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+Project Gutenberg Etext of A History of Science, V 4, by Williams
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+A History of Science, Volume 4
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+by Henry Smith Williams
+
+April, 1999  [Etext #1708]
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+
+A History of Science, Volume 1, by Henry Smith Williams
+
+Scanned by Charles Keller with OmniPage Professional OCR software
+
+
+
+
+
+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
+
+
+
+
+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
+
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