere number and kind of atoms is important in the +architecture of a molecule. It became certain that atoms are not +thrown together haphazard to build a molecule, any more than +bricks are thrown together at random to form a house. + +How delicate may be the gradations of architectural design in +building a molecule was well illustrated about 1850, when Pasteur +discovered that some carbon compounds--as certain sugars--can +only be distinguished from one another, when in solution, by the +fact of their twisting or polarizing a ray of light to the left +or to the right, respectively. But no inkling of an explanation +of these strange variations of molecular structure came until the +discovery of the law of valency. Then much of the mystery was +cleared away; for it was plain that since each atom in a molecule +can hold to itself only a fixed number of other atoms, complex +molecules must have their atoms linked in definite chains or +groups. And it is equally plain that where the atoms are +numerous, the exact plan of grouping may sometimes be susceptible +of change without doing violence to the law of valency. It is in +such cases that isomerism is observed to occur. + +By paying constant heed to this matter of the affinities, +chemists are able to make diagrammatic pictures of the plan of +architecture of any molecule whose composition is known. In the +simple molecule of water (H2O), for example, the two hydrogen +atoms must have released each other before they could join the +oxygen, and the manner of linking must apparently be that +represented in the graphic formula H--O--H. With molecules +composed of a large number of atoms, such graphic representation +of the scheme of linking is of course increasingly difficult, +yet, with the affinities for a guide, it is always possible. Of +course no one supposes that such a formula, written in a single +plane, can possibly represent the true architecture of the +molecule: it is at best suggestive or diagrammatic rather than +pictorial. Nevertheless, it affords hints as to the structure of +the molecule such as the fathers of chemistry would not have +thought it possible ever to attain. + + +PERIODICITY OF ATOMIC WEIGHTS + +These utterly novel studies of molecular architecture may seem at +first sight to take from the atom much of its former prestige as +the all-important personage of the chemical world. Since so much +depends upon the mere position of the atoms, it may appear that +comparatively little depends upon the nature of the atoms +themselves. But such a view is incorrect, for on closer +consideration it will appear that at no time has the atom been +seen to renounce its peculiar personality. Within certain limits +the character of a molecule may be altered by changing the +positions of its atoms (just as different buildings may be +constructed of the same bricks), but these limits are sharply +defined, and it would be as impossible to exceed them as it would +be to build a stone building with bricks. From first to last the +brick remains a brick, whatever the style of architecture it +helps to construct; it never becomes a stone. And just as closely +does each atom retain its own peculiar properties, regardless of +its surroundings. + +Thus, for example, the carbon atom may take part in the formation +at one time of a diamond, again of a piece of coal, and yet again +of a particle of sugar, of wood fibre, of animal tissue, or of a +gas in the atmosphere; but from first to last--from glass-cutting +gem to intangible gas--there is no demonstrable change whatever +in any single property of the atom itself. So far as we know, its +size, its weight, its capacity for vibration or rotation, and its +inherent affinities, remain absolutely unchanged throughout all +these varying fortunes of position and association. And the same +thing is true of every atom of all of the seventy-odd elementary +substances with which the modern chemist is acquainted. Every one +appears always to maintain its unique integrity, gaining nothing +and losing nothing. + +All this being true, it would seem as if the position of the +Daltonian atom as a primordial bit of matter, indestructible and +non-transmutable, had been put to the test by the chemistry of +our century, and not found wanting. Since those early days of the +century when the electric battery performed its miracles and +seemingly reached its limitations in the hands of Davy, many new +elementary substances have been discovered, but no single element +has been displaced from its position as an undecomposable body. +Rather have the analyses of the chemist seemed to make it more +and more certain that all elementary atoms are in truth what John +Herschel called them, "manufactured articles"--primordial, +changeless, indestructible. + +And yet, oddly enough, it has chanced that hand in hand with the +experiments leading to such a goal have gone other experiments +arid speculations of exactly the opposite tenor. In each +generation there have been chemists among the leaders of their +science who have refused to admit that the so-called elements are +really elements at all in any final sense, and who have sought +eagerly for proof which might warrant their scepticism. The first +bit of evidence tending to support this view was furnished by an +English physician, Dr. William Prout, who in 1815 called +attention to a curious relation to be observed between the atomic +weight of the various elements. Accepting the figures given by +the authorities of the time (notably Thomson and Berzelius), it +appeared that a strikingly large proportion of the atomic weights +were exact multiples of the weight of hydrogen, and that others +differed so slightly that errors of observation might explain the +discrepancy. Prout felt that it could not be accidental, and he +could think of no tenable explanation, unless it be that the +atoms of the various alleged elements are made up of different +fixed numbers of hydrogen atoms. Could it be that the one true +element--the one primal matter--is hydrogen, and that all other +forms of matter are but compounds of this original substance? + +Prout advanced this startling idea at first tentatively, in an +anonymous publication; but afterwards he espoused it openly and +urged its tenability. Coming just after Davy's dissociation of +some supposed elements, the idea proved alluring, and for a time +gained such popularity that chemists were disposed to round out +the observed atomic weights of all elements into whole numbers. +But presently renewed determinations of the atomic weights seemed +to discountenance this practice, and Prout's alleged law fell +into disrepute. It was revived, however, about 1840, by Dumas, +whose great authority secured it a respectful hearing, and whose +careful redetermination of the weight of carbon, making it +exactly twelve times that of hydrogen, aided the cause. + +Subsequently Stas, the pupil of Dumas, undertook a long series of +determinations of atomic weights, with the expectation of +confirming the Proutian hypothesis. But his results seemed to +disprove the hypothesis, for the atomic weights of many elements +differed from whole numbers by more, it was thought, than the +limits of error of the experiments. It was noteworthy, however, +that the confidence of Dumas was not shaken, though he was led to +modify the hypothesis, and, in accordance with previous +suggestions of Clark and of Marignac, to recognize as the +primordial element, not hydrogen itself, but an atom half the +weight, or even one-fourth the weight, of that of hydrogen, of +which primordial atom the hydrogen atom itself is compounded. But +even in this modified form the hypothesis found great opposition +from experimental observers. + +In 1864, however, a novel relation between the weights of the +elements and their other characteristics was called to the +attention of chemists by Professor John A. R. Newlands, of +London, who had noticed that if the elements are arranged +serially in the numerical order of their atomic weights, there is +a curious recurrence of similar properties at intervals of eight +elements This so-called "law of octaves" attracted little +immediate attention, but the facts it connotes soon came under +the observation of other chemists, notably of Professors Gustav +Hinrichs in America, Dmitri Mendeleeff in Russia, and Lothar +Meyer in Germany. Mendeleeff gave the discovery fullest +expression, explicating it in 1869, under the title of "the +periodic law." + +Though this early exposition of what has since been admitted to +be a most important discovery was very fully outlined, the +generality of chemists gave it little heed till a decade or so +later, when three new elements, gallium, scandium, and germanium, +were discovered, which, on being analyzed, were quite +unexpectedly found to fit into three gaps which Mendeleeff had +left in his periodic scale. In effect the periodic law had +enabled Mendeleeff to predicate the existence of the new elements +years before they were discovered. Surely a system that leads to +such results is no mere vagary. So very soon the periodic law +took its place as one of the most important generalizations of +chemical science. + +This law of periodicity was put forward as an expression of +observed relations independent of hypothesis; but of course the +theoretical bearings of these facts could not be overlooked. As +Professor J. H. Gladstone has said, it forces upon us "the +conviction that the elements are not separate bodies created +without reference to one another, but that they have been +originally fashioned, or have been built up, from one another, +according to some general plan." It is but a short step from +that proposition to the Proutian hypothesis. + + +NEW WEAPONS--SPECTROSCOPE AND CAMERA + +But the atomic weights are not alone in suggesting the compound +nature of the alleged elements. Evidence of a totally different +kind has contributed to the same end, from a source that could +hardly have been imagined when the Proutian hypothesis, was +formulated, through the tradition of a novel weapon to the +armamentarium of the chemist--the spectroscope. The perfection +of this instrument, in the hands of two German scientists, Gustav +Robert Kirchhoff and Robert Wilhelm Bunsen, came about through +the investigation, towards the middle of the century, of the +meaning of the dark lines which had been observed in the solar +spectrum by Fraunhofer as early as 1815, and by Wollaston a +decade earlier. It was suspected by Stokes and by Fox Talbot in +England, but first brought to demonstration by Kirchhoff and +Bunsen, that these lines, which were known to occupy definite +positions in the spectrum, are really indicative of particular +elementary substances. By means of the spectroscope, which is +essentially a magnifying lens attached to a prism of glass, it is +possible to locate the lines with great accuracy, and it was soon +shown that here was a new means of chemical analysis of the most +exquisite delicacy. It was found, for example, that the +spectroscope could detect the presence of a quantity of sodium so +infinitesimal as the one two-hundred-thousandth of a grain. But +what was even more important, the spectroscope put no limit upon +the distance of location of the substance it tested, provided +only that sufficient light came from it. The experiments it +recorded might be performed in the sun, or in the most distant +stars or nebulae; indeed, one of the earliest feats of the +instrument was to wrench from the sun the secret of his chemical +constitution. + +To render the utility of the spectroscope complete, however, it +was necessary to link with it another new chemical +agency--namely, photography. This now familiar process is based +on the property of light to decompose certain unstable compounds +of silver, and thus alter their chemical composition. Davy and +Wedgwood barely escaped the discovery of the value of the +photographic method early in the nineteenth century. Their +successors quite overlooked it until about 1826, when Louis J. M. +Daguerre, the French chemist, took the matter in hand, and after +many years of experimentation brought it to relative perfection +in 1839, in which year the famous daguerreotype first brought the +matter to popular attention. In the same year Mr. Fox Talbot read +a paper on the subject before the Royal Society, and soon +afterwards the efforts of Herschel and numerous other natural +philosophers contributed to the advancement of the new method. + +In 1843 Dr. John W. Draper, the famous English-American chemist +and physiologist, showed that by photography the Fraunhofer lines +in the solar spectrum might be mapped with absolute accuracy; +also proving that the silvered film revealed many lines invisible +to the unaided eye. The value of this method of observation was +recognized at once, and, as soon as the spectroscope was +perfected, the photographic method, in conjunction with its use, +became invaluable to the chemist. By this means comparisons of +spectra may be made with a degree of accuracy not otherwise +obtainable; and, in case of the stars, whole clusters of spectra +may be placed on record at a single observation. + +As the examination of the sun and stars proceeded, chemists were +amazed or delighted, according to their various preconceptions, +to witness the proof that many familiar terrestrial elements are +to be found in the celestial bodies. But what perhaps surprised +them most was to observe the enormous preponderance in the +sidereal bodies of the element hydrogen. Not only are there vast +quantities of this element in the sun's atmosphere, but some +other suns appeared to show hydrogen lines almost exclusively in +their spectra. Presently it appeared that the stars of which +this is true are those white stars, such as Sirius, which had +been conjectured to be the hottest; whereas stars that are only +red-hot, like our sun, show also the vapors of many other +elements, including iron and other metals. + +In 1878 Professor J. Norman Lockyer, in a paper before the Royal +Society, called attention to the possible significance of this +series of observations. He urged that the fact of the sun showing +fewer elements than are observed here on the cool earth, while +stars much hotter than the sun show chiefly one element, and that +one hydrogen, the lightest of known elements, seemed to give +color to the possibility that our alleged elements are really +compounds, which at the temperature of the hottest stars may be +decomposed into hydrogen, the latter "element" itself being also +doubtless a compound, which might be resolved under yet more +trying conditions. + +Here, then, was what might be termed direct experimental evidence +for the hypothesis of Prout. Unfortunately, however, it is +evidence of a kind which only a few experts are competent to +discuss--so very delicate a matter is the spectral analysis of +the stars. What is still more unfortunate, the experts do not +agree among themselves as to the validity of Professor Lockyer's +conclusions. Some, like Professor Crookes, have accepted them +with acclaim, hailing Lockyer as "the Darwin of the inorganic +world," while others have sought a different explanation of the +facts he brings forward. As yet it cannot be said that the +controversy has been brought to final settlement. Still, it is +hardly to be doubted that now, since the periodic law has seemed +to join hands with the spectroscope, a belief in the compound +nature of the so-called elements is rapidly gaining ground among +chemists. More and more general becomes the belief that the +Daltonian atom is really a compound radical, and that back of the +seeming diversity of the alleged elements is a single form of +primordial matter. Indeed, in very recent months, direct +experimental evidence for this view has at last come to hand, +through the study of radio-active substances. In a later chapter +we shall have occasion to inquire how this came about. + + + +IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH CENTURY + +ALBRECHT VON HALLER + +An epoch in physiology was made in the eighteenth century by the +genius and efforts of Albrecht von Haller (1708-1777), of Berne, +who is perhaps as worthy of the title "The Great" as any +philosopher who has been so christened by his contemporaries +since the time of Hippocrates. Celebrated as a physician, he was +proficient in various fields, being equally famed in his own time +as poet, botanist, and statesman, and dividing his attention +between art and science. + +As a child Haller was so sickly that he was unable to amuse +himself with the sports and games common to boys of his age, and +so passed most of his time poring over books. When ten years of +age he began writing poems in Latin and German, and at fifteen +entered the University of Tubingen. At seventeen he wrote +learned articles in opposition to certain accepted doctrines, and +at nineteen he received his degree of doctor. Soon after this he +visited England, where his zeal in dissecting brought him under +suspicion of grave-robbery, which suspicion made it expedient for +him to return to the Continent. After studying botany in Basel +for some time he made an extended botanical journey through +Switzerland, finally settling in his native city, Berne, as a +practising physician. During this time he did not neglect either +poetry or botany, publishing anonymously a collection of poems. + +In 1736 he was called to Gottingen as professor of anatomy, +surgery, chemistry, and botany. During his labors in the +university he never neglected his literary work, sometimes living +and sleeping for days and nights together in his library, eating +his meals while delving in his books, and sleeping only when +actually compelled to do so by fatigue. During all this time he +was in correspondence with savants from all over the world, and +it is said of him that he never left a letter of any kind +unanswered. + +Haller's greatest contribution to medical science was his famous +doctrine of irritability, which has given him the name of "father +of modern nervous physiology," just as Harvey is called "the +father of the modern physiology of the blood." It has been said +of this famous doctrine of irritability that "it moved all the +minds of the century--and not in the departments of medicine +alone--in a way of which we of the present day have no +satisfactory conception, unless we compare it with our modern +Darwinism."[1] + +The principle of general irritability had been laid down by +Francis Glisson (1597-1677) from deductive studies, but Haller +proved by experiments along the line of inductive methods that +this irritability was not common to all "fibre as well as to the +fluids of the body," but something entirely special, and peculiar +only to muscular substance. He distinguished between irritability +of muscles and sensibility of nerves. In 1747 he gave as the +three forces that produce muscular movements: elasticity, or +"dead nervous force"; irritability, or "innate nervous force"; +and nervous force in itself. And in 1752 he described one +hundred and ninety experiments for determining what parts of the +body possess "irritability"--that is, the property of contracting +when stimulated. His conclusion that this irritability exists in +muscular substance alone and is quite independent of the nerves +proceeding to it aroused a controversy that was never definitely +settled until late in the nineteenth century, when Haller's +theory was found to be entirely correct. + +It was in pursuit of experiments to establish his theory of +irritability that Haller made his chief discoveries in embryology +and development. He proved that in the process of incubation of +the egg the first trace of the heart of the chick shows itself in +the thirty-eighth hour, and that the first trace of red blood +showed in the forty-first hour. By his investigations upon the +lower animals he attempted to confirm the theory that since the +creation of genus every individual is derived from a preceding +individual--the existing theory of preformation, in which he +believed, and which taught that "every individual is fully and +completely preformed in the germ, simply growing from microscopic +to visible proportions, without developing any new parts." + +In physiology, besides his studies of the nervous system, Haller +studied the mechanism of respiration, refuting the teachings of +Hamberger (1697-1755), who maintained that the lungs contract +independently. Haller, however, in common with his +contemporaries, failed utterly to understand the true function of +the lungs. The great physiologist's influence upon practical +medicine, while most profound, was largely indirect. He was a +theoretical rather than a practical physician, yet he is credited +with being the first physician to use the watch in counting the +pulse. + + +BATTISTA MORGAGNI AND MORBID ANATOMY + +A great contemporary of Haller was Giovanni Battista Morgagni +(1682-1771), who pursued what Sydenham had neglected, the +investigation in anatomy, thus supplying a necessary counterpart +to the great Englishman's work. Morgagni's investigations were +directed chiefly to the study of morbid anatomy--the study of the +structure of diseased tissue, both during life and post mortem, +in contrast to the normal anatomical structures. This work cannot +be said to have originated with him; for as early as 1679 Bonnet +had made similar, although less extensive, studies; and later +many investigators, such as Lancisi and Haller, had made +post-mortem studies. But Morgagni's De sedibus et causis +morborum per anatomen indagatis was the largest, most accurate, +and best-illustrated collection of cases that had ever been +brought together, and marks an epoch in medical science. From the +time of the publication of Morgagni's researches, morbid anatomy +became a recognized branch of the medical science, and the effect +of the impetus thus given it has been steadily increasing since +that time. + + +WILLIAM HUNTER + +William Hunter (1718-1783) must always be remembered as one of +the greatest physicians and anatomists of the eighteenth century, +and particularly as the first great teacher of anatomy in +England; but his fame has been somewhat overshadowed by that of +his younger brother John. + +Hunter had been intended and educated for the Church, but on the +advice of the surgeon William Cullen he turned his attention to +the study of medicine. His first attempt at teaching was in 1746, +when he delivered a series of lectures on surgery for the Society +of Naval Practitioners. These lectures proved so interesting and +instructive that he was at once invited to give others, and his +reputation as a lecturer was soon established. He was a natural +orator and story-teller, and he combined with these attractive +qualities that of thoroughness and clearness in demonstrations, +and although his lectures were two hours long he made them so +full of interest that his pupils seldom tired of listening. He +believed that he could do greater good to the world by "publicly +teaching his art than by practising it," and even during the last +few days of his life, when he was so weak that his friends +remonstrated against it, he continued his teaching, fainting from +exhaustion at the end of his last lecture, which preceded his +death by only a few days. + +For many years it was Hunter's ambition to establish a museum +where the study of anatomy, surgery, and medicine might be +advanced, and in 1765 he asked for a grant of a plot of ground +for this purpose, offering to spend seven thousand pounds on its, +erection besides endowing it with a professorship of anatomy. Not +being able to obtain this grant, however, he built a house, in +which were lecture and dissecting rooms, and his museum. In this +museum were anatomical preparations, coins, minerals, and +natural-history specimens. + +Hunter's weakness was his love of controversy and his resentment +of contradiction. This brought him into strained relations with +many of the leading physicians of his time, notably his own +brother John, who himself was probably not entirely free from +blame in the matter. Hunter is said to have excused his own +irritability on the grounds that being an anatomist, and +accustomed to "the passive submission of dead bodies," +contradictions became the more unbearable. Many of the +physiological researches begun by him were carried on and +perfected by his more famous brother, particularly his +investigations of the capillaries, but he added much to the +anatomical knowledge of several structures of the body, notably +as to the structure of cartilages and joints. + + +JOHN HUNTER + +In Abbot Islip's chapel in Westminster Abbey, close to the +resting-place of Ben Jonson, rest the remains of John Hunter +(1728-1793), famous in the annals of medicine as among the +greatest physiologists and surgeons that the world has ever +produced: a man whose discoveries and inventions are counted by +scores, and whose field of research was only limited by the +outermost boundaries of eighteenth-century science, although his +efforts were directed chiefly along the lines of his profession. + +Until about twenty years of age young Hunter had shown little +aptitude for study, being unusually fond of out-door sports and +amusements; but about that time, realizing that some occupation +must be selected, he asked permission of his brother William to +attempt some dissections in his anatomical school in London. To +the surprise of his brother he made this dissection unusually +well; and being given a second, he acquitted himself with such +skill that his brother at once predicted that he would become a +great anatomist. Up to this time he had had no training of any +kind to prepare him for his professional career, and knew little +of Greek or Latin--languages entirely unnecessary for him, as he +proved in all of his life work. Ottley tells the story that, +when twitted with this lack of knowledge of the "dead languages" +in after life, he said of his opponent, "I could teach him that +on the dead body which he never knew in any language, dead or +living." + +By his second year in dissection he had become so skilful that he +was given charge of some of the classes in his brother's school; +in 1754 he became a surgeon's pupil in St. George's Hospital, and +two years later house-surgeon. Having by overwork brought on +symptoms that seemed to threaten consumption, he accepted the +position of staff-surgeon to an expedition to Belleisle in 1760, +and two years later was serving with the English army at +Portugal. During all this time he was constantly engaged in +scientific researches, many of which, such as his observations of +gun-shot wounds, he put to excellent use in later life. On +returning to England much improved in health in 1763, he entered +at once upon his career as a London surgeon, and from that time +forward his progress was a practically uninterrupted series of +successes in his profession. + +Hunter's work on the study of the lymphatics was of great service +to the medical profession. This important net-work of minute +vessels distributed throughout the body had recently been made +the object of much study, and various students, including Haller, +had made extensive investigations since their discovery by +Asellius. But Hunter, in 1758, was the first to discover the +lymphatics in the neck of birds, although it was his brother +William who advanced the theory that the function of these +vessels was that of absorbents. One of John Hunter's pupils, +William Hewson (1739-1774), first gave an account, in 1768, of +the lymphatics in reptiles and fishes, and added to his teacher's +investigations of the lymphatics in birds. These studies of the +lymphatics have been regarded, perhaps with justice, as Hunter's +most valuable contributions to practical medicine. + +In 1767 he met with an accident by which he suffered a rupture of +the tendo Achillis--the large tendon that forms the attachment of +the muscles of the calf to the heel. From observations of this +accident, and subsequent experiments upon dogs, he laid the +foundation for the now simple and effective operation for the +cure of club feet and other deformities involving the tendons. +In 1772 he moved into his residence at Earlscourt, Brompton, +where he gathered about him a great menagerie of animals, birds, +reptiles, insects, and fishes, which he used in his physiological +and surgical experiments. Here he performed a countless number of +experiments--more, probably, than "any man engaged in +professional practice has ever conducted." These experiments +varied in nature from observations of the habits of bees and +wasps to major surgical operations performed upon hedgehogs, +dogs, leopards, etc. It is said that for fifteen years he kept a +flock of geese for the sole purpose of studying the process of +development in eggs. + +Hunter began his first course of lectures in 1772, being forced +to do this because he had been so repeatedly misquoted, and +because he felt that he could better gauge his own knowledge in +this way. Lecturing was a sore trial to him, as he was extremely +diffident, and without writing out his lectures in advance he was +scarcely able to speak at all. In this he presented a marked +contrast to his brother William, who was a fluent and brilliant +speaker. Hunter's lectures were at best simple readings of the +facts as he had written them, the diffident teacher seldom +raising his eyes from his manuscript and rarely stopping until +his complete lecture had been read through. His lectures were, +therefore, instructive rather than interesting, as he used +infinite care in preparing them; but appearing before his classes +was so dreaded by him that he is said to have been in the habit +of taking a half-drachm of laudanum before each lecture to nerve +him for the ordeal. One is led to wonder by what name he shall +designate that quality of mind that renders a bold and fearless +surgeon like Hunter, who is undaunted in the face of hazardous +and dangerous operations, a stumbling, halting, and "frightened" +speaker before a little band of, at most, thirty young medical +students. And yet this same thing is not unfrequently seen among +the boldest surgeons. + + +Hunter's Operation for the Cure of Aneurisms + +It should be an object-lesson to those who, ignorantly or +otherwise, preach against the painless vivisection as practised +to-day, that by the sacrifice of a single deer in the cause of +science Hunter discovered a fact in physiology that has been the +means of saving thousands of human lives and thousands of human +bodies from needless mutilation. We refer to the discovery of the +"collateral circulation" of the blood, which led, among other +things, to Hunter's successful operation upon aneurisms. + +Simply stated, every organ or muscle of the body is supplied by +one large artery, whose main trunk distributes the blood into its +lesser branches, and thence through the capillaries. Cutting off +this main artery, it would seem, should cut off entirely the +blood-supply to the particular organ which is supplied by this +vessel; and until the time of Hunter's demonstration this belief +was held by most physiologists. But nature has made a provision +for this possible stoppage of blood-supply from a single source, +and has so arranged that some of the small arterial branches +coming from the main supply-trunk are connected with other +arterial branches coming from some other supply-trunk. Under +normal conditions the main arterial trunks supply their +respective organs, the little connecting arterioles playing an +insignificant part. But let the main supply-trunk be cut off or +stopped for whatever reason, and a remarkable thing takes place. +The little connecting branches begin at once to enlarge and draw +blood from the neighboring uninjured supply-trunk, This +enlargement continues until at last a new route for the +circulation has been established, the organ no longer depending +on the now defunct original arterial trunk, but getting on as +well as before by this "collateral" circulation that has been +established. + +The thorough understanding of this collateral circulation is one +of the most important steps in surgery, for until it was +discovered amputations were thought necessary in such cases as +those involving the artery supplying a leg or arm, since it was +supposed that, the artery being stopped, death of the limb and +the subsequent necessity for amputation were sure to follow. +Hunter solved this problem by a single operation upon a deer, and +his practicality as a surgeon led him soon after to apply this +knowledge to a certain class of surgical cases in a most +revolutionary and satisfactory manner. + +What led to Hunter's far-reaching discovery was his investigation +as to the cause of the growth of the antlers of the deer. Wishing +to ascertain just what part the blood-supply on the opposite +sides of the neck played in the process of development, or, +perhaps more correctly, to see what effect cutting off the main +blood-supply would have, Hunter had one of the deer of Richmond +Park caught and tied, while he placed a ligature around one of +the carotid arteries--one of the two principal arteries that +supply the head with blood. He observed that shortly after this +the antler (which was only half grown and consequently very +vascular) on the side of the obliterated artery became cold to +the touch--from the lack of warmth-giving blood. There was +nothing unexpected in this, and Hunter thought nothing of it +until a few days later, when he found, to his surprise, that the +antler had become as warm as its fellow, and was apparently +increasing in size. Puzzled as to how this could be, and +suspecting that in some way his ligature around the artery had +not been effective, he ordered the deer killed, and on +examination was astonished to find that while his ligature had +completely shut off the blood-supply from the source of that +carotid artery, the smaller arteries had become enlarged so as to +supply the antler with blood as well as ever, only by a different +route. + +Hunter soon had a chance to make a practical application of the +knowledge thus acquired. This was a case of popliteal aneurism, +operations for which had heretofore proved pretty uniformly +fatal. An aneurism, as is generally understood, is an enlargement +of a certain part of an artery, this enlargement sometimes +becoming of enormous size, full of palpitating blood, and likely +to rupture with fatal results at any time. If by any means the +blood can be allowed to remain quiet for even a few hours in this +aneurism it will form a clot, contract, and finally be absorbed +and disappear without any evil results. The problem of keeping +the blood quiet, with the heart continually driving it through +the vessel, is not a simple one, and in Hunter's time was +considered so insurmountable that some surgeons advocated +amputation of any member having an aneurism, while others cut +down upon the tumor itself and attempted to tie off the artery +above and below. The first of these operations maimed the patient +for life, while the second was likely to prove fatal. + +In pondering over what he had learned about collateral +circulation and the time required for it to become fully +established, Hunter conceived the idea that if the blood-supply +was cut off from above the aneurism, thus temporarily preventing +the ceaseless pulsations from the heart, this blood would +coagulate and form a clot before the collateral circulation could +become established or could affect it. The patient upon whom he +performed his now celebrated operation was afflicted with a +popliteal aneurism--that is, the aneurism was located on the +large popliteal artery just behind the knee-joint. Hunter, +therefore, tied off the femoral, or main supplying artery in the +thigh, a little distance above the aneurism. The operation was +entirely successful, and in six weeks' time the patient was able +to leave the hospital, and with two sound limbs. Naturally the +simplicity and success of this operation aroused the attention of +Europe, and, alone, would have made the name of Hunter immortal +in the annals of surgery. The operation has ever since been +called the "Hunterian" operation for aneurism, but there is +reason to believe that Dominique Anel (born about 1679) performed +a somewhat similar operation several years earlier. It is +probable, however, that Hunter had never heard of this work of +Anel, and that his operation was the outcome of his own +independent reasoning from the facts he had learned about +collateral circulation. Furthermore, Hunter's mode of operation +was a much better one than Anel's, and, while Anel's must claim +priority, the credit of making it widely known will always be +Hunter's. + +The great services of Hunter were recognized both at home and +abroad, and honors and positions of honor and responsibility were +given him. In 1776 he was appointed surgeon-extraordinary to the +king; in 1783 he was elected a member of the Royal Society of +Medicine and of the Royal Academy of Surgery at Paris; in 1786 he +became deputy surgeon-general of the army; and in 1790 he was +appointed surgeon-general and inspector-general of hospitals. All +these positions he filled with credit, and he was actively +engaged in his tireless pursuit of knowledge and in discharging +his many duties when in October, 1793, he was stricken while +addressing some colleagues, and fell dead in the arms of a +fellow-physician. + + +LAZZARO SPALLANZANI + +Hunter's great rival among contemporary physiologists was the +Italian Lazzaro Spallanzani (1729-1799), one of the most +picturesque figures in the history of science. He was not +educated either as a scientist or physician, devoting, himself at +first to philosophy and the languages, afterwards studying law, +and later taking orders. But he was a keen observer of nature and +of a questioning and investigating mind, so that he is remembered +now chiefly for his discoveries and investigations in the +biological sciences. One important demonstration was his +controversion of the theory of abiogenesis, or "spontaneous +generation," as propounded by Needham and Buffon. At the time of +Needham's experiments it had long been observed that when animal +or vegetable matter had lain in water for a little time--long +enough for it to begin to undergo decomposition--the water became +filled with microscopic creatures, the "infusoria animalculis." +This would tend to show, either that the water or the animal or +vegetable substance contained the "germs" of these minute +organisms, or else that they were generated spontaneously. It was +known that boiling killed these animalcules, and Needham agreed, +therefore, that if he first heated the meat or vegetables, and +also the water containing them, and then placed them in +hermetically scaled jars--if he did this, and still the +animalcules made their appearance, it would be proof-positive +that they had been generated spontaneously. Accordingly be made +numerous experiments, always with the same results--that after a +few days the water was found to swarm with the microscopic +creatures. The thing seemed proven beyond question--providing, of +course, that there had been no slips in the experiments. + +But Abbe Spallanzani thought that he detected such slips in +Needham's experiment. The possibility of such slips might come +in several ways: the contents of the jar might not have been +boiled for a sufficient length of time to kill all the germs, or +the air might not have been excluded completely by the sealing +process. To cover both these contingencies, Spallanzani first +hermetically sealed the glass vessels and then boiled them for +three-quarters of an hour. Under these circumstances no +animalcules ever made their appearance--a conclusive +demonstration that rendered Needham's grounds for his theory at +once untenable.[2] + +Allied to these studies of spontaneous generation were +Spallanzani's experiments and observations on the physiological +processes of generation among higher animals. He experimented +with frogs, tortoises, and dogs; and settled beyond question the +function of the ovum and spermatozoon. Unfortunately he +misinterpreted the part played by the spermatozoa in believing +that their surrounding fluid was equally active in the +fertilizing process, and it was not until some forty years later +(1824) that Dumas corrected this error. + + +THE CHEMICAL THEORY OF DIGESTION + +Among the most interesting researches of Spallanzani were his +experiments to prove that digestion, as carried on in the +stomach, is a chemical process. In this he demonstrated, as Rene +Reaumur had attempted to demonstrate, that digestion could be +carried on outside the walls of the stomach as an ordinary +chemical reaction, using the gastric juice as the reagent for +performing the experiment. The question as to whether the stomach +acted as a grinding or triturating organ, rather than as a +receptacle for chemical action, had been settled by Reaumur and +was no longer a question of general dispute. Reaumur had +demonstrated conclusively that digestion would take place in the +stomach in the same manner and the same time if the substance to +be digested was protected from the peristalic movements of the +stomach and subjected to the action of the gastric juice only. He +did this by introducing the substances to be digested into the +stomach in tubes, and thus protected so that while the juices of +the stomach could act upon them freely they would not be affected +by any movements of the organ. + +Following up these experiments, he attempted to show that +digestion could take place outside the body as well as in it, as +it certainly should if it were a purely chemical process. He +collected quantities of gastric juice, and placing it in suitable +vessels containing crushed grain or flesh, kept the mixture at +about the temperature of the body for several hours. After +repeated experiments of this kind, apparently conducted with +great care, Reaumur reached the conclusion that "the gastric +juice has no more effect out of the living body in dissolving or +digesting the food than water, mucilage, milk, or any other bland +fluid."[3] Just why all of these experiments failed to +demonstrate a fact so simple does not appear; but to Spallanzani, +at least, they were by no means conclusive, and he proceeded to +elaborate upon the experiments of Reaumur. He made his +experiments in scaled tubes exposed to a certain degree of heat, +and showed conclusively that the chemical process does go on, +even when the food and gastric juice are removed from their +natural environment in the stomach. In this he was opposed by +many physiologists, among them John Hunter, but the truth of his +demonstrations could not be shaken, and in later years we find +Hunter himself completing Spallanzani's experiments by his +studies of the post-mortem action of the gastric juice upon the +stomach walls. + +That Spallanzani's and Hunter's theories of the action of the +gastric juice were not at once universally accepted is shown by +an essay written by a learned physician in 1834. In speaking of +some of Spallanzani's demonstrations, he writes: "In some of the +experiments, in order to give the flesh or grains steeped in the +gastric juice the same temperature with the body, the phials were +introduced under the armpits. But this is not a fair mode of +ascertaining the effects of the gastric juice out of the body; +for the influence which life may be supposed to have on the +solution of the food would be secured in this case. The +affinities connected with life would extend to substances in +contact with any part of the system: substances placed under the +armpits are not placed at least in the same circumstances with +those unconnected with a living animal." But just how this writer +reaches the conclusion that "the experiments of Reaumur and +Spallanzani give no evidence that the gastric juice has any +peculiar influence more than water or any other bland fluid in +digesting the food"[4] is difficult to understand. + +The concluding touches were given to the new theory of digestion +by John Hunter, who, as we have seen, at first opposed +Spallanzani, but who finally became an ardent champion of the +chemical theory. Hunter now carried Spallanzani's experiments +further and proved the action of the digestive fluids after +death. For many years anatomists had been puzzled by pathological +lesion of the stomach, found post mortem, when no symptoms of any +disorder of the stomach had been evinced during life. Hunter +rightly conceived that these lesions were caused by the action of +the gastric juice, which, while unable to act upon the living +tissue, continued its action chemically after death, thus +digesting the walls of the stomach in which it had been formed. +And, as usual with his observations, be turned this discovery to +practical use in accounting for certain phenomena of digestion. +The following account of the stomach being digested after death +was written by Hunter at the desire of Sir John Pringle, when he +was president of the Royal Society, and the circumstance which +led to this is as follows: "I was opening, in his presence, the +body of a patient of his own, where the stomach was in part +dissolved, which appeared to him very unaccountable, as there had +been no previous symptom that could have led him to suspect any +disease in the stomach. I took that opportunity of giving him my +ideas respecting it, and told him that I had long been making +experiments on digestion, and considered this as one of the facts +which proved a converting power in the gastric juice. . . . There +are a great many powers in nature which the living principle does +not enable the animal matter, with which it is combined, to +resist--viz., the mechanical and most of the strongest chemical +solvents. It renders it, however, capable of resisting the powers +of fermentation, digestion, and perhaps several others, which are +well known to act on the same matter when deprived of the living +principle and entirely to decompose it. " + +Hunter concludes his paper with the following paragraph: "These +appearances throw considerable light on the principle of +digestion, and show that it is neither a mechanical power, nor +contractions of the stomach, nor heat, but something secreted in +the coats of the stomach, and thrown into its cavity, which there +animalizes the food or assimilates it to the nature of the blood. +The power of this juice is confined or limited to certain +substances, especially of the vegetable and animal kingdoms; and +although this menstruum is capable of acting independently of the +stomach, yet it is indebted to that viscus for its +continuance.[5] + + +THE FUNCTION OF RESPIRATION + +It is a curious commentary on the crude notions of mechanics of +previous generations that it should have been necessary to prove +by experiment that the thin, almost membranous stomach of a +mammal has not the power to pulverize, by mere attrition, the +foods that are taken into it. However, the proof was now for the +first time forthcoming, and the question of the general character +of the function of digestion was forever set at rest. Almost +simultaneously with this great advance, corresponding progress +was made in an allied field: the mysteries of respiration were +at last cleared up, thanks to the new knowledge of chemistry. The +solution of the problem followed almost as a matter of course +upon the advances of that science in the latter part of the +century. Hitherto no one since Mayow, of the previous century, +whose flash of insight had been strangely overlooked and +forgotten, had even vaguely surmised the true function of the +lungs. The great Boerhaave had supposed that respiration is +chiefly important as an aid to the circulation of the blood; his +great pupil, Haller, had believed to the day of his death in 1777 +that the main purpose of the function is to form the voice. No +genius could hope to fathom the mystery of the lungs so long as +air was supposed to be a simple element, serving a mere +mechanical purpose in the economy of the earth. + +But the discovery of oxygen gave the clew, and very soon all the +chemists were testing the air that came from the lungs--Dr. +Priestley, as usual, being in the van. His initial experiments +were made in 1777, and from the outset the problem was as good as +solved. Other experimenters confirmed his results in all their +essentials--notably Scheele and Lavoisier and Spallanzani and +Davy. It was clearly established that there is chemical action +in the contact of the air with the tissue of the lungs; that some +of the oxygen of the air disappears, and that carbonic-acid gas +is added to the inspired air. It was shown, too, that the blood, +having come in contact with the air, is changed from black to red +in color. These essentials were not in dispute from the first. +But as to just what chemical changes caused these results was the +subject of controversy. Whether, for example, oxygen is actually +absorbed into the blood, or whether it merely unites with carbon +given off from the blood, was long in dispute. + +Each of the main disputants was biased by his own particular +views as to the moot points of chemistry. Lavoisier, for +example, believed oxygen gas to be composed of a metal oxygen +combined with the alleged element heat; Dr. Priestley thought it +a compound of positive electricity and phlogiston; and Humphry +Davy, when he entered the lists a little later, supposed it to be +a compound of oxygen and light. Such mistaken notions naturally +complicated matters and delayed a complete understanding of the +chemical processes of respiration. It was some time, too, before +the idea gained acceptance that the most important chemical +changes do not occur in the lungs themselves, but in the ultimate +tissues. Indeed, the matter was not clearly settled at the close +of the century. Nevertheless, the problem of respiration had +been solved in its essentials. Moreover, the vastly important +fact had been established that a process essentially identical +with respiration is necessary to the existence not only of all +creatures supplied with lungs, but to fishes, insects, and even +vegetables--in short, to every kind of living organism. + + +ERASMUS DARWIN AND VEGETABLE PHYSIOLOGY + +Some interesting experiments regarding vegetable respiration were +made just at the close of the century by Erasmus Darwin, and +recorded in his Botanic Garden as a foot-note to the verse: + +"While spread in air the leaves respiring play." + + +These notes are worth quoting at some length, as they give a +clear idea of the physiological doctrines of the time (1799), +while taking advance ground as to the specific matter in +question: + + +"There have been various opinions," Darwin says, "concerning the +use of the leaves of plants in the vegetable economy. Some have +contended that they are perspiratory organs. This does not seem +probable from an experiment of Dr. Hales, Vegetable Statics, p. +30. He, found, by cutting off branches of trees with apples on +them and taking off the leaves, that an apple exhaled about as +much as two leaves the surfaces of which were nearly equal to the +apple; whence it would appear that apples have as good a claim to +be termed perspiratory organs as leaves. Others have believed +them excretory organs of excrementitious juices, but as the vapor +exhaled from vegetables has no taste, this idea is no more +probable than the other; add to this that in most weathers they +do not appear to perspire or exhale at all. + +"The internal surface of the lungs or air-vessels in men is said +to be equal to the external surface of the whole body, or almost +fifteen square feet; on this surface the blood is exposed to the +influence of the respired air through the medium, however, of a +thin pellicle; by this exposure to the air it has its color +changed from deep red to bright scarlet, and acquires something +so necessary to the existence of life that we can live scarcely a +minute without this wonderful process. + +"The analogy between the leaves of plants and the lungs or gills +of animals seems to embrace so many circumstances that we can +scarcely withhold our consent to their performing similar +offices. + +"1. The great surface of leaves compared to that of the trunk +and branches of trees is such that it would seem to be an organ +well adapted for the purpose of exposing the vegetable juices to +the influence of the air; this, however, we shall see afterwards +is probably performed only by their upper surfaces, yet even in +this case the surface of the leaves in general bear a greater +proportion to the surface of the tree than the lungs of animals +to their external surfaces. + +"2. In the lung of animals the blood, after having been exposed +to the air in the extremities of the pulmonary artery, is changed +in color from deep red to bright scarlet, and certainly in some +of its essential properties it is then collected by the pulmonary +vein and returned to the heart. To show a similarity of +circumstances in the leaves of plants, the following experiment +was made, June 24, 1781. A stalk with leaves and seed-vessels of +large spurge (Euphorbia helioscopia) had been several days placed +in a decoction of madder (Rubia tinctorum) so that the lower part +of the stem and two of the undermost leaves were immersed in it. +After having washed the immersed leaves in clear water I could +readily discover the color of the madder passing along the middle +rib of each leaf. The red artery was beautifully visible on the +under and on the upper surface of the leaf; but on the upper side +many red branches were seen going from it to the extremities of +the leaf, which on the other side were not visible except by +looking through it against the light. On this under side a system +of branching vessels carrying a pale milky fluid were seen coming +from the extremities of the leaf, and covering the whole under +side of it, and joining two large veins, one on each side of the +red artery in the middle rib of the leaf, and along with it +descending to the foot-stalk or petiole. On slitting one of these +leaves with scissors, and having a magnifying-glass ready, the +milky blood was seen oozing out of the returning veins on each +side of the red artery in the middle rib, but none of the red +fluid from the artery. + +"All these appearances were more easily seen in a leaf of Picris +treated in the same manner; for in this milky plant the stems and +middle rib of the leaves are sometimes naturally colored reddish, +and hence the color of the madder seemed to pass farther into the +ramifications of their leaf-arteries, and was there beautifully +visible with the returning branches of milky veins on each side." + + +Darwin now goes on to draw an incorrect inference from his +observations: + + +"3. From these experiments," he says, "the upper surface of the +leaf appeared to be the immediate organ of respiration, because +the colored fluid was carried to the extremities of the leaf by +vessels most conspicuous on the upper surface, and there changed +into a milky fluid, which is the blood of the plant, and then +returned by concomitant veins on the under surface, which were +seen to ooze when divided with scissors, and which, in Picris, +particularly, render the under surface of the leaves greatly +whiter than the upper one." + + +But in point of fact, as studies of a later generation were to +show, it is the under surface of the leaf that is most abundantly +provided with stomata, or "breathing-pores." From the stand-point +of this later knowledge, it is of interest to follow our author a +little farther, to illustrate yet more fully the possibility of +combining correct observations with a faulty inference. + + +"4. As the upper surface of leaves constitutes the organ of +respiration, on which the sap is exposed in the termination of +arteries beneath a thin pellicle to the action of the atmosphere, +these surfaces in many plants strongly repel moisture, as cabbage +leaves, whence the particles of rain lying over their surfaces +without touching them, as observed by Mr. Melville (Essays +Literary and Philosophical: Edinburgh), have the appearance of +globules of quicksilver. And hence leaves with the upper +surfaces on water wither as soon as in the dry air, but continue +green for many days if placed with the under surface on water, as +appears in the experiments of Monsieur Bonnet (Usage des +Feuilles). Hence some aquatic plants, as the water-lily +(Nymphoea), have the lower sides floating on the water, while the +upper surfaces remain dry in the air. + +"5. As those insects which have many spiracula, or breathing +apertures, as wasps and flies, are immediately suffocated by +pouring oil upon them, I carefully covered with oil the surfaces +of several leaves of phlomis, of Portugal laurel, and balsams, +and though it would not regularly adhere, I found them all die in +a day or two. + +"It must be added that many leaves are furnished with muscles +about their foot-stalks, to turn their surfaces to the air or +light, as mimosa or Hedysarum gyrans. From all these analogies I +think there can be no doubt but that leaves of trees are their +lungs, giving out a phlogistic material to the atmosphere, and +absorbing oxygen, or vital air. + +"6. The great use of light to vegetation would appear from this +theory to be by disengaging vital air from the water which they +perspire, and thence to facilitate its union with their blood +exposed beneath the thin surface of their leaves; since when pure +air is thus applied it is probable that it can be more readily +absorbed. Hence, in the curious experiments of Dr. Priestley and +Mr. Ingenhouz, some plants purified less air than others--that +is, they perspired less in the sunshine; and Mr. Scheele found +that by putting peas into water which about half covered them +they converted the vital air into fixed air, or carbonic-acid +gas, in the same manner as in animal respiration. + +"7. The circulation in the lungs or leaves of plants is very +similar to that of fish. In fish the blood, after having passed +through their gills, does not return to the heart as from the +lungs of air-breathing animals, but the pulmonary vein taking the +structure of an artery after having received the blood from the +gills, which there gains a more florid color, distributes it to +the other parts of their bodies. The same structure occurs in the +livers of fish, whence we see in those animals two circulations +independent of the power of the heart--viz., that beginning at +the termination of the veins of the gills and branching through +the muscles, and that which passes through the liver; both which +are carried on by the action of those respective arteries and +veins."[6] + +Darwin is here a trifle fanciful in forcing the analogy between +plants and animals. The circulatory system of plants is really +not quite so elaborately comparable to that of fishes as he +supposed. But the all-important idea of the uniformity underlying +the seeming diversity of Nature is here exemplified, as elsewhere +in the writings of Erasmus Darwin; and, more specifically, a +clear grasp of the essentials of the function of respiration is +fully demonstrated. + + +ZOOLOGY AT THE CLOSE OF THE EIGHTEENTH CENTURY + + +Several causes conspired to make exploration all the fashion +during the closing epoch of the eighteenth century. New aid to +the navigator had been furnished by the perfected compass and +quadrant, and by the invention of the chronometer; medical +science had banished scurvy, which hitherto had been a perpetual +menace to the voyager; and, above all, the restless spirit of the +age impelled the venturesome to seek novelty in fields altogether +new. Some started for the pole, others tried for a northeast or +northwest passage to India, yet others sought the great +fictitious antarctic continent told of by tradition. All these of +course failed of their immediate purpose, but they added much to +the world's store of knowledge and its fund of travellers' tales. + +Among all these tales none was more remarkable than those which +told of strange living creatures found in antipodal lands. And +here, as did not happen in every field, the narratives were often +substantiated by the exhibition of specimens that admitted no +question. Many a company of explorers returned more or less laden +with such trophies from the animal and vegetable kingdoms, to the +mingled astonishment, delight, and bewilderment of the closet +naturalists. The followers of Linnaeus in the "golden age of +natural history," a few decades before, had increased the number +of known species of fishes to about four hundred, of birds to one +thousand, of insects to three thousand, and of plants to ten +thousand. But now these sudden accessions from new territories +doubled the figure for plants, tripled it for fish and birds, and +brought the number of described insects above twenty thousand. +Naturally enough, this wealth of new material was sorely puzzling +to the classifiers. The more discerning began to see that the +artificial system of Linnaeus, wonderful and useful as it had +been, must be advanced upon before the new material could be +satisfactorily disposed of. The way to a more natural system, +based on less arbitrary signs, had been pointed out by Jussieu in +botany, but the zoologists were not prepared to make headway +towards such a system until they should gain a wider +understanding of the organisms with which they had to deal +through comprehensive studies of anatomy. Such studies of +individual forms in their relations to the entire scale of +organic beings were pursued in these last decades of the century, +but though two or three most important generalizations were +achieved (notably Kaspar Wolff's conception of the cell as the +basis of organic life, and Goethe's all-important doctrine of +metamorphosis of parts), yet, as a whole, the work of the +anatomists of the period was germinative rather than +fruit-bearing. Bichat's volumes, telling of the recognition of +the fundamental tissues of the body, did not begin to appear till +the last year of the century. The announcement by Cuvier of the +doctrine of correlation of parts bears the same date, but in +general the studies of this great naturalist, which in due time +were to stamp him as the successor of Linnaeus, were as yet only +fairly begun. + + + + V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH CENTURY + +CUVIER AND THE CORRELATION OF PARTS + +We have seen that the focal points of the physiological world +towards the close of the eighteenth century were Italy and +England, but when Spallanzani and Hunter passed away the scene +shifted to France. The time was peculiarly propitious, as the +recent advances in many lines of science had brought fresh data +for the student of animal life which were in need of +classification, and, as several minds capable of such a task were +in the field, it was natural that great generalizations should +have come to be quite the fashion. Thus it was that Cuvier came +forward with a brand-new classification of the animal kingdom, +establishing four great types of being, which he called +vertebrates, mollusks, articulates, and radiates. Lamarck had +shortly before established the broad distinction between animals +with and those without a backbone; Cuvier's Classification +divided the latter--the invertebrates--into three minor groups. +And this division, familiar ever since to all students of +zoology, has only in very recent years been supplanted, and then +not by revolution, but by a further division, which the elaborate +recent studies of lower forms of life seemed to make desirable. + +In the course of those studies of comparative anatomy which led +to his new classification, Cuvier's attention was called +constantly to the peculiar co-ordination of parts in each +individual organism. Thus an animal with sharp talons for +catching living prey--as a member of the cat tribe--has also +sharp teeth, adapted for tearing up the flesh of its victim, and +a particular type of stomach, quite different from that of +herbivorous creatures. This adaptation of all the parts of the +animal to one another extends to the most diverse parts of the +organism, and enables the skilled anatomist, from the observation +of a single typical part, to draw inferences as to the structure +of the entire animal--a fact which was of vast aid to Cuvier in +his studies of paleontology. It did not enable Cuvier, nor does +it enable any one else, to reconstruct fully the extinct animal +from observation of a single bone, as has sometimes been +asserted, but what it really does establish, in the hands of an +expert, is sufficiently astonishing. + +"While the study of the fossil remains of the greater quadrupeds +is more satisfactory," he writes, "by the clear results which it +affords, than that of the remains of other animals found in a +fossil state, it is also complicated with greater and more +numerous difficulties. Fossil shells are usually found quite +entire, and retaining all the characters requisite for comparing +them with the specimens contained in collections of natural +history, or represented in the works of naturalists. Even the +skeletons of fishes are found more or less entire, so that the +general forms of their bodies can, for the most part, be +ascertained, and usually, at least, their generic and specific +characters are determinable, as these are mostly drawn from their +solid parts. In quadrupeds, on the contrary, even when their +entire skeletons are found, there is great difficulty in +discovering their distinguishing characters, as these are chiefly +founded upon their hairs and colors and other marks which have +disappeared previous to their incrustation. It is also very rare +to find any fossil skeletons of quadrupeds in any degree +approaching to a complete state, as the strata for the most part +only contain separate bones, scattered confusedly and almost +always broken and reduced to fragments, which are the only means +left to naturalists for ascertaining the species or genera to +which they have belonged. + +"Fortunately comparative anatomy, when thoroughly understood, +enables us to surmount all these difficulties, as a careful +application of its principles instructs us in the correspondences +and dissimilarities of the forms of organized bodies of different +kinds, by which each may be rigorously ascertained from almost +every fragment of its various parts and organs. + +"Every organized individual forms an entire system of its own, +all the parts of which naturally correspond, and concur to +produce a certain definite purpose, by reciprocal reaction, or by +combining towards the same end. Hence none of these separate +parts can change their forms without a corresponding change in +the other parts of the same animal, and consequently each of +these parts, taken separately, indicates all the other parts to +which it has belonged. Thus, as I have elsewhere shown, if the +viscera of an animal are so organized as only to be fitted for +the digestion of recent flesh, it is also requisite that the jaws +should be so constructed as to fit them for devouring prey; the +claws must be constructed for seizing and tearing it to pieces; +the teeth for cutting and dividing its flesh; the entire system +of the limbs, or organs of motion, for pursuing and overtaking +it; and the organs of sense for discovering it at a distance. +Nature must also have endowed the brain of the animal with +instincts sufficient for concealing itself and for laying plans +to catch its necessary victims. . . . . . . . . . + +"To enable the animal to carry off its prey when seized, a +corresponding force is requisite in the muscles which elevate the +head, and this necessarily gives rise to a determinate form of +the vertebrae to which these muscles are attached and of the +occiput into which they are inserted. In order that the teeth of +a carnivorous animal may be able to cut the flesh, they require +to be sharp, more or less so in proportion to the greater or less +quantity of flesh that they have to cut. It is requisite that +their roots should be solid and strong, in proportion to the +quantity and size of the bones which they have to break to +pieces. The whole of these circumstances must necessarily +influence the development and form of all the parts which +contribute to move the jaws. . . . . . . . . . + +After these observations, it will be easily seen that similar +conclusions may be drawn with respect to the limbs of carnivorous +animals, which require particular conformations to fit them for +rapidity of motion in general; and that similar considerations +must influence the forms and connections of the vertebrae and +other bones constituting the trunk of the body, to fit them for +flexibility and readiness of motion in all directions. The bones +also of the nose, of the orbit, and of the ears require certain +forms and structures to fit them for giving perfection to the +senses of smell, sight, and hearing, so necessary to animals of +prey. In short, the shape and structure of the teeth regulate the +forms of the condyle, of the shoulder-blade, and of the claws, in +the same manner as the equation of a curve regulates all its +other properties; and as in regard to any particular curve all +its properties may be ascertained by assuming each separate +property as the foundation of a particular equation, in the same +manner a claw, a shoulder-blade, a condyle, a leg or arm bone, or +any other bone separately considered, enables us to discover the +description of teeth to which they have belonged; and so also +reciprocally we may determine the forms of the other bones from +the teeth. Thus commencing our investigations by a careful +survey of any one bone by itself, a person who is sufficiently +master of the laws of organic structure may, as it were, +reconstruct the whole animal to which that bone belonged."[1] + +We have already pointed out that no one is quite able to perform +the necromantic feat suggested in the last sentence; but the +exaggeration is pardonable in the enthusiast to whom the +principle meant so much and in whose hands it extended so far. + +Of course this entire principle, in its broad outlines, is +something with which every student of anatomy had been familiar +from the time when anatomy was first studied, but the full +expression of the "law of co-ordination," as Cuvier called it, +had never been explicitly made before; and, notwithstanding its +seeming obviousness, the exposition which Cuvier made of it in +the introduction to his classical work on comparative anatomy, +which was published during the first decade of the nineteenth +century, ranks as a great discovery. It is one of those +generalizations which serve as guideposts to other discoveries. + + +BICHAT AND THE BODILY TISSUES + +Much the same thing may be said of another generalization +regarding the animal body, which the brilliant young French +physician Marie Francois Bichat made in calling attention to the +fact that each vertebrate organism, including man, has really two +quite different sets of organs--one set under volitional control, +and serving the end of locomotion, the other removed from +volitional control, and serving the ends of the "vital processes" +of digestion, assimilation, and the like. He called these sets of +organs the animal system and the organic system, respectively. +The division thus pointed out was not quite new, for Grimaud, +professor of physiology in the University of Montpellier, had +earlier made what was substantially the same classification of +the functions into "internal or digestive and external or +locomotive"; but it was Bichat's exposition that gave currency to +the idea. + +Far more important, however, was another classification which +Bichat put forward in his work on anatomy, published just at the +beginning of the last century. This was the division of all +animal structures into what Bichat called tissues, and the +pointing out that there are really only a few kinds of these in +the body, making up all the diverse organs. Thus muscular organs +form one system; membranous organs another; glandular organs a +third; the vascular mechanism a fourth, and so on. The +distinction is so obvious that it seems rather difficult to +conceive that it could have been overlooked by the earliest +anatomists; but, in point of fact, it is only obvious because now +it has been familiarly taught for almost a century. It had never +been given explicit expression before the time of Bichat, though +it is said that Bichat himself was somewhat indebted for it to +his master, Desault, and to the famous alienist Pinel. + +However that may be, it is certain that all subsequent anatomists +have found Bichat's classification of the tissues of the utmost +value in their studies of the animal functions. Subsequent +advances were to show that the distinction between the various +tissues is not really so fundamental as Bichat supposed, but that +takes nothing from the practical value of the famous +classification. + +It was but a step from this scientific classification of tissues +to a similar classification of the diseases affecting them, and +this was one of the greatest steps towards placing medicine on +the plane of an exact science. This subject of these branches +completely fascinated Bichat, and he exclaimed, enthusiastically: +"Take away some fevers and nervous trouble, and all else belongs +to the kingdom of pathological anatomy." But out of this +enthusiasm came great results. Bichat practised as he preached, +and, believing that it was only possible to understand disease by +observing the symptoms carefully at the bedside, and, if the +disease terminated fatally, by post-mortem examination, he was so +arduous in his pursuit of knowledge that within a period of less +than six months he had made over six hundred autopsies--a record +that has seldom, if ever, been equalled. Nor were his efforts +fruitless, as a single example will suffice to show. By his +examinations he was able to prove that diseases of the chest, +which had formerly been classed under the indefinite name +"peripneumonia," might involve three different structures, the +pleural sac covering the lungs, the lung itself, and the +bronchial tubes, the diseases affecting these organs being known +respectively as pleuritis, pneumonia, and bronchitis, each one +differing from the others as to prognosis and treatment. The +advantage of such an exact classification needs no demonstration. + + +LISTER AND THE PERFECTED MICROSCOPE + +At the same time when these broad macroscopical distinctions were +being drawn there were other workers who were striving to go even +deeper into the intricacies of the animal mechanism with the aid +of the microscope. This undertaking, however, was beset with +very great optical difficulties, and for a long time little +advance was made upon the work of preceding generations. Two +great optical barriers, known technically as spherical and +chromatic aberration--the one due to a failure of the rays of +light to fall all in one plane when focalized through a lens, the +other due to the dispersive action of the lens in breaking the +white light into prismatic colors--confronted the makers of +microscopic lenses, and seemed all but insuperable. The making of +achromatic lenses for telescopes had been accomplished, it is +true, by Dolland in the previous century, by the union of lenses +of crown glass with those of flint glass, these two materials +having different indices of refraction and dispersion. But, aside +from the mechanical difficulties which arise when the lens is of +the minute dimensions required for use with the microscope, other +perplexities are introduced by the fact that the use of a wide +pencil of light is a desideratum, in order to gain sufficient +illumination when large magnification is to be secured. + +In the attempt to overcome those difficulties, the foremost +physical philosophers of the time came to the aid of the best +opticians. Very early in the century, Dr. (afterwards Sir David) +Brewster, the renowned Scotch physicist, suggested that certain +advantages might accrue from the use of such gems as have high +refractive and low dispersive indices, in place of lenses made of +glass. Accordingly lenses were made of diamond, of sapphire, and +so on, and with some measure of success. But in 1812 a much more +important innovation was introduced by Dr. William Hyde +Wollaston, one of the greatest and most versatile, and, since the +death of Cavendish, by far the most eccentric of English natural +philosophers. This was the suggestion to use two plano-convex +lenses, placed at a prescribed distance apart, in lieu of the +single double-convex lens generally used. This combination +largely overcame the spherical aberration, and it gained +immediate fame as the "Wollaston doublet." + +To obviate loss of light in such a doublet from increase of +reflecting surfaces, Dr. Brewster suggested filling the +interspace between the two lenses with a cement having the same +index of refraction as the lenses themselves--an improvement of +manifest advantage. An improvement yet more important was made by +Dr. Wollaston himself in the introduction of the diaphragm to +limit the field of vision between the lenses, instead of in front +of the anterior lens. A pair of lenses thus equipped Dr. +Wollaston called the periscopic microscope. Dr. Brewster +suggested that in such a lens the same object might be attained +with greater ease by grinding an equatorial groove about a thick +or globular lens and filling the groove with an opaque cement. +This arrangement found much favor, and came subsequently to be +known as a Coddington lens, though Mr. Coddington laid no claim +to being its inventor. + +Sir John Herschel, another of the very great physicists of the +time, also gave attention to the problem of improving the +microscope, and in 1821 he introduced what was called an +aplanatic combination of lenses, in which, as the name implies, +the spherical aberration was largely done away with. It was +thought that the use of this Herschel aplanatic combination as an +eyepiece, combined with the Wollaston doublet for the objective, +came as near perfection as the compound microscope was likely +soon to come. But in reality the instrument thus constructed, +though doubtless superior to any predecessor, was so defective +that for practical purposes the simple microscope, such as the +doublet or the Coddington, was preferable to the more complicated +one. + +Many opticians, indeed, quite despaired of ever being able to +make a satisfactory refracting compound microscope, and some of +them had taken up anew Sir Isaac Newton's suggestion in reference +to a reflecting microscope. In particular, Professor Giovanni +Battista Amici, a very famous mathematician and practical +optician of Modena, succeeded in constructing a reflecting +microscope which was said to be superior to any compound +microscope of the time, though the events of the ensuing years +were destined to rob it of all but historical value. For there +were others, fortunately, who did not despair of the +possibilities of the refracting microscope, and their efforts +were destined before long to be crowned with a degree of success +not even dreamed of by any preceding generation. + +The man to whom chief credit is due for directing those final +steps that made the compound microscope a practical implement +instead of a scientific toy was the English amateur optician +Joseph Jackson Lister. Combining mathematical knowledge with +mechanical ingenuity, and having the practical aid of the +celebrated optician Tulley, he devised formulae for the +combination of lenses of crown glass with others of flint glass, +so adjusted that the refractive errors of one were corrected or +compensated by the other, with the result of producing lenses of +hitherto unequalled powers of definition; lenses capable of +showing an image highly magnified, yet relatively free from those +distortions and fringes of color that had heretofore been so +disastrous to true interpretation of magnified structures. + +Lister had begun his studies of the lens in 1824, but it was not +until 1830 that he contributed to the Royal Society the famous +paper detailing his theories and experiments. Soon after this +various continental opticians who had long been working along +similar lines took the matter up, and their expositions, in +particular that of Amici, introduced the improved compound +microscope to the attention of microscopists everywhere. And it +required but the most casual trial to convince the experienced +observers that a new implement of scientific research had been +placed in their hands which carried them a long step nearer the +observation of the intimate physical processes which lie at the +foundation of vital phenomena. For the physiologist this +perfection of the compound microscope had the same significance +that the, discovery of America had for the fifteenth-century +geographers--it promised a veritable world of utterly novel +revelations. Nor was the fulfilment of that promise long delayed. + +Indeed, so numerous and so important were the discoveries now +made in the realm of minute anatomy that the rise of histology to +the rank of an independent science may be said to date from this +period. Hitherto, ever since the discovery of magnifying-glasses, +there had been here and there a man, such as Leuwenhoek or +Malpighi, gifted with exceptional vision, and perhaps unusually +happy in his conjectures, who made important contributions to the +knowledge of the minute structure of organic tissues; but now of +a sudden it became possible for the veriest tyro to confirm or +refute the laborious observations of these pioneers, while the +skilled observer could step easily beyond the barriers of vision +that hitherto were quite impassable. And so, naturally enough, +the physiologists of the fourth decade of the nineteenth century +rushed as eagerly into the new realm of the microscope as, for +example, their successors of to-day are exploring the realm of +the X-ray. + +Lister himself, who had become an eager interrogator of the +instrument he had perfected, made many important discoveries, the +most notable being his final settlement of the long-mooted +question as to the true form of the red corpuscles of the human +blood. In reality, as everybody knows nowadays, these are +biconcave disks, but owing to their peculiar figure it is easily +possible to misinterpret the appearances they present when seen +through a poor lens, and though Dr. Thomas Young and various +other observers had come very near the truth regarding them, +unanimity of opinion was possible only after the verdict of the +perfected microscope was given. + +These blood corpuscles are so infinitesimal in size that +something like five millions of them are found in each cubic +millimetre of the blood, yet they are isolated particles, each +having, so to speak, its own personality. This, of course, had +been known to microscopists since the days of the earliest +lenses. It had been noticed, too, by here and there an observer, +that certain of the solid tissues seemed to present something of +a granular texture, as if they, too, in their ultimate +constitution, were made up of particles. And now, as better and +better lenses were constructed, this idea gained ground +constantly, though for a time no one saw its full significance. +In the case of vegetable tissues, indeed, the fact that little +particles encased a membranous covering, and called cells, are +the ultimate visible units of structure had long been known. But +it was supposed that animal tissues differed radically from this +construction. The elementary particles of vegetables "were +regarded to a certain extent as individuals which composed the +entire plant, while, on the other hand, no such view was taken of +the elementary parts of animals." + + +ROBERT BROWN AND THE CELL NUCLEUS + +In the year 1833 a further insight into the nature of the +ultimate particles of plants was gained through the observation +of the English microscopist Robert Brown, who, in the course of +his microscopic studies of the epidermis of orchids, discovered +in the cells "an opaque spot," which he named the nucleus. +Doubtless the same "spot" had been seen often enough before by +other observers, but Brown was the first to recognize it as a +component part of the vegetable cell and to give it a name. + + +"I shall conclude my observations on Orchideae," said Brown, +"with a notice of some points of their general structure, which +chiefly relate to the cellular tissue. In each cell of the +epidermis of a great part of this family, especially of those +with membranous leaves, a single circular areola, generally +somewhat more opaque than, the membrane of the cell, is +observable. This areola, which is more or less distinctly +granular, is slightly convex, and although it seems to be on the +surface is in reality covered by the outer lamina of the cell. +There is no regularity as to its place in the cell; it is not +unfrequently, however, central or nearly so. + +"As only one areola belongs to each cell, and as in many cases +where it exists in the common cells of the epidermis, it is also +visible in the cutaneous glands or stomata, and in these is +always double--one being on each side of the limb--it is highly +probable that the cutaneous gland is in all cases composed of two +cells of peculiar form, the line of union being the longitudinal +axis of the disk or pore. + +"This areola, or nucleus of the cell as perhaps it might be +termed, is not confined to the epidermis, being also found, not +only in the pubescence of the surface, particularly when jointed, +as in cypripedium, but in many cases in the parenchyma or +internal cells of the tissue, especially when these are free from +the deposition of granular matter. + +"In the compressed cells of the epidermis the nucleus is in a +corresponding degree flattened; but in the internal tissue it is +often nearly spherical, more or less firmly adhering to one of +the walls, and projecting into the cavity of the cell. In this +state it may not unfrequently be found. in the substance of the +column and in that of the perianthium. + +"The nucleus is manifest also in the tissue of the stigma, where +in accordance with the compression of the utriculi, it has an +intermediate form, being neither so much flattened as in the +epidermis nor so convex as it is in the internal tissue of the +column. + +"I may here remark that I am acquainted with one case of apparent +exception to the nucleus being solitary in each utriculus or +cell--namely, in Bletia Tankervilliae. In the utriculi of the +stigma of this plant, I have generally, though not always, found +a second areola apparently on the surface, and composed of much +larger granules than the ordinary nucleus, which is formed of +very minute granular matter, and seems to be deep seated. + +"Mr. Bauer has represented the tissue of the stigma, in the +species of Bletia, both before and, as he believes, after +impregnation; and in the latter state the utriculi are marked +with from one to three areolae of similar appearance. + +"The nucleus may even be supposed to exist in the pollen of this +family. In the early stages of its formation, at least a minute +areola is of ten visible in the simple grain, and in each of the +constituent parts of cells of the compound grain. But these +areolae may perhaps rather be considered as merely the points of +production of the tubes. + +"This nucleus of the cell is not confined to orchideae, but is +equally manifest in many other monocotyledonous families; and I +have even found it, hitherto however in very few cases, in the +epidermis of dicotyledonous plants; though in this primary +division it may perhaps be said to exist in the early stages of +development of the pollen. Among monocotyledons, the orders in +which it is most remarkable are Liliaceae, Hemerocallideae, +Asphodeleae, Irideae, and Commelineae. + +"In some plants belonging to this last-mentioned family, +especially in Tradascantia virginica, and several nearly related +species, it is uncommonly distinct, not in the epidermis and in +the jointed hairs of the filaments, but in the tissue of the +stigma, in the cells of the ovulum even before impregnation, and +in all the stages of formation of the grains of pollen, the +evolution of which is so remarkable in tradascantia. + +"The few indications of the presence of this nucleus, or areola, +that I have hitherto met with in the publications of botanists +are chiefly in some figures of epidermis, in the recent works of +Meyen and Purkinje, and in one case, in M. Adolphe Broigniart's +memoir on the structure of leaves. But so little importance +seems to be attached to it that the appearance is not always +referred to in the explanations of the figures in which it is +represented. Mr. Bauer, however, who has also figured it in the +utriculi of the stigma of Bletia Tankervilliae has more +particularly noticed it, and seems to consider it as only visible +after impregnation."[2] + + +SCHLEIDEN AND SCHWANN AND THE CELL THEORY + +That this newly recognized structure must be important in the +economy of the cell was recognized by Brown himself, and by the +celebrated German Meyen, who dealt with it in his work on +vegetable physiology, published not long afterwards; but it +remained for another German, the professor of botany in the +University of Jena, Dr. M. J. Schleiden, to bring the nucleus to +popular attention, and to assert its all-importance in the +economy of the cell. + +Schleiden freely acknowledged his indebtedness to Brown for first +knowledge of the nucleus, but he soon carried his studies of that +structure far beyond those of its discoverer. He came to believe +that the nucleus is really the most important portion of the +cell, in that it is the original structure from which the +remainder of the cell is developed. Hence he named it the +cytoblast. He outlined his views in an epochal paper published +in Muller's Archives in 1838, under title of "Beitrage zur +Phytogenesis." This paper is in itself of value, yet the most +important outgrowth of Schleiden's observations of the nucleus +did not spring from his own labors, but from those of a friend to +whom he mentioned his discoveries the year previous to their +publication. This friend was Dr. Theodor Schwann, professor of +physiology in the University of Louvain. + +At the moment when these observations were communicated to him +Schwann was puzzling over certain details of animal histology +which he could not clearly explain. His great teacher, Johannes +Muller, had called attention to the strange resemblance to +vegetable cells shown by certain cells of the chorda dorsalis +(the embryonic cord from which the spinal column is developed), +and Schwann himself had discovered a corresponding similarity in +the branchial cartilage of a tadpole. Then, too, the researches +of Friedrich Henle had shown that the particles that make up the +epidermis of animals are very cell-like in appearance. Indeed, +the cell-like character of certain animal tissues had come to be +matter of common note among students of minute anatomy. Schwann +felt that this similarity could not be mere coincidence, but he +had gained no clew to further insight until Schleiden called his +attention to the nucleus. Then at once he reasoned that if there +really is the correspondence between vegetable and animal tissues +that he suspected, and if the nucleus is so important in the +vegetable cell as Schleiden believed, the nucleus should also be +found in the ultimate particles of animal tissues. + +Schwann's researches soon showed the entire correctness of this +assumption. A closer study of animal tissues under the microscope +showed, particularly in the case of embryonic tissues, that +"opaque spots" such as Schleiden described are really to be found +there in abundance--forming, indeed, a most characteristic phase +of the structure. The location of these nuclei at comparatively +regular intervals suggested that they are found in definite +compartments of the tissue, as Schleiden had shown to be the case +with vegetables; indeed, the walls that separated such cell-like +compartments one from another were in some cases visible. +Particularly was this found to be the case with embryonic +tissues, and the study of these soon convinced Schwann that his +original surmise had been correct, and that all animal tissues +are in their incipiency composed of particles not unlike the +ultimate particles of vegetables in short, of what the botanists +termed cells. Adopting this name, Schwann propounded what soon +became famous as his cell theory, under title of Mikroskopische +Untersuchungen uber die Ubereinstimmung in der Structur und dent +Wachsthum der Thiere und Pflanzen. So expeditious had been his +work that this book was published early in 1839, only a few +months after the appearance of Schleiden's paper. + +As the title suggests, the main idea that actuated Schwann was to +unify vegetable and animal tissues. Accepting cell-structure as +the basis of all vegetable tissues, he sought to show that the +same is true of animal tissues, all the seeming diversities of +fibre being but the alteration and development of what were +originally simple cells. And by cell Schwann meant, as did +Schleiden also, what the word ordinarily implies--a cavity walled +in on all sides. He conceived that the ultimate constituents of +all tissues were really such minute cavities, the most important +part of which was the cell wall, with its associated nucleus. He +knew, indeed, that the cell might be filled with fluid contents, +but he regarded these as relatively subordinate in importance to +the wall itself. This, however, did not apply to the nucleus, +which was supposed to lie against the cell wall and in the +beginning to generate it. Subsequently the wall might grow so +rapidly as to dissociate itself from its contents, thus becoming +a hollow bubble or true cell; but the nucleus, as long as it +lasted, was supposed to continue in contact with the cell wall. +Schleiden had even supposed the nucleus to be a constituent part +of the wall, sometimes lying enclosed between two layers of its +substance, and Schwann quoted this view with seeming approval. +Schwann believed, however, that in the mature cell the nucleus +ceased to be functional and disappeared. + +The main thesis as to the similarity of development of vegetable +and animal tissues and the cellular nature of the ultimate +constitution of both was supported by a mass of carefully +gathered evidence which a multitude of microscopists at once +confirmed, so Schwann's work became a classic almost from the +moment of its publication. Of course various other workers at +once disputed Schwann's claim to priority of discovery, in +particular the English microscopist Valentin, who asserted, not +without some show of justice, that he was working closely along +the same lines. Put so, for that matter, were numerous others, +as Henle, Turpin, Du-mortier, Purkinje, and Muller, all of whom +Schwann himself had quoted. Moreover, there were various +physiologists who earlier than any of these had foreshadowed the +cell theory--notably Kaspar Friedrich Wolff, towards the close of +the previous century, and Treviranus about 1807, But, as we have +seen in so many other departments of science, it is one thing to +foreshadow a discovery, it is quite another to give it full +expression and make it germinal of other discoveries. And when +Schwann put forward the explicit claim that "there is one +universal principle of development for the elementary parts, of +organisms, however different, and this principle is the formation +of cells," he enunciated a doctrine which was for all practical +purposes absolutely new and opened up a novel field for the +microscopist to enter. A most important era in physiology dates +from the publication of his book in 1839. + + +THE CELL THEORY ELABORATED + +That Schwann should have gone to embryonic tissues for the +establishment of his ideas was no doubt due very largely to the +influence of the great Russian Karl Ernst von Baer, who about ten +years earlier had published the first part of his celebrated work +on embryology, and whose ideas were rapidly gaining ground, +thanks largely to the advocacy of a few men, notably Johannes +Muller, in Germany, and William B. Carpenter, in England, and to +the fact that the improved microscope had made minute anatomy +popular. Schwann's researches made it plain that the best field +for the study of the animal cell is here, and a host of explorers +entered the field. The result of their observations was, in the +main, to confirm the claims of Schwann as to the universal +prevalence of the cell. The long-current idea that animal tissues +grow only as a sort of deposit from the blood-vessels was now +discarded, and the fact of so-called plantlike growth of animal +cells, for which Schwann contended, was universally accepted. Yet +the full measure of the affinity between the two classes of cells +was not for some time generally apprehended. + +Indeed, since the substance that composes the cell walls of +plants is manifestly very different from the limiting membrane of +the animal cell, it was natural, so long as the, wall was +considered the most essential part of the structure, that the +divergence between the two classes of cells should seem very +pronounced. And for a time this was the conception of the matter +that was uniformly accepted. But as time went on many observers +had their attention called to the peculiar characteristics of the +contents of the cell, and were led to ask themselves whether +these might not be more important than had been supposed. In +particular, Dr. Hugo von Mohl, professor of botany in the +University of Tubingen, in the course of his exhaustive studies +of the vegetable cell, was impressed with the peculiar and +characteristic appearance of the cell contents. He observed +universally within the cell "an opaque, viscid fluid, having +granules intermingled in it," which made up the main substance of +the cell, and which particularly impressed him because under +certain conditions it could be seen to be actively in motion, its +parts separated into filamentous streams. + +Von Mohl called attention to the fact that this motion of the +cell contents had been observed as long ago as 1774 by +Bonaventura Corti, and rediscovered in 1807 by Treviranus, and +that these observers had described the phenomenon under the "most +unsuitable name of 'rotation of the cell sap.' Von Mohl +recognized that the streaming substance was something quite +different from sap. He asserted that the nucleus of the cell lies +within this substance and not attached to the cell wall as +Schleiden had contended. He saw, too, that the chlorophyl +granules, and all other of the cell contents, are incorporated +with the "opaque, viscid fluid," and in 1846 he had become so +impressed with the importance of this universal cell substance +that be gave it the name of protoplasm. Yet in so doing he had no +intention of subordinating the cell wall. The fact that Payen, in +1844, had demonstrated that the cell walls of all vegetables, +high or low, are composed largely of one substance, cellulose, +tended to strengthen the position of the cell wall as the really +essential structure, of which the protoplasmic contents were only +subsidiary products. + +Meantime, however, the students of animal histology were more and +more impressed with the seeming preponderance of cell contents +over cell walls in the tissues they studied. They, too, found +the cell to be filled with a viscid, slimy fluid capable of +motion. To this Dujardin gave the name of sarcode. Presently it +came to be known, through the labors of Kolliker, Nageli, +Bischoff, and various others, that there are numerous lower forms +of animal life which seem to be composed of this sarcode, without +any cell wall whatever. The same thing seemed to be true of +certain cells of higher organisms, as the blood corpuscles. +Particularly in the case of cells that change their shape +markedly, moving about in consequence of the streaming of their +sarcode, did it seem certain that no cell wall is present, or +that, if present, its role must be insignificant. + +And so histologists came to question whether, after all, the cell +contents rather than the enclosing wall must not be the really +essential structure, and the weight of increasing observations +finally left no escape from the conclusion that such is really +the case. But attention being thus focalized on the cell +contents, it was at once apparent that there is a far closer +similarity between the ultimate particles of vegetables and those +of animals than had been supposed. Cellulose and animal membrane +being now regarded as more by-products, the way was clear for the +recognition of the fact that vegetable protoplasm and animal +sarcode are marvellously similar in appearance and general +properties. The closer the observation the more striking seemed +this similarity; and finally, about 1860, it was demonstrated by +Heinrich de Bary and by Max Schultze that the two are to all +intents and purposes identical. Even earlier Remak had reached a +similar conclusion, and applied Von Mohl's word protoplasm to +animal cell contents, and now this application soon became +universal. Thenceforth this protoplasm was to assume the utmost +importance in the physiological world, being recognized as the +universal "physical basis of life," vegetable and animal alike. +This amounted to the logical extension and culmination of +Schwann's doctrine as to the similarity of development of the two +animate kingdoms. Yet at the, same time it was in effect the +banishment of the cell that Schwann had defined. The word cell +was retained, it is true, but it no longer signified a minute +cavity. It now implied, as Schultze defined it, "a small mass of +protoplasm endowed with the attributes of life." This definition +was destined presently to meet with yet another modification, as +we shall see; but the conception of the protoplasmic mass as the +essential ultimate structure, which might or might not surround +itself with a protective covering, was a permanent addition to +physiological knowledge. The earlier idea had, in effect, +declared the shell the most important part of the egg; this +developed view assigned to the yolk its true position. + +In one other important regard the theory of Schleiden and Schwann +now became modified. This referred to the origin of the cell. +Schwann had regarded cell growth as a kind of crystallization, +beginning with the deposit of a nucleus about a granule in the +intercellular substance--the cytoblastema, as Schleiden called +it. But Von Mohl, as early as 1835, had called attention to the +formation of new vegetable cells through the division of a +pre-existing cell. Ehrenberg, another high authority of the time, +contended that no such division occurs, and the matter was still +in dispute when Schleiden came forward with his discovery of +so-called free cell-formation within the parent cell, and this +for a long time diverted attention from the process of division +which Von Mohl had described. All manner of schemes of +cell-formation were put forward during the ensuing years by a +multitude of observers, and gained currency notwithstanding Von +Mohl's reiterated contention that there are really but two ways +in which the formation of new cells takes place--namely, "first, +through division of older cells; secondly, through the formation +of secondary cells lying free in the cavity of a cell." + +But gradually the researches of such accurate observers as Unger, +Nageli, Kolliker, Reichart, and Remak tended to confirm the +opinion of Von Mohl that cells spring only from cells, and +finally Rudolf Virchow brought the matter to demonstration about +1860. His Omnis cellula e cellula became from that time one of +the accepted data of physiology. This was supplemented a little +later by Fleming's Omnis nucleus e nucleo, when still more +refined methods of observation had shown that the part of the +cell which always first undergoes change preparatory to new +cell-formation is the all-essential nucleus. Thus the nucleus was +restored to the important position which Schwann and Schleiden +had given it, but with greatly altered significance. Instead of +being a structure generated de novo from non-cellular substance, +and disappearing as soon as its function of cell-formation was +accomplished, the nucleus was now known as the central and +permanent feature of every cell, indestructible while the cell +lives, itself the division-product of a pre-existing nucleus, and +the parent, by division of its substance, of other generations of +nuclei. The word cell received a final definition as "a small +mass of protoplasm supplied with a nucleus." + +In this widened and culminating general view of the cell theory +it became clear that every animate organism, animal or vegetable, +is but a cluster of nucleated cells, all of which, in each +individual case, are the direct descendants of a single +primordial cell of the ovum. In the developed individuals of +higher organisms the successive generations of cells become +marvellously diversified in form and in specific functions; there +is a wonderful division of labor, special functions being chiefly +relegated to definite groups of cells; but from first to last +there is no function developed that is not present, in a +primitive way, in every cell, however isolated; nor does the +developed cell, however specialized, ever forget altogether any +one of its primordial functions or capacities. All physiology, +then, properly interpreted, becomes merely a study of cellular +activities; and the development of the cell theory takes its +place as the great central generalization in physiology of the +nineteenth century. Something of the later developments of this +theory we shall see in another connection. + + +ANIMAL CHEMISTRY + +Just at the time when the microscope was opening up the paths +that were to lead to the wonderful cell theory, another novel +line of interrogation of the living organism was being put +forward by a different set of observers. Two great schools of +physiological chemistry had arisen--one under guidance of Liebig +and Wohler, in Germany, the other dominated by the great French +master Jean Baptiste Dumas. Liebig had at one time contemplated +the study of medicine, and Dumas had achieved distinction in +connection with Prevost, at Geneva, in the field of pure +physiology before he turned his attention especially to +chemistry. Both these masters, therefore, and Wohler as well, +found absorbing interest in those phases of chemistry that have +to do with the functions of living tissues; and it was largely +through their efforts and the labors of their followers that the +prevalent idea that vital processes are dominated by unique laws +was discarded and physiology was brought within the recognized +province of the chemist. So at about the time when the microscope +had taught that the cell is the really essential structure of the +living organism, the chemists had come to understand that every +function of the organism is really the expression of a chemical +change--that each cell is, in short, a miniature chemical +laboratory. And it was this combined point of view of anatomist +and chemist, this union of hitherto dissociated forces, that made +possible the inroads into the unexplored fields of physiology +that were effected towards the middle of the nineteenth century. + +One of the first subjects reinvestigated and brought to proximal +solution was the long-mooted question of the digestion of foods. +Spallanzani and Hunter had shown in the previous century that +digestion is in some sort a solution of foods; but little advance +was made upon their work until 1824, when Prout detected the +presence of hydrochloric acid in the gastric juice. A decade +later Sprott and Boyd detected the existence of peculiar glands +in the gastric mucous membrane; and Cagniard la Tour and Schwann +independently discovered that the really active principle of the +gastric juice is a substance which was named pepsin, and which +was shown by Schwann to be active in the presence of hydrochloric +acid. + +Almost coincidently, in 1836, it was discovered by Purkinje and +Pappenheim that another organ than the stomach--namely, the +pancreas--has a share in digestion, and in the course of the +ensuing decade it came to be known, through the efforts of +Eberle, Valentin, and Claude Bernard, that this organ is +all-important in the digestion of starchy and fatty foods. It was +found, too, that the liver and the intestinal glands have each an +important share in the work of preparing foods for absorption, as +also has the saliva--that, in short, a coalition of forces is +necessary for the digestion of all ordinary foods taken into the +stomach. + +And the chemists soon discovered that in each one of the +essential digestive juices there is at least one substance having +certain resemblances to pepsin, though acting on different kinds +of food. The point of resemblance between all these essential +digestive agents is that each has the remarkable property of +acting on relatively enormous quantities of the substance which +it can digest without itself being destroyed or apparently even +altered. In virtue of this strange property, pepsin and the +allied substances were spoken of as ferments, but more recently +it is customary to distinguish them from such organized ferments +as yeast by designating them enzymes. The isolation of these +enzymes, and an appreciation of their mode of action, mark a long +step towards the solution of the riddle of digestion, but it must +be added that we are still quite in the dark as to the real +ultimate nature of their strange activity. + +In a comprehensive view, the digestive organs, taken as a whole, +are a gateway between the outside world and the more intimate +cells of the organism. Another equally important gateway is +furnished by the lungs, and here also there was much obscurity +about the exact method of functioning at the time of the revival +of physiological chemistry. That oxygen is consumed and carbonic +acid given off during respiration the chemists of the age of +Priestley and Lavoisier had indeed made clear, but the mistaken +notion prevailed that it was in the lungs themselves that the +important burning of fuel occurs, of which carbonic acid is a +chief product. But now that attention had been called to the +importance of the ultimate cell, this misconception could not +long hold its ground, and as early as 1842 Liebig, in the course +of his studies of animal heat, became convinced that it is not in +the lungs, but in the ultimate tissues to which they are +tributary, that the true consumption of fuel takes place. +Reviving Lavoisier's idea, with modifications and additions, +Liebig contended, and in the face of opposition finally +demonstrated, that the source of animal heat is really the +consumption of the fuel taken in through the stomach and the +lungs. He showed that all the activities of life are really the +product of energy liberated solely through destructive processes, +amounting, broadly speaking, to combustion occurring in the +ultimate cells of the organism. Here is his argument: + + +LIEBIG ON ANIMAL HEAT + +"The oxygen taken into the system is taken out again in the same +forms, whether in summer or in winter; hence we expire more +carbon in cold weather, and when the barometer is high, than we +do in warm weather; and we must consume more or less carbon in +our food in the same proportion; in Sweden more than in Sicily; +and in our more temperate climate a full eighth more in winter +than in summer. + +"Even when we consume equal weights of food in cold and warm +countries, infinite wisdom has so arranged that the articles of +food in different climates are most unequal in the proportion of +carbon they contain. The fruits on which the natives of the South +prefer to feed do not in the fresh state contain more than twelve +per cent. of carbon, while the blubber and train-oil used by the +inhabitants of the arctic regions contain from sixty-six to +eighty per cent. of carbon. + +"It is no difficult matter, in warm climates, to study moderation +in eating, and men can bear hunger for a long time under the +equator; but cold and hunger united very soon exhaust the body. + +"The mutual action between the elements of the food and the +oxygen conveyed by the circulation of the blood to every part of +the body is the source of animal heat. + +"All living creatures whose existence depends on the absorption +of oxygen possess within themselves a source of heat independent +of surrounding objects. + +"This truth applies to all animals, and extends besides to the +germination of seeds, to the flowering of plants, and to the +maturation of fruits. It is only in those parts of the body to +which arterial blood, and with it the oxygen absorbed in +respiration, is conveyed that heat is produced. Hair, wool, or +feathers do not possess an elevated temperature. This high +temperature of the animal body, or, as it may be called, +disengagement of heat, is uniformly and under all circumstances +the result of the combination of combustible substance with +oxygen. + +"In whatever way carbon may combine with oxygen, the act of +combination cannot take place without the disengagement of heat. +It is a matter of indifference whether the combination takes +place rapidly or slowly, at a high or at a low temperature; the +amount of heat liberated is a constant quantity. The carbon of +the food, which is converted into carbonic acid within the body, +must give out exactly as much heat as if it had been directly +burned in the air or in oxygen gas; the only difference is that +the amount of heat produced is diffused over unequal times. In +oxygen the combustion is more rapid and the heat more intense; in +air it is slower, the temperature is not so high, but it +continues longer. + +"It is obvious that the amount of heat liberated must increase or +diminish with the amount of oxygen introduced in equal times by +respiration. Those animals which respire frequently, and +consequently consume much oxygen, possess a higher temperature +than others which, with a body of equal size to be heated, take +into the system less oxygen. The temperature of a child (102 +degrees) is higher than that of an adult (99.5 degrees). That of +birds (104 to 105.4 degrees) is higher than that of quadrupeds +(98.5 to 100.4 degrees), or than that of fishes or amphibia, +whose proper temperature is from 3.7 to 2.6 degrees higher than +that of the medium in which they live. All animals, strictly +speaking, are warm-blooded; but in those only which possess lungs +is the temperature of the body independent of the surrounding +medium. + +"The most trustworthy observations prove that in all climates, in +the temperate zones as well as at the equator or the poles, the +temperature of the body in man, and of what are commonly called +warm-blooded animals, is invariably the same; yet how different +are the circumstances in which they live. + +"The animal body is a heated mass, which bears the same relation +to surrounding objects as any other heated mass. It receives heat +when the surrounding objects are hotter, it loses heat when they +are colder than itself. We know that the rapidity of cooling +increases with the difference between the heated body and that of +the surrounding medium--that is, the colder the surrounding +medium the shorter the time required for the cooling of the +heated body. How unequal, then, must be the loss of heat of a man +at Palermo, where the actual temperature is nearly equal to that +of the body, and in the polar regions, where the external +temperature is from 70 to 90 degrees lower. + +"Yet notwithstanding this extremely unequal loss of heat, +experience has shown that the blood of an inhabitant of the +arctic circle has a temperature as high as that of the native of +the South, who lives in so different a medium. This fact, when +its true significance is perceived, proves that the heat given +off to the surrounding medium is restored within the body with +great rapidity. This compensation takes place more rapidly in +winter than in summer, at the pole than at the equator. + +"Now in different climates the quantity of oxygen introduced into +the system of respiration, as has been already shown, varies +according to the temperature of the external air; the quantity of +inspired oxygen increases with the loss of heat by external +cooling, and the quantity of carbon or hydrogen necessary to +combine with this oxygen must be increased in like ratio. It is +evident that the supply of heat lost by cooling is effected by +the mutual action of the elements of the food and the inspired +oxygen, which combine together. To make use of a familiar, but +not on that account a less just illustration, the animal body +acts, in this respect, as a furnace, which we supply with fuel. +It signifies nothing what intermediate forms food may assume, +what changes it may undergo in the body, the last change is +uniformly the conversion of carbon into carbonic acid and of its +hydrogen into water; the unassimilated nitrogen of the food, +along with the unburned or unoxidized carbon, is expelled in the +excretions. In order to keep up in a furnace a constant +temperature, we must vary the supply of fuel according to the +external temperature--that is, according to the supply of oxygen. + +"In the animal body the food is the fuel; with a proper supply of +oxygen we obtain the heat given out during its oxidation or +combustion."[3] + + +BLOOD CORPUSCLES, MUSCLES, AND GLANDS + +Further researches showed that the carriers of oxygen, from the +time of its absorption in the lungs till its liberation in the +ultimate tissues, are the red corpuscles, whose function had been +supposed to be the mechanical one of mixing of the blood. It +transpired that the red corpuscles are composed chiefly of a +substance which Kuhne first isolated in crystalline form in 1865, +and which was named haemoglobin--a substance which has a +marvellous affinity for oxygen, seizing on it eagerly at the +lungs vet giving it up with equal readiness when coursing among +the remote cells of the body. When freighted with oxygen it +becomes oxyhaemoglobin and is red in color; when freed from its +oxygen it takes a purple hue; hence the widely different +appearance of arterial and venous blood, which so puzzled the +early physiologists. + +This proof of the vitally important role played by the red-blood +corpuscles led, naturally, to renewed studies of these +infinitesimal bodies. It was found that they may vary greatly in +number at different periods in the life of the same individual, +proving that they may be both developed and destroyed in the +adult organism. Indeed, extended observations left no reason to +doubt that the process of corpuscle formation and destruction may +be a perfectly normal one--that, in short, every red-blood +corpuscle runs its course and dies like any more elaborate +organism. They are formed constantly in the red marrow of bones, +and are destroyed in the liver, where they contribute to the +formation of the coloring matter of the bile. Whether there are +other seats of such manufacture and destruction of the corpuscles +is not yet fully determined. Nor are histologists agreed as to +whether the red-blood corpuscles themselves are to be regarded as +true cells, or merely as fragments of cells budded out from a +true cell for a special purpose; but in either case there is not +the slightest doubt that the chief function of the red corpuscle +is to carry oxygen. + +If the oxygen is taken to the ultimate cells before combining +with the combustibles it is to consume, it goes without saying +that these combustibles themselves must be carried there also. +Nor could it be in doubt that the chiefest of these ultimate +tissues, as regards, quantity of fuel required, are the muscles. +A general and comprehensive view of the organism includes, then, +digestive apparatus and lungs as the channels of fuel-supply; +blood and lymph channels as the transportation system; and muscle +cells, united into muscle fibres, as the consumption furnaces, +where fuel is burned and energy transformed and rendered +available for the purposes of the organism, supplemented by a set +of excretory organs, through which the waste products--the +ashes--are eliminated from the system. + +But there remain, broadly speaking, two other sets of organs +whose size demonstrates their importance in the economy of the +organism, yet whose functions are not accounted for in this +synopsis. These are those glandlike organs, such as the spleen, +which have no ducts and produce no visible secretions, and the +nervous mechanism, whose central organs are the brain and spinal +cord. What offices do these sets of organs perform in the great +labor-specializing aggregation of cells which we call a living +organism? + +As regards the ductless glands, the first clew to their function +was given when the great Frenchman Claude Bernard (the man of +whom his admirers loved to say, "He is not a physiologist merely; +he is physiology itself") discovered what is spoken of as the +glycogenic function of the liver. The liver itself, indeed, is +not a ductless organ, but the quantity of its biliary output +seems utterly disproportionate to its enormous size, particularly +when it is considered that in the case of the human species the +liver contains normally about one-fifth of all the blood in the +entire body. Bernard discovered that the blood undergoes a change +of composition in passing through the liver. The liver cells +(the peculiar forms of which had been described by Purkinje, +Henle, and Dutrochet about 1838) have the power to convert +certain of the substances that come to them into a starchlike +compound called glycogen, and to store this substance away till +it is needed by the organism. This capacity of the liver cells +is quite independent of the bile-making power of the same cells; +hence the discovery of this glycogenic function showed that an +organ may have more than one pronounced and important specific +function. But its chief importance was in giving a clew to those +intermediate processes between digestion and final assimilation +that are now known to be of such vital significance in the +economy of the organism. + +In the forty odd years that have elapsed since this pioneer +observation of Bernard, numerous facts have come to light showing +the extreme importance of such intermediate alterations of +food-supplies in the blood as that performed by the liver. It has +been shown that the pancreas, the spleen, the thyroid gland, the +suprarenal capsules are absolutely essential, each in its own +way, to the health of the organism, through metabolic changes +which they alone seem capable of performing; and it is suspected +that various other tissues, including even the muscles +themselves, have somewhat similar metabolic capacities in +addition to their recognized functions. But so extremely +intricate is the chemistry of the substances involved that in no +single case has the exact nature of the metabolisms wrought by +these organs been fully made out. Each is in its way a chemical +laboratory indispensable to the right conduct of the organism, +but the precise nature of its operations remains inscrutable. The +vast importance of the operations of these intermediate organs is +unquestioned. + +A consideration of the functions of that other set of organs +known collectively as the nervous system is reserved for a later +chapter. + + + +VI. THEORIES OF ORGANIC EVOLUTION + +GOETHE AND THE METAMORPHOSIS OF PARTS + +When Coleridge said of Humphry Davy that he might have been the +greatest poet of his time had he not chosen rather to be the +greatest chemist, it is possible that the enthusiasm of the +friend outweighed the caution of the critic. But however that +may be, it is beyond dispute that the man who actually was the +greatest poet of that time might easily have taken the very +highest rank as a scientist had not the muse distracted his +attention. Indeed, despite these distractions, Johann Wolfgang +von Goethe achieved successes in the field of pure science that +would insure permanent recognition for his name had he never +written a stanza of poetry. Such is the versatility that marks +the highest genius. + +It was in 1790 that Goethe published the work that laid the +foundations of his scientific reputation--the work on the +Metamorphoses of Plants, in which he advanced the novel doctrine +that all parts of the flower are modified or metamorphosed +leaves. + +"Every one who observes the growth of plants, even +superficially," wrote Goethe, "will notice that certain external +parts of them become transformed at times and go over into the +forms of the contiguous parts, now completely, now to a greater +or less degree. Thus, for example, the single flower is +transformed into a double one when, instead of stamens, petals +are developed, which are either exactly like the other petals of +the corolla in form, and color or else still bear visible signs +of their origin. + +"When we observe that it is possible for a plant in this way to +take a step backward, we shall give so much the more heed to the +regular course of nature and learn the laws of transformation +according to which she produces one part through another, and +displays the most varying forms through the modification of one +single organ. + +"Let us first direct our attention to the plant at the moment +when it develops out of the seed-kernel. The first organs of its +upward growth are known by the name of cotyledons; they have also +been called seed-leaves. + +"They often appear shapeless, filled with new matter, and are +just as thick as they are broad. Their vessels are +unrecognizable and are hardly to be distinguished from the mass +of the whole; they bear almost no resemblance to a leaf, and we +could easily be misled into regarding them as special organs. +Occasionally, however, they appear as real leaves, their vessels +are capable of the most minute development, their similarity to +the following leaves does not permit us to take them for special +organs, but we recognize them instead to be the first leaves of +the stalk. + +"The cotyledons are mostly double, and there is an observation to +be made here which will appear still more important as we +proceed--that is, that the leaves of the first node are often +paired, even when the following leaves of the stalk stand +alternately upon it. Here we see an approximation and a joining +of parts which nature afterwards separates and places at a +distance from one another. It is still more remarkable when the +cotyledons take the form of many little leaves gathered about an +axis, and the stalk which grows gradually from their midst +produces the following leaves arranged around it singly in a +whorl. This may be observed very exactly in the growth of the +pinus species. Here a corolla of needles forms at the same time a +calyx, and we shall have occasion to remember the present case in +connection with similar phenomena later. + +"On the other hand, we observe that even the cotyledons which are +most like a leaf when compared with the following leaves of the +stalk are always more undeveloped or less developed. This is +chiefly noticeable in their margin which is extremely simple and +shows few traces of indentation. + +"A few or many of the next following leaves are often already +present in the seed, and lie enclosed between the cotyledons; in +their folded state they are known by the name of plumules. Their +form, as compared with the cotyledons and the following leaves, +varies in different plants. Their chief point of variance, +however, from the cotyledons is that they are flat, delicate, and +formed like real leaves generally. They are wholly green, rest on +a visible node, and can no longer deny their relationship to the +following leaves of the stalk, to which, however, they are +usually still inferior, in so far as that their margin is not +completely developed. + +"The further development, however, goes on ceaselessly in the +leaf, from node to node; its midrib is elongated, and more or +less additional ribs stretch out from this towards the sides. The +leaves now appear notched, deeply indented, or composed of +several small leaves, in which last case they seem to form +complete little branches. The date-palm furnishes a striking +example of such a successive transformation of the simplest leaf +form. A midrib is elongated through a succession of several +leaves, the single fan-shaped leaf becomes torn and diverted, and +a very complicated leaf is developed, which rivals a branch in +form. + +"The transition to inflorescence takes place more or less +rapidly. In the latter case we usually observe that the leaves of +the stalk loose their different external divisions, and, on the +other hand, spread out more or less in their lower parts where +they are attached to the stalk. If the transition takes place +rapidly, the stalk, suddenly become thinner and more elongated +since the node of the last-developed leaf, shoots up and collects +several leaves around an axis at its end. + +"That the petals of the calyx are precisely the same organs which +have hitherto appeared as leaves on the stalk, but now stand +grouped about a common centre in an often very different form, +can, as it seems to me, be most clearly demonstrated. Already in +connection with the cotyledons above, we noticed a similar +working of nature. The first species, while they are developing +out of the seed-kernel, display a radiate crown of unmistakable +needles; and in the first childhood of these plants we see +already indicated that force of nature whereby when they are +older their flowering and fruit-giving state will be produced. + +"We see this force of nature, which collects several leaves +around an axis, produce a still closer union and make these +approximated, modified leaves still more unrecognizable by +joining them together either wholly or partially. The +bell-shaped or so-called one-petalled calices represent these +cloudy connected leaves, which, being more or less indented from +above, or divided, plainly show their origin. + +"We can observe the transition from the calyx to the corolla in +more than one instance, for, although the color of the calyx is +still usually green, and like the color of the leaves of the +stalk, it nevertheless often varies in one or another of its +parts--at the tips, the margins, the back, or even, the inward +side--while the outer still remains on green. + +"The relationship of the corolla to the leaves of the stalk is +shown in more than one way, since on the stalks of some plants +appear leaves which are already more or less colored long before +they approach inflorescence; others are fully colored when near +inflorescence. Nature also goes over at once to the corolla, +sometimes by skipping over the organs of the calyx, and in such a +case we likewise have an opportunity to observe that leaves of +the stalk become transformed into petals. Thus on the stalk of +tulips, for instance, there sometimes appears an almost +completely developed and colored petal. Even more remarkable is +the case when such a leaf, half green and half of it belonging to +the stalk, remains attached to the latter, while another colored +part is raised with the corolla, and the leaf is thus torn in +two. + +"The relationship between the petals and stamens is very close. +In some instances nature makes the transition regular--e.g., +among the Canna and several plants of the same family. A true, +little-modified petal is drawn together on its upper margin, and +produces a pollen sac, while the rest of the petal takes the +place of the stamen. In double flowers we can observe this +transition in all its stages. In several kinds of roses, within +the fully developed and colored petals there appear other ones +which are drawn together in the middle or on the side. This +drawing together is produced by a small weal, which appears as a +more or less complete pollen sac, and in the same proportion the +leaf approaches the simple form of a stamen. + +"The pistil in many cases looks almost like a stamen without +anthers, and the relationship between the formation of the two is +much closer than between the other parts. In retrograde fashion +nature often produces cases where the style and stigma (Narben) +become retransformed into petals--that is, the Ranunculus +Asiaticus becomes double by transforming the stigma and style of +the fruit-receptacle into real petals, while the stamens are +often found unchanged immediately behind the corolla. + +"In the seed receptacles, in spite of their formation, of their +special object, and of their method of being joined together, we +cannot fail to recognize the leaf form. Thus, for instance, the +pod would be a simple leaf folded and grown together on its +margin; the siliqua would consist of more leaves folded over +another; the compound receptacles would be explained as being +several leaves which, being united above one centre, keep their +inward parts separate and are joined on their margins. We can +convince ourselves of this by actual sight when such composite +capsules fall apart after becoming ripe, because then every part +displays an opened pod."[1] + + +The theory thus elaborated of the metamorphosis of parts was +presently given greater generality through extension to the +animal kingdom, in the doctrine which Goethe and Oken advanced +independently, that the vertebrate skull is essentially a +modified and developed vertebra. These were conceptions worthy of +a poet--impossible, indeed, for any mind that had not the poetic +faculty of correlation. But in this case the poet's vision was +prophetic of a future view of the most prosaic science. The +doctrine of metamorphosis of parts soon came to be regarded as of +fundamental importance. + +But the doctrine had implications that few of its early advocates +realized. If all the parts of a flower--sepal, petal, stamen, +pistil, with their countless deviations of contour and color--are +but modifications of the leaf, such modification implies a +marvellous differentiation and development. To assert that a +stamen is a metamorphosed leaf means, if it means anything, that +in the long sweep of time the leaf has by slow or sudden +gradations changed its character through successive generations, +until the offspring, so to speak, of a true leaf has become a +stamen. But if such a metamorphosis as this is possible--if the +seemingly wide gap between leaf and stamen may be spanned by the +modification of a line of organisms--where does the possibility +of modification of organic type find its bounds? Why may not the +modification of parts go on along devious lines until the remote +descendants of an organism are utterly unlike that organism? Why +may we not thus account for the development of various species of +beings all sprung from one parent stock? That, too, is a poet's +dream; but is it only a dream? Goethe thought not. Out of his +studies of metamorphosis of parts there grew in his mind the +belief that the multitudinous species of plants and animals about +us have been evolved from fewer and fewer earlier parent types, +like twigs of a giant tree drawing their nurture from the same +primal root. It was a bold and revolutionary thought, and the +world regarded it as but the vagary of a poet. + + +ERASMUS DARWIN + +Just at the time when this thought was taking form in Goethe's +brain, the same idea was germinating in the mind of another +philosopher, an Englishman of international fame, Dr. Erasmus +Darwin, who, while he lived, enjoyed the widest popularity as a +poet, the rhymed couplets of his Botanic Garden being quoted +everywhere with admiration. And posterity repudiating the verse +which makes the body of the book, yet grants permanent value to +the book itself, because, forsooth, its copious explanatory +foot-notes furnish an outline of the status of almost every +department of science of the time. + +But even though he lacked the highest art of the versifier, +Darwin had, beyond peradventure, the imagination of a poet +coupled with profound scientific knowledge; and it was his poetic +insight, correlating organisms seemingly diverse in structure and +imbuing the lowliest flower with a vital personality, which led +him to suspect that there are no lines of demarcation in nature. +"Can it be," he queries, "that one form of organism has developed +from another; that different species are really but modified +descendants of one parent stock?" The alluring thought nestled +in his mind and was nurtured there, and grew in a fixed belief, +which was given fuller expression in his Zoonomia and in the +posthumous Temple of Nature. + +Here is his rendering of the idea as versified in the Temple of +Nature: + + "Organic life beneath the shoreless waves + Was born, and nursed in Ocean's pearly caves; + First forms minute, unseen by spheric glass, + Move on the mud, or pierce the watery mass; + These, as successive generations bloom, + New powers acquire and larger limbs assume; + Whence countless groups of vegetation spring, + And breathing realms of fin, and feet, and wing. + + "Thus the tall Oak, the giant of the wood, + Which bears Britannia's thunders on the flood; + The Whale, unmeasured monster of the main; + The lordly lion, monarch of the plain; + The eagle, soaring in the realms of air, + Whose eye, undazzled, drinks the solar glare; + Imperious man, who rules the bestial crowd, + Of language, reason, and reflection proud, + With brow erect, who scorns this earthy sod, + And styles himself the image of his God-- + Arose from rudiments of form and sense, + An embryon point or microscopic ens!"[2] + + +Here, clearly enough, is the idea of evolution. But in that day +there was little proof forthcoming of its validity that could +satisfy any one but a poet, and when Erasmus Darwin died, in +1802, the idea of transmutation of species was still but an +unsubstantiated dream. + +It was a dream, however, which was not confined to Goethe and +Darwin. Even earlier the idea had come more or less vaguely to +another great dreamer--and worker--of Germany, Immanuel Kant, and +to several great Frenchmen, including De Maillet, Maupertuis, +Robinet, and the famous naturalist Buffon--a man who had the +imagination of a poet, though his message was couched in most +artistic prose. Not long after the middle of the eighteenth +century Buffon had put forward the idea of transmutation of +species, and he reiterated it from time to time from then on till +his death in 1788. But the time was not yet ripe for the idea of +transmutation of species to burst its bonds. + +And yet this idea, in a modified or undeveloped form, had taken +strange hold upon the generation that was upon the scene at the +close of the eighteenth century. Vast numbers of hitherto unknown +species of animals had been recently discovered in previously +unexplored regions of the globe, and the wise men were sorely +puzzled to account for the disposal of all of these at the time +of the deluge. It simplified matters greatly to suppose that +many existing species had been developed since the episode of the +ark by modification of the original pairs. The remoter bearings +of such a theory were overlooked for the time, and the idea that +American animals and birds, for example, were modified +descendants of Old-World forms--the jaguar of the leopard, the +puma of the lion, and so on--became a current belief with that +class of humanity who accept almost any statement as true that +harmonizes with their prejudices without realizing its +implications. + +Thus it is recorded with eclat that the discovery of the close +proximity of America at the northwest with Asia removes all +difficulties as to the origin of the Occidental faunas and +floras, since Oriental species might easily have found their way +to America on the ice, and have been modified as we find them by +"the well-known influence of climate." And the persons who gave +expression to this idea never dreamed of its real significance. +In truth, here was the doctrine of evolution in a nutshell, and, +because its ultimate bearings were not clear, it seemed the most +natural of doctrines. But most of the persons who advanced it +would have turned from it aghast could they have realized its +import. As it was, however, only here and there a man like Buffon +reasoned far enough to inquire what might be the limits of such +assumed transmutation; and only here and there a Darwin or a +Goethe reached the conviction that there are no limits. + + +LAMARCK VERSUS CUVIER + +And even Goethe and Darwin had scarcely passed beyond that +tentative stage of conviction in which they held the thought of +transmutation of species as an ancillary belief not ready for +full exposition. There was one of their contemporaries, however, +who, holding the same conception, was moved to give it full +explication. This was the friend and disciple of Buffon, Jean +Baptiste de Lamarck. Possessed of the spirit of a poet and +philosopher, this great Frenchman had also the widest range of +technical knowledge, covering the entire field of animate nature. +The first half of his long life was devoted chiefly to botany, in +which he attained high distinction. Then, just at the beginning +of the nineteenth century, he turned to zoology, in particular to +the lower forms of animal life. Studying these lowly organisms, +existing and fossil, he was more and more impressed with the +gradations of form everywhere to be seen; the linking of diverse +families through intermediate ones; and in particular with the +predominance of low types of life in the earlier geological +strata. Called upon constantly to classify the various forms of +life in the course of his systematic writings, he found it more +and more difficult to draw sharp lines of demarcation, and at +last the suspicion long harbored grew into a settled conviction +that there is really no such thing as a species of organism in +nature; that "species" is a figment of the human imagination, +whereas in nature there are only individuals. + +That certain sets of individuals are more like one another than +like other sets is of course patent, but this only means, said +Lamarck, that these similar groups have had comparatively recent +common ancestors, while dissimilar sets of beings are more +remotely related in consanguinity. But trace back the lines of +descent far enough, and all will culminate in one original stock. +All forms of life whatsoever are modified descendants of an +original organism. From lowest to highest, then, there is but one +race, one species, just as all the multitudinous branches and +twigs from one root are but one tree. For purposes of convenience +of description, we may divide organisms into orders, families, +genera, species, just as we divide a tree into root, trunk, +branches, twigs, leaves; but in the one case, as in the other, +the division is arbitrary and artificial. + +In Philosophie Zoologique (1809), Lamarck first explicitly +formulated his ideas as to the transmutation of species, though +he had outlined them as early as 1801. In this memorable +publication not only did he state his belief more explicitly and +in fuller detail than the idea had been expressed by any +predecessor, but he took another long forward step, carrying him +far beyond all his forerunners except Darwin, in that he made an +attempt to explain the way in which the transmutation of species +had been brought about. The changes have been wrought, he said, +through the unceasing efforts of each organism to meet the needs +imposed upon it by its environment. Constant striving means the +constant use of certain organs. Thus a bird running by the +seashore is constantly tempted to wade deeper and deeper in +pursuit of food; its incessant efforts tend to develop its legs, +in accordance with the observed principle that the use of any +organ tends to strengthen and develop it. But such slightly +increased development of the legs is transmitted to the off +spring of the bird, which in turn develops its already improved +legs by its individual efforts, and transmits the improved +tendency. Generation after generation this is repeated, until the +sum of the infinitesimal variations, all in the same direction, +results in the production of the long-legged wading-bird. In a +similar way, through individual effort and transmitted tendency, +all the diversified organs of all creatures have been +developed--the fin of the fish, the wing of the bird, the hand of +man; nay, more, the fish itself, the bird, the man, even. +Collectively the organs make up the entire organism; and what is +true of the individual organs must be true also of their +ensemble, the living being. + +Whatever might be thought of Lamarck's explanation of the cause +of transmutation--which really was that already suggested by +Erasmus Darwin--the idea of the evolution for which he contended +was but the logical extension of the conception that American +animals are the modified and degenerated descendants of European +animals. But people as a rule are little prone to follow ideas to +their logical conclusions, and in this case the conclusions were +so utterly opposed to the proximal bearings of the idea that the +whole thinking world repudiated them with acclaim. The very +persons who had most eagerly accepted the idea of transmutation +of European species into American species, and similar limited +variations through changed environment, because of the relief +thus given the otherwise overcrowded ark, were now foremost in +denouncing such an extension of the doctrine of transmutation as +Lamarck proposed. + +And, for that matter, the leaders of the scientific world were +equally antagonistic to the Lamarckian hypothesis. Cuvier in +particular, once the pupil of Lamarck, but now his colleague, and +in authority more than his peer, stood out against the +transmutation doctrine with all his force. He argued for the +absolute fixity of species, bringing to bear the resources of a +mind which, as a mere repository of facts, perhaps never was +excelled. As a final and tangible proof of his position, he +brought forward the bodies of ibises that had been embalmed by +the ancient Egyptians, and showed by comparison that these do not +differ in the slightest particular from the ibises that visit the +Nile to-day. + +Cuvier's reasoning has such great historical interest--being the +argument of the greatest opponent of evolution of that day--that +we quote it at some length. + +"The following objections," he says, "have already been started +against my conclusions. Why may not the presently existing races +of mammiferous land quadrupeds be mere modifications or varieties +of those ancient races which we now find in the fossil state, +which modifications may have been produced by change of climate +and other local circumstances, and since raised to the present +excessive difference by the operations of similar causes during a +long period of ages? + +"This objection may appear strong to those who believe in the +indefinite possibility of change of form in organized bodies, and +think that, during a succession of ages and by alterations of +habitudes, all the species may change into one another, or one of +them give birth to all the rest. Yet to these persons the +following answer may be given from their own system: If the +species have changed by degrees, as they assume, we ought to find +traces of this gradual modification. Thus, between the +palaeotherium and the species of our own day, we should be able +to discover some intermediate forms; and yet no such discovery +has ever been made. Since the bowels of the earth have not +preserved monuments of this strange genealogy, we have no right +to conclude that the ancient and now extinct species were as +permanent in their forms and characters as those which exist at +present; or, at least, that the catastrophe which destroyed them +did not leave sufficient time for the productions of the changes +that are alleged to have taken place. + +"In order to reply to those naturalists who acknowledge that the +varieties of animals are restrained by nature within certain +limits, it would be necessary to examine how far these limits +extend. This is a very curious inquiry, and in itself exceedingly +interesting under a variety of relations, but has been hitherto +very little attended to. . . . . . . . . + +Wild animals which subsist upon herbage feel the influence of +climate a little more extensively, because there is added to it +the influence of food, both in regard to its abundance and its +quality. Thus the elephants of one forest are larger than those +of another; their tusks also grow somewhat longer in places where +their food may happen to be more favorable for the production of +the substance of ivory. The same may take place in regard to the +horns of stags and reindeer. But let us examine two elephants, +the most dissimilar that can be conceived, we shall not discover +the smallest difference in the number and articulations of the +bones, the structure of the teeth, etc. . . . . . . . . + +"Nature appears also to have guarded against the alterations of +species which might proceed from mixture of breeds by influencing +the various species of animals with mutual aversion from one +another. Hence all the cunning and all the force that man is able +to exert is necessary to accomplish such unions, even between +species that have the nearest resemblances. And when the mule +breeds that are thus produced by these forced conjunctions happen +to be fruitful, which is seldom the case, this fecundity never +continues beyond a few generations, and would not probably +proceed so far without a continuance of the same cares which +excited it at first. Thus we never see in a wild state +intermediate productions between the hare and the rabbit, between +the stag and the doe, or between the marten and the weasel. But +the power of man changes this established order, and continues to +produce all these intermixtures of which the various species are +susceptible, but which they would never produce if left to +themselves. + +"The degrees of these variations are proportional to the +intensity of the causes that produced them--namely, the slavery +or subjection under which those animals are to man. They do not +proceed far in half-domesticated species. In the cat, for +example, a softer or harsher fur, more brilliant or more varied +colors, greater or less size--these form the whole extent of +variety in the species; the skeleton of the cat of Angora differs +in no regular and constant circumstances from the wild-cat of +Europe. . . . . . . . + +The most remarkable effects of the influence of man are produced +upon that animal which he has reduced most completely under +subjection. Dogs have been transported by mankind into every part +of the world and have submitted their action to his entire +direction. Regulated in their unions by the pleasure or caprice +of their masters, the almost endless varieties of dogs differ +from one another in color, in length, and abundance of hair, +which is sometimes entirely wanting; in their natural instincts; +in size, which varies in measure as one to five, mounting in some +instances to more than a hundredfold in bulk; in the form of +their ears, noses, and tails; in the relative length of their +legs; in the progressive development of the brain, in several of +the domesticated varieties occasioning alterations even in the +form of the head, some of them having long, slender muzzles with +a flat forehead, others having short muzzles with a forehead +convex, etc., insomuch that the apparent difference between a +mastiff and a water-spaniel and between a greyhound and a pugdog +are even more striking than between almost any of the wild +species of a genus. . . . . . . . + +It follows from these observations that animals have certain +fixed and natural characters which resist the effects of every +kind of influence, whether proceeding from natural causes or +human interference; and we have not the smallest reason to +suspect that time has any more effect on them than climate. + +"I am aware that some naturalists lay prodigious stress upon the +thousands which they can call into action by a dash of their +pens. In such matters, however, our only way of judging as to the +effects which may be produced by a long period of time is by +multiplying, as it were, such as are produced by a shorter time. +With this view I have endeavored to collect all the ancient +documents respecting the forms of animals; and there are none +equal to those furnished by the Egyptians, both in regard to +their antiquity and abundance. They have not only left us +representatives of animals, but even their identical bodies +embalmed and preserved in the catacombs. + +"I have examined, with the greatest attention, the engraved +figures of quadrupeds and birds brought from Egypt to ancient +Rome, and all these figures, one with another, have a perfect +resemblance to their intended objects, such as they still are +to-day. + +"From all these established facts, there does not seem to be the +smallest foundation for supposing that the new genera which I +have discovered or established among extraneous fossils, such as +the paleoetherium, anoplotherium, megalonyx, mastodon, +pterodactylis, etc., have ever been the sources of any of our +present animals, which only differ so far as they are influenced +by time or climate. Even if it should prove true, which I am far +from believing to be the case, that the fossil elephants, +rhinoceroses, elks, and bears do not differ further from the +existing species of the same genera than the present races of +dogs differ among themselves, this would by no means be a +sufficient reason to conclude that they were of the same species; +since the races or varieties of dogs have been influenced by the +trammels of domesticity, which those other animals never did, and +indeed never could, experience."[3] + + +To Cuvier's argument from the fixity of Egyptian mummified birds +and animals, as above stated, Lamarck replied that this proved +nothing except that the ibis had become perfectly adapted to its +Egyptian surroundings in an early day, historically speaking, and +that the climatic and other conditions of the Nile Valley had not +since then changed. His theory, he alleged, provided for the +stability of species under fixed conditions quite as well as for +transmutation under varying conditions. + +But, needless to say, the popular verdict lay with Cuvier; talent +won for the time against genius, and Lamarck was looked upon as +an impious visionary. His faith never wavered, however. He +believed that he had gained a true insight into the processes of +animate nature, and he reiterated his hypotheses over and over, +particularly in the introduction to his Histoire Naturelle des +Animaux sans Vertebres, in 1815, and in his Systeme des +Connaissances Positives de l'Homme, in 1820. He lived on till +1829, respected as a naturalist, but almost unrecognized as a +prophet. + + +TENTATIVE ADVANCES + +While the names of Darwin and Goethe, and in particular that of +Lamarck, must always stand out in high relief in this generation +as the exponents of the idea of transmutation of species, there +are a few others which must not be altogether overlooked in this +connection. Of these the most conspicuous is that of Gottfried +Reinhold Treviranus, a German naturalist physician, professor of +mathematics in the lyceum at Bremen. + +It was an interesting coincidence that Treviranus should have +published the first volume of his Biologie, oder Philosophie der +lebenden Natur, in which his views on the transmutation of +species were expounded, in 1802, the same twelvemonth in which +Lamarck's first exposition of the same doctrine appeared in his +Recherches sur l'Organisation des Corps Vivants. It is singular, +too, that Lamarck, in his Hydrogelogie of the same date, should +independently have suggested "biology" as an appropriate word to +express the general science of living things. It is significant +of the tendency of thought of the time that the need of such a +unifying word should have presented itself simultaneously to +independent thinkers in different countries. + +That same memorable year, Lorenz Oken, another philosophical +naturalist, professor in the University of Zurich, published the +preliminary outlines of his Philosophie der Natur, which, as +developed through later publications, outlined a theory of +spontaneous generation and of evolution of species. Thus it +appears that this idea was germinating in the minds of several of +the ablest men of the time during the first decade of our +century. But the singular result of their various explications +was to give sudden check to that undercurrent of thought which +for some time had been setting towards this conception. As soon +as it was made clear whither the concession that animals may be +changed by their environment must logically trend, the recoil +from the idea was instantaneous and fervid. Then for a generation +Cuvier was almost absolutely dominant, and his verdict was +generally considered final. + +There was, indeed, one naturalist of authority in France who had +the hardihood to stand out against Cuvier and his school, and who +was in a position to gain a hearing, though by no means to divide +the following. This was Etienne Geoffroy Saint-Hilaire, the +famous author of the Philosophie Anatomique, and for many years +the colleague of Lamarck at the Jardin des Plantes. Like Goethe, +Geoffroy was pre-eminently an anatomist, and, like the great +German, he had early been impressed with the resemblances between +the analogous organs of different classes of beings. He +conceived the idea that an absolute unity of type prevails +throughout organic nature as regards each set of organs. Out of +this idea grew his gradually formed belief that similarity of +structure might imply identity of origin--that, in short, one +species of animal might have developed from another. + +Geoffroy's grasp of this idea of transmutation was by no means so +complete as that of Lamarck, and he seems never to have fully +determined in his own mind just what might be the limits of such +development of species. Certainly he nowhere includes all organic +creatures in one line of descent, as Lamarck had done; +nevertheless, he held tenaciously to the truth as he saw it, in +open opposition to Cuvier, with whom he held a memorable debate +at the Academy of Sciences in 1830--the debate which so aroused +the interest and enthusiasm of Goethe, but which, in the opinion +of nearly every one else, resulted in crushing defeat for +Geoffrey, and brilliant, seemingly final, victory for the +advocate of special creation and the fixity of species. + +With that all ardent controversy over the subject seemed to end, +and for just a quarter of a century to come there was published +but a single argument for transmutation of species which +attracted any general attention whatever. This oasis in a desert +generation was a little book called Vestiges of the Natural +History of Creation, which appeared anonymously in England in +1844, and which passed through numerous editions, and was the +subject of no end of abusive and derisive comment. This book, the +authorship of which remained for forty years a secret, is now +conceded to have been the work of Robert Chambers, the well-known +English author and publisher. The book itself is remarkable as +being an avowed and unequivocal exposition of a general doctrine +of evolution, its view being as radical and comprehensive as that +of Lamarck himself. But it was a resume of earlier efforts rather +than a new departure, to say nothing of its technical +shortcomings, which may best be illustrated by a quotation. + +"The whole question," says Chambers, "stands thus: For the +theory of universal order--that is, order as presiding in both +the origin and administration of the world--we have the testimony +of a vast number of facts in nature, and this one in +addition--that whatever is left from the domain of ignorance, and +made undoubted matter of science, forms a new support to the same +doctrine. The opposite view, once predominant, has been +shrinking for ages into lesser space, and now maintains a footing +only in a few departments of nature which happen to be less +liable than others to a clear investigation. The chief of these, +if not almost the only one, is the origin of the organic +kingdoms. So long as this remains obscure, the supernatural will +have a certain hold upon enlightened persons. Should it ever be +cleared up in a way that leaves no doubt of a natural origin of +plants and animals, there must be a complete revolution in the +view which is generally taken of the relation of the Father of +our being. + +"This prepares the way for a few remarks on the present state of +opinion with regard to the origin of organic nature. The great +difficulty here is the apparent determinateness of species. These +forms of life being apparently unchangeable, or at least always +showing a tendency to return to the character from which they +have diverged, the idea arises that there can have been no +progression from one to another; each must have taken its special +form, independently of other forms, directly from the appointment +of the Creator. The Edinburgh Review writer says, 'they were +created by the hand of God and adapted to the conditions of the +period.' Now it is, in the first place, not certain that species +constantly maintain a fixed character, for we have seen that what +were long considered as determinate species have been transmuted +into others. Passing, however, from this fact, as it is not +generally received among men of science, there remain some great +difficulties in connection with the idea of special creation. +First we should have to suppose, as pointed out in my former +volume, a most startling diversity of plan in the divine +workings, a great general plan or system of law in the leading +events of world-making, and a plan of minute, nice operation, and +special attention in some of the mere details of the process. The +discrepancy between the two conceptions is surely overpowering, +when we allow ourselves to see the whole matter in a steady and +rational light. There is, also, the striking fact of an +ascertained historical progress of plants and animals in the +order of their organization; marine and cellular plants and +invertebrated animals first, afterwards higher examples of both. +In an arbitrary system we had surely no reason to expect mammals +after reptiles; yet in this order they came. The writer in the +Edinburgh Review speaks of animals as coming in adaptation to +conditions, but this is only true in a limited sense. The groves +which formed the coal-beds might have been a fitting habitation +for reptiles, birds, and mammals, as such groves are at the +present day; yet we see none of the last of these classes and +hardly any traces of the two first at that period of the earth. +Where the iguanodon lived the elephant might have lived, but +there was no elephant at that time. The sea of the Lower Silurian +era was capable of supporting fish, but no fish existed. It +hence forcibly appears that theatres of life must have remained +unserviceable, or in the possession of a tenantry inferior to +what might have enjoyed them, for many ages: there surely would +have been no such waste allowed in a system where Omnipotence was +working upon the plan of minute attention to specialities. The +fact seems to denote that the actual procedure of the peopling of +the earth was one of a natural kind, requiring a long space of +time for its evolution. In this supposition the long existence +of land without land animals, and more particularly without the +noblest classes and orders, is only analogous to the fact, not +nearly enough present to the minds of a civilized people, that to +this day the bulk of the earth is a waste as far as man is +concerned. + +"Another startling objection is in the infinite local variation +of organic forms. Did the vegetable and animal kingdoms consist +of a definite number of species adapted to peculiarities of soil +and climate, and universally distributed, the fact would be in +harmony with the idea of special exertion. But the truth is that +various regions exhibit variations altogether without apparent +end or purpose. Professor Henslow enumerates forty-five distinct +flowers or sets of plants upon the surface of the earth, +notwithstanding that many of these would be equally suitable +elsewhere. The animals of different continents are equally +various, few species being the same in any two, though the +general character may conform. The inference at present drawn +from this fact is that there must have been, to use the language +of the Rev. Dr. Pye Smith, 'separate and original creations, +perhaps at different and respectively distinct epochs.' It seems +hardly conceivable that rational men should give an adherence to +such a doctrine when we think of what it involves. In the single +fact that it necessitates a special fiat of the inconceivable +Author of this sand-cloud of worlds to produce the flora of St. +Helena, we read its more than sufficient condemnation. It surely +harmonizes far better with our general ideas of nature to suppose +that, just as all else in this far-spread science was formed on +the laws impressed upon it at first by its Author, so also was +this. An exception presented to us in such a light appears +admissible only when we succeed in forbidding our minds to follow +out those reasoning processes to which, by another law of the +Almighty, they tend, and for which they are adapted."[4] + + +Such reasoning as this naturally aroused bitter animadversions, +and cannot have been without effect in creating an undercurrent +of thought in opposition to the main trend of opinion of the +time. But the book can hardly be said to have done more than +that. Indeed, some critics have denied it even this merit. After +its publication, as before, the conception of transmutation of +species remained in the popular estimation, both lay and +scientific, an almost forgotten "heresy." + +It is true that here and there a scientist of greater or less +repute--as Von Buch, Meckel, and Von Baer in Germany, Bory +Saint-Vincent in France, Wells, Grant, and Matthew in England, +and Leidy in America--had expressed more or less tentative +dissent from the doctrine of special creation and immutability of +species, but their unaggressive suggestions, usually put forward +in obscure publications, and incidentally, were utterly +overlooked and ignored. And so, despite the scientific advances +along many lines at the middle of the century, the idea of the +transmutability of organic races had no such prominence, either +in scientific or unscientific circles, as it had acquired fifty +years before. Special creation held the day, seemingly unopposed. + + +DARWIN AND THE ORIGIN OF SPECIES + +But even at this time the fancied security of the +special-creation hypothesis was by no means real. Though it +seemed so invincible, its real position was that of an apparently +impregnable fortress beneath which, all unbeknown to the +garrison, a powder-mine has been dug and lies ready for +explosion. For already there existed in the secluded work-room of +an English naturalist, a manuscript volume and a portfolio of +notes which might have sufficed, if given publicity, to shatter +the entire structure of the special-creation hypothesis. The +naturalist who, by dint of long and patient effort, had +constructed this powder-mine of facts was Charles Robert Darwin, +grandson of the author of Zoonomia. + +As long ago as July 1, 1837, young Darwin, then twenty-eight +years of age, had opened a private journal, in which he purposed +to record all facts that came to him which seemed to have any +bearing on the moot point of the doctrine of transmutation of +species. Four or five years earlier, during the course of that +famous trip around the world with Admiral Fitzroy, as naturalist +to the Beagle, Darwin had made the personal observations which +first tended to shake his belief of the fixity of species. In +South America, in the Pampean formation, he had discovered "great +fossil animals covered with armor like that on the existing +armadillos," and had been struck with this similarity of type +between ancient and existing faunas of the same region. He was +also greatly impressed by the manner in which closely related +species of animals were observed to replace one another as he +proceeded southward over the continent; and "by the +South-American character of most of the productions of the +Galapagos Archipelago, and more especially by the manner in which +they differ slightly on each island of the group, none of the +islands appearing to be very ancient in a geological sense." + +At first the full force of these observations did not strike him; +for, under sway of Lyell's geological conceptions, he tentatively +explained the relative absence of life on one of the Galapagos +Islands by suggesting that perhaps no species had been created +since that island arose. But gradually it dawned upon him that +such facts as he had observed "could only be explained on the +supposition that species gradually become modified." From then +on, as he afterwards asserted, the subject haunted him; hence the +journal of 1837. + +It will thus be seen that the idea of the variability of species +came to Charles Darwin as an inference from personal observations +in the field, not as a thought borrowed from books. He had, of +course, read the works of his grandfather much earlier in life, +but the arguments of Zoonomia and The Temple of Nature had not +served in the least to weaken his acceptance of the current +belief in fixity of species. Nor had he been more impressed with +the doctrine of Lamarck, so closely similar to that of his +grandfather. Indeed, even after his South-American experience +had aroused him to a new point of view he was still unable to see +anything of value in these earlier attempts at an explanation of +the variation of species. In opening his journal, therefore, he +had no preconceived notion of upholding the views of these or any +other makers of hypotheses, nor at the time had he formulated any +hypothesis of his own. His mind was open and receptive; he was +eager only for facts which might lead him to an understanding of +a problem which seemed utterly obscure. It was something to feel +sure that species have varied; but how have such variations been +brought about? + +It was not long before Darwin found a clew which he thought might +lead to the answer he sought. In casting about for facts he had +soon discovered that the most available field for observation lay +among domesticated animals, whose numerous variations within +specific lines are familiar to every one. Thus under +domestication creatures so tangibly different as a mastiff and a +terrier have sprung from a common stock. So have the Shetland +pony, the thoroughbred, and the draught-horse. In short, there is +no domesticated animal that has not developed varieties deviating +more or less widely from the parent stock. Now, how has this been +accomplished? Why, clearly, by the preservation, through +selective breeding, of seemingly accidental variations. Thus one +horseman, by constantly selecting animals that "chance" to have +the right build and stamina, finally develops a race of +running-horses; while another horseman, by selecting a different +series of progenitors, has developed a race of slow, heavy +draught animals. + +So far, so good; the preservation of "accidental" variations +through selective breeding is plainly a means by which races may +be developed that are very different from their original parent +form. But this is under man's supervision and direction. By what +process could such selection be brought about among creatures in +a state of nature? Here surely was a puzzle, and one that must be +solved before another step could be taken in this direction. + +The key to the solution of this puzzle came into Darwin's mind +through a chance reading of the famous essay on "Population" +which Thomas Robert Malthus had published almost half a century +before. This essay, expositing ideas by no means exclusively +original with Malthus, emphasizes the fact that organisms tend to +increase at a geometrical ratio through successive generations, +and hence would overpopulate the earth if not somehow kept in +check. Cogitating this thought, Darwin gained a new insight into +the processes of nature. He saw that in virtue of this tendency +of each race of beings to overpopulate the earth, the entire +organic world, animal and vegetable, must be in a state of +perpetual carnage and strife, individual against individual, +fighting for sustenance and life. + +That idea fully imagined, it becomes plain that a selective +influence is all the time at work in nature, since only a few +individuals, relatively, of each generation can come to maturity, +and these few must, naturally, be those best fitted to battle +with the particular circumstances in the midst of which they are +placed. In other words, the individuals best adapted to their +surroundings will, on the average, be those that grow to maturity +and produce offspring. To these offspring will be transmitted the +favorable peculiarities. Thus these peculiarities will become +permanent, and nature will have accomplished precisely what the +human breeder is seen to accomplish. Grant that organisms in a +state of nature vary, however slightly, one from another (which +is indubitable), and that such variations will be transmitted by +a parent to its offspring (which no one then doubted); grant, +further, that there is incessant strife among the various +organisms, so that only a small proportion can come to +maturity--grant these things, said Darwin, and we have an +explanation of the preservation of variations which leads on to +the transmutation of species themselves. + +This wonderful coign of vantage Darwin had reached by 1839. Here +was the full outline of his theory; here were the ideas which +afterwards came to be embalmed in familiar speech in the phrases +"spontaneous variation," and the "survival of the fittest," +through "natural selection." After such a discovery any ordinary +man would at once have run through the streets of science, so to +speak, screaming "Eureka!" Not so Darwin. He placed the +manuscript outline of his theory in his portfolio, and went on +gathering facts bearing on his discovery. In 1844 he made an +abstract in a manuscript book of the mass of facts by that time +accumulated. He showed it to his friend Hooker, made careful +provision for its publication in the event of his sudden death, +then stored it away in his desk and went ahead with the gathering +of more data. This was the unexploded powder-mine to which I have +just referred. + +Twelve years more elapsed--years during which the silent worker +gathered a prodigious mass of facts, answered a multitude of +objections that arose in his own mind, vastly fortified his +theory. All this time the toiler was an invalid, never knowing a +day free from illness and discomfort, obliged to husband his +strength, never able to work more than an hour and a half at a +stretch; yet he accomplished what would have been vast +achievements for half a dozen men of robust health. Two friends +among the eminent scientists of the day knew of his labors--Sir +Joseph Hooker, the botanist, and Sir Charles Lyell, the +geologist. Gradually Hooker had come to be more than half a +convert to Darwin's views. Lyell was still sceptical, yet he +urged Darwin to publish his theory without further delay lest he +be forestalled. At last the patient worker decided to comply with +this advice, and in 1856 he set to work to make another and +fuller abstract of the mass of data he had gathered. + +And then a strange thing happened. After Darwin had been at work +on his "abstract" about two years, but before he had published a +line of it, there came to him one day a paper in manuscript, sent +for his approval by a naturalist friend named Alfred Russel +Wallace, who had been for some time at work in the East India +Archipelago. He read the paper, and, to his amazement, found +that it contained an outline of the same theory of "natural +selection" which he himself had originated and for twenty years +had worked upon. Working independently, on opposite sides of the +globe, Darwin and Wallace had hit upon the same explanation of +the cause of transmutation of species. "Were Wallace's paper an +abstract of my unpublished manuscript of 1844," said Darwin, "it +could not better express my ideas." + +Here was a dilemma. To publish this paper with no word from +Darwin would give Wallace priority, and wrest from Darwin the +credit of a discovery which he had made years before his +codiscoverer entered the field. Yet, on the other hand, could +Darwin honorably do otherwise than publish his friend's paper and +himself remain silent? It was a complication well calculated to +try a man's soul. Darwin's was equal to the test. Keenly alive +to the delicacy of the position, he placed the whole matter +before his friends Hooker and Lyell, and left the decision as to +a course of action absolutely to them. Needless to say, these +great men did the one thing which insured full justice to all +concerned. They counselled a joint publication, to include on the +one hand Wallace's paper, and on the other an abstract of +Darwin's ideas, in the exact form in which it had been outlined +by the author in a letter to Asa Gray in the previous year--an +abstract which was in Gray's hands before Wallace's paper was in +existence. This joint production, together with a full statement +of the facts of the case, was presented to the Linnaean Society +of London by Hooker and Lyell on the evening of July 1, 1858, +this being, by an odd coincidence, the twenty-first anniversary +of the day on which Darwin had opened his journal to collect +facts bearing on the "species question." Not often before in the +history of science has it happened that a great theory has been +nurtured in its author's brain through infancy and adolescence to +its full legal majority before being sent out into the world. + +Thus the fuse that led to the great powder-mine had been lighted. +The explosion itself came more than a year later, in November, +1859, when Darwin, after thirteen months of further effort, +completed the outline of his theory, which was at first begun as +an abstract for the Linnaean Society, but which grew to the size +of an independent volume despite his efforts at condensation, and +which was given that ever-to-be-famous title, The Origin of +Species by Means of Natural Selection, or the Preservation of +Favored Races in the Struggle for Life. And what an explosion it +was! The joint paper of 1858 had made a momentary flare, causing +the hearers, as Hooker said, to "speak of it with bated breath," +but beyond that it made no sensation. What the result was when +the Origin itself appeared no one of our generation need be told. +The rumble and roar that it made in the intellectual world have +not yet altogether ceased to echo after more than forty years of +reverberation. + + +NEW CHAMPIONS + +To the Origin of Species, then, and to its author, Charles +Darwin, must always be ascribed chief credit for that vast +revolution in the fundamental beliefs of our race which has come +about since 1859, and which made the second half of the century +memorable. But it must not be overlooked that no such sudden +metamorphosis could have been effected had it not been for the +aid of a few notable lieutenants, who rallied to the standards of +the leader immediately after the publication of the Origin. +Darwin had all along felt the utmost confidence in the ultimate +triumph of his ideas. "Our posterity," he declared, in a letter +to Hooker, "will marvel as much about the current belief [in +special creation] as we do about fossil shells having been +thought to be created as we now see them." But he fully realized +that for the present success of his theory of transmutation the +championship of a few leaders of science was all-essential. He +felt that if he could make converts of Hooker and Lyell and of +Thomas Henry Huxley at once, all would be well. + +His success in this regard, as in others, exceeded his +expectations. Hooker was an ardent disciple from reading the +proof-sheets before the book was published; Lyell renounced his +former beliefs and fell into line a few months later; while +Huxley, so soon as he had mastered the central idea of natural +selection, marvelled that so simple yet all-potent a thought had +escaped him so long, and then rushed eagerly into the fray, +wielding the keenest dialectic blade that was drawn during the +entire controversy. Then, too, unexpected recruits were found in +Sir John Lubbock and John Tyndall, who carried the war eagerly +into their respective territories; while Herbert Spencer, who had +advocated a doctrine of transmutation on philosophic grounds some +years before Darwin published the key to the mystery--and who +himself had barely escaped independent discovery of that +key--lent his masterful influence to the cause. In America the +famous botanist Asa Gray, who had long been a correspondent of +Darwin's but whose advocacy of the new theory had not been +anticipated, became an ardent propagandist; while in Germany +Ernst Heinrich Haeckel, the youthful but already noted zoologist, +took up the fight with equal enthusiasm. + +Against these few doughty champions--with here and there another +of less general renown--was arrayed, at the outset, practically +all Christendom. The interest of the question came home to every +person of intelligence, whatever his calling, and the more deeply +as it became more and more clear how far-reaching are the real +bearings of the doctrine of natural selection. Soon it was seen +that should the doctrine of the survival of the favored races +through the struggle for existence win, there must come with it +as radical a change in man's estimate of his own position as had +come in the day when, through the efforts of Copernicus and +Galileo, the world was dethroned from its supposed central +position in the universe. The whole conservative majority of +mankind recoiled from this necessity with horror. And this +conservative majority included not laymen merely, but a vast +preponderance of the leaders of science also. + +With the open-minded minority, on the other hand, the theory of +natural selection made its way by leaps and bounds. Its +delightful simplicity--which at first sight made it seem neither +new nor important--coupled with the marvellous comprehensiveness +of its implications, gave it a hold on the imagination, and +secured it a hearing where other theories of transmutation of +species had been utterly scorned. Men who had found Lamarck's +conception of change through voluntary effort ridiculous, and the +vaporings of the Vestiges altogether despicable, men whose +scientific cautions held them back from Spencer's deductive +argument, took eager hold of that tangible, ever-present +principle of natural selection, and were led on and on to its +goal. Hour by hour the attitude of the thinking world towards +this new principle changed; never before was so great a +revolution wrought so suddenly. + +Nor was this merely because "the times were ripe" or "men's minds +prepared for evolution." Darwin himself bears witness that this +was not altogether so. All through the years in which he brooded +this theory he sounded his scientific friends, and could find +among them not one who acknowledged a doctrine of transmutation. +The reaction from the stand-point of Lamarck and Erasmus Darwin +and Goethe had been complete, and when Charles Darwin avowed his +own conviction he expected always to have it met with ridicule or +contempt. In 1857 there was but one man speaking with any large +degree of authority in the world who openly avowed a belief in +transmutation of species--that man being Herbert Spencer. But +the Origin of Species came, as Huxley has said, like a flash in +the darkness, enabling the benighted voyager to see the way. The +score of years during which its author had waited and worked had +been years well spent. Darwin had become, as he himself says, a +veritable Croesus, "overwhelmed with his riches in facts"--facts +of zoology, of selective artificial breeding, of geographical +distribution of animals, of embryology, of paleontology. He had +massed his facts about his theory, condensed them and +recondensed, until his volume of five hundred pages was an +encyclopaedia in scope. During those long years of musing he had +thought out almost every conceivable objection to his theory, and +in his book every such objection was stated with fullest force +and candor, together with such reply as the facts at command +might dictate. It was the force of those twenty years of effort +of a master-mind that made the sudden breach in the +breaswtork{sic} of current thought. + +Once this breach was effected the work of conquest went rapidly +on. Day by day squads of the enemy capitulated and struck their +arms. By the time another score of years had passed the doctrine +of evolution had become the working hypothesis of the scientific +world. The revolution had been effected. + +And from amid the wreckage of opinion and belief stands forth the +figure of Charles Darwin, calm, imperturbable, serene; scatheless +to ridicule, contumely, abuse; unspoiled by ultimate success; +unsullied alike by the strife and the victory--take him for all +in all, for character, for intellect, for what he was and what he +did, perhaps the most Socratic figure of the century. When, in +1882, he died, friend and foe alike conceded that one of the +greatest sons of men had rested from his labors, and all the +world felt it fitting that the remains of Charles Darwin should +be entombed in Westminster Abbey close beside the honored grave +of Isaac Newton. Nor were there many who would dispute the +justice of Huxley's estimate of his accomplishment: "He found a +great truth trodden under foot. Reviled by bigots, and ridiculed +by all the world, he lived long enough to see it, chiefly by his +own efforts, irrefragably established in science, inseparably +incorporated with the common thoughts of men, and only hated and +feared by those who would revile but dare not." + + +THE ORIGIN OF THE FITTEST + +Wide as are the implications of the great truth which Darwin and +his co-workers established, however, it leaves quite untouched +the problem of the origin of those "favored variations" upon +which it operates. That such variations are due to fixed and +determinate causes no one understood better than Darwin; but in +his original exposition of his doctrine he made no assumption as +to what these causes are. He accepted the observed fact of +variation--as constantly witnessed, for example, in the +differences between parents and offspring--and went ahead from +this assumption. + +But as soon as the validity of the principle of natural selection +came to be acknowledged speculators began to search for the +explanation of those variations which, for purposes of argument, +had been provisionally called "spontaneous." Herbert Spencer had +all along dwelt on this phase of the subject, expounding the +Lamarckian conceptions of the direct influence of the environment +(an idea which had especially appealed to Buffon and to Geoffroy +Saint-Hilaire), and of effort in response to environment and +stimulus as modifying the individual organism, and thus supplying +the basis for the operation of natural selection. Haeckel also +became an advocate of this idea, and presently there arose a +so-called school of neo-Lamarckians, which developed particular +strength and prominence in America under the leadership of +Professors A. Hyatt and E. D. Cope. + +But just as the tide of opinion was turning strongly in this +direction, an utterly unexpected obstacle appeared in the form of +the theory of Professor August Weismann, put forward in 1883, +which antagonized the Lamarckian conception (though not touching +the Darwinian, of which Weismann is a firm upholder) by denying +that individual variations, however acquired by the mature +organism, are transmissible. The flurry which this denial created +has not yet altogether subsided, but subsequent observations seem +to show that it was quite disproportionate to the real merits of +the case. Notwithstanding Professor Weismann's objections, the +balance of evidence appears to favor the view that the Lamarckian +factor of acquired variations stands as the complement of the +Darwinian factor of natural selection in effecting the +transmutation of species. + +Even though this partial explanation of what Professor Cope calls +the "origin of the fittest" be accepted, there still remains one +great life problem which the doctrine of evolution does not +touch. The origin of species, genera, orders, and classes of +beings through endless transmutations is in a sense explained; +but what of the first term of this long series? Whence came that +primordial organism whose transmuted descendants make up the +existing faunas and floras of the globe? + +There was a time, soon after the doctrine of evolution gained a +hearing, when the answer to that question seemed to some +scientists of authority to have been given by experiment. +Recurring to a former belief, and repeating some earlier +experiments, the director of the Museum of Natural History at +Rouen, M. F. A. Pouchet, reached the conclusion that organic +beings are spontaneously generated about us constantly, in the +familiar processes of putrefaction, which were known to be due to +the agency of microscopic bacteria. But in 1862 Louis Pasteur +proved that this seeming spontaneous generation is in reality due +to the existence of germs in the air. Notwithstanding the +conclusiveness of these experiments, the claims of Pouchet were +revived in England ten years later by Professor Bastian; but then +the experiments of John Tyndall, fully corroborating the results +of Pasteur, gave a final quietus to the claim of "spontaneous +generation" as hitherto formulated. + +There for the moment the matter rests. But the end is not yet. +Fauna and flora are here, and, thanks to Lamarck and Wallace and +Darwin, their development, through the operation of those +"secondary causes" which we call laws of nature, has been +proximally explained. The lowest forms of life have been linked +with the highest in unbroken chains of descent. Meantime, +through the efforts of chemists and biologists, the gap between +the inorganic and the organic worlds, which once seemed almost +infinite, has been constantly narrowed. Already philosophy can +throw a bridge across that gap. But inductive science, which +builds its own bridges, has not yet spanned the chasm, small +though it appear. Until it shall have done so, the bridge of +organic evolution is not quite complete; yet even as it stands +to-day it is perhaps the most stupendous scientific structure of +the nineteenth century. + + + +VII. EIGHTEENTH-CENTURY MEDICINE + +THE SYSTEM OF BOERHAAVE + +At least two pupils of William Harvey distinguished themselves in +medicine, Giorgio Baglivi (1669-1707), who has been called the +"Italian Sydenham," and Hermann Boerhaave (1668-1738). The work +of Baglivi was hardly begun before his early death removed one of +the most promising of the early eighteenth-century physicians. +Like Boerhaave, he represents a type of skilled, practical +clinitian rather than the abstract scientist. One of his +contributions to medical literature is the first accurate +description of typhoid, or, as he calls it, mesenteric fever. + +If for nothing else, Boerhaave must always be remembered as the +teacher of Von Haller, but in his own day he was the widest known +and the most popular teacher in the medical world. He was the +idol of his pupils at Leyden, who flocked to his lectures in such +numbers that it became necessary to "tear down the walls of +Leyden to accommodate them." His fame extended not only all over +Europe but to Asia, North America, and even into South America. +A letter sent him from China was addressed to "Boerhaave in +Europe." His teachings represent the best medical knowledge of +his day, a high standard of morality, and a keen appreciation of +the value of observation; and it was through such teachings +imparted to his pupils and advanced by them, rather than to any +new discoveries, that his name is important in medical history. +His arrangement and classification of the different branches of +medicine are interesting as representing the attitude of the +medical profession towards these various branches at that time. + + +"In the first place we consider Life; then Health, afterwards +Diseases; and lastly their several Remedies. + +"Health the first general branch of Physic in our Institutions is +termed Physiology, or the Animal Oeconomy; demonstrating the +several Parts of the human Body, with their Mechanism and +Actions. + +"The second branch of Physic is called Pathology, treating of +Diseases, their Differences, Causes and Effects, or Symptoms; by +which the human Body is known to vary from its healthy state. + +"The third part of Physic is termed Semiotica, which shows the +Signs distinguishing between sickness and Health, Diseases and +their Causes in the human Body; it also imports the State and +Degrees of Health and Diseases, and presages their future Events. + +"The fourth general branch of Physic is termed Hygiene, or +Prophylaxis. + +"The fifth and last part of Physic is called Therapeutica; which +instructs us in the Nature, Preparation and uses of the Materia +Medica; and the methods of applying the same, in order to cure +Diseases and restore lost Health."[1] + +From this we may gather that his general view of medicine was not +unlike that taken at the present time. + +Boerhaave's doctrines were arranged into a "system" by Friedrich +Hoffmann, of Halle (1660-1742), this system having the merit of +being simple and more easily comprehended than many others. In +this system forces were considered inherent in matter, being +expressed as mechanical movements, and determined by mass, +number, and weight. Similarly, forces express themselves in the +body by movement, contraction, and relaxation, etc., and life +itself is movement, "particularly movement of the heart." Life +and death are, therefore, mechanical phenomena, health is +determined by regularly recurring movements, and disease by +irregularity of them. The body is simply a large hydraulic +machine, controlled by "the aether" or "sensitive soul," and the +chief centre of this soul lies in the medulla. + +In the practical application of medicines to diseases Hoffman +used simple remedies, frequently with happy results, for whatever +the medical man's theory may be he seldom has the temerity to +follow it out logically, and use the remedies indicated by his +theory to the exclusion of long-established, although perhaps +purely empirical, remedies. Consequently, many vague theorists +have been excellent practitioners, and Hoffman was one of these. +Some of the remedies he introduced are still in use, notably the +spirits of ether, or "Hoffman's anodyne." + + +ANIMISTS, VITALISTS, AND ORGANICISTS + +Besides Hoffman's system of medicine, there were numerous others +during the eighteenth century, most of which are of no importance +whatever; but three, at least, that came into existence and +disappeared during the century are worthy of fuller notice. One +of these, the Animists, had for its chief exponent Georg Ernst +Stahl of "phlogiston" fame; another, the Vitalists, was +championed by Paul Joseph Barthez (1734-1806); and the third was +the Organicists. This last, while agreeing with the other two +that vital activity cannot be explained by the laws of physics +and chemistry, differed in not believing that life "was due to +some spiritual entity," but rather to the structure of the body +itself. + +The Animists taught that the soul performed functions of ordinary +life in man, while the life of lower animals was controlled by +ordinary mechanical principles. Stahl supported this theory +ardently, sometimes violently, at times declaring that there were +"no longer any doctors, only mechanics and chemists." He denied +that chemistry had anything to do with medicine, and, in the +main, discarded anatomy as useless to the medical man. The soul, +he thought, was the source of all vital movement; and the +immediate cause of death was not disease but the direct action of +the soul. When through some lesion, or because the machinery of +the body has become unworkable, as in old age, the soul leaves +the body and death is produced. The soul ordinarily selects the +channels of the circulation, and the contractile parts, as the +route for influencing the body. Hence in fever the pulse is +quickened, due to the increased activity of the soul, and +convulsions and spasmodic movements in disease are due, to the, +same cause. Stagnation of the, blood was supposed to be a +fertile cause of diseases, and such diseases were supposed to +arise mostly from "plethora"--an all-important element in Stahl's +therapeutics. By many this theory is regarded as an attempt on +the part of the pious Stahl to reconcile medicine and theology in +a way satisfactory to both physicians and theologians, but, like +many conciliatory attempts, it was violently opposed by both +doctors and ministers. + +A belief in such a theory would lead naturally to simplicity in +therapeutics, and in this respect at least Stahl was consistent. +Since the soul knew more about the body than any physician could +know, Stahl conceived that it would be a hinderance rather than a +help for the physician to interfere with complicated doses of +medicine. As he advanced in age this view of the administration +of drugs grew upon him, until after rejecting quinine, and +finally opium, he at last used only salt and water in treating +his patients. From this last we may judge that his "system," if +not doing much good, was at least doing little harm. + +The theory of the Vitalists was closely allied to that of the +Animists, and its most important representative, Paul Joseph +Barthez, was a cultured and eager scientist. After an eventful +and varied career as physician, soldier, editor, lawyer, and +philosopher in turn, he finally returned to the field of +medicine, was made consulting physician by Napoleon in 1802, and +died in Paris four years later. + +The theory that he championed was based on the assumption that +there was a "vital principle," the nature of which was unknown, +but which differed from the thinking mind, and was the cause of +the phenomena of life. This "vital principle" differed from the +soul, and was not exhibited in human beings alone, but even in +animals and plants. This force, or whatever it might be called, +was supposed to be present everywhere in the body, and all +diseases were the results of it. + +The theory of the Organicists, like that of the Animists and +Vitalists, agreed with the other two that vital activity could +not be explained by the laws of physics and chemistry, but, +unlike them, it held that it was a part of the structure of the +body itself. Naturally the practical physicians were more +attracted by this tangible doctrine than by vague theories "which +converted diseases into unknown derangements of some equally +unknown 'principle.' " + +It is perhaps straining a point to include this brief description +of these three schools of medicine in the history of the progress +of the science. But, on the whole, they were negatively at least +prominent factors in directing true progress along its proper +channel, showing what courses were not to be pursued. Some one +has said that science usually stumbles into the right course only +after stumbling into all the wrong ones; and if this be only +partially true, the wrong ones still play a prominent if not a +very creditable part. Thus the medical systems of William Cullen +(1710-1790), and John Brown (1735-1788), while doing little +towards the actual advancement of scientific medicine, played so +conspicuous a part in so wide a field that the "Brunonian system" +at least must be given some little attention. + +According to Brown's theory, life, diseases, and methods of cure +are explained by the property of "excitability." All exciting +powers were supposed to be stimulating, the apparent debilitating +effects of some being due to a deficiency in the amount of +stimulus. Thus "the whole phenomena of life, health, as well as +disease, were supposed to consist of stimulus and nothing else." +This theory created a great stir in the medical world, and +partisans and opponents sprang up everywhere. In Italy it was +enthusiastically supported; in England it was strongly opposed; +while in Scotland riots took place between the opposing factions. +Just why this system should have created any stir, either for or +against it, is not now apparent. + +Like so many of the other "theorists" of his century, Brown's +practical conclusions deduced from his theory (or perhaps in +spite of it) were generally beneficial to medicine, and some of +them extremely valuable in the treatment of diseases. He first +advocated the modern stimulant, or "feeding treatment" of fevers, +and first recognized the usefulness of animal soups and beef-tea +in certain diseases. + + +THE SYSTEM OF HAHNEMANN + +Just at the close of the century there came into prominence the +school of homoeopathy, which was destined to influence the +practice of medicine very materially and to outlive all the other +eighteenth-century schools. It was founded by Christian Samuel +Friedrich Hahnemann (1755-1843), a most remarkable man, who, +after propounding a theory in his younger days which was at least +as reasonable as most of the existing theories, had the +misfortune to outlive his usefulness and lay his doctrine open to +ridicule by the unreasonable teachings of his dotage, + +Hahnemann rejected all the teachings of morbid anatomy and +pathology as useless in practice, and propounded his famous +"similia similibus curantur"--that all diseases were to be cured +by medicine which in health produced symptoms dynamically similar +to the disease under treatment. If a certain medicine produced a +headache when given to a healthy person, then this medicine was +indicated in case of headaches, etc. At the present time such a +theory seems crude enough, but in the latter part of the +eighteenth century almost any theory was as good as the ones +propounded by Animists, Vitalists, and other such schools. It +certainly had the very commendable feature of introducing +simplicity in the use of drugs in place of the complicated +prescriptions then in vogue. Had Hahnemann stopped at this point +he could not have been held up to the indefensible ridicule that +was brought upon him, with considerable justice, by his later +theories. But he lived onto propound his extraordinary theory of +"potentiality"--that medicines gained strength by being +diluted--and his even more extraordinary theory that all chronic +diseases are caused either by the itch, syphilis, or fig-wart +disease, or are brought on by medicines. + +At the time that his theory of potentialities was promulgated, +the medical world had gone mad in its administration of huge +doses of compound mixtures of drugs, and any reaction against +this was surely an improvement. In short, no medicine at all was +much better than the heaping doses used in common practice; and +hence one advantage, at least, of Hahnemann's methods. Stated +briefly, his theory was that if a tincture be reduced to +one-fiftieth in strength, and this again reduced to one-fiftieth, +and this process repeated up to thirty such dilutions, the +potency of such a medicine will be increased by each dilution, +Hahnemann himself preferring the weakest, or, as he would call +it, the strongest dilution. The absurdity of such a theory is +apparent when it is understood that long before any drug has been +raised to its thirtieth dilution it has been so reduced in +quantity that it cannot be weighed, measured, or recognized as +being present in the solution at all by any means known to +chemists. It is but just to modern followers of homoeopathy to +say that while most of them advocate small dosage, they do not +necessarily follow the teachings of Hahnemann in this respect, +believing that the theory of the dose "has nothing more to do +with the original law of cure than the psora (itch) theory has; +and that it was one of the later creations of Hahnemann's mind." + +Hahnemann's theory that all chronic diseases are derived from +either itch, syphilis, or fig-wart disease is no longer advocated +by his followers, because it is so easily disproved, particularly +in the case of itch. Hahnemann taught that fully three-quarters +of all diseases were caused by "itch struck in," and yet it had +been demonstrated long before his day, and can be demonstrated +any time, that itch is simply a local skin disease caused by a +small parasite. + + +JENNER AND VACCINATION + +All advances in science have a bearing, near or remote, on the +welfare of our race; but it remains to credit to the closing +decade of the eighteenth century a discovery which, in its power +of direct and immediate benefit to humanity, surpasses any other +discovery of this or any previous epoch. Needless to say, I refer +to Jenner's discovery of the method of preventing smallpox by +inoculation with the virus of cow-pox. It detracts nothing from +the merit of this discovery to say that the preventive power of +accidental inoculation had long been rumored among the peasantry +of England. Such vague, unavailing half-knowledge is often the +forerunner of fruitful discovery. + +To all intents and purposes Jenner's discovery was original and +unique. Nor, considered as a perfect method, was it in any sense +an accident. It was a triumph of experimental science. The +discoverer was no novice in scientific investigation, but a +trained observer, who had served a long apprenticeship in +scientific observation under no less a scientist than the +celebrated John Hunter. At the age of twenty-one Jenner had gone +to London to pursue his medical studies, and soon after he proved +himself so worthy a pupil that for two years he remained a member +of Hunter's household as his favorite pupil. His taste for +science and natural history soon attracted the attention of Sir +Joseph Banks, who intrusted him with the preparation of the +zoological specimens brought back by Captain Cook's expedition in +1771. He performed this task so well that he was offered the +position of naturalist to the second expedition, but declined it, +preferring to take up the practice of his profession in his +native town of Berkeley. + +His many accomplishments and genial personality soon made him a +favorite both as a physician and in society. He was a good +singer, a fair violinist and flute-player, and a very successful +writer of prose and verse. But with all his professional and +social duties he still kept up his scientific investigations, +among other things making some careful observations on the +hibernation of hedgehogs at the instigation of Hunter, the +results of which were laid before the Royal Society. He also +made quite extensive investigations as to the geological +formations and fossils found in his neighborhood. + +Even during his student days with Hunter he had been much +interested in the belief, current in the rural districts of +Gloucestershire, of the antagonism between cow-pox and small-pox, +a person having suffered from cow-pox being immuned to small-pox. +At various times Jenner had mentioned the subject to Hunter, and +he was constantly making inquiries of his fellow-practitioners as +to their observations and opinions on the subject. Hunter was too +fully engrossed in other pursuits to give the matter much serious +attention, however, and Jenner's brothers of the profession gave +scant credence to the rumors, although such rumors were common +enough. + +At this time the practice of inoculation for preventing +small-pox, or rather averting the severer forms of the disease, +was widely practised. It was customary, when there was a mild +case of the disease, to take some of the virus from the patient +and inoculate persons who had never had the disease, producing a +similar attack in them. Unfortunately there were many objections +to this practice. The inoculated patient frequently developed a +virulent form of the disease and died; or if he recovered, even +after a mild attack, he was likely to be "pitted" and disfigured. +But, perhaps worst of all, a patient so inoculated became the +source of infection to others, and it sometimes happened that +disastrous epidemics were thus brought about. The case was a +most perplexing one, for the awful scourge of small-pox hung +perpetually over the head of every person who had not already +suffered and recovered from it. The practice of inoculation was +introduced into England by Lady Mary Wortley Montague +(1690-1762), who had seen it practised in the East, and who +announced her intention of "introducing it into England in spite +of the doctors." + +From the fact that certain persons, usually milkmaids, who had +suffered from cow-pox seemed to be immuned to small-pox, it would +seem a very simple process of deduction to discover that cow-pox +inoculation was the solution of the problem of preventing the +disease. But there was another form of disease which, while +closely resembling cow-pox and quite generally confounded with +it, did not produce immunity. The confusion of these two forms of +the disease had constantly misled investigations as to the +possibility of either of them immunizing against smallpox, and +the confusion of these two diseases for a time led Jenner to +question the possibility of doing so. After careful +investigations, however, he reached the conclusion that there was +a difference in the effects of the two diseases, only one of +which produced immunity from small-pox. + +"There is a disease to which the horse, from his state of +domestication, is frequently subject," wrote Jenner, in his +famous paper on vaccination. "The farriers call it the grease. +It is an inflammation and swelling in the heel, accompanied at +its commencement with small cracks or fissures, from which issues +a limpid fluid possessing properties of a very peculiar kind. +This fluid seems capable of generating a disease in the human +body (after it has undergone the modification I shall presently +speak of) which bears so strong a resemblance to small-pox that I +think it highly probable it may be the source of that disease. + +"In this dairy country a great number of cows are kept, and the +office of milking is performed indiscriminately by men and maid +servants. One of the former having been appointed to apply +dressings to the heels of a horse affected with the malady I have +mentioned, and not paying due attention to cleanliness, +incautiously bears his part in milking the cows with some +particles of the infectious matter adhering to his fingers. When +this is the case it frequently happens that a disease is +communicated to the cows, and from the cows to the dairy-maids, +which spreads through the farm until most of the cattle and +domestics feel its unpleasant consequences. This disease has +obtained the name of Cow-Pox. It appears on the nipples of the +cows in the form of irregular pustules. At their first appearance +they are commonly of a palish blue, or rather of a color somewhat +approaching to livid, and are surrounded by an inflammation. +These pustules, unless a timely remedy be applied, frequently +degenerate into phagedenic ulcers, which prove extremely +troublesome. The animals become indisposed, and the secretion of +milk is much lessened. Inflamed spots now begin to appear on +different parts of the hands of the domestics employed in +milking, and sometimes on the wrists, which run on to +suppuration, first assuming the appearance of the small +vesications produced by a burn. Most commonly they appear about +the joints of the fingers and at their extremities; but whatever +parts are affected, if the situation will admit the superficial +suppurations put on a circular form with their edges more +elevated than their centre and of a color distinctly approaching +to blue. Absorption takes place, and tumors appear in each +axilla. The system becomes affected, the pulse is quickened; +shiverings, succeeded by heat, general lassitude, and pains about +the loins and limbs, with vomiting, come on. The head is +painful, and the patient is now and then even affected with +delirium. These symptoms, varying in their degrees of violence, +generally continue from one day to three or four, leaving +ulcerated sores about the hands which, from the sensibility of +the parts, are very troublesome and commonly heal slowly, +frequently becoming phagedenic, like those from which they +sprang. During the progress of the disease the lips, nostrils, +eyelids, and other parts of the body are sometimes affected with +sores; but these evidently arise from their being heedlessly +rubbed or scratched by the patient's infected fingers. No +eruptions on the skin have followed the decline of the feverish +symptoms in any instance that has come under my inspection, one +only excepted, and in this case a very few appeared on the arms: +they were very minute, of a vivid red color, and soon died away +without advancing to maturation, so that I cannot determine +whether they had any connection with the preceding symptoms. + +"Thus the disease makes its progress from the horse (as I +conceive) to the nipple of the cow, and from the cow to the human +subject. + +"Morbid matter of various kinds, when absorbed into the system, +may produce effects in some degree similar; but what renders the +cow-pox virus so extremely singular is that the person that has +been thus affected is forever after secure from the infection of +small-pox, neither exposure to the variolous effluvia nor the +insertion of the matter into the skin producing this +distemper."[2] + + +In 1796 Jenner made his first inoculation with cowpox matter, and +two months later the same subject was inoculated with small-pox +matter. But, as Jenner had predicted, no attack of small-pox +followed. Although fully convinced by this experiment that the +case was conclusively proven, he continued his investigations, +waiting two years before publishing his discovery. Then, +fortified by indisputable proofs, he gave it to the world. The +immediate effects of his announcement have probably never been +equalled in the history of scientific discovery, unless, perhaps, +in the single instance of the discovery of anaesthesia. In Geneva +and Holland clergymen advocated the practice of vaccination from +their pulpits; in some of the Latin countries religious +processions were formed for receiving vaccination; Jenner's +birthday was celebrated as a feast in Germany; and the first +child vaccinated in Russia was named "Vaccinov" and educated at +public expense. In six years the discovery had penetrated to the +most remote corners of civilization; it had even reached some +savage nations. And in a few years small-pox had fallen from the +position of the most dreaded of all diseases to that of being +practically the only disease for which a sure and easy preventive +was known. + +Honors were showered upon Jenner from the Old and the New World, +and even Napoleon, the bitter hater of the English, was among the +others who honored his name. On one occasion Jenner applied to +the Emperor for the release of certain Englishmen detained in +France. The petition was about to be rejected when the name of +the petitioner was mentioned. "Ah," said Napoleon, "we can refuse +nothing to that name!" + +It is difficult for us of to-day clearly to conceive the +greatness of Jenner's triumph, for we can only vaguely realize +what a ruthless and ever-present scourge smallpox had been to all +previous generations of men since history began. Despite all +efforts to check it by medication and by direct inoculation, it +swept now and then over the earth as an all-devastating +pestilence, and year by year it claimed one-tenth of all the +beings in Christendom by death as its average quota of victims. +"From small-pox and love but few remain free," ran the old saw. A +pitted face was almost as much a matter of course a hundred years +ago as a smooth one is to-day. + +Little wonder, then, that the world gave eager acceptance to +Jenner's discovery. No urging was needed to induce the majority +to give it trial; passengers on a burning ship do not hold aloof +from the life-boats. Rich and poor, high and low, sought succor +in vaccination and blessed the name of their deliverer. Of all +the great names that were before the world in the closing days of +the century, there was perhaps no other one at once so widely +known and so uniformly reverenced as that of the great English +physician Edward Jenner. Surely there was no other one that +should be recalled with greater gratitude by posterity. + + + +VIII. NINETEENTH-CENTURY MEDICINE + +PHYSICAL DIAGNOSIS + +Although Napoleon Bonaparte, First Consul, was not lacking in +self-appreciation, he probably did not realize that in selecting +a physician for his own needs he was markedly influencing the +progress of medical science as a whole. Yet so strangely are +cause and effect adjusted in human affairs that this simple act +of the First Consul had that very unexpected effect. For the man +chosen was the envoy of a new method in medical practice, and the +fame which came to him through being physician to the First +Consul, and subsequently to the Emperor, enabled him to +promulgate the method in a way otherwise impracticable. Hence the +indirect but telling value to medical science of Napoleon's +selection. + +The physician in question was Jean Nicolas de Corvisart. His +novel method was nothing more startling than the now-familiar +procedure of tapping the chest of a patient to elicit sounds +indicative of diseased tissues within. Every one has seen this +done commonly enough in our day, but at the beginning of the +century Corvisart, and perhaps some of his pupils, were probably +the only physicians in the world who resorted to this simple and +useful procedure. Hence Napoleon's surprise when, on calling in +Corvisart, after becoming somewhat dissatisfied with his other +physicians Pinel and Portal, his physical condition was +interrogated in this strange manner. With characteristic +shrewdness Bonaparte saw the utility of the method, and the +physician who thus attempted to substitute scientific method for +guess-work in the diagnosis of disease at once found favor in his +eyes and was installed as his regular medical adviser. + +For fifteen years before this Corvisart had practised percussion, +as the chest-tapping method is called, without succeeding in +convincing the profession of its value. The method itself, it +should be added, had not originated with Corvisart, nor did the +French physician for a moment claim it as his own. The true +originator of the practice was the German physician Avenbrugger, +who published a book about it as early as 1761. This book had +even been translated into French, then the language of +international communication everywhere, by Roziere de la +Chassagne, of Montpellier, in 1770; but no one other than +Corvisart appears to have paid any attention to either original +or translation. It was far otherwise, however, when Corvisart +translated Avenbrugger's work anew, with important additions of +his own, in 1808. + +"I know very well how little reputation is allotted to translator +and commentators," writes Corvisart, "and I might easily have +elevated myself to the rank of an author if I had elaborated anew +the doctrine of Avenbrugger and published an independent work on +percussion. In this way, however, I should have sacrificed the +name of Avenbrugger to my own vanity, a thing which I am +unwilling to do. It is he, and the beautiful invention which of +right belongs to him, that I desire to recall to life."[1] + +By this time a reaction had set in against the metaphysical +methods in medicine that had previously been so alluring; the +scientific spirit of the time was making itself felt in medical +practice; and this, combined with Corvisart's fame, brought the +method of percussion into immediate and well-deserved popularity. +Thus was laid the foundation for the method of so-called physical +diagnosis, which is one of the corner-stones of modern medicine. + +The method of physical diagnosis as practised in our day was by +no means completed, however, with the work of Corvisart. +Percussion alone tells much less than half the story that may be +elicited from the organs of the chest by proper interrogation. +The remainder of the story can only be learned by applying the +ear itself to the chest, directly or indirectly. Simple as this +seems, no one thought of practising it for some years after +Corvisart had shown the value of percussion. + +Then, in 1815, another Paris physician, Rene Theophile Hyacinthe +Laennec, discovered, almost by accident, that the sound of the +heart-beat could be heard surprisingly through a cylinder of +paper held to the ear and against the patient's chest. Acting on +the hint thus received, Laennec substituted a hollow cylinder of +wood for the paper, and found himself provided with an instrument +through which not merely heart sounds but murmurs of the lungs in +respiration could be heard with almost startling distinctness. + +The possibility of associating the varying chest sounds with +diseased conditions of the organs within appealed to the fertile +mind of Laennec as opening new vistas in therapeutics, which he +determined to enter to the fullest extent practicable. His +connection with the hospitals of Paris gave him full opportunity +in this direction, and his labors of the next few years served +not merely to establish the value of the new method as an aid to +diagnosis, but laid the foundation also for the science of morbid +anatomy. In 1819 Laennec published the results of his labors in +a work called Traite d'Auscultation Mediate,[2] a work which +forms one of the landmarks of scientific medicine. By mediate +auscultation is meant, of course, the interrogation of the chest +with the aid of the little instrument already referred to, an +instrument which its originator thought hardly worth naming until +various barbarous appellations were applied to it by others, +after which Laennec decided to call it the stethoscope, a name +which it has ever since retained. + +In subsequent years the form of the stethoscope, as usually +employed, was modified and its value augmented by a binauricular +attachment, and in very recent years a further improvement has +been made through application of the principle of the telephone; +but the essentials of auscultation with the stethoscope were +established in much detail by Laennec, and the honor must always +be his of thus taking one of the longest single steps by which +practical medicine has in our century acquired the right to be +considered a rational science. Laennec's efforts cost him his +life, for he died in 1826 of a lung disease acquired in the +course of his hospital practice; but even before this his fame +was universal, and the value of his method had been recognized +all over the world. Not long after, in 1828, yet another French +physician, Piorry, perfected the method of percussion by +introducing the custom of tapping, not the chest directly, but +the finger or a small metal or hard-rubber plate held against the +chest-mediate percussion, in short. This perfected the methods +of physical diagnosis of diseases of the chest in all essentials; +and from that day till this percussion and auscultation have held +an unquestioned place in the regular armamentarium of the +physician. + +Coupled with the new method of physical diagnosis in the effort +to substitute knowledge for guess-work came the studies of the +experimental physiologists--in particular, Marshall Hall in +England and Francois Magendie in France; and the joint efforts of +these various workers led presently to the abandonment of those +severe and often irrational depletive methods--blood-letting and +the like--that had previously dominated medical practice. To this +end also the "statistical method," introduced by Louis and his +followers, largely contributed; and by the close of the first +third of our century the idea was gaining ground that the +province of therapeutics is to aid nature in combating disease, +and that this may often be accomplished better by simple means +than by the heroic measures hitherto thought necessary. In a +word, scientific empiricism was beginning to gain a hearing in +medicine as against the metaphysical preconceptions of the +earlier generations. + + +PARASITIC DISEASES + +I have just adverted to the fact that Napoleon Bonaparte, as +First Consul and as Emperor, was the victim of a malady which +caused him to seek the advice of the most distinguished +physicians of Paris. It is a little shocking to modern +sensibilities to read that these physicians, except Corvisart, +diagnosed the distinguished patient's malady as "gale +repercutee"--that is to say, in idiomatic English, the itch +"struck in." It is hardly necessary to say that no physician of +today would make so inconsiderate a diagnosis in the case of a +royal patient. If by any chance a distinguished patient were +afflicted with the itch, the sagacious physician would carefully +hide the fact behind circumlocutions and proceed to eradicate the +disease with all despatch. That the physicians of Napoleon did +otherwise is evidence that at the beginning of the century the +disease in question enjoyed a very different status. At that +time itch, instead of being a most plebeian malady, was, so to +say, a court disease. It enjoyed a circulation, in high circles +and in low, that modern therapeutics has quite denied it; and the +physicians of the time gave it a fictitious added importance by +ascribing to its influence the existence of almost any obscure +malady that came under their observation. Long after Napoleon's +time gale continued to hold this proud distinction. For example, +the imaginative Dr. Hahnemann did not hesitate to affirm, as a +positive maxim, that three-fourths of all the ills that flesh is +heir to were in reality nothing but various forms of "gale +repercutee." + +All of which goes to show how easy it may be for a masked +pretender to impose on credulous humanity, for nothing is more +clearly established in modern knowledge than the fact that "gale +repercutee" was simply a name to hide a profound ignorance; no +such disease exists or ever did exist. Gale itself is a +sufficiently tangible reality, to be sure, but it is a purely +local disease of the skin, due to a perfectly definite cause, and +the dire internal conditions formerly ascribed to it have really +no causal connection with it whatever. This definite cause, as +every one nowadays knows, is nothing more or less than a +microscopic insect which has found lodgment on the skin, and has +burrowed and made itself at home there. Kill that insect and the +disease is no more; hence it has come to be an axiom with the +modern physician that the itch is one of the three or four +diseases that he positively is able to cure, and that very +speedily. But it was far otherwise with the physicians of the +first third of our century, because to them the cause of the +disease was an absolute mystery. + +It is true that here and there a physician had claimed to find an +insect lodged in the skin of a sufferer from itch, and two or +three times the claim had been made that this was the cause of +the malady, but such views were quite ignored by the general +profession, and in 1833 it was stated in an authoritative medical +treatise that the "cause of gale is absolutely unknown." But +even at this time, as it curiously happened, there were certain +ignorant laymen who had attained to a bit of medical knowledge +that was withheld from the inner circles of the profession. As +the peasantry of England before Jenner had known of the curative +value of cow-pox over small-pox, so the peasant women of Poland +had learned that the annoying skin disease from which they +suffered was caused by an almost invisible insect, and, +furthermore, had acquired the trick of dislodging the pestiferous +little creature with the point of a needle. From them a youth of +the country, F. Renucci by name, learned the open secret. He +conveyed it to Paris when he went there to study medicine, and in +1834 demonstrated it to his master Alibert. This physician, at +first sceptical, soon was convinced, and gave out the discovery +to the medical world with an authority that led to early +acceptance. + +Now the importance of all this, in the present connection, is not +at all that it gave the clew to the method of cure of a single +disease. What makes the discovery epochal is the fact that it +dropped a brand-new idea into the medical ranks--an idea +destined, in the long-run, to prove itself a veritable bomb--the +idea, namely, that a minute and quite unsuspected animal parasite +may be the cause of a well-known, widely prevalent, and important +human disease. Of course the full force of this idea could only +be appreciated in the light of later knowledge; but even at the +time of its coming it sufficed to give a great impetus to that +new medical knowledge, based on microscopical studies, which had +but recently been made accessible by the inventions of the +lens-makers. The new knowledge clarified one very turbid medical +pool and pointed the way to the clarification of many others. + +Almost at the same time that the Polish medical student was +demonstrating the itch mite in Paris, it chanced, curiously +enough, that another medical student, this time an Englishman, +made an analogous discovery of perhaps even greater importance. +Indeed, this English discovery in its initial stages slightly +antedated the other, for it was in 1833 that the student in +question, James Paget, interne in St. Bartholomew's Hospital, +London, while dissecting the muscular tissues of a human subject, +found little specks of extraneous matter, which, when taken to +the professor of comparative anatomy, Richard Owen, were +ascertained, with the aid of the microscope, to be the cocoon of +a minute and hitherto unknown insect. Owen named the insect +Trichina spiralis. After the discovery was published it +transpired that similar specks had been observed by several +earlier investigators, but no one had previously suspected or, at +any rate, demonstrated their nature. Nor was the full story of +the trichina made out for a long time after Owen's discovery. It +was not till 1847 that the American anatomist Dr. Joseph Leidy +found the cysts of trichina in the tissues of pork; and another +decade or so elapsed after that before German workers, chief +among whom were Leuckart, Virchow, and Zenker, proved that the +parasite gets into the human system through ingestion of infected +pork, and that it causes a definite set of symptoms of disease +which hitherto had been mistaken for rheumatism, typhoid fever, +and other maladies. Then the medical world was agog for a time +over the subject of trichinosis; government inspection of pork +was established in some parts of Germany; American pork was +excluded altogether from France; and the whole subject thus came +prominently to public attention. But important as the trichina +parasite proved on its own account in the end, its greatest +importance, after all, was in the share it played in directing +attention at the time of its discovery in 1833 to the subject of +microscopic parasites in general. + +The decade that followed that discovery was a time of great +activity in the study of microscopic organisms and microscopic +tissues, and such men as Ehrenberg and Henle and Bory +Saint-Vincent and Kolliker and Rokitansky and Remak and Dujardin +were widening the bounds of knowledge of this new subject with +details that cannot be more than referred to here. But the +crowning achievement of the period in this direction was the +discovery made by the German, J. L. Schoenlein, in 1839, that a +very common and most distressing disease of the scalp, known as +favus, is really due to the presence and growth on the scalp of a +vegetable organism of microscopic size. Thus it was made clear +that not merely animal but also vegetable organisms of obscure, +microscopic species have causal relations to the diseases with +which mankind is afflicted. This knowledge of the parasites was +another long step in the direction of scientific medical +knowledge; but the heights to which this knowledge led were not +to be scaled, or even recognized, until another generation of +workers had entered the field. + + +PAINLESS SURGERY + +Meantime, in quite another field of medicine, events were +developing which led presently to a revelation of greater +immediate importance to humanity than any other discovery that +had come in the century, perhaps in any field of science +whatever. This was the discovery of the pain-dispelling power of +the vapor of sulphuric ether inhaled by a patient undergoing a +surgical operation. This discovery came solely out of America, +and it stands curiously isolated, since apparently no minds in +any other country were trending towards it even vaguely. Davy, +in England, had indeed originated the method of medication by +inhalation, and earned out some most interesting experiments +fifty years earlier, and it was doubtless his experiments with +nitrous oxide gas that gave the clew to one of the American +investigators; but this was the sole contribution of preceding +generations to the subject, and since the beginning of the +century, when Davy turned his attention to other matters, no one +had made the slightest advance along the same line until an +American dentist renewed the investigation. + +In view of the sequel, Davy's experiments merit full attention. +Here is his own account of them, as written in 1799: + + +"Immediately after a journey of one hundred and twenty-six miles, +in which I had no sleep the preceding night, being much +exhausted, I respired seven quarts of nitrous oxide gas for near +three minutes. It produced the usual pleasurable effects and +slight muscular motion. I continued exhilarated for some minutes +afterwards, but in half an hour found myself neither more nor +less exhausted than before the experiment. I had a great +propensity to sleep. + +"To ascertain with certainty whether the more extensive action of +nitrous oxide compatible with life was capable of producing +debility, I resolved to breathe the gas for such a time, and in +such quantities, as to produce excitement equal in duration and +superior in intensity to that occasioned by high intoxication +from opium or alcohol. + +"To habituate myself to the excitement, and to carry it on +gradually, on December 26th I was enclosed in an air-tight +breathing-box, of the capacity of about nine and one-half cubic +feet, in the presence of Dr. Kinglake. After I had taken a +situation in which I could by means of a curved thermometer +inserted under the arm, and a stop-watch, ascertain the +alterations in my pulse and animal heat, twenty quarts of nitrous +oxide were thrown into the box. + +"For three minutes I experienced no alteration in my sensations, +though immediately after the introduction of the nitrous oxide +the smell and taste of it were very evident. In four minutes I +began to feel a slight glow in the cheeks and a generally +diffused warmth over the chest, though the temperature of the box +was not quite 50 degrees. . . . In twenty-five minutes the animal +heat was 100 degrees, pulse 124. In thirty minutes twenty quarts +more of gas were introduced. + +"My sensations were now pleasant; I had a generally diffused +warmth without the slightest moisture of the skin, a sense of +exhilaration similar to that produced by a small dose of wine, +and a disposition to muscular motion and to merriment. + +"In three-quarters of an hour the pulse was 104 and the animal +heat not 99.5 degrees, the temperature of the chamber 64 degrees. +The pleasurable feelings continued to increase, the pulse became +fuller and slower, till in about an hour it was 88, when the +animal heat was 99 degrees. Twenty quarts more of air were +admitted. I had now a great disposition to laugh, luminous points +seemed frequently to pass before my eyes, my hearing was +certainly more acute, and I felt a pleasant lightness and power +of exertion in my muscles. In a short time the symptoms became +stationary; breathing was rather oppressed, and on account of the +great desire for action rest was painful. + +"I now came out of the box, having been in precisely an hour and +a quarter. The moment after I began to respire twenty quarts of +unmingled nitrous oxide. A thrilling extending from the chest to +the extremities was almost immediately produced. I felt a sense +of tangible extension highly pleasurable in every limb; my +visible impressions were dazzling and apparently magnified, I +heard distinctly every sound in the room, and was perfectly aware +of my situation. By degrees, as the pleasurable sensations +increased, I lost all connection with external things; trains of +vivid visible images rapidly passed through my mind and were +connected with words in such a manner as to produce perceptions +perfectly novel. + +"I existed in a world of newly connected and newly modified +ideas. I theorized; I imagined that I made discoveries. When I +was awakened from this semi-delirious trance by Dr. Kinglake, who +took the bag from my mouth, indignation and pride were the first +feelings produced by the sight of persons about me. My emotions +were enthusiastic and sublime; and for a minute I walked about +the room perfectly regardless of what was said to me. As I +recovered my former state of mind, I felt an inclination to +communicate the discoveries I had made during the experiment. I +endeavored to recall the ideas--they were feeble and indistinct; +one collection of terms, however, presented itself, and, with +most intense belief and prophetic manner, I exclaimed to Dr. +Kinglake, 'Nothing exists but thoughts!--the universe is composed +of impressions, ideas, pleasures, and pains.' "[3] + + +From this account we see that Davy has anaesthetized himself to a +point where consciousness of surroundings was lost, but not past +the stage of exhilaration. Had Dr. Kinglake allowed the +inhaling-bag to remain in Davy's mouth for a few moments longer +complete insensibility would have followed. As it was, Davy +appears to have realized that sensibility was dulled, for he adds +this illuminative suggestion: "As nitrous oxide in its extensive +operation appears capable of destroying physical pain, it may +probably be used with advantage during surgical operations in +which no great effusion of blood takes place."[4] + +Unfortunately no one took advantage of this suggestion at the +time, and Davy himself became interested in other fields of +science and never returned to his physiological studies, thus +barely missing one of the greatest discoveries in the entire +field of science. In the generation that followed no one seems to +have thought of putting Davy's suggestion to the test, and the +surgeons of Europe had acknowledged with one accord that all hope +of finding a means to render operations painless must be utterly +abandoned--that the surgeon's knife must ever remain a synonym +for slow and indescribable torture. By an odd coincidence it +chanced that Sir Benjamin Brodie, the acknowledged leader of +English surgeons, had publicly expressed this as his deliberate +though regretted opinion at a time when the quest which he +considered futile had already led to the most brilliant success +in America, and while the announcement of the discovery, which +then had no transatlantic cable to convey it, was actually on its +way to the Old World. + +The American dentist just referred to, who was, with one +exception to be noted presently, the first man in the world to +conceive that the administration of a definite drug might render +a surgical operation painless and to give the belief application +was Dr. Horace Wells, of Hartford, Connecticut. The drug with +which he experimented was nitrous oxide--the same that Davy had +used; the operation that he rendered painless was no more +important than the extraction of a tooth--yet it sufficed to mark +a principle; the year of the experiment was 1844. + +The experiments of Dr. Wells, however, though important, were not +sufficiently demonstrative to bring the matter prominently to the +attention of the medical world. The drug with which he +experimented proved not always reliable, and he himself seems +ultimately to have given the matter up, or at least to have +relaxed his efforts. But meantime a friend, to whom he had +communicated his belief and expectations, took the matter up, and +with unremitting zeal carried forward experiments that were +destined to lead to more tangible results. This friend was +another dentist, Dr. W. T. G. Morton, of Boston, then a young man +full of youthful energy and enthusiasm. He seems to have felt +that the drug with which Wells had experimented was not the most +practicable one for the purpose, and so for several months he +experimented with other allied drugs, until finally he hit upon +sulphuric ether, and with this was able to make experiments upon +animals, and then upon patients in the dental chair, that seemed +to him absolutely demonstrative. + +Full of eager enthusiasm, and absolutely confident of his +results, he at once went to Dr. J. C. Warren, one of the foremost +surgeons of Boston, and asked permission to test his discovery +decisively on one of the patients at the Boston Hospital during a +severe operation. The request was granted; the test was made on +October 16, 1846, in the presence of several of the foremost +surgeons of the city and of a body of medical students. The +patient slept quietly while the surgeon's knife was plied, and +awoke to astonished comprehension that the ordeal was over. The +impossible, the miraculous, had been accomplished.[5] + +Swiftly as steam could carry it--slowly enough we should think it +to-day--the news was heralded to all the world. It was received +in Europe with incredulity, which vanished before repeated +experiments. Surgeons were loath to believe that ether, a drug +that had long held a place in the subordinate armamentarium of +the physician, could accomplish such a miracle. But scepticism +vanished before the tests which any surgeon might make, and which +surgeons all over the world did make within the next few weeks. +Then there came a lingering outcry from a few surgeons, notably +some of the Parisians, that the shock of pain was beneficial to +the patient, hence that anaesthesia--as Dr. Oliver Wendell Holmes +had christened the new method--was a procedure not to be advised. +Then, too, there came a hue-and-cry from many a pulpit that pain +was God-given, and hence, on moral grounds, to be clung to rather +than renounced. But the outcry of the antediluvians of both +hospital and pulpit quickly received its quietus; for soon it was +clear that the patient who did not suffer the shock of pain +during an operation rallied better than the one who did so +suffer, while all humanity outside the pulpit cried shame to the +spirit that would doom mankind to suffer needless agony. And so +within a few months after that initial operation at the Boston +Hospital in 1846, ether had made good its conquest of pain +throughout the civilized world. Only by the most active use of +the imagination can we of this present day realize the full +meaning of that victory. + +It remains to be added that in the subsequent bickerings over the +discovery--such bickerings as follow every great advance--two +other names came into prominent notice as sharers in the glory of +the new method. Both these were Americans--the one, Dr. Charles +T. Jackson, of Boston; the other, Dr. Crawford W. Long, of +Alabama. As to Dr. Jackson, it is sufficient to say that he +seems to have had some vague inkling of the peculiar properties +of ether before Morton's discovery. He even suggested the use of +this drug to Morton, not knowing that Morton had already tried +it; but this is the full measure of his association with the +discovery. Hence it is clear that Jackson's claim to equal share +with Morton in the discovery was unwarranted, not to say absurd. + +Dr. Long's association with the matter was far different and +altogether honorable. By one of those coincidences so common in +the history of discovery, he was experimenting with ether as a +pain-destroyer simultaneously with Morton, though neither so much +as knew of the existence of the other. While a medical student he +had once inhaled ether for the intoxicant effects, as other +medical students were wont to do, and when partially under +influence of the drug he had noticed that a chance blow to his +shins was painless. This gave him the idea that ether might be +used in surgical operations; and in subsequent years, in the +course of his practice in a small Georgia town, he put the idea +into successful execution. There appears to be no doubt whatever +that he performed successful minor operations under ether some +two or three years before Morton's final demonstration; hence +that the merit of first using the drug, or indeed any drug, in +this way belongs to him. But, unfortunately, Dr. Long did not +quite trust the evidence of his own experiments. Just at that +time the medical journals were full of accounts of experiments in +which painless operations were said to be performed through +practice of hypnotism, and Dr. Long feared that his own success +might be due to an incidental hypnotic influence rather than to +the drug. Hence he delayed announcing his apparent discovery +until he should have opportunity for further tests--and +opportunities did not come every day to the country practitioner. +And while he waited, Morton anticipated him, and the discovery +was made known to the world without his aid. It was a true +scientific caution that actuated Dr. Long to this delay, but the +caution cost him the credit, which might otherwise have been his, +of giving to the world one of the greatest blessings--dare we +not, perhaps, say the very greatest?--that science has ever +conferred upon humanity. + +A few months after the use of ether became general, the Scotch +surgeon Sir J. Y. Simpson[6] discovered that another drug, +chloroform, could be administered with similar effects; that it +would, indeed, in many cases produce anaesthesia more +advantageously even than ether. From that day till this surgeons +have been more or less divided in opinion as to the relative +merits of the two drugs; but this fact, of course, has no bearing +whatever upon the merit of the first discovery of the method of +anaesthesia. Even had some other drug subsequently quite +banished ether, the honor of the discovery of the beneficent +method of anaesthesia would have been in no wise invalidated. And +despite all cavillings, it is unequivocally established that the +man who gave that method to the world was William T. G. Morton. + + +PASTEUR AND THE GERM THEORY OF DISEASE + +The discovery of the anaesthetic power of drugs was destined +presently, in addition to its direct beneficences, to aid greatly +in the progress of scientific medicine, by facilitating those +experimental studies of animals from which, before the day of +anaesthesia, many humane physicians were withheld, and which in +recent years have led to discoveries of such inestimable value to +humanity. But for the moment this possibility was quite +overshadowed by the direct benefits of anaesthesia, and the long +strides that were taken in scientific medicine during the first +fifteen years after Morton's discovery were mainly independent of +such aid. These steps were taken, indeed, in a field that at +first glance might seem to have a very slight connection with +medicine. Moreover, the chief worker in the field was not himself +a physician. He was a chemist, and the work in which he was now +engaged was the study of alcoholic fermentation in vinous +liquors. Yet these studies paved the way for the most important +advances that medicine has made in any century towards the plane +of true science; and to this man more than to any other single +individual--it might almost be said more than to all other +individuals--was due this wonderful advance. It is almost +superfluous to add that the name of this marvellous chemist was +Louis Pasteur. + +The studies of fermentation which Pasteur entered upon in 1854 +were aimed at the solution of a controversy that had been waging +in the scientific world with varying degrees of activity for a +quarter of a century. Back in the thirties, in the day of the +early enthusiasm over the perfected microscope, there had arisen +a new interest in the minute forms of life which Leeuwenhoek and +some of the other early workers with the lens had first +described, and which now were shown to be of almost universal +prevalence. These minute organisms had been studied more or less +by a host of observers, but in particular by the Frenchman +Cagniard Latour and the German of cell-theory fame, Theodor +Schwann. These men, working independently, had reached the +conclusion, about 1837, that the micro-organisms play a vastly +more important role in the economy of nature than any one +previously had supposed. They held, for example, that the minute +specks which largely make up the substance of yeast are living +vegetable organisms, and that the growth of these organisms is +the cause of the important and familiar process of fermentation. +They even came to hold, at least tentatively, the opinion that +the somewhat similar micro-organisms to be found in all +putrefying matter, animal or vegetable, had a causal relation to +the process of putrefaction. + +This view, particularly as to the nature of putrefaction, was +expressed even more outspokenly a little later by the French +botanist Turpin. Views so supported naturally gained a +following; it was equally natural that so radical an innovation +should be antagonized. In this case it chanced that one of the +most dominating scientific minds of the time, that of Liebig, +took a firm and aggressive stand against the new doctrine. In +1839 he promulgated his famous doctrine of fermentation, in which +he stood out firmly against any "vitalistic" explanation of the +phenomena, alleging that the presence of micro-organisms in +fermenting and putrefying substances was merely incidental, and +in no sense causal. This opinion of the great German chemist was +in a measure substantiated by experiments of his compatriot +Helmholtz, whose earlier experiments confirmed, but later ones +contradicted, the observations of Schwann, and this combined +authority gave the vitalistic conception a blow from which it had +not rallied at the time when Pasteur entered the field. Indeed, +it was currently regarded as settled that the early students of +the subject had vastly over-estimated the importance of +micro-organisms. + +And so it came as a new revelation to the generality of +scientists of the time, when, in 1857 and the succeeding +half-decade, Pasteur published the results of his researches, in +which the question had been put to a series of altogether new +tests, and brought to unequivocal demonstration. + +He proved that the micro-organisms do all that his most +imaginative predecessors had suspected, and more. Without them, +he proved, there would be no fermentation, no putrefaction--no +decay of any tissues, except by the slow process of oxidation. It +is the microscopic yeast-plant which, by seizing on certain atoms +of the molecule, liberates the remaining atoms in the form of +carbonic-acid and alcohol, thus effecting fermentation; it is +another microscopic plant--a bacterium, as Devaine had christened +it--which in a similar way effects the destruction of organic +molecules, producing the condition which we call putrefaction. +Pasteur showed, to the amazement of biologists, that there are +certain forms of these bacteria which secure the oxygen which all +organic life requires, not from the air, but by breaking up +unstable molecules in which oxygen is combined; that +putrefaction, in short, has its foundation in the activities of +these so-called anaerobic bacteria. + +In a word, Pasteur showed that all the many familiar processes of +the decay of organic tissues are, in effect, forms of +fermentation, and would not take place at all except for the +presence of the living micro-organisms. A piece of meat, for +example, suspended in an atmosphere free from germs, will dry up +gradually, without the slightest sign of putrefaction, regardless +of the temperature or other conditions to which it may have been +subjected. Let us witness one or two series of these experiments +as presented by Pasteur himself in one of his numerous papers +before the Academy of Sciences. + + +EXPERIMENTS WITH GRAPE SUGAR + +"In the course of the discussion which took place before the +Academy upon the subject of the generation of ferments properly +so-called, there was a good deal said about that of wine, the +oldest fermentation known. On this account I decided to disprove +the theory of M. Fremy by a decisive experiment bearing solely +upon the juice of grapes. + +"I prepared forty flasks of a capacity of from two hundred and +fifty to three hundred cubic centimetres and filled them half +full with filtered grape-must, perfectly clear, and which, as is +the case of all acidulated liquids that have been boiled for a +few seconds, remains uncontaminated although the curved neck of +the flask containing them remain constantly open during several +months or years. + +"In a small quantity of water I washed a part of a bunch of +grapes, the grapes and the stalks together, and the stalks +separately. This washing was easily done by means of a small +badger's-hair brush. The washing-water collected the dust upon +the surface of the grapes and the stalks, and it was easily shown +under the microscope that this water held in suspension a +multitude of minute organisms closely resembling either fungoid +spores, or those of alcoholic Yeast, or those of Mycoderma vini, +etc. This being done, ten of the forty flasks were preserved for +reference; in ten of the remainder, through the straight tube +attached to each, some drops of the washing-water were +introduced; in a third series of ten flasks a few drops of the +same liquid were placed after it had been boiled; and, finally, +in the ten remaining flasks were placed some drops of grape-juice +taken from the inside of a perfect fruit. In order to carry out +this experiment, the straight tube of each flask was drawn out +into a fine and firm point in the lamp, and then curved. This +fine and closed point was filed round near the end and inserted +into the grape while resting upon some hard substance. When the +point was felt to touch the support of the grape it was by a +slight pressure broken off at the point file mark. Then, if care +had been taken to create a slight vacuum in the flask, a drop of +the juice of the grape got into it, the filed point was +withdrawn, and the aperture immediately closed in the alcohol +lamp. This decreased pressure of the atmosphere in the flask was +obtained by the following means: After warming the sides of the +flask either in the hands or in the lamp-flame, thus causing a +small quantity of air to be driven out of the end of the curved +neck, this end was closed in the lamp. After the flask was +cooled, there was a tendency to suck in the drop of grape-juice +in the manner just described. + +"The drop of grape-juice which enters into the flask by this +suction ordinarily remains in the curved part of the tube, so +that to mix it with the must it was necessary to incline the +flask so as to bring the must into contact with the juice and +then replace the flask in its normal position. The four series of +comparative experiments produced the following results: + +"The first ten flasks containing the grape-must boiled in pure +air did not show the production of any organism. The grape-must +could possibly remain in them for an indefinite number of years. +Those in the second series, containing the water in which the +grapes had been washed separately and together, showed without +exception an alcoholic fermentation which in several cases began +to appear at the end of forty-eight hours when the experiment +took place at ordinary summer temperature. At the same time that +the yeast appeared, in the form of white traces, which little by +little united themselves in the form of a deposit on the sides of +all the flasks, there were seen to form little flakes of +Mycellium, often as a single fungoid growth or in combination, +these fungoid growths being quite independent of the must or of +any alcoholic yeast. Often, also, the Mycoderma vini appeared +after some days upon the surface of the liquid. The Vibria and +the lactic ferments properly so called did not appear on account +of the nature of the liquid. + +"The third series of flasks, the washing-water in which had been +previously boiled, remained unchanged, as in the first series. +Those of the fourth series, in which was the juice of the +interior of the grapes, remained equally free from change, +although I was not always able, on account of the delicacy of the +experiment, to eliminate every chance of error. These experiments +cannot leave the least doubt in the mind as to the following +facts: + +Grape-must, after heating, never ferments on contact with the +air, when the air has been deprived of the germs which it +ordinarily holds in a state of suspension. + +"The boiled grape-must ferments when there is introduced into it +a very small quantity of water in which the surface of the grapes +or their stalks have been washed. + +"The grape-must does not ferment when this washing-water has been +boiled and afterwards cooled. + +"The grape-must does not ferment when there is added to it a +small quantity of the juice of the inside of the grape. + +"The yeast, therefore, which causes the fermentation of the +grapes in the vintage-tub comes from the outside and not from the +inside of the grapes. Thus is destroyed the hypothesis of MM. +Trecol and Fremy, who surmised that the albuminous matter +transformed itself into yeast on account of the vital germs which +were natural to it. With greater reason, therefore, there is no +longer any question of the theory of Liebig of the transformation +of albuminoid matter into ferments on account of the oxidation." + + +FOREIGN ORGANISMS AND THE WORT OF BEER + +"The method which I have just followed," Pasteur continues, "in +order to show that there exists a correlation between the +diseases of beer and certain microscopic organisms leaves no room +for doubt, it seems to me, in regard to the principles I am +expounding. + +"Every time that the microscope reveals in the leaven, and +especially in the active yeast, the production of organisms +foreign to the alcoholic yeast properly so called, the flavor of +the beer leaves something to be desired, much or little, +according to the abundance and the character of these little +germs. Moreover, when a finished beer of good quality loses after +a time its agreeable flavor and becomes sour, it can be easily +shown that the alcoholic yeast deposited in the bottles or the +casks, although originally pure, at least in appearance, is found +to be contaminated gradually with these filiform or other +ferments. All this can be deduced from the facts already given, +but some critics may perhaps declare that these foreign ferments +are the consequences of the diseased condition, itself produced +by unknown causes. + +"Although this gratuitous hypothesis may be difficult to uphold, +I will endeavor to corroborate the preceding observations by a +clearer method of investigation. This consists in showing that +the beer never has any unpleasant taste in all cases when the +alcoholic ferment properly so called is not mixed with foreign +ferments; that it is the same in the case of wort, and that wort, +liable to changes as it is, can be preserved unaltered if it is +kept from those microscopic parasites which find in it a suitable +nourishment and a field for growth. + +"The employment of this second method has, moreover, the +advantage of proving with certainty the proposition that I +advanced at first--namely, that the germs of these organisms are +derived from the dust of the atmosphere, carried about and +deposited upon all objects, or scattered over the utensils and +the materials used in a brewery-materials naturally charged with +microscopic germs, and which the various operations in the +store-rooms and the malt-house may multiply indefinitely. + +"Let us take a glass flask with a long neck of from two hundred +and fifty to three hundred cubic centimetres capacity, and place +in it some wort, with or without hops, and then in the flame of a +lamp draw out the neck of the flask to a fine point, afterwards +heating the liquid until the steam comes out of the end of the +neck. It can then be allowed to cool without any other +precautions; but for additional safety there can be introduced +into the little point a small wad of asbestos at the moment that +the flame is withdrawn from beneath the flask. Before thus +placing the asbestos it also can be passed through the flame, as +well as after it has been put into the end of the tube. The air +which then first re-enters the flask will thus come into contact +with the heated glass and the heated liquid, so as to destroy the +vitality of any dust germs that may exist in the air. The air +itself will re-enter very gradually, and slowly enough to enable +any dust to be taken up by the drop of water which the air forces +up the curvature of the tube. Ultimately the tube will be dry, +but the re-entering of the air will be so slow that the particles +of dust will fall upon the sides of the tube. The experiments +show that with this kind of vessel, allowing free communication +with the air, and the dust not being allowed to enter, the dust +will not enter at all events for a period of ten or twelve years, +which has been the longest period devoted to these trials; and +the liquid, if it were naturally limpid, will not be in the least +polluted neither on its surface nor in its mass, although the +outside of the flask may become thickly coated with dust. This is +a most irrefutable proof of the impossibility of dust getting +inside the flask. + +"The wort thus prepared remains uncontaminated indefinitely, in +spite of its susceptibility to change when exposed to the air +under conditions which allow it to gather the dusty particles +which float in the atmosphere. It is the same in the case of +urine, beef-tea, and grape-must, and generally with all those +putrefactable and fermentable liquids which have the property +when heated to boiling-point of destroying the vitality of dust +germs."[7] + + +There was nothing in these studies bearing directly upon the +question of animal diseases, yet before they were finished they +had stimulated progress in more than one field of pathology. At +the very outset they sufficed to start afresh the inquiry as to +the role played by micro-organisms in disease. In particular they +led the French physician Devaine to return to some interrupted +studies which he had made ten years before in reference to the +animal disease called anthrax, or splenic fever, a disease that +cost the farmers of Europe millions of francs annually through +loss of sheep and cattle. In 1850 Devaine had seen multitudes of +bacteria in the blood of animals who had died of anthrax, but he +did not at that time think of them as having a causal relation to +the disease. Now, however, in 1863, stimulated by Pasteur's new +revelations regarding the power of bacteria, he returned to the +subject, and soon became convinced, through experiments by means +of inoculation, that the microscopic organisms he had discovered +were the veritable and the sole cause of the infectious disease +anthrax. + +The publication of this belief in 1863 aroused a furor of +controversy. That a microscopic vegetable could cause a virulent +systemic disease was an idea altogether too startling to be +accepted in a day, and the generality of biologists and +physicians demanded more convincing proofs than Devaine as yet +was able to offer. + +Naturally a host of other investigators all over the world +entered the field. Foremost among these was the German Dr. Robert +Koch, who soon corroborated all that Devaine had observed, and +carried the experiments further in the direction of the +cultivation of successive generations of the bacteria in +artificial media, inoculations being made from such pure cultures +of the eighth generation, with the astonishing result that +animals thus inoculated succumbed to the disease. + +Such experiments seem demonstrative, yet the world was +unconvinced, and in 1876, while the controversy was still at its +height, Pasteur was prevailed upon to take the matter in hand. +The great chemist was becoming more and more exclusively a +biologist as the years passed, and in recent years his famous +studies of the silk-worm diseases, which he proved due to +bacterial infection, and of the question of spontaneous +generation, had given him unequalled resources in microscopical +technique. And so when, with the aid of his laboratory associates +Duclaux and Chamberland and Roux, he took up the mooted anthrax +question the scientific world awaited the issue with bated +breath. And when, in 1877, Pasteur was ready to report on his +studies of anthrax, he came forward with such a wealth of +demonstrative experiments--experiments the rigid accuracy of +which no one would for a moment think of questioning--going to +prove the bacterial origin of anthrax, that scepticism was at +last quieted for all time to come. + +Henceforth no one could doubt that the contagious disease anthrax +is due exclusively to the introduction into an animal's system of +a specific germ--a microscopic plant--which develops there. And +no logical mind could have a reasonable doubt that what is proved +true of one infectious disease would some day be proved true also +of other, perhaps of all, forms of infectious maladies. + +Hitherto the cause of contagion, by which certain maladies spread +from individual to individual, had been a total mystery, quite +unillumined by the vague terms "miasm," "humor," "virus," and the +like cloaks of ignorance. Here and there a prophet of science, +as Schwann and Henle, had guessed the secret; but guessing, in +science, is far enough from knowing. Now, for the first time, the +world KNEW, and medicine had taken another gigantic stride +towards the heights of exact science. + + +LISTER AND ANTISEPTIC SURGERY + +Meantime, in a different though allied field of medicine there +had been a complementary growth that led to immediate results of +even more practical importance. I mean the theory and practice +of antisepsis in surgery. This advance, like the other, came as +a direct outgrowth of Pasteur's fermentation studies of alcoholic +beverages, though not at the hands of Pasteur himself. Struck by +the boundless implications of Pasteur's revelations regarding the +bacteria, Dr. Joseph Lister (the present Lord Lister), then of +Glasgow, set about as early as 1860 to make a wonderful +application of these ideas. If putrefaction is always due to +bacterial development, he argued, this must apply as well to +living as to dead tissues; hence the putrefactive changes which +occur in wounds and after operations on the human subject, from +which blood-poisoning so often follows, might be absolutely +prevented if the injured surfaces could be kept free from access +of the germs of decay. + +In the hope of accomplishing this result, Lister began +experimenting with drugs that might kill the bacteria without +injury to the patient, and with means to prevent further access +of germs once a wound was freed from them. How well he succeeded +all the world knows; how bitterly he was antagonized for about a +score of years, most of the world has already forgotten. As early +as 1867 Lister was able to publish results pointing towards +success in his great project; yet so incredulous were surgeons in +general that even some years later the leading surgeons on the +Continent had not so much as heard of his efforts. In 1870 the +soldiers of Paris died, as of old, of hospital gangrene; and +when, in 1871, the French surgeon Alphonse Guerin, stimulated by +Pasteur's studies, conceived the idea of dressing wounds with +cotton in the hope of keeping germs from entering them, he was +quite unaware that a British contemporary had preceded him by a +full decade in this effort at prevention and had made long +strides towards complete success. Lister's priority, however, and +the superiority of his method, were freely admitted by the French +Academy of Sciences, which in 1881 officially crowned his +achievement, as the Royal Society of London had done the year +before. + +By this time, to be sure, as everybody knows, Lister's new +methods had made their way everywhere, revolutionizing the +practice of surgery and practically banishing from the earth +maladies that hitherto had been the terror of the surgeon and the +opprobrium of his art. And these bedside studies, conducted in +the end by thousands of men who had no knowledge of microscopy, +had a large share in establishing the general belief in the +causal relation that micro-organisms bear to disease, which by +about the year 1880 had taken possession of the medical world. +But they did more; they brought into equal prominence the idea +that, the cause of a diseased condition being known, it maybe +possible as never before to grapple with and eradicate that +condition. + + +PREVENTIVE INOCULATION + +The controversy over spontaneous generation, which, thanks to +Pasteur and Tyndall, had just been brought to a termination, made +it clear that no bacterium need be feared where an antecedent +bacterium had not found lodgment; Listerism in surgery had now +shown how much might be accomplished towards preventing the +access of germs to abraded surfaces of the body and destroying +those that already had found lodgment there. As yet, however, +there was no inkling of a way in which a corresponding onslaught +might be made upon those other germs which find their way into +the animal organism by way of the mouth and the nostrils, and +which, as was now clear, are the cause of those contagious +diseases which, first and last, claim so large a proportion of +mankind for their victims. How such means might be found now +became the anxious thought of every imaginative physician, of +every working microbiologist. + +As it happened, the world was not kept long in suspense. Almost +before the proposition had taken shape in the minds of the other +leaders, Pasteur had found a solution. Guided by the empirical +success of Jenner, he, like many others, had long practised +inoculation experiments, and on February 9, 1880, he announced to +the French Academy of Sciences that he had found a method of so +reducing the virulence of a disease germ that when introduced +into the system of a susceptible animal it produced only a mild +form of the disease, which, however, sufficed to protect against +the usual virulent form exactly as vaccinia protects against +small-pox. The particular disease experimented with was that +infectious malady of poultry known familiarly as "chicken +cholera." In October of the same year Pasteur announced the +method by which this "attenuation of the virus," as he termed it, +had been brought about--by cultivation of the disease germs in +artificial media, exposed to the air, and he did not hesitate to +assert his belief that the method would prove "susceptible of +generalization"--that is to say, of application to other diseases +than the particular one in question. + +Within a few months he made good this prophecy, for in February, +1881, he announced to the Academy that with the aid, as before, +of his associates MM. Chamberland and Roux, he had produced an +attenuated virus of the anthrax microbe by the use of which, as +he affirmed with great confidence, he could protect sheep, and +presumably cattle, against that fatal malady. "In some recent +publications," said Pasteur, "I announced the first case of the +attenuation of a virus by experimental methods only. Formed of a +special microbe of an extreme minuteness, this virus may be +multiplied by artificial culture outside the animal body. These +cultures, left alone without any possible external contamination, +undergo, in the course of time, modifications of their virulency +to a greater or less extent. The oxygen of the atmosphere is +said to be the chief cause of these attenuations--that is, this +lessening of the facilities of multiplication of the microbe; for +it is evident that the difference of virulence is in some way +associated with differences of development in the parasitic +economy. + +"There is no need to insist upon the interesting character of +these results and the deductions to be made therefrom. To seek to +lessen the virulence by rational means would be to establish, +upon an experimental basis, the hope of preparing from an active +virus, easily cultivated either in the human or animal body, a +vaccine-virus of restrained development capable of preventing the +fatal effects of the former. Therefore, we have applied all our +energies to investigate the possible generalizing action of +atmospheric oxygen in the attenuation of virus. + +"The anthrax virus, being one that has been most carefully +studied, seemed to be the first that should attract our +attention. Every time, however, we encountered a difficulty. +Between the microbe of chicken cholera and the microbe of anthrax +there exists an essential difference which does not allow the new +experiment to be verified by the old. The microbes of chicken +cholera do not, in effect, seem to resolve themselves, in their +culture, into veritable germs. The latter are merely cells, or +articulations always ready to multiply by division, except when +the particular conditions in which they become true germs are +known. + +"The yeast of beer is a striking example of these cellular +productions, being able to multiply themselves indefinitely +without the apparition of their original spores. There exist +many mucedines (Mucedinae?) of tubular mushrooms, which in +certain conditions of culture produce a chain of more or less +spherical cells called Conidae. The latter, detached from their +branches, are able to reproduce themselves in the form of cells, +without the appearance, at least with a change in the conditions +of culture, of the spores of their respective mucedines. These +vegetable organisms can be compared to plants which are +cultivated by slipping, and to produce which it is not necessary +to have the fruits or the seeds of the mother plant. + +The anthrax bacterium, in its artificial cultivation, behaves +very differently. Its mycelian filaments, if one may so describe +them, have been produced scarcely for twenty-four or forty-eight +hours when they are seen to transform themselves, those +especially which are in free contact with the air, into very +refringent corpuscles, capable of gradually isolating themselves +into true germs of slight organization. Moreover, observation +shows that these germs, formed so quickly in the culture, do not +undergo, after exposure for a time to atmospheric air, any change +either in their vitality or their virulence. I was able to +present to the Academy a tube containing some spores of anthrax +bacteria produced four years ago, on March 21, 1887. Each year +the germination of these little corpuscles has been tried, and +each year the germination has been accomplished with the same +facility and the same rapidity as at first. Each year also the +virulence of the new cultures has been tested, and they have not +shown any visible falling off. Therefore, how can we experiment +with the action of the air upon the anthrax virus with any +expectation of making it less virulent? + +"The crucial difficulty lies perhaps entirely in this rapid +reproduction of the bacteria germs which we have just related. In +its form of a filament, and in its multiplication by division, is +not this organism at all points comparable with the microbe of +the chicken cholera? + +"That a germ, properly so called, that a seed, does not suffer +any modification on account of the air is easily conceived; but +it is conceivable not less easily that if there should be any +change it would occur by preference in the case of a mycelian +fragment. It is thus that a slip which may have been abandoned in +the soil in contact with the air does not take long to lose all +vitality, while under similar conditions a seed is preserved in +readiness to reproduce the plant. If these views have any +foundation, we are led to think that in order to prove the action +of the air upon the anthrax bacteria it will be indispensable to +submit to this action the mycelian development of the minute +organism under conditions where there cannot be the least +admixture of corpuscular germs. Hence the problem of submitting +the bacteria to the action of oxygen comes back to the question +of presenting entirely the formation of spores. The question +being put in this way, we are beginning to recognize that it is +capable of being solved. + +"We can, in fact, prevent the appearance of spores in the +artificial cultures of the anthrax parasite by various artifices. +At the lowest temperature at which this parasite can be +cultivated--that is to say, about +16 degrees Centigrade--the +bacterium does not produce germs--at any rate, for a very long +time. The shapes of the minute microbe at this lowest limit of +its development are irregular, in the form of balls and pears--in +a word, they are monstrosities--but they are without spores. In +the last regard also it is the same at the highest temperatures +at which the parasite can be cultivated, temperatures which vary +slightly according to the means employed. In neutral chicken +bouillon the bacteria cannot be cultivated above 45 degrees. +Culture, however, is easy and abundant at 42 to 43 degrees, but +equally without any formation of spores. Consequently a culture +of mycelian bacteria can be kept entirely free from germs while +in contact with the open air at a temperature of from 42 to 43 +degrees Centigrade. Now appear the three remarkable results. +After about one month of waiting the culture dies--that is to +say, if put into a fresh bouillon it becomes absolutely sterile. + +"So much for the life and nutrition of this organism. In respect +to its virulence, it is an extraordinary fact that it disappears +entirely after eight days' culture at 42 to 43 degrees +Centigrade, or, at any rate, the cultures are innocuous for the +guinea-pig, the rabbit, and the sheep, the three kinds of animals +most apt to contract anthrax. We are thus able to obtain, not +only the attenuation of the virulence, but also its complete +suppression by a simple method of cultivation. Moreover, we see +also the possibility of preserving and cultivating the terrible +microbe in an inoffensive state. What is it that happens in these +eight days at 43 degrees that suffices to take away the virulence +of the bacteria? Let us remember that the microbe of chicken +cholera dies in contact with the air, in a period somewhat +protracted, it is true, but after successive attenuations. Are +we justified in thinking that it ought to be the same in regard +to the microbe of anthrax? This hypothesis is confirmed by +experiment. Before the disappearance of its virulence the anthrax +microbe passes through various degrees of attenuation, and, +moreover, as is also the case with the microbe of chicken +cholera, each of these attenuated states of virulence can be +obtained by cultivation. Moreover, since, according to one of our +recent Communications, anthrax is not recurrent, each of our +attenuated anthrax microbes is, for the better-developed microbe, +a vaccine--that is to say, a virus producing a less-malignant +malady. What, therefore, is easier than to find in these a virus +that will infect with anthrax sheep, cows, and horses, without +killing them, and ultimately capable of warding off the mortal +malady? We have practised this experiment with great success upon +sheep, and when the season comes for the assembling of the flocks +at Beauce we shall try the experiment on a larger scale. + +"Already M. Toussaint has announced that sheep can be saved by +preventive inoculations; but when this able observer shall have +published his results; on the subject of which we have made such +exhaustive studies, as yet unpublished, we shall be able to see +the whole difference which exists between the two methods--the +uncertainty of the one and the certainty of the other. That which +we announce has, moreover, the very great advantage of resting +upon the existence of a poison vaccine cultivable at will, and +which can be increased indefinitely in the space of a few hours +without having recourse to infected blood."[8] + + +This announcement was immediately challenged in a way that +brought it to the attention of the entire world. The president of +an agricultural society, realizing the enormous importance of the +subject, proposed to Pasteur that his alleged discovery should be +submitted to a decisive public test. He proposed to furnish a +drove of fifty sheep half of which were to be inoculated with the +attenuated virus of Pasteur. Subsequently all the sheep were to +be inoculated with virulent virus, all being kept together in one +pen under precisely the same conditions. The "protected" sheep +were to remain healthy; the unprotected ones to die of anthrax; +so read the terms of the proposition. Pasteur accepted the +challenge; he even permitted a change in the programme by which +two goats were substituted for two of the sheep, and ten cattle +added, stipulating, however, that since his experiments had not +yet been extended to cattle these should not be regarded as +falling rigidly within the terms of the test. + +It was a test to try the soul of any man, for all the world +looked on askance, prepared to deride the maker of so +preposterous a claim as soon as his claim should be proved +baseless. Not even the fame of Pasteur could make the public at +large, lay or scientific, believe in the possibility of what he +proposed to accomplish. There was time for all the world to be +informed of the procedure, for the first "preventive" +inoculation--or vaccination, as Pasteur termed it--was made on +May 5th, the second on May 17th, and another interval of two +weeks must elapse before the final inoculations with the +unattenuated virus. Twenty-four sheep, one goat, and five cattle +were submitted to the preliminary vaccinations. Then, on May 31 +st, all sixty of the animals were inoculated, a protected and +unprotected one alternately, with an extremely virulent culture +of anthrax microbes that had been in Pasteur's laboratory since +1877. This accomplished, the animals were left together in one +enclosure to await the issue. + +Two days later, June 2d, at the appointed hour of rendezvous, a +vast crowd, composed of veterinary surgeons, newspaper +correspondents, and farmers from far and near, gathered to +witness the closing scenes of this scientific tourney. What they +saw was one of the most dramatic scenes in the history of +peaceful science--a scene which, as Pasteur declared afterwards, +"amazed the assembly." Scattered about the enclosure, dead, +dying, or manifestly sick unto death, lay the unprotected +animals, one and all, while each and every "protected" animal +stalked unconcernedly about with every appearance of perfect +health. Twenty of the sheep and the one goat were already dead; +two other sheep expired under the eyes of the spectators; the +remaining victims lingered but a few hours longer. Thus in a +manner theatrical enough, not to say tragic, was proclaimed the +unequivocal victory of science. Naturally enough, the unbelievers +struck their colors and surrendered without terms; the principle +of protective vaccination, with a virus experimentally prepared +in the laboratory, was established beyond the reach of +controversy. + +That memorable scientific battle marked the beginning of a new +era in medicine. It was a foregone conclusion that the principle +thus established would be still further generalized; that it +would be applied to human maladies; that in all probability it +would grapple successfully, sooner or later, with many infectious +diseases. That expectation has advanced rapidly towards +realization. Pasteur himself made the application to the human +subject in the disease hydrophobia in 1885, since which time that +hitherto most fatal of maladies has largely lost its terrors. +Thousands of persons bitten by mad dogs have been snatched from +the fatal consequences of that mishap by this method at the +Pasteur Institute in Paris, and at the similar institutes, built +on the model of this parent one, that have been established all +over the world in regions as widely separated as New York and +Nha-Trang. + + +SERUM-THERAPY + +In the production of the rabies vaccine Pasteur and his +associates developed a method of attenuation of a virus quite +different from that which had been employed in the case of the +vaccines of chicken cholera and of anthrax. The rabies virus was +inoculated into the system of guinea-pigs or rabbits and, in +effect, cultivated in the systems of these animals. The spinal +cord of these infected animals was found to be rich in the virus, +which rapidly became attenuated when the cord was dried in the +air. The preventive virus, of varying strengths, was made by +maceration of these cords at varying stages of desiccation. This +cultivation of a virus within the animal organism suggested, no +doubt, by the familiar Jennerian method of securing small-pox +vaccine, was at the same time a step in the direction of a new +therapeutic procedure which was destined presently to become of +all-absorbing importance--the method, namely, of so-called +serum-therapy, or the treatment of a disease with the blood serum +of an animal that has been subjected to protective inoculation +against that disease. + +The possibility of such a method was suggested by the familiar +observation, made by Pasteur and numerous other workers, that +animals of different species differ widely in their +susceptibility to various maladies, and that the virus of a given +disease may become more and more virulent when passed through the +systems of successive individuals of one species, and, +contrariwise, less and less virulent when passed through the +systems of successive individuals of another species. These facts +suggested the theory that the blood of resistant animals might +contain something directly antagonistic to the virus, and the +hope that this something might be transferred with curative +effect to the blood of an infected susceptible animal. Numerous +experimenters all over the world made investigations along the +line of this alluring possibility, the leaders perhaps being Drs. +Behring and Kitasato, closely followed by Dr. Roux and his +associates of the Pasteur Institute of Paris. Definite results +were announced by Behring in 1892 regarding two important +diseases--tetanus and diphtheria--but the method did not come +into general notice until 1894, when Dr. Roux read an +epoch-making paper on the subject at the Congress of Hygiene at +Buda-Pesth. + +In this paper Dr. Roux, after adverting to the labors of Behring, +Ehrlich, Boer, Kossel, and Wasserman, described in detail the +methods that had been developed at the Pasteur Institute for the +development of the curative serum, to which Behring had given the +since-familiar name antitoxine. The method consists, first, of +the cultivation, for some months, of the diphtheria bacillus +(called the Klebs-Loeffler bacillus, in honor of its discoverers) +in an artificial bouillon, for the development of a powerful +toxine capable of giving the disease in a virulent form. + +This toxine, after certain details of mechanical treatment, is +injected in small but increasing doses into the system of an +animal, care being taken to graduate the amount so that the +animal does not succumb to the disease. After a certain course of +this treatment it is found that a portion of blood serum of the +animal so treated will act in a curative way if injected into the +blood of another animal, or a human patient, suffering with +diphtheria. In other words, according to theory, an antitoxine +has been developed in the system of the animal subjected to the +progressive inoculations of the diphtheria toxine. In Dr. Roux's +experience the animal best suited for the purpose is the horse, +though almost any of the domesticated animals will serve the +purpose. + +But Dr. Roux's paper did not stop with the description of +laboratory methods. It told also of the practical application of +the serum to the treatment of numerous cases of diphtheria in the +hospitals of Paris--applications that had met with a gratifying +measure of success. He made it clear that a means had been found +of coping successfully with what had been one of the most +virulent and intractable of the diseases of childhood. Hence it +was not strange that his paper made a sensation in all circles, +medical and lay alike. + +Physicians from all over the world flocked to Paris to learn the +details of the open secret, and within a few months the new +serum-therapy had an acknowledged standing with the medical +profession everywhere. What it had accomplished was regarded as +but an earnest of what the new method might accomplish presently +when applied to the other infectious diseases. + +Efforts at such applications were immediately begun in numberless +directions--had, indeed, been under way in many a laboratory for +some years before. It is too early yet to speak of the results in +detail. But enough has been done to show that this method also is +susceptible of the widest generalization. It is not easy at the +present stage to sift that which is tentative from that which +will be permanent; but so great an authority as Behring does not +hesitate to affirm that today we possess, in addition to the +diphtheria antitoxine, equally specific antitoxines of tetanus, +cholera, typhus fever, pneumonia, and tuberculosis--a set of +diseases which in the aggregate account for a startling +proportion of the general death-rate. Then it is known that Dr. +Yersin, with the collaboration of his former colleagues of the +Pasteur Institute, has developed, and has used with success, an +antitoxine from the microbe of the plague which recently ravaged +China. + +Dr. Calmette, another graduate of the Pasteur Institute, has +extended the range of the serum-therapy to include the prevention +and treatment of poisoning by venoms, and has developed an +antitoxine that has already given immunity from the lethal +effects of snake bites to thousands of persons in India and +Australia. + +Just how much of present promise is tentative, just what are the +limits of the methods--these are questions for the future to +decide. But, in any event, there seems little question that the +serum treatment will stand as the culminating achievement in +therapeutics of our century. It is the logical outgrowth of those +experimental studies with the microscope begun by our +predecessors of the thirties, and it represents the present +culmination of the rigidly experimental method which has brought +medicine from a level of fanciful empiricism to the plane of a +rational experimental science. + + + +IX. THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY + +BRAIN AND MIND + +A little over a hundred years ago a reform movement was afoot in +the world in the interests of the insane. As was fitting, the +movement showed itself first in America, where these unfortunates +were humanely cared for at a time when their treatment elsewhere +was worse than brutal; but England and France quickly fell into +line. The leader on this side of the water was the famous +Philadelphian, Dr. Benjamin Rush, "the Sydenham of America"; in +England, Dr. William Tuke inaugurated the movement; and in +France, Dr. Philippe Pinel, single-handed, led the way. Moved by +a common spirit, though acting quite independently, these men +raised a revolt against the traditional custom which, spurning +the insane as demon-haunted outcasts, had condemned these +unfortunates to dungeons, chains, and the lash. Hitherto few +people had thought it other than the natural course of events +that the "maniac" should be thrust into a dungeon, and perhaps +chained to the wall with the aid of an iron band riveted +permanently about his neck or waist. Many an unfortunate, thus +manacled, was held to the narrow limits of his chain for years +together in a cell to which full daylight never penetrated; +sometimes--iron being expensive--the chain was so short that the +wretched victim could not rise to the upright posture or even +shift his position upon his squalid pallet of straw. + +In America, indeed, there being no Middle Age precedents to +crystallize into established customs, the treatment accorded the +insane had seldom or never sunk to this level. Partly for this +reason, perhaps, the work of Dr. Rush at the Philadelphia +Hospital, in 1784, by means of which the insane came to be +humanely treated, even to the extent of banishing the lash, has +been but little noted, while the work of the European leaders, +though belonging to later decades, has been made famous. And +perhaps this is not as unjust as it seems, for the step which +Rush took, from relatively bad to good, was a far easier one to +take than the leap from atrocities to good treatment which the +European reformers were obliged to compass. In Paris, for +example, Pinel was obliged to ask permission of the authorities +even to make the attempt at liberating the insane from their +chains, and, notwithstanding his recognized position as a leader +of science, he gained but grudging assent, and was regarded as +being himself little better than a lunatic for making so +manifestly unwise and hopeless an attempt. Once the attempt had +been made, however, and carried to a successful issue, the +amelioration wrought in the condition of the insane was so patent +that the fame of Pinel's work at the Bicetre and the Salpetriere +went abroad apace. It required, indeed, many years to complete it +in Paris, and a lifetime of effort on the part of Pinel's pupil +Esquirol and others to extend the reform to the provinces; but +the epochal turning-point had been reached with Pinel's labors of +the closing years of the eighteenth century. + +The significance of this wise and humane reform, in the present +connection, is the fact that these studies of the insane gave +emphasis to the novel idea, which by-and-by became accepted as +beyond question, that "demoniacal possession" is in reality no +more than the outward expression of a diseased condition of the +brain. This realization made it clear, as never before, how +intimately the mind and the body are linked one to the other. +And so it chanced that, in striking the shackles from the insane, +Pinel and his confreres struck a blow also, unwittingly, at +time-honored philosophical traditions. The liberation of the +insane from their dungeons was an augury of the liberation of +psychology from the musty recesses of metaphysics. Hitherto +psychology, in so far as it existed at all, was but the +subjective study of individual minds; in future it must become +objective as well, taking into account also the relations which +the mind bears to the body, and in particular to the brain and +nervous system. + +The necessity for this collocation was advocated quite as +earnestly, and even more directly, by another worker of this +period, whose studies were allied to those of alienists, and who, +even more actively than they, focalized his attention upon the +brain and its functions. This earliest of specialists in brain +studies was a German by birth but Parisian by adoption, Dr. Franz +Joseph Gall, originator of the since-notorious system of +phrenology. The merited disrepute into which this system has +fallen through the exposition of peripatetic charlatans should +not make us forget that Dr. Gall himself was apparently a highly +educated physician, a careful student of the brain and mind +according to the best light of his time, and, withal, an earnest +and honest believer in the validity of the system he had +originated. The system itself, taken as a whole, was hopelessly +faulty, yet it was not without its latent germ of truth, as later +studies were to show. How firmly its author himself believed in +it is evidenced by the paper which he contributed to the French +Academy of Sciences in 1808. The paper itself was referred to a +committee of which Pinel and Cuvier were members. The verdict of +this committee was adverse, and justly so; yet the system +condemned had at least one merit which its detractors failed to +realize. It popularized the conception that the brain is the +organ of mind. Moreover, by its insistence it rallied about it a +band of scientific supporters, chief of whom was Dr. Kaspar +Spurzlieim, a man of no mean abilities, who became the +propagandist of phrenology in England and in America. Of course +such advocacy and popularity stimulated opposition as well, and +out of the disputations thus arising there grew presently a +general interest in the brain as the organ of mind, quite aside +from any preconceptions whatever as to the doctrines of Gall and +Spurzheim. + +Prominent among the unprejudiced class of workers who now +appeared was the brilliant young Frenchman Louis Antoine +Desmoulins, who studied first under the tutorage of the famous +Magendie, and published jointly with him a classical work on the +nervous system of vertebrates in 1825. Desmoulins made at least +one discovery of epochal importance. He observed that the brains +of persons dying in old age were lighter than the average and +gave visible evidence of atrophy, and he reasoned that such decay +is a normal accompaniment of senility. No one nowadays would +question the accuracy of this observation, but the scientific +world was not quite ready for it in 1825; for when Desmoulins +announced his discovery to the French Academy, that august and +somewhat patriarchal body was moved to quite unscientific wrath, +and forbade the young iconoclast the privilege of further +hearings. From which it is evident that the partially liberated +spirit of the new psychology had by no means freed itself +altogether, at the close of the first quarter of the nineteenth +century, from the metaphysical cobwebs of its long incarceration. + + +FUNCTIONS OF THE NERVES + +While studies of the brain were thus being inaugurated, the +nervous system, which is the channel of communication between the +brain and the outside world, was being interrogated with even +more tangible results. The inaugural discovery was made in 1811 +by Dr. (afterwards Sir Charles) Bell,[1] the famous English +surgeon and experimental physiologist. It consisted of the +observation that the anterior roots of the spinal nerves are +given over to the function of conveying motor impulses from the +brain outward, whereas the posterior roots convey solely sensory +impulses to the brain from without. Hitherto it had been supposed +that all nerves have a similar function, and the peculiar +distribution of the spinal nerves had been an unsolved puzzle. + +Bell's discovery was epochal; but its full significance was not +appreciated for a decade, nor, indeed, was its validity at first +admitted. In Paris, in particular, then the court of final +appeal in all matters scientific, the alleged discovery was +looked at askance, or quite ignored. But in 1823 the subject was +taken up by the recognized leader of French physiology--Francois +Magendie--in the course of his comprehensive experimental studies +of the nervous system, and Bell's conclusions were subjected to +the most rigid experimental tests and found altogether valid. +Bell himself, meanwhile, had turned his attention to the cranial +nerves, and had proved that these also are divisible into two +sets--sensory and motor. Sometimes, indeed, the two sets of +filaments are combined into one nerve cord, but if traced to +their origin these are found to arise from different brain +centres. Thus it was clear that a hitherto unrecognized duality +of function pertains to the entire extra-cranial nervous system. +Any impulse sent from the periphery to the brain must be conveyed +along a perfectly definite channel; the response from the brain, +sent out to the peripheral muscles, must traverse an equally +definite and altogether different course. If either channel is +interrupted--as by the section of its particular nerve tract--the +corresponding message is denied transmission as effectually as an +electric current is stopped by the section of the transmitting +wire. + +Experimenters everywhere soon confirmed the observations of Bell +and Magendie, and, as always happens after a great discovery, a +fresh impulse was given to investigations in allied fields. +Nevertheless, a full decade elapsed before another discovery of +comparable importance was made. Then Marshall Hall, the most +famous of English physicians of his day, made his classical +observations on the phenomena that henceforth were to be known as +reflex action. In 1832, while experimenting one day with a +decapitated newt, he observed that the headless creature's limbs +would contract in direct response to certain stimuli. Such a +response could no longer be secured if the spinal nerves +supplying a part were severed. Hence it was clear that responsive +centres exist in the spinal cord capable of receiving a sensory +message and of transmitting a motor impulse in reply--a function +hitherto supposed to be reserved for the brain. Further studies +went to show that such phenomena of reflex action on the part of +centres lying outside the range of consciousness, both in the +spinal cord and in the brain itself, are extremely common; that, +in short, they enter constantly into the activities of every +living organism and have a most important share in the sum total +of vital movements. Hence, Hall's discovery must always stand as +one of the great mile-stones of the advance of neurological +science. + +Hall gave an admirably clear and interesting account of his +experiments and conclusions in a paper before the Royal Society, +"On the Reflex Functions of the Medulla Oblongata and the Medulla +Spinalis," from which, as published in the Transactions of the +society for 1833, we may quote at some length: + +"In the entire animal, sensation and voluntary motion, functions +of the cerebrum, combine with the functions of the medulla +oblongata and medulla spinalis, and may therefore render it +difficult or impossible to determine those which are peculiar to +each; if, in an animal deprived of the brain, the spinal marrow +or the nerves supplying the muscles be stimulated, those muscles, +whether voluntary or respiratory, are equally thrown into +contraction, and, it may be added, equally in the complete and in +the mutilated animal; and, in the case of the nerves, equally in +limbs connected with and detached from the spinal marrow. + +"The operation of all these various causes may be designated +centric, as taking place AT, or at least in a direction FROM, +central parts of the nervous system. But there is another +function the phenomena of which are of a totally different order +and obey totally different laws, being excited by causes in a +situation which is EXCENTRIC in the nervous system--that is, +distant from the nervous centres. This mode of action has not, I +think, been hitherto distinctly understood by physiologists. + +"Many of the phenomena of this principle of action, as they occur +in the limbs, have certainly been observed. But, in the first +place, this function is by no means confined to the limbs; for, +while it imparts to each muscle its appropriate tone, and to each +system of muscles its appropriate equilibrium or balance, it +performs the still more important office of presiding over the +orifices and terminations of each of the internal canals in the +animal economy, giving them their due form and action; and, in +the second place, in the instances in which the phenomena of this +function have been noticed, they have been confounded, as I have +stated, with those of sensation and volition; or, if they have +been distinguished from these, they have been too indefinitely +denominated instinctive, or automatic. I have been compelled, +therefore, to adopt some new designation for them, and I shall +now give the reasons for my choice of that which is given in the +title of this paper--'Reflex Functions.' + +"This property is characterized by being EXCITED in its action +and REFLEX in its course: in every instance in which it is +exerted an impression made upon the extremities of certain nerves +is conveyed to the medulla oblongata or the medulla spinalis, and +is reflected along the nerves to parts adjacent to, or remote +from, that which has received the impression. + +"It is by this reflex character that the function to which I have +alluded is to be distinguished from every other. There are, in +the animal economy, four modes of muscular action, of muscular +contraction. The first is that designated VOLUNTARY: volition, +originated in the cerebrum and spontaneous in its acts, extends +its influence along the spinal marrow and the motor nerves in a +DIRECT LINE to the voluntary muscles. The SECOND is that of +RESPIRATION: like volition, the motive influence in respiration +passes in a DIRECT LINE from one point of the nervous system to +certain muscles; but as voluntary motion seems to originate in +the cerebrum, so the respiratory motions originate in the medulla +oblongata: like the voluntary motions, the motions of +respirations are spontaneous; they continue, at least, after the +eighth pair of nerves have been divided. The THIRD kind of +muscular action in the animal economy is that termed involuntary: +it depends upon the principle of irritability and requires the +IMMEDIATE application of a stimulus to the nervo-muscular fibre +itself. These three kinds of muscular motion are well known to +physiologists; and I believe they are all which have been +hitherto pointed out. There is, however, a FOURTH, which +subsists, in part, after the voluntary and respiratory motions +have ceased, by the removal of the cerebrum and medulla +oblongata, and which is attached to the medulla spinalis, ceasing +itself when this is removed, and leaving the irritability +undiminished. In this kind of muscular motion the motive +influence does not originate in any central part of the nervous +system, but from a distance from that centre; it is neither +spontaneous in its action nor direct in its course; it is, on the +contrary, EXCITED by the application of appropriate stimuli, +which are not, however, applied immediately to the muscular or +nervo-muscular fibre, but to certain membraneous parts, whence +the impression is carried through the medulla, REFLECTED and +reconducted to the part impressed, or conducted to a part remote +from it in which muscular contraction is effected. + +"The first three modes of muscular action are known only by +actual movements of muscular contractions. But the reflex +function exists as a continuous muscular action, as a power +presiding over organs not actually in a state of motion, +preserving in some, as the glottis, an open, in others, as the +sphincters, a closed form, and in the limbs a due degree of +equilibrium or balanced muscular action--a function not, I think, +hitherto recognized by physiologists. + +The three kinds of muscular motion hitherto known may be +distinguished in another way. The muscles of voluntary motion +and of respiration may be excited by stimulating the nerves which +supply them, in any part of their course, whether at their source +as a part of the medulla oblongata or the medulla spinalis or +exterior to the spinal canal: the muscles of involuntary motion +are chiefly excited by the actual contact of stimuli. In the +case of the reflex function alone the muscles are excited by a +stimulus acting mediately and indirectly in a curved and reflex +course, along superficial subcutaneous or submucous nerves +proceeding from the medulla. The first three of these causes of +muscular motion may act on detached limbs or muscles. The last +requires the connection with the medulla to be preserved entire. + +"All the kinds of muscular motion may be unduly excited, but the +reflex function is peculiar in being excitable in two modes of +action, not previously subsisting in the animal economy, as in +the case of sneezing, coughing, vomiting, etc. The reflex +function also admits of being permanently diminished or augmented +and of taking on some other morbid forms, of which I shall treat +hereafter. + +"Before I proceed to the details of the experiments upon which +this disposition rests, it may be well to point out several +instances in illustration of the various sources of and the modes +of muscular action which have been enumerated. None can be more +familiar than the act of swallowing. Yet how complicated is the +act! The apprehension of the food by the teeth and tongue, etc., +is voluntary, and cannot, therefore, take place in an animal from +which the cerebrum is removed. The transition of food over the +glottis and along the middle and lower part of the pharynx +depends upon the reflex action: it can take place in animals from +which the cerebrum has been removed or the ninth pair of nerves +divided; but it requires the connection with the medulla +oblongata to be preserved entirely; and the actual contact of +some substance which may act as a stimulus: it is attended by +the accurate closure of the glottis and by the contraction of the +pharynx. The completion of the act of deglutition is dependent +upon the stimulus immediately impressed upon the muscular fibre +of the oesophagus, and is the result of excited irritability. + +"However plain these observations may have made the fact that +there is a function of the nervous muscular system distinct from +sensation, from the voluntary and respiratory motions, and from +irritability, it is right, in every such inquiry as the present, +that the statements and reasonings should be made with the +experiment, as it were, actually before us. It has already been +remarked that the voluntary and respiratory motions are +spontaneous, not necessarily requiring the agency of a stimulus. +If, then, an animal can be placed in such circumstances that such +motions will certainly not take place, the power of moving +remaining, it may be concluded that volition and the motive +influence of respiration are annihilated. Now this is effected by +removing the cerebrum and the medulla oblongata. These facts are +fully proved by the experiments of Legallois and M. Flourens, and +by several which I proceed to detail, for the sake of the +opportunity afforded by doing so of stating the arguments most +clearly. + +"I divided the spinal marrow of a very lively snake between the +second and third vertebrae. The movements of the animal were +immediately before extremely vigorous and unintermitted. From the +moment of the division of the spinal marrow it lay perfectly +tranquil and motionless, with the exception of occasional +gaspings and slight movements of the head. It became quite +evident that this state of quiescence would continue indefinitely +were the animal secured from all external impressions. + +"Being now stimulated, the body began to move with great +activity, and continued to do so for a considerable time, each +change of position or situation bringing some fresh part of the +surface of the animal into contact with the table or other +objects and renewing the application of stimulants. + +"At length the animal became again quiescent; and being carefully +protected from all external impressions it moved no more, but +died in the precise position and form which it had last assumed. + +"It requires a little manoeuvre to perform this experiment +successfully: the motions of the animal must be watched and +slowly and cautiously arrested by opposing some soft substance, +as a glove or cotton wool; they are by this means gradually +lulled into quiescence. The slightest touch with a hard +substance, the slightest stimulus, will, on the other hand, renew +the movements on the animal in an active form. But that this +phenomenon does not depend upon sensation is further fully proved +by the facts that the position last assumed, and the stimuli, may +be such as would be attended by extreme or continued pain, if the +sensibility were undestroyed: in one case the animal remained +partially suspended over the acute edge of the table; in others +the infliction of punctures and the application of a lighted +taper did not prevent the animal, still possessed of active +powers of motion, from passing into a state of complete and +permanent quiescence." + + +In summing up this long paper Hall concludes with this sentence: +"The reflex function appears in a word to be the COMPLEMENT of +the functions of the nervous system hitherto known."[2] + +All these considerations as to nerve currents and nerve tracts +becoming stock knowledge of science, it was natural that interest +should become stimulated as to the exact character of these nerve +tracts in themselves, and all the more natural in that the +perfected microscope was just now claiming all fields for its +own. A troop of observers soon entered upon the study of the +nerves, and the leader here, as in so many other lines of +microscopical research, was no other than Theodor Schwann. +Through his efforts, and with the invaluable aid of such other +workers as Remak, Purkinje, Henle, Muller, and the rest, all the +mystery as to the general characteristics of nerve tracts was +cleared away. It came to be known that in its essentials a nerve +tract is a tenuous fibre or thread of protoplasm stretching +between two terminal points in the organism, one of such termini +being usually a cell of the brain or spinal cord, the other a +distribution-point at or near the periphery--for example, in a +muscle or in the skin. Such a fibril may have about it a +protective covering, which is known as the sheath of Schwann; but +the fibril itself is the essential nerve tract; and in many +cases, as Remak presently discovered, the sheath is dispensed +with, particularly in case of the nerves of the so-called +sympathetic system. + +This sympathetic system of ganglia and nerves, by-the-bye, had +long been a puzzle to the physiologists. Its ganglia, the +seeming centre of the system, usually minute in size and never +very large, are found everywhere through the organism, but in +particular are gathered into a long double chain which lies +within the body cavity, outside the spinal column, and represents +the sole nervous system of the non-vertebrated organisms. Fibrils +from these ganglia were seen to join the cranial and spinal nerve +fibrils and to accompany them everywhere, but what special +function they subserved was long a mere matter of conjecture and +led to many absurd speculations. Fact was not substituted for +conjecture until about the year 1851, when the great Frenchman +Claude Bernard conclusively proved that at least one chief +function of the sympathetic fibrils is to cause contraction of +the walls of the arterioles of the system, thus regulating the +blood-supply of any given part. Ten years earlier Henle had +demonstrated the existence of annular bands of muscle fibres in +the arterioles, hitherto a much-mooted question, and several +tentative explanations of the action of these fibres had been +made, particularly by the brothers Weber, by Stilling, who, as +early as 1840, had ventured to speak of "vaso-motor" nerves, and +by Schiff, who was hard upon the same track at the time of +Bernard's discovery. But a clear light was not thrown on the +subject until Bernard's experiments were made in 1851. The +experiments were soon after confirmed and extended by +Brown-Sequard, Waller, Budge, and numerous others, and henceforth +physiologists felt that they understood how the blood-supply of +any given part is regulated by the nervous system. + +In reality, however, they had learned only half the story, as +Bernard himself proved only a few years later by opening up a new +and quite unsuspected chapter. While experimenting in 1858 he +discovered that there are certain nerves supplying the heart +which, if stimulated, cause that organ to relax and cease +beating. As the heart is essentially nothing more than an +aggregation of muscles, this phenomenon was utterly puzzling and +without precedent in the experience of physiologists. An impulse +travelling along a motor nerve had been supposed to be able to +cause a muscular contraction and to do nothing else; yet here +such an impulse had exactly the opposite effect. The only tenable +explanation seemed to be that this particular impulse must arrest +or inhibit the action of the impulses that ordinarily cause the +heart muscles to contract. But the idea of such inhibition of one +impulse by another was utterly novel and at first difficult to +comprehend. Gradually, however, the idea took its place in the +current knowledge of nerve physiology, and in time it came to be +understood that what happens in the case of the heart +nerve-supply is only a particular case under a very general, +indeed universal, form of nervous action. Growing out of +Bernard's initial discovery came the final understanding that the +entire nervous system is a mechanism of centres subordinate and +centres superior, the action of the one of which may be +counteracted and annulled in effect by the action of the other. +This applies not merely to such physical processes as heart-beats +and arterial contraction and relaxing, but to the most intricate +functionings which have their counterpart in psychical processes +as well. Thus the observation of the inhibition of the heart's +action by a nervous impulse furnished the point of departure for +studies that led to a better understanding of the modus operandi +of the mind's activities than had ever previously been attained +by the most subtle of psychologists. + + +PSYCHO-PHYSICS + +The work of the nerve physiologists had thus an important bearing +on questions of the mind. But there was another company of +workers of this period who made an even more direct assault upon +the "citadel of thought." A remarkable school of workers had been +developed in Germany, the leaders being men who, having more or +less of innate metaphysical bias as a national birthright, had +also the instincts of the empirical scientist, and whose +educational equipment included a profound knowledge not alone of +physiology and psychology, but of physics and mathematics as +well. These men undertook the novel task of interrogating the +relations of body and mind from the standpoint of physics. They +sought to apply the vernier and the balance, as far as might be, +to the intangible processes of mind. + +The movement had its precursory stages in the early part of the +century, notably in the mathematical psychology of Herbart, but +its first definite output to attract general attention came from +the master-hand of Hermann Helmholtz in 1851. It consisted of the +accurate measurement of the speed of transit of a nervous impulse +along a nerve tract. To make such measurement had been regarded +as impossible, it being supposed that the flight of the nervous +impulse was practically instantaneous. But Helmholtz readily +demonstrated the contrary, showing that the nerve cord is a +relatively sluggish message-bearer. According to his experiments, +first performed upon the frog, the nervous "current" travels less +than one hundred feet per second. Other experiments performed +soon afterwards by Helmholtz himself, and by various followers, +chief among whom was Du Bois-Reymond, modified somewhat the exact +figures at first obtained, but did not change the general +bearings of the early results. Thus the nervous impulse was shown +to be something far different, as regards speed of transit, at +any rate, from the electric current to which it had been so often +likened. An electric current would flash halfway round the globe +while a nervous impulse could travel the length of the human +body--from a man's foot to his brain. + +The tendency to bridge the gulf that hitherto had separated the +physical from the psychical world was further evidenced in the +following decade by Helmholtz's remarkable but highly technical +study of the sensations of sound and of color in connection with +their physical causes, in the course of which he revived the +doctrine of color vision which that other great physiologist and +physicist, Thomas Young, had advanced half a century before. The +same tendency was further evidenced by the appearance, in 1852, +of Dr. Hermann Lotze's famous Medizinische Psychologie, oder +Physiologie der Seele, with its challenge of the old myth of a +"vital force." But the most definite expression of the new +movement was signalized in 1860, when Gustav Fechner published +his classical work called Psychophysik. That title introduced a +new word into the vocabulary of science. Fechner explained it by +saying, "I mean by psychophysics an exact theory of the relation +between spirit and body, and, in a general way, between the +physical and the psychic worlds." The title became famous and the +brunt of many a controversy. So also did another phrase which +Fechner introduced in the course of his book--the phrase +"physiological psychology." In making that happy collocation of +words Fechner virtually christened a new science. + + +FECHNER EXPOUNDS WEBER'S LAW + +The chief purport of this classical book of the German +psycho-physiologist was the elaboration and explication of +experiments based on a method introduced more than twenty years +earlier by his countryman E. H. Weber, but which hitherto had +failed to attract the attention it deserved. The method consisted +of the measurement and analysis of the definite relation existing +between external stimuli of varying degrees of intensity (various +sounds, for example) and the mental states they induce. Weber's +experiments grew out of the familiar observation that the nicety +of our discriminations of various sounds, weights, or visual +images depends upon the magnitude of each particular cause of a +sensation in its relation with other similar causes. Thus, for +example, we cannot see the stars in the daytime, though they +shine as brightly then as at night. Again, we seldom notice the +ticking of a clock in the daytime, though it may become almost +painfully audible in the silence of the night. Yet again, the +difference between an ounce weight and a two-ounce weight is +clearly enough appreciable when we lift the two, but one cannot +discriminate in the same way between a five-pound weight and a +weight of one ounce over five pounds. + +This last example, and similar ones for the other senses, gave +Weber the clew to his novel experiments. Reflection upon +every-day experiences made it clear to him that whenever we +consider two visual sensations, or two auditory sensations, or +two sensations of weight, in comparison one with another, there +is always a limit to the keenness of our discrimination, and that +this degree of keenness varies, as in the case of the weights +just cited, with the magnitude of the exciting cause. + +Weber determined to see whether these common experiences could be +brought within the pale of a general law. His method consisted of +making long series of experiments aimed at the determination, in +each case, of what came to be spoken of as the least observable +difference between the stimuli. Thus if one holds an ounce weight +in each hand, and has tiny weights added to one of them, grain by +grain, one does not at first perceive a difference; but +presently, on the addition of a certain grain, he does become +aware of the difference. Noting now how many grains have been +added to produce this effect, we have the weight which represents +the least appreciable difference when the standard is one ounce. + +Now repeat the experiment, but let the weights be each of five +pounds. Clearly in this case we shall be obliged to add not +grains, but drachms, before a difference between the two heavy +weights is perceived. But whatever the exact amount added, that +amount represents the stimulus producing a just-perceivable +sensation of difference when the standard is five pounds. And so +on for indefinite series of weights of varying magnitudes. Now +came Weber's curious discovery. Not only did he find that in +repeated experiments with the same pair of weights the measure of +"just-{p}erceivable difference" remained approximately fixed, but +he found, further, that a remarkable fixed relation exists +between the stimuli of different magnitude. If, for example, he +had found it necessary, in the case of the ounce weights, to add +one-fiftieth of an ounce to the one before a difference was +detected, he found also, in the case of the five-pound weights, +that one-fiftieth of five pounds must be added before producing +the same result. And so of all other weights; the amount added +to produce the stimulus of "least-appreciable difference" always +bore the same mathematical relation to the magnitude of the +weight used, be that magnitude great or small. + +Weber found that the same thing holds good for the stimuli of the +sensations of sight and of hearing, the differential stimulus +bearing always a fixed ratio to the total magnitude of the +stimuli. Here, then, was the law he had sought. + +Weber's results were definite enough and striking enough, yet +they failed to attract any considerable measure of attention +until they were revived and extended by Fechner and brought +before the world in the famous work on psycho-physics. Then they +precipitated a veritable melee. Fechner had not alone verified +the earlier results (with certain limitations not essential to +the present consideration), but had invented new methods of +making similar tests, and had reduced the whole question to +mathematical treatment. He pronounced Weber's discovery the +fundamental law of psycho-physics. In honor of the discoverer, he +christened it Weber's Law. He clothed the law in words and in +mathematical formulae, and, so to say, launched it full tilt at +the heads of the psychological world. It made a fine commotion, +be assured, for it was the first widely heralded bulletin of the +new psychology in its march upon the strongholds of the +time-honored metaphysics. The accomplishments of the +microscopists and the nerve physiologists had been but +preliminary--mere border skirmishes of uncertain import. But here +was proof that the iconoclastic movement meant to invade the very +heart of the sacred territory of mind--a territory from which +tangible objective fact had been supposed to be forever barred. + + +PHYSIOLOGICAL PSYCHOLOGY + +Hardly had the alarm been sounded, however, before a new movement +was made. While Fechner's book was fresh from the press, steps +were being taken to extend the methods of the physicist in yet +another way to the intimate processes of the mind. As Helmholtz +had shown the rate of nervous impulsion along the nerve tract to +be measurable, it was now sought to measure also the time +required for the central nervous mechanism to perform its work of +receiving a message and sending out a response. This was coming +down to the very threshold of mind. The attempt was first made by +Professor Donders in 1861, but definitive results were only +obtained after many years of experiment on the part of a host of +observers. The chief of these, and the man who has stood in the +forefront of the new movement and has been its recognized leader +throughout the remainder of the century, is Dr. Wilhelm Wundt, of +Leipzig. + +The task was not easy, but, in the long run, it was accomplished. +Not alone was it shown that the nerve centre requires a +measurable time for its operations, but much was learned as to +conditions that modify this time. Thus it was found that +different persons vary in the rate of their central nervous +activity--which explained the "personal equation" that the +astronomer Bessel had noted a half-century before. It was found, +too, that the rate of activity varies also for the same person +under different conditions, becoming retarded, for example, under +influence of fatigue, or in case of certain diseases of the +brain. All details aside, the essential fact emerges, as an +experimental demonstration, that the intellectual +processes--sensation, apperception, volition--are linked +irrevocably with the activities of the central nervous tissues, +and that these activities, like all other physical processes, +have a time element. To that old school of psychologists, who +scarcely cared more for the human head than for the heels--being +interested only in the mind--such a linking of mind and body as +was thus demonstrated was naturally disquieting. But whatever the +inferences, there was no escaping the facts. + +Of course this new movement has not been confined to Germany. +Indeed, it had long had exponents elsewhere. Thus in England, a +full century earlier, Dr. Hartley had championed the theory of +the close and indissoluble dependence of the mind upon the brain, +and formulated a famous vibration theory of association that +still merits careful consideration. Then, too, in France, at the +beginning of the century, there was Dr. Cabanis with his +tangible, if crudely phrased, doctrine that the brain digests +impressions and secretes thought as the stomach digests food and +the liver secretes bile. Moreover, Herbert Spencer's Principles +of Psychology, with its avowed co-ordination of mind and body and +its vitalizing theory of evolution, appeared in 1855, half a +decade before the work of Fechner. But these influences, though +of vast educational value, were theoretical rather than +demonstrative, and the fact remains that the experimental work +which first attempted to gauge mental operations by physical +principles was mainly done in Germany. Wundt's Physiological +Psychology, with its full preliminary descriptions of the anatomy +of the nervous system, gave tangible expression to the growth of +the new movement in 1874; and four years later, with the opening +of his laboratory of physiological psychology at the University +of Leipzig, the new psychology may be said to have gained a +permanent foothold and to have forced itself into official +recognition. From then on its conquest of the world was but a +matter of time. + +It should be noted, however, that there is one other method of +strictly experimental examination of the mental field, latterly +much in vogue, which had a different origin. This is the +scientific investigation of the phenomena of hypnotism. This +subject was rescued from the hands of charlatans, rechristened, +and subjected to accurate investigation by Dr. James Braid, of +Manchester, as early as 1841. But his results, after attracting +momentary attention, fell from view, and, despite desultory +efforts, the subject was not again accorded a general hearing +from the scientific world until 1878, when Dr. Charcot took it up +at the Salpetriere, in Paris, followed soon afterwards by Dr. +Rudolf Heidenhain, of Breslau, and a host of other experimenters. +The value of the method in the study of mental states was soon +apparent. Most of Braid's experiments were repeated, and in the +main his results were confirmed. His explanation of hypnotism, +or artificial somnambulism, as a self-induced state, independent +of any occult or supersensible influence, soon gained general +credence. His belief that the initial stages are due to fatigue +of nervous centres, usually from excessive stimulation, has not +been supplanted, though supplemented by notions growing out of +the new knowledge as to subconscious mentality in general, and +the inhibitory influence of one centre over another in the +central nervous mechanism. + + +THE BRAIN AS THE ORGAN OF MIND + +These studies of the psychologists and pathologists bring the +relations of mind and body into sharp relief. But even more +definite in this regard was the work of the brain physiologists. +Chief of these, during the middle period of the century, was the +man who is sometimes spoken of as the "father of brain +physiology," Marie Jean Pierre Flourens, of the Jardin des +Plantes of Paris, the pupil and worthy successor of Magendie. +His experiments in nerve physiology were begun in the first +quarter of the century, but his local experiments upon the brain +itself were not culminated until about 1842. At this time the old +dispute over phrenology had broken out afresh, and the studies of +Flourens were aimed, in part at least, at the strictly scientific +investigation of this troublesome topic. + +In the course of these studies Flourens discovered that in the +medulla oblongata, the part of the brain which connects that +organ with the spinal cord, there is a centre of minute size +which cannot be injured in the least without causing the instant +death of the animal operated upon. It may be added that it is +this spot which is reached by the needle of the garroter in +Spanish executions, and that the same centre also is destroyed +when a criminal is "successfully" hanged, this time by the forced +intrusion of a process of the second cervical vertebra. Flourens +named this spot the "vital knot." Its extreme importance, as is +now understood, is due to the fact that it is the centre of +nerves that supply the heart; but this simple explanation, +annulling the conception of a specific "life centre," was not at +once apparent. + +Other experiments of Flourens seemed to show that the cerebellum +is the seat of the centres that co-ordinate muscular activities, +and that the higher intellectual faculties are relegated to the +cerebrum. But beyond this, as regards localization, experiment +faltered. Negative results, as regards specific faculties, were +obtained from all localized irritations of the cerebrum, and +Flourens was forced to conclude that the cerebral lobe, while +being undoubtedly the seat of higher intellection, performs its +functions with its entire structure. This conclusion, which +incidentally gave a quietus to phrenology, was accepted +generally, and became the stock doctrine of cerebral physiology +for a generation. + +It will be seen, however, that these studies of Flourens had a +double bearing. They denied localization of cerebral functions, +but they demonstrated the localization of certain nervous +processes in other portions of the brain. On the whole, then, +they spoke positively for the principle of localization of +function in the brain, for which a certain number of students +contended; while their evidence against cerebral localization was +only negative. There was here and there an observer who felt that +this negative testimony was not conclusive. In particular, the +German anatomist Meynert, who had studied the disposition of +nerve tracts in the cerebrum, was led to believe that the +anterior portions of the cerebrum must have motor functions in +preponderance; the posterior positions, sensory functions. +Somewhat similar conclusions were reached also by Dr. +Hughlings-Jackson, in England, from his studies of epilepsy. But +no positive evidence was forthcoming until 1861, when Dr. Paul +Broca brought before the Academy of Medicine in Paris a case of +brain lesion which he regarded as having most important bearings +on the question of cerebral localization. + +The case was that of a patient at the Bicetre, who for twenty +years had been deprived of the power of speech, seemingly through +loss of memory of words. In 1861 this patient died, and an +autopsy revealed that a certain convolution of the left frontal +lobe of his cerebrum had been totally destroyed by disease, the +remainder of his brain being intact. Broca felt that this +observation pointed strongly to a localization of the memory of +words in a definite area of the brain. Moreover, it transpired +that the case was not without precedent. As long ago as 1825 Dr. +Boillard had been led, through pathological studies, to locate +definitely a centre for the articulation of words in the frontal +lobe, and here and there other observers had made tentatives in +the same direction. Boillard had even followed the matter up with +pertinacity, but the world was not ready to listen to him. Now, +however, in the half-decade that followed Broca's announcements, +interest rose to fever-beat, and through the efforts of Broca, +Boillard, and numerous others it was proved that a veritable +centre having a strange domination over the memory of articulate +words has its seat in the third convolution of the frontal lobe +of the cerebrum, usually in the left hemisphere. That part of the +brain has since been known to the English-speaking world as the +convolution of Broca, a name which, strangely enough, the +discoverer's compatriots have been slow to accept. + +This discovery very naturally reopened the entire subject of +brain localization. It was but a short step to the inference +that there must be other definite centres worth the seeking, and +various observers set about searching for them. In 1867 a clew +was gained by Eckhard, who, repeating a forgotten experiment by +Haller and Zinn of the previous century, removed portions of the +brain cortex of animals, with the result of producing +convulsions. But the really vital departure was made in 1870 by +the German investigators Fritsch and Hitzig, who, by stimulating +definite areas of the cortex of animals with a galvanic current, +produced contraction of definite sets of muscles of the opposite +side of the body. These most important experiments, received at +first with incredulity, were repeated and extended in 1873 by Dr. +David Ferrier, of London, and soon afterwards by a small army of +independent workers everywhere, prominent among whom were Franck +and Pitres in France, Munck and Goltz in Germany, and Horsley and +Schafer in England. The detailed results, naturally enough, were +not at first all in harmony. Some observers, as Goltz, even +denied the validity of the conclusions in toto. But a consensus +of opinion, based on multitudes of experiments, soon placed the +broad general facts for which Fritsch and Hitzig contended beyond +controversy. It was found, indeed, that the cerebral centres of +motor activities have not quite the finality at first ascribed to +them by some observers, since it may often happen that after the +destruction of a centre, with attending loss of function, there +may be a gradual restoration of the lost function, proving that +other centres have acquired the capacity to take the place of the +one destroyed. There are limits to this capacity for +substitution, however, and with this qualification the +definiteness of the localization of motor functions in the +cerebral cortex has become an accepted part of brain physiology. + +Nor is such localization confined to motor centres. Later +experiments, particularly of Ferrier and of Munck, proved that +the centres of vision are equally restricted in their location, +this time in the posterior lobes of the brain, and that hearing +has likewise its local habitation. Indeed, there is every reason +to believe that each form of primary sensation is based on +impressions which mainly come to a definitely localized goal in +the brain. But all this, be it understood, has no reference to +the higher forms of intellection. All experiment has proved +futile to localize these functions, except indeed to the extent +of corroborating the familiar fact of their dependence upon the +brain, and, somewhat problematically, upon the anterior lobes of +the cerebrum in particular. But this is precisely what should be +expected, for the clearer insight into the nature of mental +processes makes it plain that in the main these alleged +"faculties" are not in themselves localized. Thus, for example, +the "faculty" of language is associated irrevocably with centres +of vision, of hearing, and of muscular activity, to go no +further, and only becomes possible through the association of +these widely separated centres. The destruction of Broca's +centre, as was early discovered, does not altogether deprive a +patient of his knowledge of language. He may be totally unable to +speak (though as to this there are all degrees of variation), and +yet may comprehend what is said to him, and be able to read, +think, and even write correctly. Thus it appears that Broca's +centre is peculiarly bound up with the capacity for articulate +speech, but is far enough from being the seat of the faculty of +language in its entirety. + +In a similar way, most of the supposed isolated "faculties" of +higher intellection appear, upon clearer analysis, as complex +aggregations of primary sensations, and hence necessarily +dependent upon numerous and scattered centres. Some "faculties," +as memory and volition, may be said in a sense to be primordial +endowments of every nerve cell--even of every body cell. Indeed, +an ultimate analysis relegates all intellection, in its +primordial adumbrations, to every particle of living matter. But +such refinements of analysis, after all, cannot hide the fact +that certain forms of higher intellection involve a pretty +definite collocation and elaboration of special sensations. Such +specialization, indeed, seems a necessary accompaniment of mental +evolution. That every such specialized function has its +localized centres of co-ordination, of some such significance as +the demonstrated centres of articulate speech, can hardly be in +doubt--though this, be it understood, is an induction, not as yet +a demonstration. In other words, there is every reason to +believe that numerous "centres," in this restricted sense, exist +in the brain that have as yet eluded the investigator. Indeed, +the current conception regards the entire cerebral cortex as +chiefly composed of centres of ultimate co-ordination of +impressions, which in their cruder form are received by more +primitive nervous tissues--the basal ganglia, the cerebellum and +medulla, and the spinal cord. + +This, of course, is equivalent to postulating the cerebral cortex +as the exclusive seat of higher intellection. This proposition, +however, to which a safe induction seems to lead, is far afield +from the substantiation of the old conception of brain +localization, which was based on faulty psychology and equally +faulty inductions from few premises. The details of Gall's +system, as propounded by generations of his mostly unworthy +followers, lie quite beyond the pale of scientific discussion. +Yet, as I have said, a germ of truth was there--the idea of +specialization of cerebral functions--and modern investigators +have rescued that central conception from the phrenological +rubbish heap in which its discoverer unfortunately left it +buried. + + +THE MINUTE STRUCTURE OF THE BRAIN + +The common ground of all these various lines of investigations of +pathologist, anatomist, physiologist, physicist, and psychologist +is, clearly, the central nervous system--the spinal cord and the +brain. The importance of these structures as the foci of nervous +and mental activities has been recognized more and more with each +new accretion of knowledge, and the efforts to fathom the secrets +of their intimate structure has been unceasing. For the earlier +students, only the crude methods of gross dissections and +microscopical inspection were available. These could reveal +something, but of course the inner secrets were for the keener +insight of the microscopist alone. And even for him the task of +investigation was far from facile, for the central nervous +tissues are the most delicate and fragile, and on many accounts +the most difficult of manipulation of any in the body. + +Special methods, therefore, were needed for this essay, and brain +histology has progressed by fitful impulses, each forward jet +marking the introduction of some ingenious improvement of +mechanical technique, which placed a new weapon in the hands of +the investigators. + +The very beginning was made in 1824 by Rolando, who first thought +of cutting chemically hardened pieces of brain tissues into thin +sections for microscopical examination--the basal structure upon +which almost all the later advances have been conducted. Muller +presently discovered that bichromate of potassium in solution +makes the best of fluids for the preliminary preservation and +hardening of the tissues. Stilling, in 1842, perfected the +method by introducing the custom of cutting a series of +consecutive sections of the same tissue, in order to trace nerve +tracts and establish spacial relations. Then from time to time +mechanical ingenuity added fresh details of improvement. It was +found that pieces of hardened tissue of extreme delicacy can be +made better subject to manipulation by being impregnated with +collodion or celloidine and embedded in paraffine. Latterly it +has become usual to cut sections also from fresh tissues, +unchanged by chemicals, by freezing them suddenly with vaporized +ether or, better, carbonic acid. By these methods, and with the +aid of perfected microtomes, the worker of recent periods avails +himself of sections of brain tissues of a tenuousness which the +early investigators could not approach. + +But more important even than the cutting of thin sections is the +process of making the different parts of the section visible, one +tissue differentiated from another. The thin section, as the +early workers examined it, was practically colorless, and even +the crudest details of its structure were made out with extreme +difficulty. Remak did, indeed, manage to discover that the brain +tissue is cellular, as early as 1833, and Ehrenberg in the same +year saw that it is also fibrillar, but beyond this no great +advance was made until 1858, when a sudden impulse was received +from a new process introduced by Gerlach. The process itself was +most simple, consisting essentially of nothing more than the +treatment of a microscopical section with a solution of carmine. +But the result was wonderful, for when such a section was placed +under the lens it no longer appeared homogeneous. Sprinkled +through its substance were seen irregular bodies that had taken +on a beautiful color, while the matrix in which they were +embedded remained unstained. In a word, the central nerve cell +had sprung suddenly into clear view. + +A most interesting body it proved, this nerve cell, or ganglion +cell, as it came to be called. It was seen to be exceedingly +minute in size, requiring high powers of the microscope to make +it visible. It exists in almost infinite numbers, not, however, +scattered at random through the brain and spinal cord. On the +contrary, it is confined to those portions of the central nervous +masses which to the naked eye appear gray in color, being +altogether wanting in the white substance which makes up the +chief mass of the brain. Even in the gray matter, though +sometimes thickly distributed, the ganglion cells are never in +actual contact one with another; they always lie embedded in +intercellular tissues, which came to be known, following Virchow, +as the neuroglia. + +Each ganglion cell was seen to be irregular in contour, and to +have jutting out from it two sets of minute fibres, one set +relatively short, indefinitely numerous, and branching in every +direction; the other set limited in number, sometimes even +single, and starting out directly from the cell as if bent on a +longer journey. The numerous filaments came to be known as +protoplasmic processes; the other fibre was named, after its +discoverer, the axis cylinder of Deiters. It was a natural +inference, though not clearly demonstrable in the sections, that +these filamentous processes are the connecting links between the +different nerve cells and also the channels of communication +between nerve cells and the periphery of the body. The white +substance of brain and cord, apparently, is made up of such +connecting fibres, thus bringing the different ganglion cells +everywhere into communication one with another. + +In the attempt to trace the connecting nerve tracts through this +white substance by either macroscopical or microscopical methods, +most important aid is given by a method originated by Waller in +1852. Earlier than that, in 1839, Nasse had discovered that a +severed nerve cord degenerates in its peripheral portions. Waller +discovered that every nerve fibre, sensory or motor, has a nerve +cell to or from which it leads, which dominates its nutrition, so +that it can only retain its vitality while its connection with +that cell is intact. Such cells he named trophic centres. +Certain cells of the anterior part of the spinal cord, for +example, are the trophic centres of the spinal motor nerves. +Other trophic centres, governing nerve tracts in the spinal cord +itself, are in the various regions of the brain. It occurred to +Waller that by destroying such centres, or by severing the +connection at various regions between a nervous tract and its +trophic centre, sharply defined tracts could be made to +degenerate, and their location could subsequently be accurately +defined, as the degenerated tissues take on a changed aspect, +both to macroscopical and microscopical observation. Recognition +of this principle thus gave the experimenter a new weapon of +great efficiency in tracing nervous connections. Moreover, the +same principle has wide application in case of the human subject +in disease, such as the lesion of nerve tracts or the destruction +of centres by localized tumors, by embolisms, or by traumatisms. + +All these various methods of anatomical examination combine to +make the conclusion almost unavoidable that the central ganglion +cells are the veritable "centres" of nervous activity to which so +many other lines of research have pointed. The conclusion was +strengthened by experiments of the students of motor +localization, which showed that the veritable centres of their +discovery lie, demonstrably, in the gray cortex of the brain, not +in the white matter. But the full proof came from pathology. At +the hands of a multitude of observers it was shown that in +certain well-known diseases of the spinal cord, with resulting +paralysis, it is the ganglion cells themselves that are found to +be destroyed. Similarly, in the case of sufferers from chronic +insanities, with marked dementia, the ganglion cells of the +cortex of the brain are found to have undergone degeneration. The +brains of paretics in particular show such degeneration, in +striking correspondence with their mental decadence. The position +of the ganglion cell as the ultimate centre of nervous activities +was thus placed beyond dispute. + +Meantime, general acceptance being given the histological scheme +of Gerlach, according to which the mass of the white substance of +the brain is a mesh-work of intercellular fibrils, a proximal +idea seemed attainable of the way in which the ganglionic +activities are correlated, and, through association, built up, so +to speak, into the higher mental processes. Such a conception +accorded beautifully with the ideas of the associationists, who +had now become dominant in psychology. But one standing puzzle +attended this otherwise satisfactory correlation of anatomical +observations and psychic analyses. It was this: Since, according +to the histologist, the intercellular fibres, along which +impulses are conveyed, connect each brain cell, directly or +indirectly, with every other brain cell in an endless mesh-work, +how is it possible that various sets of cells may at times be +shut off from one another? Such isolation must take place, for +all normal ideation depends for its integrity quite as much upon +the shutting-out of the great mass of associations as upon the +inclusion of certain other associations. For example, a student +in solving a mathematical problem must for the moment become +quite oblivious to the special associations that have to do with +geography, natural history, and the like. But does histology give +any clew to the way in which such isolation may be effected? + +Attempts were made to find an answer through consideration of the +very peculiar character of the blood-supply in the brain. Here, +as nowhere else, the terminal twigs of the arteries are arranged +in closed systems, not anastomosing freely with neighboring +systems. Clearly, then, a restricted area of the brain may, +through the controlling influence of the vasomotor nerves, be +flushed with arterial blood while neighboring parts remain +relatively anaemic. And since vital activities unquestionably +depend in part upon the supply of arterial blood, this peculiar +arrangement of the vascular mechanism may very properly be +supposed to aid in the localized activities of the central +nervous ganglia. But this explanation left much to be desired--in +particular when it is recalled that all higher intellection must +in all probability involve multitudes of widely scattered +centres. + +No better explanation was forthcoming, however, until the year +1889, when of a sudden the mystery was cleared away by a fresh +discovery. Not long before this the Italian histologist Dr. +Camille Golgi had discovered a method of impregnating hardened +brain tissues with a solution of nitrate of silver, with the +result of staining the nerve cells and their processes almost +infinitely better than was possible by the methods of Gerlach, or +by any of the multiform methods that other workers had +introduced. Now for the first time it became possible to trace +the cellular prolongations definitely to their termini, for the +finer fibrils had not been rendered visible by any previous +method of treatment. Golgi himself proved that the set of fibrils +known as protoplasmic prolongations terminate by free +extremities, and have no direct connection with any cell save the +one from which they spring. He showed also that the axis +cylinders give off multitudes of lateral branches not hitherto +suspected. But here he paused, missing the real import of the +discovery of which he was hard on the track. It remained for the +Spanish histologist Dr. S. Ramon y Cajal to follow up the +investigation by means of an improved application of Golgi's +method of staining, and to demonstrate that the axis cylinders, +together with all their collateral branches, though sometimes +extending to a great distance, yet finally terminate, like the +other cell prolongations, in arborescent fibrils having free +extremities. In a word, it was shown that each central nerve +cell, with its fibrillar offshoots, is an isolated entity. +Instead of being in physical connection with a multitude of other +nerve cells, it has no direct physical connection with any other +nerve cell whatever. + +When Dr. Cajal announced his discovery, in 1889, his +revolutionary claims not unnaturally amazed the mass of +histologists. There were some few of them, however, who were not +quite unprepared for the revelation; in particular His, who had +half suspected the independence of the cells, because they seemed +to develop from dissociated centres; and Forel, who based a +similar suspicion on the fact that he had never been able +actually to trace a fibre from one cell to another. These +observers then came readily to repeat Cajal's experiments. So +also did the veteran histologist Kolliker, and soon afterwards +all the leaders everywhere. The result was a practically +unanimous confirmation of the Spanish histologist's claims, and +within a few months after his announcements the old theory of +union of nerve cells into an endless mesh-work was completely +discarded, and the theory of isolated nerve elements--the theory +of neurons, as it came to be called--was fully established in its +place. + +As to how these isolated nerve cells functionate, Dr. Cajal gave +the clew from the very first, and his explanation has met with +universal approval. + +In the modified view, the nerve cell retains its old position as +the storehouse of nervous energy. Each of the filaments jutting +out from the cell is held, as before, to be indeed a transmitter +of impulses, but a transmitter that operates intermittently, like +a telephone wire that is not always "connected," and, like that +wire, the nerve fibril operates by contact and not by continuity. +Under proper stimulation the ends of the fibrils reach out, come +in contact with other end fibrils of other cells, and conduct +their destined impulse. Again they retract, and communication +ceases for the time between those particular cells. Meantime, by +a different arrangement of the various conductors, different sets +of cells are placed in communication, different associations of +nervous impulses induced, different trains of thought engendered. +Each fibril when retracted becomes a non-conductor, but when +extended and in contact with another fibril, or with the body of +another cell, it conducts its message as readily as a continuous +filament could do--precisely as in the case of an electric wire. + +This conception, founded on a most tangible anatomical basis, +enables us to answer the question as to how ideas are isolated, +and also, as Dr. Cajal points out, throws new light on many other +mental processes. One can imagine, for example, by keeping in +mind the flexible nerve prolongations, how new trains of thought +may be engendered through novel associations of cells; how +facility of thought or of action in certain directions is +acquired through the habitual making of certain nerve-cell +connections; how certain bits of knowledge may escape our memory +and refuse to be found for a time because of a temporary +incapacity of the nerve cells to make the proper connections, and +so on indefinitely. + +If one likens each nerve cell to a central telephone office, each +of its filamentous prolongations to a telephone wire, one can +imagine a striking analogy between the modus operandi of nervous +processes and of the telephone system. The utility of new +connections at the central office, the uselessness of the +mechanism when the connections cannot be made, the "wires in use" +that retard your message, perhaps even the crossing of wires, +bringing you a jangle of sounds far different from what you +desire--all these and a multiplicity of other things that will +suggest themselves to every user of the telephone may be imagined +as being almost ludicrously paralleled in the operations of the +nervous mechanism. And that parallel, startling as it may seem, +is not a mere futile imagining. It is sustained and rendered +plausible by a sound substratum of knowledge of the anatomical +conditions under which the central nervous mechanism exists, and +in default of which, as pathology demonstrates with no less +certitude, its functionings are futile to produce the normal +manifestations of higher intellection. + + + +X. THE NEW SCIENCE OF ORIENTAL ARCHAEOLOGY + +HOW THE "RIDDLE OF THE SPHINX" WAS READ + +Conspicuously placed in the great hall of Egyptian antiquities in +the British Museum is a wonderful piece of sculpture known as the +Rosetta Stone. I doubt if any other piece in the entire exhibit +attracts so much attention from the casual visitor as this slab +of black basalt on its telescope-like pedestal. The hall itself, +despite its profusion of strangely sculptured treasures, is never +crowded, but before this stone you may almost always find some +one standing, gazing with more or less of discernment at the +strange characters that are graven neatly across its upturned, +glass-protected face. A glance at this graven surface suffices to +show that three sets of inscriptions are recorded there. The +upper one, occupying about one-fourth of the surface, is a +pictured scroll, made up of chains of those strange outlines of +serpents, hawks, lions, and so on, which are recognized, even by +the least initiated, as hieroglyphics. The middle inscription, +made up of lines, angles, and half-pictures, one might surmise to +be a sort of abbreviated or short-hand hieroglyphic. The third or +lower inscription is Greek--obviously a thing of words. If the +screeds above be also made of words, only the elect have any way +of proving the fact. + +Fortunately, however, even the least scholarly observer is left +in no doubt as to the real import of the thing he sees, for an +obliging English label tells us that these three inscriptions are +renderings of the same message, and that this message is a +"decree of the priests of Memphis conferring divine honors on +Ptolemy V. (Epiphenes), King of Egypt, B.C. 195." The label goes +on to state that the upper inscription (of which, unfortunately, +only part of the last dozen lines or so remains, the slab being +broken) is in "the Egyptian language, in hieroglyphics, or +writing of the priests"; the second inscription "in the same +language is in Demotic, or the writing of the people"; and the +third "the Greek language and character." Following this is a +brief biography of the Rosetta Stone itself, as follows: "The +stone was found by the French in 1798 among the ruins of Fort +Saint Julien, near the Rosetta mouth of the Nile. It passed into +the hands of the British by the treaty of Alexandria, and was +deposited in the British Museum in the year 1801." There is a +whole volume of history in that brief inscription--and a bitter +sting thrown in, if the reader chance to be a Frenchman. Yet the +facts involved could scarcely be suggested more modestly. They +are recorded much more bluntly in a graven inscription on the +side of the stone, which reads: "Captured in Egypt by the British +Army, 1801." No Frenchman could read those words without a +veritable sinking of the heart. + +The value of the Rosetta Stone depended on the fact that it gave +promise, even when casually inspected, of furnishing a key to the +centuries-old mystery of the hieroglyphics. For two thousand +years the secret of these strange markings had been forgotten. +Nowhere in the world--quite as little in Egypt as elsewhere--had +any man the slightest clew to their meaning; there were those who +even doubted whether these droll picturings really had any +specific meaning, questioning whether they were not rather vague +symbols of esoteric religious import and nothing more. And it was +the Rosetta Stone that gave the answer to these doubters and +restored to the world a lost language and a forgotten literature. + +The trustees of the museum recognized at once that the problem of +the Rosetta Stone was one on which the scientists of the world +might well exhaust their ingenuity, and promptly published to the +world a carefully lithographed copy of the entire inscription, so +that foreign scholarship had equal opportunity with the British +to try at the riddle. It was an Englishman, however, who first +gained a clew to the solution. This was none other than the +extraordinary Dr. Thomas Young, the demonstrator of the vibratory +nature of light. + +Young's specific discoveries were these: (1) That many of the +pictures of the hieroglyphics stand for the names of the objects +actually delineated; (2) that other pictures are sometimes only +symbolic; (3) that plural numbers are represented by repetition; +(4) that numerals are represented by dashes; (5) that +hieroglyphics may read either from the right or from the left, +but always from the direction in which the animal and human +figures face; (6) that proper names are surrounded by a graven +oval ring, making what he called a cartouche; (7) that the +cartouches of the preserved portion of the Rosetta Stone stand +for the name of Ptolemy alone; (8) that the presence of a female +figure after such cartouches in other inscriptions always denotes +the female sex; (9) that within the cartouches the hieroglyphic +symbols have a positively phonetic value, either alphabetic or +syllabic; and (10) that several different characters may have the +same phonetic value. + +Just what these phonetic values are Young pointed out in the case +of fourteen characters representing nine sounds, six of which are +accepted to-day as correctly representing the letters to which he +ascribed them, and the three others as being correct regarding +their essential or consonant element. It is clear, therefore, +that he was on the right track thus far, and on the very verge of +complete discovery. But, unfortunately, he failed to take the +next step, which would have been to realize that the same +phonetic values which were given to the alphabetic characters +within the cartouches were often ascribed to them also when used +in the general text of an inscription; in other words, that the +use of an alphabet was not confined to proper names. This was the +great secret which Young missed and which his French successor, +Jean Francois Champollion, working on the foundation that Young +had laid, was enabled to ferret out. + +Young's initial studies of the Rosetta Stone were made in 1814; +his later publication bore date of 1819. Champollion's first +announcement of results came in 1822; his second and more +important one in 1824. By this time, through study of the +cartouches of other inscriptions, Champollion had made out almost +the complete alphabet, and the "riddle of the Sphinx" was +practically solved. He proved that the Egyptians had developed a +relatively complete alphabet (mostly neglecting the vowels, as +early Semitic alphabets did also) centuries before the +Phoenicians were heard of in history. What relation this alphabet +bore to the Phoenician we shall have occasion to ask in another +connection; for the moment it suffices to know that those strange +pictures of the Egyptian scroll are really letters. + +Even this statement, however, must be in a measure modified. +These pictures are letters and something more. Some of them are +purely alphabetical in character and some are symbolic in another +way. Some characters represent syllables. Others stand sometimes +as mere representatives of sounds, and again, in a more extended +sense, as representations of things, such as all hieroglyphics +doubtless were in the beginning. In a word, this is an alphabet, +but not a perfected alphabet, such as modern nations are +accustomed to; hence the enormous complications and difficulties +it presented to the early investigators. + +Champollion did not live to clear up all these mysteries. His +work was taken up and extended by his pupil Rossellini, and in +particular by Dr. Richard Lepsius in Germany, followed by M. +Bernouf, and by Samuel Birch of the British Museum, and more +recently by such well-known Egyptologists as MM. Maspero and +Mariette and Chabas, in France, Dr. Brugsch, in Germany, and Dr. +E. Wallis Budge, the present head of the Department of Oriental +Antiquities at the British Museum. But the task of later +investigators has been largely one of exhumation and translation +of records rather than of finding methods. + + +TREASURES FROM NINEVEH + +The most casual wanderer in the British Museum can hardly fail to +notice two pairs of massive sculptures, in the one case winged +bulls, in the other winged lions, both human-headed, which guard +the entrance to the Egyptian hall, close to the Rosetta Stone. +Each pair of these weird creatures once guarded an entrance to +the palace of a king in the famous city of Nineveh. As one +stands before them his mind is carried back over some +twenty-seven intervening centuries, to the days when the "Cedar +of Lebanon" was "fair in his greatness" and the scourge of +Israel. + +The very Sculptures before us, for example, were perhaps seen by +Jonah when he made that famous voyage to Nineveh some seven or +eight hundred years B.C. A little later the Babylonian and the +Mede revolted against Assyrian tyranny and descended upon the +fair city of Nineveh, and almost literally levelled it to the +ground. But these great sculptures, among other things, escaped +destruction, and at once hidden and preserved by the accumulating +debris of the centuries, they stood there age after age, their +very existence quite forgotten. When Xenophon marched past their +site with the ill-starred expedition of the ten thousand, in the +year 400 B.C., he saw only a mound which seemed to mark the site +of some ancient ruin; but the Greek did not suspect that he +looked upon the site of that city which only two centuries before +had been the mistress of the world. + +So ephemeral is fame! And yet the moral scarcely holds in the +sequel; for we of to-day, in this new, undreamed-of Western +world, behold these mementos of Assyrian greatness fresh from +their twenty-five hundred years of entombment, and with them +records which restore to us the history of that long-forgotten +people in such detail as it was not known to any previous +generation since the fall of Nineveh. For two thousand five +hundred years no one saw these treasures or knew that they +existed. One hundred generations of men came and went without +once pronouncing the name of kings Shalmaneser or Asumazirpal or +Asurbanipal. And to-day, after these centuries of oblivion, +these names are restored to history, and, thanks to the character +of their monuments, are assured a permanency of fame that can +almost defy time itself. It would be nothing strange, but rather +in keeping with their previous mutations of fortune, if the names +of Asurnazirpal and Asurbanipal should be familiar as household +words to future generations that have forgotten the existence of +an Alexander, a Caesar, and a Napoleon. For when Macaulay's +prospective New Zealander explores the ruins of the British +Museum the records of the ancient Assyrians will presumably still +be there unscathed, to tell their story as they have told it to +our generation, though every manuscript and printed book may have +gone the way of fragile textures. + +But the past of the Assyrian sculptures is quite necromantic +enough without conjuring for them a necromantic future. The story +of their restoration is like a brilliant romance of history. +Prior to the middle of this century the inquiring student could +learn in an hour or so all that was known in fact and in fable of +the renowned city of Nineveh. He had but to read a few chapters +of the Bible and a few pages of Diodorus to exhaust the important +literature on the subject. If he turned also to the pages of +Herodotus and Xenophon, of Justin and Aelian, these served +chiefly to confirm the suspicion that the Greeks themselves knew +almost nothing more of the history of their famed Oriental +forerunners. The current fables told of a first King Ninus and +his wonderful queen Semiramis; of Sennacherib the conqueror; of +the effeminate Sardanapalus, who neglected the warlike ways of +his ancestors but perished gloriously at the last, with Nineveh +itself, in a self-imposed holocaust. And that was all. How much +of this was history, how much myth, no man could say; and for all +any one suspected to the contrary, no man could ever know. And +to-day the contemporary records of the city are before us in such +profusion as no other nation of antiquity, save Egypt alone, can +at all rival. Whole libraries of Assyrian books are at hand that +were written in the seventh century before our era. These, be it +understood, are the original books themselves, not copies. The +author of that remote time appeals to us directly, hand to eye, +without intermediary transcriber. And there is not a line of any +Hebrew or Greek manuscript of a like age that has been preserved +to us; there is little enough that can match these ancient books +by a thousand years. When one reads Moses or Isaiah, Homer, +Hesiod, or Herodotus, he is but following the +transcription--often unquestionably faulty and probably never in +all parts perfect--of successive copyists of later generations. +The oldest known copy of the Bible, for example, dates probably +from the fourth century A.D., a thousand years or more after the +last Assyrian records were made and read and buried and +forgotten. + +There was at least one king of Assyria--namely, Asurbanipal, +whose palace boasted a library of some ten thousand volumes--a +library, if you please, in which the books were numbered and +shelved systematically, and classified and cared for by an +official librarian. If you would see some of the documents of +this marvellous library you have but to step past the winged +lions of Asurnazirpal and enter the Assyrian hall just around the +corner from the Rosetta Stone. Indeed, the great slabs of stone +from which the lions themselves are carved are in a sense books, +inasmuch as there are written records inscribed on their surface. +A glance reveals the strange characters in which these records +are written, graven neatly in straight lines across the stone, +and looking to casual inspection like nothing so much as random +flights of arrow-heads. The resemblance is so striking that this +is sometimes called the arrow-head character, though it is more +generally known as the wedge or cuneiform character. The +inscriptions on the flanks of the lions are, however, only +makeshift books. But the veritable books are no farther away +than the next room beyond the hall of Asurnazirpal. They occupy +part of a series of cases placed down the centre of this room. +Perhaps it is not too much to speak of this collection as the +most extraordinary set of documents of all the rare treasures of +the British Museum, for it includes not books alone, but public +and private letters, business announcements, marriage +contracts--in a word, all the species of written records that +enter into the every-day life of an intelligent and cultured +community. + +But by what miracle have such documents been preserved through +all these centuries? A glance makes the secret evident. It is +simply a case of time-defying materials. Each one of these +Assyrian documents appears to be, and in reality is, nothing more +or less than an inscribed fragment of brick, having much the +color and texture of a weathered terra-cotta tile of modern +manufacture. These slabs are usually oval or oblong in shape, +and from two or three to six or eight inches in length and an +inch or so in thickness. Each of them was originally a portion +of brick-clay, on which the scribe indented the flights of +arrowheads with some sharp-cornered instrument, after which the +document was made permanent by baking. They are somewhat fragile, +of course, as all bricks are, and many of them have been more or +less crumbled in the destruction of the palace at Nineveh; but to +the ravages of mere time they are as nearly invulnerable as +almost anything in nature. Hence it is that these records of a +remote civilization have been preserved to us, while the similar +records of such later civilizations as the Grecian have utterly +perished, much as the flint implements of the cave-dweller come +to us unchanged, while the iron implements of a far more recent +age have crumbled away. + + +HOW THE RECORDS WERE READ + +After all, then, granted the choice of materials, there is +nothing so very extraordinary in the mere fact of preservation of +these ancient records. To be sure, it is vastly to the credit of +nineteenth-century enterprise to have searched them out and +brought them back to light. But the real marvel in connection +with them is the fact that nineteenth-century scholarship should +have given us, not the material documents themselves, but a +knowledge of their actual contents. The flight of arrow-heads on +wall or slab or tiny brick have surely a meaning; but how shall +we guess that meaning? These must be words; but what words? The +hieroglyphics of the Egyptians were mysterious enough in all +conscience; yet, after all, their symbols have a certain +suggestiveness, whereas there is nothing that seems to promise a +mental leverage in the unbroken succession of these cuneiform +dashes. Yet the Assyrian scholar of to-day can interpret these +strange records almost as readily and as surely as the classical +scholar interprets a Greek manuscript. And this evidences one of +the greatest triumphs of nineteenth-century scholarship, for +within almost two thousand years no man has lived, prior to our +century, to whom these strange inscriptions would not have been +as meaningless as they are to the most casual stroller who looks +on them with vague wonderment here in the museum to-day. For the +Assyrian language, like the Egyptian, was veritably a dead +language; not, like Greek and Latin, merely passed from practical +every-day use to the closet of the scholar, but utterly and +absolutely forgotten by all the world. Such being the case, it is +nothing less than marvellous that it should have been restored. + +It is but fair to add that this restoration probably never would +have been effected, with Assyrian or with Egyptian, had the +language in dying left no cognate successor; for the powers of +modern linguistry, though great, are not actually miraculous. +But, fortunately, a language once developed is not blotted out in +toto; it merely outlives its usefulness and is gradually +supplanted, its successor retaining many traces of its origin. +So, just as Latin, for example, has its living representatives in +Italian and the other Romance tongues, the language of Assyria is +represented by cognate Semitic languages. As it chances, however, +these have been of aid rather in the later stages of Assyrian +study than at the very outset; and the first clew to the message +of the cuneiform writing came through a slightly different +channel. + +Curiously enough, it was a trilingual inscription that gave the +clew, as in the case of the Rosetta Stone, though with very +striking difference withal. The trilingual inscription now in +question, instead of being a small, portable monument, covers the +surface of a massive bluff at Behistun in western Persia. +Moreover, all three of its inscriptions are in cuneiform +characters, and all three are in languages that at the beginning +of our century were absolutely unknown. This inscription itself, +as a striking monument of unknown import, had been seen by +successive generations. Tradition ascribed it, as we learn from +Ctesias, through Diodorus, to the fabled Assyrian queen +Semiramis. Tradition was quite at fault in this; but it is only +recently that knowledge has availed to set it right. The +inscription, as is now known, was really written about the year +515 B.C., at the instance of Darius I., King of Persia, some of +whose deeds it recounts in the three chief languages of his +widely scattered subjects. + +The man who at actual risk of life and limb copied this wonderful +inscription, and through interpreting it became the veritable +"father of Assyriology," was the English general Sir Henry +Rawlinson. His feat was another British triumph over the same +rivals who had competed for the Rosetta Stone; for some French +explorers had been sent by their government, some years earlier, +expressly to copy this strange record, and had reported that it +was impossible to reach the inscription. But British courage did +not find it so, and in 1835 Rawlinson scaled the dangerous height +and made a paper cast of about half the inscription. Diplomatic +duties called him away from the task for some years, but in 1848 +he returned to it and completed the copy of all parts of the +inscription that have escaped the ravages of time. And now the +material was in hand for a new science, which General Rawlinson +himself soon, assisted by a host of others, proceeded to +elaborate. + +The key to the value of this unique inscription lies in the fact +that its third language is ancient Persian. It appears that the +ancient Persians had adopted the cuneiform character from their +western neighbors, the Assyrians, but in so doing had made one of +those essential modifications and improvements which are scarcely +possible to accomplish except in the transition from one race to +another. Instead of building with the arrow-head a multitude of +syllabic characters, including many homophones, as had been and +continued to be the custom with the Assyrians, the Persians +selected a few of these characters and ascribed to them phonetic +values that were almost purely alphabetic. In a word, while +retaining the wedge as the basal stroke of their script, they +developed an alphabet, making the last wonderful analysis of +phonetic sounds which even to this day has escaped the Chinese, +which the Egyptians had only partially effected, and which the +Phoenicians were accredited by the Greeks with having introduced +to the Western world. In addition to this all-essential step, the +Persians had introduced the minor but highly convenient custom of +separating the words of a sentence from one another by a +particular mark, differing in this regard not only from the +Assyrians and Egyptians, but from the early Greek scribes as +well. + +Thanks to these simplifications, the old Persian language had +been practically restored about the beginning of the nineteenth +century, through the efforts of the German Grotefend, and further +advances in it were made just at this time by Renouf, in France, +and by Lassen, in Germany, as well as by Rawlinson himself, who +largely solved the problem of the Persian alphabet independently. +So the Persian portion of the Behistun inscription could be at +least partially deciphered. This in itself, however, would have +been no very great aid towards the restoration of the languages +of the other portions had it not chanced, fortunately, that the +inscription is sprinkled with proper names. Now proper names, +generally speaking, are not translated from one language to +another, but transliterated as nearly as the genius of the +language will permit. It was the fact that the Greek word +Ptolemaics was transliterated on the Rosetta Stone that gave the +first clew to the sounds of the Egyptian characters. Had the +upper part of the Rosetta Stone been preserved, on which, +originally, there were several other names, Young would not have +halted where he did in his decipherment. + +But fortune, which had been at once so kind and so tantalizing in +the case of the Rosetta Stone, had dealt more gently with the +Behistun inscriptions; for no fewer than ninety proper names were +preserved in the Persian portion and duplicated, in another +character, in the Assyrian inscription. A study of these gave a +clew to the sounds of the Assyrian characters. The decipherment +of this character, however, even with this aid, proved enormously +difficult, for it was soon evident that here it was no longer a +question of a nearly perfect alphabet of a few characters, but of +a syllabary of several hundred characters, including many +homophones, or different forms for representing the same sound. +But with the Persian translation for a guide on the one hand, and +the Semitic languages, to which family the Assyrian belonged, on +the other, the appalling task was gradually accomplished, the +leading investigators being General Rawlinson, Professor Hincks, +and Mr. Fox-Talbot, in England, Professor Jules Oppert, in Paris, +and Professor Julian Schrader, in Germany, though a host of other +scholars soon entered the field. + +This great linguistic feat was accomplished about the middle of +the nineteenth century. But so great a feat was it that many +scholars of the highest standing, including Joseph Erneste Renan, +in France, and Sir G. Cornewall Lewis, in England, declined at +first to accept the results, contending that the Assyriologists +had merely deceived themselves by creating an arbitrary language. +The matter was put to a test in 1855 at the suggestion of Mr. +Fox-Talbot, when four scholars, one being Mr. Talbot himself and +the others General Rawlinson, Professor Hincks, and Professor +Oppert, laid before the Royal Asiatic Society their independent +interpretations of a hitherto untranslated Assyrian text. A +committee of the society, including England's greatest historian +of the century, George Grote, broke the seals of the four +translations, and reported that they found them unequivocally in +accord as regards their main purport, and even surprisingly +uniform as regards the phraseology of certain passages--in short, +as closely similar as translations from the obscure texts of any +difficult language ever are. This decision gave the work of the +Assyriologists official status, and the reliability of their +method has never since been in question. Henceforth Assyriology +was an established science. + + + +APPENDIX + +REFERENCE-LIST + +CHAPTER I. MODERN DEVELOPMENT OF THE PHYSICAL SCIENCES + +[1] Robert Boyle, Philosophical Works (3 vols.). London, 1738. + +CHAPTER II. THE BEGINNINGS OF MODERN CHEMISTRY + +[1] For a complete account of the controversy called the "Water +Controversy," see The Life of the Hon. Henry Cavendish, by George +Wilson, M.D., F.R.S.E. London, 1850. + +[2] Henry Cavendish, in Phil. Trans. for 1784, P. 119. + +[3] Lives of the Philosophers of the Time of George III., by +Henry, Lord Brougham, F.R.S., p. 106. London, 1855. + +[4] Experiments and Observations on Different Kinds of Air, by +Joseph Priestley (3 vols.). Birmingham, 790, vol. II, pp. +103-107. + +[5] Lectures on Experimental Philosophy, by Joseph Priestley, +lecture IV., pp. 18, ig. J. Johnson, London, 1794. + +[6] Translated from Scheele's Om Brunsten, eller Magnesia, och +dess Egenakaper. Stockholm, 1774, and published as Alembic Club +Reprints, No. 13, 1897, p. 6. + +[7] According to some writers this was discovered by Berzelius. + +[8] Histoire de la Chimie, par Ferdinand Hoefer. Paris, 1869, +Vol. CL, p. 289. + +[9] Elements of Chemistry, by Anton Laurent Lavoisier, translated +by Robert Kerr, p. 8. London and Edinburgh, 1790. + +[10] Ibid., pp. 414-416. + +CHAPTER III. CHEMISTRY SINCE THE TIME OF DALTON + +[1] Sir Humphry Davy, in Phil. Trans., Vol. VIII. + +CHAPTER IV. ANATOMY AND PHYSIOLOGY IN THE EIGHTEENTH CENTURY + +[1] Baas, History of Medicine, p. 692. + +[2] Based on Thomas H. Huxley's Presidential Address to the +British Association for the Advancement of Science, 1870. + +[3] Essays on Digestion, by James Carson. London, 1834, p. 6. + +[4] Ibid., p. 7. + +[5] John Hunter, On the Digestion of the Stomach after Death, +first edition, pp. 183-188. + +[6] Erasmus Darwin, The Botanic Garden, pp. 448-453. London, +1799. + +CHAPTER V. ANATOMY AND PHYSIOLOGY IN THE NINETEENTH CENTURY + +[1] Baron de Cuvier's Theory of the Earth. New York, 1818, p. +123. + +[2] On the Organs and Mode of Fecundation of Orchidex and +Asclepiadea, by Robert Brown, Esq., in Miscellaneous Botanical +Works. London, 1866, Vol. I., pp. 511-514. + +[3] Justin Liebig, Animal Chemistry. London, 1843, p. 17f. + +CHAPTER VI. THEORIES OF ORGANIC EVOLUTION + +[1] "Essay on the Metamorphoses of Plants," by Goethe, translated +for the present work from Grundriss einer Geschichte der +Naturwissenschaften, by Friederich Dannemann (2 vols.). Leipzig, +1896, Vol. I., p. 194. + +[2] The Temple of Nature, or The Origin of Society, by Erasmus +Darwin, edition published in 1807, p. 35. + +[3] Baron de Cuvier, Theory of the Earth. New York, 1818, p.74. +(This was the introduction to Cuvier's great work.) + +[4] Robert Chambers, Explanations: a sequel to Vestiges of +Creation. London, Churchill, 1845, pp. 148-153. + +CHAPTER VII. EIGHTEENTH-CENTURY MEDICINE + +[1] Condensed from Dr. Boerhaave's Academical Lectures on the +Theory of Physic. London, 1751, pp. 77, 78. Boerhaave's lectures +were published as Aphorismi de cognoscendis et curandis Morbis, +Leyden, 1709. On this book Van Swieten wrote commentaries filling +five volumes. Another very celebrated work of Boerhaave is his +Institutiones et Experimenta Chemic, Paris, 1724, the germs of +this being given as a lecture on his appointment to the chair of +chemistry in the University of Leyden in 1718. + +[2] An Inquiry into the Causes and Effects of the Variola +Vaccine, etc., by Edward Jenner, M.D., F.R.S., etc. London, 1799, +pp. 2-7. He wrote several other papers, most of which were +communications to the Royal Society. His last publication was, On +the Influence of Artificial Eruptions in Certain Diseases +(London, 1822), a subject to which he had given much time and +study. + +CHAPTER VIII. NINETEENTH-CENTURY MEDICINE + +[1] In the introduction to Corvisart's translation of +Avenbrugger's work. Paris, 1808. + +[2] Laennec, Traite d'Auscultation Mediate. Paris, 1819. This was +Laennec's chief work, and was soon translated into several +different languages. Before publishing this he had written also, +Propositions sur la doctrine midicale d'Hippocrate, Paris, 1804, +and Memoires sur les vers visiculaires, in the same year. + +[3] Researches, Chemical and Philosophical, chiefly concerning +Nitrous Oxide or Dephlogisticated Nitrous Air and its +Respiration, by Humphry Davy. London, 1800, pp. 479-556. + +[4] Ibid. + +[5] For accounts of the discovery of anaesthesia, see Report of +the Board of Trustees of the Massachusetts General Hospital, +Boston, 1888. Also, The Ether Controversy: Vindication of the +Hospital Reports of 1848, by N. L Bowditch, Boston, 1848. An +excellent account is given in Littell's Living Age, for March, +1848, written by R. H. Dana, Jr. There are also two Congressional +Reports on the question of the discovery of etherization, one for +1848, the other for 11852. + +[6] Simpson made public this discovery of the anaesthetic +properties of chloroform in a paper read before the +Medico-Chirurgical Society of Edinburgh, in March, 1847, about +three months after he had first seen a surgical operation +performed upon a patient to whom ether had been administered. + +[7] Louis Pasteur, Studies on Fermentation. London, 1870. + +[8] Louis Pasteur, in Comptes Rendus des Sciences de L'Academie +des Sciences, vol. XCII., 1881, pp. 429-435. + +CHAPTER IX. THE NEW SCIENCE OF EXPERIMENTAL PSYCHOLOGY + +[1] Bell's communications were made to the Royal Society, but his +studies and his discoveries in the field of anatomy of the +nervous system were collected and published, in 1824, as An +Exposition of the Natural System of Nerves of the Human Body: +being a Republication of the Papers delivered to the Royal +Society on the Subject of the Nerves. + +[2] Marshall Hall, M.D., F.R.S.L., On the Reflex Functions of the +Medulla Oblongata and the Medulla Spinalis, in Phil. Trans. of +Royal Soc., vol. XXXIII., 1833. + + + + + +End of Project Gutenberg Etext of A History of Science, V 4, by Williams + diff --git a/old/4hsci10.zip b/old/4hsci10.zip Binary files differnew file mode 100644 index 0000000..284685f --- /dev/null +++ b/old/4hsci10.zip |