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| author | Roger Frank <rfrank@pglaf.org> | 2025-10-14 20:00:23 -0700 |
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| committer | Roger Frank <rfrank@pglaf.org> | 2025-10-14 20:00:23 -0700 |
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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: The Mechanism of Life + +Author: Stéphane Leduc + +Translator: W Deane Butcher + +Release Date: October 15, 2010 [EBook #33862] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK THE MECHANISM OF LIFE *** + + + + +Produced by David Garcia, James Nugen, Keith Edkins and +the Online Distributed Proofreading Team at +http://www.pgdp.net + + + + + + +</pre> + + +<table border="0" cellpadding="10" style="background-color: #ccccff;"> +<tr> +<td style="width:25%; vertical-align:top"> +Transcriber's note: +</td> +<td> +A few typographical errors have been corrected. They +appear in the text <span class="correction" title="explanation will pop up">like this</span>, and the +explanation will appear when the mouse pointer is moved over the marked +passage.<br /><br /> + +</td> +</tr> +</table> + +<h3>THE MECHANISM OF LIFE</h3> + + <div class="figcenter" style="width:71%;"> + <a href="images/Fig0.jpg"><img style="width:100%" src="images/Fig0.jpg" + alt="Fig. 0." title="Fig. 0." /></a> + Osmotic Productions. [<i>Frontispiece</i> + </div> + +<p class="cenhead">THE</p> + +<h1>MECHANISM OF LIFE</h1> + +<p class="cenhead"><span class="scac">BY</span></p> + +<h2><span class="sc">Dr. Stéphane LEDUC</span></h2> + +<p class="cenhead"><span class="scac">PROFESSEUR À L'ÉCOLE DE MÉDECINE DE NANTES</span></p> + +<p class="cenhead"><span class="scac">TRANSLATED BY</span></p> + +<h3>W. DEANE BUTCHER</h3> + +<p class="cenhead"><span class="scac">FORMERLY PRESIDENT OF THE RÖNTGEN SOCIETY, AND OF THE</span><br /> +<span class="scac">ELECTRO-THERAPEUTICAL SECTION OF THE ROYAL SOCIETY OF MEDICINE</span></p> + + <p> </p> + + <div class="contents"> + <div class="stanza"> + </div> + + <div class="stanza"> + <p class="hg3">"La nature a formé, et forme tous</p> + <p>les jours les êtres les plus simples par</p> + <p>génération spontanée." <span class="sc">Lamarck.</span></p> + </div> + + <div class="stanza"> + </div> + </div> + + <p> </p> + + <div class="figcenter" style="width:9%;"> + <a href="images/pmark.png"><img style="width:100%" src="images/pmark.png" + alt="Printers mark." title="Printers mark." /></a> + </div> +<h3>NEW YORK</h3> + +<h2>R<span class="gsp"> </span>E<span class="gsp"> </span>B<span class="gsp"> </span>M<span class="gsp"> </span>A<span class="gsp"> </span>N C<span class="gsp"> </span>O<span class="gsp"> </span>M<span class="gsp"> </span>P<span class="gsp"> </span>A<span class="gsp"> </span>N<span class="gsp"> </span>Y</h2> + +<h3><span class="sc">Herald Square Building</span><br /> +<span class="sc">141-145, West 36th Street</span></h3> + + <div class="poem"> + <div class="stanza"> + <p><i>First Impression March 1911</i></p> + </div> + + <div class="stanza"> + <p><i>Second Impression January 1914</i></p> + </div> + + <div class="stanza"> + <p><i>Printed in England</i></p> + </div> + </div> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page vii --><span class="pagenum"><a name="pagevii"></a>{vii}</span></p> + +<h3>TRANSLATOR'S PREFACE</h3> + + <p>Professor Leduc's <i>Théorie Physico-chimique de la Vie et Générations + Spontanées</i> has excited a good deal of attention, and not a little + opposition, on the Continent. As recently as 1907 the Académie des + Sciences excluded from its <i>Comptes Rendus</i> the report of these + experimental researches on diffusion and osmosis, because it touched too + closely on the burning question of spontaneous generation.</p> + + <p>As the author points out, Lamarck's early evolutionary hypothesis was + killed by opposition and neglect, and had to be reborn in England before + it obtained universal acceptance as the Darwinian Theory. Not + unnaturally, therefore, he turns for an appreciation of his work to the + free air and wide horizon of the English-speaking countries.</p> + + <p>He has entitled his book "The Mechanism of Life," since however little + we may know of the origin of life, we may yet hope to get a glimpse of + the machinery, and perhaps even hear the whirr of the wheels in Nature's + workshop. The subject is of entrancing interest to the biologist and the + physician, quite apart from its bearing on the question of spontaneous + generation. Whatever view may be entertained by the different schools of + thought as to the nature and significance of life, all alike will welcome + this new and important contribution to our knowledge of the mechanism by + which Nature constructs the bewildering variety of her forms.</p> + + <p>There is, I think, no more wonderful and illuminating spectacle than + that of an osmotic growth,—a crude lump of brute inanimate matter + germinating before our very eyes, putting forth bud and stem and root and + branch and leaf and fruit, with no stimulus from germ or seed, without + even <!-- Page viii --><span class="pagenum"><a + name="pageviii"></a>{viii}</span>the presence of organic matter. For + these mineral growths are not mere crystallizations as many suppose; they + increase by intussusception and not by accretion. They exhibit the + phenomena of circulation and respiration, and a crude sort of + reproduction by budding; they have a period of vigorous youthful growth, + of old age, of death and of decay. They imitate the forms, the colour, + the texture, and even the microscopical structure of organic growth so + closely as to deceive the very elect. When we find, moreover, that the + processes of nutrition are carried on in these osmotic productions just + as in living beings, that an injury to an osmotic growth is repaired by + the coagulation of its internal sap, and that it is able to perform + periodic movements just as an animal or a plant, we are at a loss to + define any line of separation between these mineral forms and those of + organic life.</p> + + <p>In the present volume the author has collected all the data necessary + for a complete survey of the mechanism of life, which consists + essentially of those phenomena which are exhibited at the contact of + solutions of different degrees of concentration. Whatever may be the + verdict as to the author's case for spontaneous generation, all will + agree that the book is a most brilliant and stimulating study, founded on + the personal investigation of a born experimenter.</p> + + <p> </p> + + <p>The present volume is a translation of Dr. Leduc's French edition, but + it is more than this, the work has been translated, revised and + corrected, and in many places re-written, by the author's own hand. I am + responsible only for the English form of the treatise, and can but regret + that I have been able to reproduce so imperfectly the charm of the + original.</p> + + <div class="poem"> + <div class="stanza"> + <p>W. DEANE BUTCHER.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Ealing.</span></p> + </div> + </div> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page ix --><span class="pagenum"><a name="pageix"></a>{ix}</span></p> + +<h3>PREFACE TO THE ENGLISH EDITION</h3> + + <p>C'est par l'initiative du Dr. Deane Butcher que cette ouvrage est + presenté aux lecteurs anglais, à la race qui a doté l'humanité de tant de + découvertes originales, geniales et d'une portée très générale.</p> + + <p>Comme un être vivant, une idée exige pour naître et se développer le + germe et le milieu de développement. Il est indéniable que le peuple + anglo-américain constitue un milieu particulièrement favorable à la + naissance et au développement des idées nouvelles.</p> + + <p>Pendant notre collaboration le Dr. Deane Butcher a été un critique + judicieux et éclairé, tous les changements dans l'édition anglaise sont + dus à ses observations. Il s'est assimilé l'ouvrage pour le traduire, et + dans beaucoup de parties, il a mis plus de clarté et de concision qu'il + n'y en avait dans le texte original.</p> + + <div class="poem"> + <div class="stanza"> + <p>STÉPHANE LEDUC.</p> + </div> + + <div class="stanza"> + <p><span class="sc">Nantes, 1911.</span></p> + </div> + </div> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page xi --><span class="pagenum"><a name="pagexi"></a>{xi}</span></p> + +<h3>TABLE OF CONTENTS</h3> + +<table class="nobctr" summary="Table of contents." title="Table of contents."> +<tr><td class="spacsingle"> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> PAGE</td></tr> +<tr><td class="spacsingle"> <span class="sc">Translator's Preface</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#pagevii">vii</a></td></tr> +<tr><td class="spacsingle"> <span class="sc">Author's Preface</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#pageix">ix</a></td></tr> +<tr><td class="spacsingle"> <span class="sc">Introduction</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#pagexiii">xiii</a></td></tr> +<tr><td class="spacsingle"> I. <span class="sc">Life and Living Beings</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page1">1</a></td></tr> +<tr><td class="spacsingle"> II. <span class="sc">Solutions</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page14">14</a></td></tr> +<tr><td class="spacsingle"> III. <span class="sc">Electrolytic Solutions</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page24">24</a></td></tr> +<tr><td class="spacsingle"> IV. <span class="sc">Colloids</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page36">36</a></td></tr> +<tr><td class="spacsingle"> V. <span class="sc">Diffusion and Osmosis</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page43">43</a></td></tr> +<tr><td class="spacsingle"> VI. <span class="sc">Periodicity</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page67">67</a></td></tr> +<tr><td class="spacsingle"> VII. <span class="sc">Cohesion and Crystallization</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page78">78</a></td></tr> +<tr><td class="spacsingle"> VIII. <span class="sc">Karyokinesis</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page89">89</a></td></tr> +<tr><td class="spacsingle"> IX. <span class="sc">Energetics</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page97">97</a></td></tr> +<tr><td class="spacsingle"> X. <span class="sc">Synthetic Biology</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page113">113</a></td></tr> +<tr><td class="spacsingle"> XI. <span class="sc">Osmotic Growth: A Study in Morphogenesis</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page123">123</a></td></tr> +<tr><td class="spacsingle"> XII. <span class="sc">The Phenomena of Life and Osmotic Productions:</span><br /> + <span class="sc"> A Study in Physiogenesis</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page147">147</a></td></tr> +<tr><td class="spacsingle"> XIII. <span class="sc">Evolution and Spontaneous Generation</span> </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> <a href="#page160">160</a></td></tr> +</table> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page xiii --><span class="pagenum"><a name="pagexiii"></a>{xiii}</span></p> + +<h3>INTRODUCTION</h3> + + <p>Life was formerly regarded as a phenomenon entirely separated from the + other phenomena of Nature, and even up to the present time Science has + proved wholly unable to give a definition of Life; evolution, nutrition, + sensibility, growth, organization, none of these, not even the faculty of + reproduction, is the exclusive appanage of life.</p> + + <p>Living things are made of the same chemical elements as minerals; a + living being is the arena of the same physical forces as those which + affect the inorganic world.</p> + + <p>Life is difficult to define because it differs from one living being + to another; the life of a man is not that of a polyp or of a plant, and + if we find it impossible to discover the line which separates life from + the other phenomena of Nature, it is in fact because no such line of + demarcation exists—the passage from animate to inanimate is gradual + and insensible. The step between a stalagmite and a polyp is less than + that between a polyp and a man, and even the trained biologist is often + at a loss to determine whether a given borderland form is the result of + life, or of the inanimate forces of the mineral world.</p> + + <p>A living being is a transformer of matter and energy—both matter + and energy being uncreateable and indestructible, i.e. invariable in + quantity. A living being is only a current of matter and of energy, both + of which change from moment to moment while passing through the + organism.</p> + + <p>That which constitutes a living being is its form; for a living thing + is born, develops, and dies with the form and structure of its organism. + This ephemeral nature of the living being, which perishes with the + destruction of its form, is in <!-- Page xiv --><span class="pagenum"><a + name="pagexiv"></a>{xiv}</span>marked contrast to the perennial character + of the matter and the energy which circulate within it.</p> + + <p>The elementary phenomenon of life is the contact between an alimentary + liquid and a cell. For the essential phenomenon of life is nutrition, and + in order to be assimilated all the elements of an organism must be + brought into a state of solution. Hence the study of life may be best + begun by the study of those physico-chemical phenomena which result from + the contact of two different liquids. Biology is thus but a branch of the + physico-chemistry of liquids; it includes the study of electrolytic and + colloidal solutions, and of the molecular forces brought into play by + solution, osmosis, diffusion, cohesion, and crystallization.</p> + + <p>In this volume I have endeavoured to give as much of the science of + energetics as can be treated without the use of mathematical formulæ; the + conception of entropy and Carnot's law of thermodynamics are also + discussed.</p> + + <p>The phenomena of catalysis and of diastatic fermentation have for the + first time been brought under the general laws of energetics. This I have + done by showing that catalysis is only one instance of the general law of + the transformation of potential into kinetic energy, viz. by the + intervention of a foreign exciting and stimulating energy which may be + infinitely smaller than the energy it transforms. This conception brings + life into line with other catalytic actions, and shows us a living being + as a store of potential energy, to be set free by an external stimulus + which may also excite sensation.</p> + + <p>In a subsequent chapter I have dealt with the rise of Synthetic + Biology, whose history and methods I have described. It is only of late + that the progress of physico-chemical science has enabled us to enter + into this field of research, the final one in the evolution of biological + science.</p> + + <p>The present work contains some of the earliest results of this + synthetic biology. We shall see how it is possible by the mere diffusion + of liquids to obtain forms which imitate with the greatest accuracy not + only the ordinary cellular tissues, but the more complicated striated + structures, such as muscle and mother-of-pearl. We shall also see how it + is <!-- Page xv --><span class="pagenum"><a + name="pagexv"></a>{xv}</span>possible by simple liquid diffusion to + reproduce in ordered and regular succession complicated movements like + those observed in the karyokinesis of the living cell.</p> + + <p>The essential character of the living being is its Form. This is the + only characteristic which it retains during the whole of its existence, + with which it is born, which causes its development, and disappears with + its death. The task of synthetic biology is the recognition of those + physico-chemical forces and conditions which can produce forms and + structures analogous to those of living beings. This is the subject of + the chapter on Morphogenesis.</p> + + <p>The last chapter deals with the doctrine of Evolution. The chain of + life is of necessity a continuous one, from the mineral at one end to the + most complicated organism at the other. We cannot allow that it is broken + at any point, or that there is a link missing between animate and + inanimate nature. Hence the theory of evolution necessarily admits the + physico-chemical nature of life and the fact of spontaneous generation. + Only thus can the evolutionary theory become a rational one, a + stimulating and fertile inspirer of research. We seek for the + physico-chemical forces which produce forms and structures analogous to + those of living beings, and phenomena analogous to those of life. We + study the alterations in environment which modify these forms, and we + seek in the past history of our planet for those natural phenomena which + have brought these physico-chemical forces into play. In this way we may + find the road which will, we hope, lead some day to the discovery of the + origin and the evolution of life upon the earth.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 1 --><span class="pagenum"><a name="page1"></a>{1}</span></p> + +<h2>THE MECHANISM OF LIFE</h2> + +<h3>CHAPTER I</h3> + +<p class="cenhead">LIFE AND LIVING BEINGS</p> + + <p>Primitive man distinguished but two kinds of bodies in nature, those + which were motionless and those which were animated. Movement was for him + the expression of life. The stream, the wind, the waves, all were alive, + and each was endowed with all the attributes of life—will, + sentiment, and passion. Ancient Greek mythology is but the poetic + expression of this primitive conception.</p> + + <p>In the evolution of the intelligence, as in that of the body, the + development of the individual is but a repetition of the development of + the race. Even now children attribute life to everything that moves. For + them a little bird still lives in the inside of a watch, and produces the + tick-tick of the wheels. In modern times, however, we have learnt that + everything in nature moves, so that motion of itself cannot be considered + as the characteristic of life.</p> + + <p>Heraclitus aptly compares life to a flame. Aristotle says, "Life is + nutrition, growth, and decay,—having for its cause a principle + which has its end in itself, namely <span title="entelecheia" class="grk" + >ἐντελέχεια</span>." + This principle is itself in need of definition, and Aristotle only + substitutes one unknown epithet for another.</p> + + <p>Bichat defined life as the ensemble of the functions which resist + death. This is to define life in terms of death,—but death is but + the end of life, and cannot be defined without first defining life. + Claude Bernard rejects all definition of life as insufficient, and + incompatible with experimental science. <!-- Page 2 --><span + class="pagenum"><a name="page2"></a>{2}</span></p> + + <p>Some modern physiologists regard sensibility, others irritability, as + the characteristic of life, and define life as the faculty of responding, + by some sort of change, to an external stimulus. As in the case of + movement, we have found by more attentive observation that this faculty + also is universal in nature. There is no action without reaction; an + elastic body repels the body that strikes it. Every object in nature + dilates with heat, contracts with cold, and is modified by the light + which it absorbs. Everything in nature responds to exterior action by a + change, and hence this faculty cannot be the characteristic of life.</p> + + <p>A distinguished professor of physiology was accustomed to teach that + the disproportion between action and reaction was the characteristic of + life. "Allow a gramme weight to fall on a nerve, and the muscle will + raise a weight of ten grammes. This disproportion is the characteristic + of life." But there is a much greater disproportion between action and + reaction when the friction of a match blows up a powder factory, or the + turning of a switch lights the lamps and animates the tramways and the + motors of a great city. The disproportion between action and reaction is + therefore no characteristic of life.</p> + + <p>The essential characteristic of life is often said to be + nutrition—the phenomenon by which a living organism absorbs matter + from its environment, subjects it to chemical metamorphosis, assimilates + it, and finally ejects the destructive products of metamorphosis into the + surrounding medium. But this characteristic is also common to a great + number of ordinary chemical reactions, so that we cannot call it peculiar + to life. Consider, for instance, a fragment of calcium chloride immersed + in a solution of sodium carbonate. It absorbs the carbonic ion, + incorporates it into a molecule of calcium carbonate, and ejects the + chlorine ion into the surrounding medium.</p> + + <p>It may be argued that this is merely a chemical process, since the + substance which determines the reaction is also modified, the chloride of + calcium changing into carbonate of calcium. But every living thing is + also changing its chemical <!-- Page 3 --><span class="pagenum"><a + name="page3"></a>{3}</span>constitution during every moment of its + existence,—it is this change which constitutes the process of + senile involution. The substance of the child is other than that of the + ovum, and the substance of the adult is not that of the child. Hence we + cannot regard nutrition as the exclusive characteristic of life.</p> + + <p>Other authorities regard growth and organization as the essentials of + life. But crystals also grow. It was said that the growth of a crystal + differed from that of a living thing, in that the former grew by the + addition of material from without—the juxtaposition of bricks, as + it were—while the latter grew by intussusception, an introduction + of fresh material into the substance of the organism. A crystal, + moreover, was homogeneous, while the tissues of a living being were + differentiated—such differentiation constituting the organization. + At the present time, however, we recognize the existence of a great + variety of purely physical productions, the so-called "osmotic growths," + which increase by a process of intussusception, and develop therefrom a + marvellous complexity of organization and of form. Hence growth and + organization cannot be considered as the essential characteristics of + life.</p> + + <p>Since, then, we are totally unable to define the exact boundary which + separates life from the physical phenomena of nature, we may fairly + conclude that no such separation exists. This is in conformity with the + "law of continuity,"—the principle which asserts that all the + phenomena of nature are continuous in time and space. Classes, divisions, + and separations are all artificial, made not by nature but by man. All + the forms and phenomena of nature are united by insensible transition; it + is impossible to separate them, and in the distinction between living and + non-living things we must content ourselves with relative definitions, + which are far from being precise.</p> + + <p>Life can only be defined as the sum of all phenomena exhibited by + living beings, and its definition thus becomes a mere corollary to the + definition of a living being.</p> + + <p>The true definition of a living being is that it is a transformer of + energy, receiving from its environment the energy <!-- Page 4 --><span + class="pagenum"><a name="page4"></a>{4}</span>which it returns to that + environment under another form. All living organisms are transformers of + energy.</p> + + <p>A living organism is also a transformer of matter. It absorbs matter + from its environment, transforms it, and returns it to its environment in + a different chemical condition. Living things are chemical transformers + of matter.</p> + + <p>Living beings are also transformers of form. They commence as a very + simple form, which gradually develops and becomes more complicated.</p> + + <p>The matter of which a living organism is constituted consists + essentially of certain solutions of crystalloids and colloids. To this we + may add an osmotic membrane to contain the liquids, and a solid skeleton + to support and protect them. Finally, it would seem that a colloid of one + of the albuminoid groups is a necessary constituent of every living + being.</p> + + <p>We may say, then, that a living being is a transformer of energy and + of matter, containing certain albuminoid substances, with an evolutionary + form, the constitution of which is essentially liquid.</p> + + <p>A living being has but a limited duration. It is born, develops, + becomes organized, declines and dies. Through all the metamorphoses of + form, of substance, and of energy, informing the whole course of its + existence, there is a certain co-ordination, a certain harmony, which is + necessary for the conservation of the individual. This harmony we call + Life. Discord is disease,—the total cessation of the harmony is + Death. When the form is profoundly altered and the substance changed, the + transformation of energy no longer follows its regular course, the + organism is dead.</p> + + <p>After death the colloids which have constituted the form of the living + thing pass from their liquid state as "sols" into their coagulated state + as "gels." The metamorphoses of form, substance, and energy still + continue, but no longer harmoniously for the conservation of the + individual, but in dis-harmony for its dissolution. Finally, the form of + the individual disappears, the substance and the energy of the living + being is resolved and dispersed into other bodies and other phenomena. + <!-- Page 5 --><span class="pagenum"><a name="page5"></a>{5}</span></p> + + <p>The results hitherto obtained from the study of life seem but + inconsiderable when compared with the time and labour devoted to the + question. Max Verworn exclaims, "Are we on a false track? Do we ask our + questions of Nature amiss, or do we not read her answers aright?"</p> + + <p>Each branch of science at its commencement employs only the simpler + methods of observation. It is purely descriptive. The next step is to + separate the different parts of the object studied—to dissect and + to analyse. The science has now become analytical. The final stage is to + reproduce the substances, the forms, and the phenomena which have been + the subject of investigation. The science has at last become + synthetical.</p> + + <p>Up to the present time, biology has made use only of the first two + methods, the descriptive and the analytical. The analytical method is at + a grave disadvantage in all biological investigations, since it is + impossible to separate and analyse the elementary phenomena of life. The + function of an organ ceases when it is isolated from the organism of + which it forms a part. This is the chief cause of our lack of progress in + the analysis of life.</p> + + <p>It is only recently that we have been able to apply the synthetic + method to the study of the phenomena of life. Now that we know that a + living organism is but the arena for the transformation of energy, we may + hope to reproduce the elementary phenomena of life, by calling into play + a similar transformation of energy in a suitable medium.</p> + + <p>Organic chemistry has already obtained numerous victories in the same + direction, and the rapid advance in the production of organic bodies by + chemical synthesis may be considered the first-fruits of synthetic + biology.</p> + + <p>A phenomenon is determined by a number of circumstances which we call + its causes, and of which it is the result. Every phenomenon, moreover, + contributes to the production of other phenomena which are called its + consequences. In order therefore to understand any phenomenon in its + entirety, we must determine all its causes both qualitatively and + quantitatively.</p> + + <p>Phenomena succeed one another in time as consequences <!-- Page 6 + --><span class="pagenum"><a name="page6"></a>{6}</span>one of another, + and thus form an uninterrupted chain from the infinite of the past into + the infinite of the future. A living being gathers from its entourage a + supply of matter and of energy, which it transforms and returns. It is + part and parcel of the medium in which it lives, which acts upon it, and + upon which it acts. The living being and the medium in which it exists + are mutually interdependent. This medium is in its turn dependent on its + entourage,—and so on from medium to medium throughout the regions + of infinite space.</p> + + <p>One of the great laws of the universe is the law of continuity in time + and space. We must not lose sight of this law when we attempt to follow + the metamorphoses of matter, of energy and of form in living beings. + Evolution is but the expression of this law of continuity, this + succession of phenomena following one another like the links of a chain, + without discontinuity through the vast extent of time and space.</p> + + <p>The other great universal law, that of conservation, applies with + equal force to living and to inanimate things. This law asserts the + uncreateability and the indestructibility of matter and of energy. A + given quantity of matter and of energy remains absolutely invariable + through all the transformations through which it may pass.</p> + + <p>We need not here discuss the question of the possible transformation + of matter into ether, or of ether into ponderable matter. Such a + transformation, if it exists, would have but little bearing on the + phenomena of life. Moreover, it also will probably be found to conform to + the law of conservation of energy.</p> + + <p>In marked contrast to the permanence of matter and of energy is the + ephemeral nature of form, as exhibited by living beings. Function, since + it is but the resultant of form, is also ephemeral. All the faculties of + life are bound up with its form,—a living being is born, exists, + and dies with its form.</p> + + <p>The phenomena of life may in certain cases slow down from their normal + rapidity and intensity, as in hibernating <!-- Page 7 --><span + class="pagenum"><a name="page7"></a>{7}</span>animals, or be entirely + suspended, as in seeds. This state of suspension of life, of latent life + as it were, reminds us of a machine that has been stopped, but which + retains its form and substance unaltered, and may be started again + whenever the obstacle to its progress is removed.</p> + + <p>During the whole course of its life a living being is intimately + dependent on its entourage. For example, the phenomena of life are + circumscribed within very narrow limits of temperature. A living + organism, consisting as it does essentially of liquid solutions, can only + exist at temperatures at which such solutions remain liquid, i.e. between + 0° C. and 100° C. Certain organisms, it is true, may be frozen, but their + life remains in a state of suspension so long as their substance remains + solid. Since the albuminoid substances which are a necessary component of + the living organism become coagulated at 44° C., the manifestations of + life diminish rapidly above this temperature. The intensity of life may + be said to augment gradually as the temperature rises from 0° to 40°, and + then to diminish rapidly as the temperature rises above that point, + becoming nearly extinct at 60° C.</p> + + <p>Another condition indispensable to life is the presence of oxygen. + Life, compared by Heraclitus to a flame, is a combustion, an oxydation, + for which the presence of oxygen at a certain pressure is indispensable. + There are, it is true, certain anærobic micro-organisms which apparently + exist without oxygen, but these in reality obtain their oxygen from the + medium in which they grow.</p> + + <p>Life is also influenced by light, by mechanical pressure, by the + chemical composition of its entourage, and by other conditions which we + do not as yet understand. In each case the conditions which are + favourable or noxious vary with the nature of the organism, some living + in air, some in fresh water, and others in the sea.</p> + + <p>Formerly it was supposed that the substance of a living being was + essentially different from that of the mineral world, so much so that two + distinct chemistries were in existence—organic chemistry, the study + of substances derived from bodies which had once possessed life, and + inorganic chemistry, dealing <!-- Page 8 --><span class="pagenum"><a + name="page8"></a>{8}</span>with minerals, metalloids, and metals. We now + know that a living organism is composed of exactly the same elements as + those which constitute the mineral world. These are carbon, oxygen, + hydrogen, nitrogen, phosphorus, calcium, iron, sulphur, chlorine, sodium, + potassium, and one or two other elements in smaller quantity. It was + formerly supposed that the organic combinations of these elements were + found only in living organisms and could be fashioned only by vital + forces. In more recent times, however, an ever increasing number of + organic substances have been produced in the laboratory.</p> + + <p>Organic bodies may be divided into four principal groups. (1) + <i>Carbohydrates</i>, including the sugars and the starches, all of which + may be considered as formed of carbon and water. (2) <i>Fats</i>, which + may be considered chemically as the ethers of glycerine, combinations of + one molecule of glycerine and three molecules of a fatty acid, with + elimination of water. (3) <i>Albuminoids</i>, substances whose molecules + are complex, containing nitrogen and sulphur in addition to carbon, + oxygen, and hydrogen. The albuminoid of the cell nucleus also contains + phosphorus, and the hæmoglobin of the blood contains iron. (4) + <i>Minerals</i> or inorganic elements, such as chloride of sodium, + phosphate of calcium, and carbonic acid. This group also includes water, + which is the most important constituent, since it forms more than a + moiety of the substance of all living creatures.</p> + + <p>Wöhler in 1828 accomplished the first synthesis of an organic + substance, urea, one of the products of the decomposition of albumin. + Since then a large number of organic substances have been prepared by the + synthesis of their inorganic elements. The most recent advance in this + direction is that of Emile Fischer, who has produced polypeptides having + the same reactions as the peptones, by combining a number of molecules of + the amides of the fatty acids.</p> + + <p>In the further synthesis of organic compounds the problems we have + before us are of the same order as those already solved. There is no + essential difference between organic and inorganic chemistry; living + organisms are formed of the <!-- Page 9 --><span class="pagenum"><a + name="page9"></a>{9}</span>same elements as the mineral world, and the + organic combinations of these elements may be realized in our + laboratories, just as in the laboratory of the living organism.</p> + + <p>Not only so, but a living being only borrows for a short time those + mineral elements which, after having passed through the living organism, + are returned once again to the mineral kingdom from which they came.</p> + + <p>All matter has life in itself—or, at any rate, all matter + susceptible of incorporation in a living cell. This life is potential + while the element is in the mineral state, and actual while the element + is passing through a living organism.</p> + + <p>Mineral matter is changed into organic matter in its passage through a + vegetable organism. The carbonic acid produced by combustion and + respiration is absorbed by the chlorophyll of the leaves under the + stimulus of light—the oxygen of the carbonic acid being returned to + the air, while the carbon is utilized by the plant for the formation of + sugar, starch, cellulose, and fats.</p> + + <p>Thus plants are fed in great part by their leaves, taking an important + part of their nourishment from the air, while by their roots they draw + from the earth the water, the phosphates, the mineral salts, and the + nitrates required for the formation of their albuminoid constituents. A + vegetable is a laboratory in which is carried out the process of organic + synthesis by which mineral materials are changed into organic matter. The + first synthetic reaction is the formation of a molecule of formic + aldehyde, CH<sub>2</sub>O, by the combination of a molecule of water with + an atom of carbon.</p> + + <p>From this formic aldehyde, or formol, we may obtain all the various + carbohydrates by simple polymerization, i.e. by the association of + several molecules, with or without elimination of water. Thus two + molecules of formol form one molecule of acetic acid, 2CH<sub>2</sub>O = + C<sub>2</sub>H<sub>4</sub>O<sub>2</sub>. Three molecules of formol form a + molecule of lactic acid, 3CH<sub>2</sub>O = + C<sub>3</sub>H<sub>6</sub>O<sub>3</sub>. Six molecules of formol + represent glucose and levulose, 6CH<sub>2</sub>O = + C<sub>6</sub>H<sub>12</sub>O<sub>6</sub>. Twelve molecules of formol + minus one molecule of water form saccharose, lactose, cane sugar, and + sugar of milk, 12CH<sub>2</sub>O = + C<sub>12</sub>H<sub>22</sub>O<sub>11</sub> + H<sub>2</sub>O; <i>n</i> + times six <!-- Page 10 --><span class="pagenum"><a + name="page10"></a>{10}</span>molecules of formol minus one molecule of + water, <i>n</i>(C<sub>6</sub>H<sub>10</sub>O<sub>5</sub>), form starch + and cellulose.</p> + + <p>Animals derive their nourishment from vegetables either directly, or + indirectly through the flesh of herbivorous animals. The mineral matter, + rendered organic in its passage through a vegetable growth, is finally + returned by the agency of animal organisms to the mineral world again, in + the form of carbonic acid, water, urea, and nitrates. Thus vegetables may + be regarded as synthetic agents, and animals and microbes as agents of + decomposition. Here also the difference is only relative, for in certain + cases vegetables produce carbonic acid, while some animal organisms + effect synthetic combinations. Moreover, there are intermediary forms, + such as fungi, which possessing no chlorophyll are nourished like animals + by organic matter, and yet like vegetables are able to manufacture + organic matter from mineral salts.</p> + + <p>The work of combustion begun by the animal organism is finished by the + action of micro-organisms, who complete the oxydation—the + re-mineralization of the chemical substances drawn originally from the + inorganic world by the agency of plant life.</p> + + <p>To sum up. Vegetables obtain their nourishment from mineral + substances, which they reduce, de-oxydize, and charge with solar energy. + Animal organisms on the contrary oxydize, and micro-organisms complete + the oxydation of these substances, returning them to the mineral world as + water, carbonates, nitrates, and sulphates.</p> + + <p>Thus matter circulates eternally from the mineral to the vegetable, + from the vegetable to the animal world, and back again. The matter which + forms our structure, which is to-day part and parcel of ourselves, has + formed the structure of an infinite number of living beings, and will + continue to pursue its endless reincarnation after our decease.</p> + + <p>This endless cycle of life is also an endless cycle of energy. The + combination of carbon with water carried out by the agency of chlorophyll + can only take place with absorption of energy. This energy comes directly + from the sun, the red and orange light radiations being absorbed by the + chlorophyll. <!-- Page 11 --><span class="pagenum"><a + name="page11"></a>{11}</span>The arrest of vegetation during the winter + months is due not so much to the lowering of temperature as to the + diminution of the radiant energy received from the sun. In the same way + shade is harmful to vegetation, since the radiant energy required for + growth is prevented from reaching the plant.</p> + + <p>The energy radiated by the sun is accumulated and stored in the plant + tissues. Later on, animals feed on the plants and utilize this energy, + excreting the products of decomposition, <i>i.e.</i> the constituents of + their food minus the energy contained in it. Thus the whole of the energy + which animates living beings, the whole of the energy which constitutes + life, comes from the sun. To the sun also we owe all artificial heat, the + energy stored up in wood and coal. We are all of us children of the + sun.</p> + + <p>The radiant energy of the sun is transformed by plants into chemical + energy. It is this chemical energy which feeds the vital activity of + animals, who return it to the external world under the form of heat, + mechanical work, and muscular contraction, light in the glow-worm, + electricity in the electric eel.</p> + + <p>There is a marked difference between the forms affected by organic and + inorganic substances. The forms of the mineral world are those of + crystals—geometrical forms, bounded by straight lines, planes, and + regular angles. Living organisms, on the contrary, affect forms which are + less regular—curved surfaces and rounded angles. The physical + reason for this difference in form lies in a difference of consistency, + crystals being solid, whereas living organisms are liquids or + semi-liquids. The liquids of nature, streams and clouds and dewdrops, + affect the same rounded forms as those of living organisms.</p> + + <p>Living beings for the most part present a remarkable degree of + symmetry. Some, like radiolarians and star-fish, have a stellate form. In + plants the various organs often radiate from an axis, in such a manner + that on turning the plant about this axis the various forms are + superposed thrice, four, or more often five times in one complete + revolution. It is remarkable how often this number five recurs in the + <!-- Page 12 --><span class="pagenum"><a + name="page12"></a>{12}</span>divisions and parts of a living organism. In + other cases the similar parts are disposed symmetrically on either side + of a median line or plane, giving a series of homologous parts which are + not superposable.</p> + + <p>The most important characteristic of a living being is its form. This + is implicitly admitted by naturalists, who classify animals and plants in + genera and species according to the differences and analogies of their + form.</p> + + <p>All living beings are composed of elementary organizations called + cells. In its complete state, a cell consists of a membrane or envelope + containing a mass of protoplasm, in the centre of which is a nucleus of + differentiated protoplasm. This nucleus may in its turn contain a + nucleolus. In some cases the cell is merely a protoplasmic mass without a + visible envelope, so that a cell may be defined as essentially a mass of + protoplasm provided with a nucleus.</p> + + <p>A living organism may consist merely of a single cell, which is able + alone to accomplish all the functions of life. Most living beings, + however, consist of a collection of innumerable cells forming a cellular + association or community. When a number of cells are thus united to + constitute a single living being, the various functions of life are + divided among different cellular groups. Certain cells become specialized + for the accomplishment of a single function, and to each function + corresponds a different form of cell. It is thus easy to recognize by + their form the nerve cells, the muscle cells which perform the function + of movement, and the glandular cells which perform the function of + secretion. The cells of a living being are microscopic in size, and it is + remarkable that they never attain to any considerable dimensions.</p> + + <p>In order that life may be maintained in a living organism, it is + necessary that a continual supply of aliment should be brought to it, and + that certain other substances, the waste-products of combustion, should + be eliminated. In order to be absorbed and assimilated, the alimentary + substances must be presented to the living organism in a liquid or + gaseous state. Thus the essential condition necessary for the <!-- Page + 13 --><span class="pagenum"><a name="page13"></a>{13}</span>maintenance + of life is the contact of a living cell with a current of liquid. The + elementary physical phenomenon of life is the contact of two different + liquids. This is the necessary condition which renders possible the + chemical exchanges and the transformations of energy which constitute + life. It is in the study of the phenomena of liquid contact and diffusion + that we may best hope to pierce the secrets of life. The physics of vital + action are the physics of the phenomena which occur in liquids, and the + study of the physics of a liquid must be the preface and the basis of all + inquiry into the nature and origin of life.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 14 --><span class="pagenum"><a name="page14"></a>{14}</span></p> + +<h3>CHAPTER II</h3> + +<p class="cenhead">SOLUTIONS</p> + + <p>We have seen that living beings are transformers of energy and of + matter, evolutionary in form and liquid in consistency; that they are + solutions of colloids and crystalloids separated by osmotic membranes to + form microscopic cells, or consisting merely of a gelatinous mass of + protoplasm, with a nucleus of slightly differentiated material. The + elementary phenomenon of life is the contact of two different solutions. + This is the initial physical phenomenon from which proceed all the other + phenomena of life in accordance with the ordinary chemical and physical + laws. Thus the basis of biological science is the study of solution and + of the phenomena which occur between two different solutions, either in + immediate contact or when separated by a membrane.</p> + + <p>A solution is a homogeneous mixture of one or more solutes in a liquid + solvent. Before solution the solute or dissolved substance may be solid, + liquid, or gaseous.</p> + + <p>Solutes, or substances capable of solution, may be divided into two + classes—substances which are capable of crystallization, or + crystalloids; and those which are incapable of crystallization, the + colloids. Crystalloids may be divided again into two classes, those whose + solutions are ionizable and therefore conduct electricity, chiefly salts, + acids, and bases; and those whose solutions are non-ionizable and are + therefore non-conductors. These latter are for the most part + crystallizable substances of organic origin, such as sugars, urea, + etc.</p> + + <p>Avogadro's law asserts that under similar conditions of temperature + and pressure, equal volumes of various gases <!-- Page 15 --><span + class="pagenum"><a name="page15"></a>{15}</span>contain an equal number + of molecules. Under similar conditions, the molecular weights of + different substances have therefore the same ratio as the weights of + equal volumes of their vapours. Hence if we fix arbitrarily the molecular + weight of any one substance, the molecular weight of all other substances + is thereby determined. The molecular weight of hydrogen has been + arbitrarily fixed as two, and hence the molecular weight of any substance + will be double its gaseous density when compared with that of + hydrogen.</p> + + <p><i>Gramme-Molecule.</i>—A gramme-molecule is the molecular + weight of a body expressed in grammes. Occasionally for brevity a + gramme-molecule is spoken of as a "molecule." Thus we may say that the + molecular weight of oxygen is 16 grammes, meaning thereby that there are + the same number of molecules in 16 grammes of oxygen as there are atoms + in 1 gramme of hydrogen.</p> + + <p><i>Concentration.</i>—The concentration of a solution is the + ratio between the quantity of the solute and the quantity of the solvent. + The concentration of a solution is expressed in various ways. (<i>a</i>) + The weight of solute dissolved in 100 grammes of the solvent. (<i>b</i>) + The weight of solute present in 100 grammes of the solution. (<i>c</i>) + The weight of solute dissolved in a litre of the solvent. (<i>d</i>) The + weight of solute in a litre of the solution. The most usual method is to + give the concentration as the weight of solute dissolved in 100 grammes + or in one litre of the solvent.</p> + + <p><i>Molecular Concentration.</i>—Many of the physical and + biological properties of a solution are proportional, not to its mass or + weight concentration, but to its molecular concentration, <i>i.e</i>. to + the number of gramme-molecules of the solute contained in a litre of the + solution. Many physical properties are quite independent of the nature of + the solute, depending only on its degree of molecular concentration.</p> + + <p><i>Normal Solution.</i>—A normal solution is one which contains + one gramme-molecule of the solute per litre. A decinormal solution + contains one-tenth of a gramme-molecule of the solute per litre, and a + centinormal solution one-hundredth of a gramme-molecule. A normal + solution of urea, for example, <!-- Page 16 --><span class="pagenum"><a + name="page16"></a>{16}</span>contains 60 grammes of urea per litre, while + a normal solution of sugar contains 342 grammes of sugar per litre.</p> + + <p><i>The Dissolved Substance is a Gas.</i>—Van t' Hoff, using the + data obtained by the botanist Pfeffer, showed that the dissolved matter + in a solution behaved exactly as if it were a gas. The analogy is + complete in every respect. Like the gaseous molecules, the molecules of a + solute are mobile with respect to one another. Like those of a gas, the + molecules of a solute tend to spread themselves equally, and to fill the + whole space at their disposal, <i>i.e.</i> the whole volume of the + solution. The surface of the solution represents the vessel containing + the gas, which confines it within definite limits and prevents further + expansion.</p> + + <p><i>Osmotic Pressure.</i>—Like the molecules of a gas, the + molecules of a solute exercise pressure on the boundaries of the space + containing it. This osmotic pressure follows exactly the same laws as + gaseous pressure. It has the same constants, and all the notions acquired + by the study of gaseous pressure are applicable to osmotic pressure. + Osmotic pressure is in fact the gaseous pressure of the molecules of the + solute.</p> + + <p>When a gas dilates and increases in volume, its temperature falls, and + cold is produced. Similarly, when a soluble substance is dissolved, it + increases in volume, and the temperature of the liquid falls. This + phenomenon is well known as a means of producing cold by a refrigerating + mixture.</p> + + <p>The phenomena of life are governed by the laws of gaseous pressure, + since all these phenomena take place in solutions. The fundamental laws + of biology are those of the distribution of substances in solution, which + is regulated by the laws of gaseous pressure, since all these laws are + applicable also to osmotic pressure.</p> + + <p><i>Boyle's Law</i>.—When a gas is compressed its volume is + diminished. If the pressure is doubled, the volume is reduced to + one-half. The quantity V × P, that is the volume multiplied by the + pressure, is constant.</p> + + <p><i>Gay-Lussac's Law.</i>—For a difference of temperature of a + degree Centigrade all gases dilate or contract by 1 / 273 of their volume + at 0° Centigrade. <!-- Page 17 --><span class="pagenum"><a + name="page17"></a>{17}</span></p> + + <p><i>Dalton's Law.</i>—In a gaseous mixture, the total pressure is + equal to the sum of the pressures which each gas would exert if it alone + filled the whole of the receptacle.</p> + + <p><i>Pressure proportional to Molecular Concentration.</i>—The + above laws are completely independent of the chemical nature of the gas, + they depend only on the number of gaseous molecules in a given space, + <i>i.e.</i> on the molecular concentration. If we double the mass of the + gas in a given space, we double the number of molecules, and we also + double the pressure, whatever the nature of the molecules. We may also + double the pressure by compressing the molecules of a gas, or of several + gases, into a space half the original size. The molecular concentration + of a gas, or of a mixture of gases, is the ratio of the number of + molecules to the volume they occupy. The pressure of a gas or of a + mixture of gases is proportional to its molecular concentration. This is + a better and a shorter way of expressing both Boyle's law and Dalton's + law.</p> + + <p>One gramme-molecule of a gas, whatever its nature, condensed into the + volume of 1 litre, has a pressure of 22.35 atmospheres. Similarly one + gramme-molecule of a solute, whatever its nature, when dissolved in a + litre of water, has the same pressure, viz. 22.35 atmospheres.</p> + + <p><i>Absolute Zero.</i>—According to Gay-Lussac's law, the volume + of a gas diminishes by 1 / 273 of its volume at 0° C. for each degree + fall of temperature. Thus if the contraction is the same for all + temperatures, the volume would be reduced to zero at -273° C. This is the + absolute zero of temperature. Temperatures measured from this point are + called absolute temperatures, and are designated by the symbol T. If + <i>t°</i> indicates the Centigrade temperature above the freezing point + of water, then the absolute temperature is equal to <i>t°</i> + 273°.</p> + + <p><i>The Gaseous Constant.</i>—Consider a mass of gas at 0° C. + under a pressure P<sub>o</sub>, with volume V<sub>o</sub>. At the + absolute temperature T, if the pressure be unaltered, the volume of this + gas will be V<sub>o</sub>T / 273. Therefore the constant PV, the product + of the pressure by the volume, will be represented by + P<sub>o</sub>V<sub>o</sub>T / 273. <!-- Page 18 --><span + class="pagenum"><a name="page18"></a>{18}</span></p> + + <p>At the same temperature, but under another pressure P′ the gas + will have a different volume V′. Since, according to Boyle's law, + PV is constant (P′V′ = P<sub>o</sub>V<sub>o</sub>), it will + still equal P<sub>o</sub>V<sub>o</sub>T / 273. Therefore + P<sub>o</sub>V<sub>o</sub> / 273 is also constant. This quantity is + called "the gaseous constant," and if we represent it by the symbol R, we + obtain the general formula PV = RT for all gases, or PV / T = R.</p> + + <p>Suppose, for instance, we have a gramme-molecule of a gas at 0° C. in + a space of 1 litre. It has a pressure of 22.35 atmospheres at 0° C., or + 273° absolute temperature. Since PV = RT, R = PV / T = 1 × 22.35 / 273 = + .0819. This number .0819 is the numerical value of the constant R for all + gases, volume being measured in litres and pressure in atmospheres.</p> + + <p>Substances in solution behave exactly like gases, they follow the same + laws and have the same constants. All the conceptions which have been + acquired by the study of gases are applicable to solutions, and therefore + to the phenomena of life. The osmotic pressure of a solution is the force + with which the molecules of the solute, like gaseous molecules, strive to + diffuse into space, and press on the limits which confine them, the + containing vessel being represented by the surfaces of the solution. + Osmotic pressure is measured in exactly the same way as gaseous pressure. + To measure steam pressure we insert a manometer in the walls of the + boiler. In the same way we may use a manometer to measure osmotic + pressure. We attach the tube to the walls of the porous vessel, allow the + solvent to increase in volume under the pressure of the solute, and + measure the rise of the liquid in the manometer tube.</p> + + <p><i>Pfeffer's Apparatus.</i>—Pfeffer has designed an apparatus + for the measurement of osmotic pressure. It consists of a vessel of + porous porcelain, the pores of which are filled with a colloidal solution + of ferrocyanide of copper. This forms a semi-permeable membrane which + permits the passage of water into the vessel, but prevents the passage of + sugar or of any <!-- Page 19 --><span class="pagenum"><a + name="page19"></a>{19}</span>colloid. The stopper which hermetically + closes the vessel is pierced for the reception of a mercury manometer. + The vessel is filled with a solution of sugar and plunged in a bath of + water. The volume of the solution in the interior of the vessel can vary, + since water passes easily in either direction through the pores of the + vessel. The boundary of the solvent has become extensible, and its volume + can increase or diminish in accordance with the osmotic pressure of the + solute. Under the pressure of the sugar water is sucked into the vessel + like air into a bellows, the solution passes into the tube of the + manometer, and raises the column of mercury until its pressure balances + the osmotic pressure of the sugar molecules.</p> + + <p><i>Osmotic Pressure follows the Laws of Gaseous + Pressure.</i>—This osmotic pressure is in fact gaseous pressure, + and may be measured in millimetres of mercury in just the same way. We + may thus show that osmotic pressure follows the laws of gaseous pressure + as defined by Boyle, Dalton, and Gay-Lussac. The coefficient of pressure + variation for change of temperature is the same for a solute as for a + gas. The formula PV = RT is applicable to both. The numerical value of + the constant R is also the same for a solute as for a gas. being .0819 + for one gramme-molecule of either, when the volume is expressed in litres + and the pressure in atmospheres. The formula PV = RT shows that for a + given mass, with the same volume, the pressure increases in proportion to + the absolute temperature.</p> + + <p><i>Osmotic Pressure of Sugar.</i>—A normal solution of sugar, + containing 342 grammes of sugar per litre, has a pressure of 22.35 + atmospheres, and it may well be asked why such an enormous pressure is + not more evident. The reason will be found in the immense frictional + resistance to diffusion. Frictional resistance is proportional to the + area of the surfaces in contact, and this area increases rapidly with + each division of the substance. When a solute is resolved into its + component molecules, its surface is enormously increased, and therefore + the friction between the molecules of the solute and those of the + solvent.</p> + + <p><i>Isotonic Solutions.</i>—Two solutions which have the same + <!-- Page 20 --><span class="pagenum"><a + name="page20"></a>{20}</span>osmotic pressure are said to be iso-osmotic + or isotonic. When comparing two solutions of different concentration, the + solution with the higher osmotic pressure is said to be hypertonic, and + that with the lower osmotic pressure hypotonic.</p> + + <p><i>Lowering of the Freezing Point.</i>—Pure water freezes at 0° + C. Raoult showed that the introduction of a non-ionizable substance, such + as sugar or alcohol, lowers the freezing point of a solution in + proportion to the molecular concentration of the solute. One + gramme-molecule of the solute introduced into one litre of the solution + lowers its temperature of congelation by 1.85° C. Thus a normal solution + of any non-ionizable substance in water freezes at -1.85° C. The + measurement of this lowering of the freezing point is called Cryoscopy, a + method which is becoming of great utility in medicine.</p> + + <p><i>Cryoscopy of Blood.</i>—In order to determine the osmotic + pressure of the blood at 37° C., <i>i.e.</i> 98.6° F., the normal + temperature, we proceed as follows. On freezing the blood, we find that + it congeals at -.56°. Its molecular concentration is therefore .56 / 1.85 + = .30, or about one-third of a gramme-molecule per litre. Its osmotic + pressure at 0° C. is therefore .3 × 22.35 = 6.7 atmospheres. The increase + of pressure with temperature is the same as for a gas, viz. 1/273, or + .00367 of its pressure at 0° for every degree rise of temperature. The + increase of pressure at 37° is therefore .00367 × 37 × 6.7 = .9 + atmospheres. The total osmotic pressure at 37° is therefore 6.7 + .9 = + 7.6 atmospheres.</p> + + <p><i>Rise of Boiling Point.</i>—Water under atmospheric pressure + boils at a temperature of 100° C. The addition of a solute whose solution + does not conduct electricity, such as sugar, causes a rise in the boiling + point proportional to the molecular concentration of that solute.</p> + + <p><i>Lowering of the Vapour Tension.</i>—The vapour tension of a + liquid is lowered by the addition of a solute. A liquid boils at the + temperature at which its vapour tension equals that of the atmosphere. + Since an aqueous solution of sugar at atmospheric pressure does not begin + to boil at 100° C., it is manifest that its vapour tension is then less + than that of the <!-- Page 21 --><span class="pagenum"><a + name="page21"></a>{21}</span>atmosphere. The addition of a solute such as + sugar, whose solution is not ionizable, and therefore does not conduct + electricity, lowers the vapour tension of the solution in proportion to + the molecular concentration of the solute.</p> + + <p><i>Corresponding Values.</i>—We have thus found five properties + of a solution which vary proportionally, so that from the measurement of + any one of them we can determine the corresponding values of all the + others. These are—</p> + + <div class="poem"> + <div class="stanza"> + <p>1. The Molecular Concentration.</p> + <p>2. The Osmotic Pressure.</p> + <p>3. The Diminution of Vapour Tension.</p> + <p>4. The Raising of the Boiling Point.</p> + <p>5. The Lowering of the Freezing Point.</p> + </div> + </div> + + <p><i>Cryoscopy.</i>—The usual method employed for the + determination of the molecular concentration and osmotic pressure of a + solution is by cryoscopy—the measurement of its temperature of + congelation. A very sensitive thermometer is used, the scale of which + extends over only 5° and is divided into hundredths of a degree. The + liquid under examination is placed in a test tube, in which the bulb of + the thermometer is plunged, and this is supported in a second tube with + an air space all round it. The whole is then suspended to the under side + of the cover of the refrigerating vessel, which may be cooled either by + filling it with a freezing mixture, or by the evaporation of ether. + During the whole of the operation the liquid is agitated by a mechanical + stirrer. The first step is to determine the freezing point of distilled + water. As the water cools the mercury gradually descends in the stem of + the thermometer till it reaches a point below the zero mark at 0° C. As + soon as ice begins to form the mercury rises, at first rapidly and then + more slowly, reaches a maximum, and finally descends again. This maximum + reading is the true point of congelation. The inner tube is then emptied, + care being taken to leave a few small ice crystals to serve as centres of + congelation for the subsequent experiment, thus avoiding supercooling of + the solution. The process is then repeated with the solution under + examination. The difference between <!-- Page 22 --><span + class="pagenum"><a name="page22"></a>{22}</span>the two freezing points + is the required "lowering of the freezing point."</p> + + <p>Cryoscopy is the method most used in biological research to determine + molecular concentration. It has, however, some grave defects. It + necessitates several cubic centimetres of the liquid under examination. + It gives us the constants of the solution at the temperature of freezing, + which is far below that of life. Organic liquids are easily altered and + are extremely sensible to minute differences of temperature, cryoscopy + therefore gives us no information as to the constitution of solutions + under normal conditions. It is desirable to have some other method of + determining molecular concentration and the other interdependent + constants at the normal temperature of life. A much better method, were + it possible, would be the direct determination of the vapour tension of + the solutions under normal conditions of temperature and pressure.</p> + + <p><i>Molecular Lowering of the Freezing Point.</i>—For every + substance whose solution is not ionized and therefore does not conduct + electricity, the lowering of the freezing point is the same, viz. 1.85° + C. for each gramme-molecule of the solute per litre of the solution.</p> + + <p><i>Determination of the Molecular Concentration.</i>—In order to + obtain the molecular concentration of a non-ionizable substance, we have + only to determine the lowering of the freezing point. Let A be the + lowering of the freezing point of any solution. On dividing it by 1.85 + (the lowering of the freezing point for a normal solution), we obtain the + number of gramme-molecules in a litre of the solution. If <i>n</i> be the + number of gramme-molecules per litre, then <i>n</i> = A / 1.85.</p> + + <p><i>Determination of the Osmotic Pressure.</i>—The osmotic + pressure P of a solution may be obtained by multiplying its molecular + concentration <i>n</i> by 22.35 atmospheres. P = <i>n</i> × 22.35 = A / + 1.85 × 22.35.</p> + + <p><i>Determination of Molecular Weight.</i>—The lowering of the + freezing point also enables us to calculate the molecular <!-- Page 23 + --><span class="pagenum"><a name="page23"></a>{23}</span>weight of any + non-ionizable solute. Thus Bouchard has been able to determine by means + of cryoscopy the mean molecular weight of the substances eliminated by + the urine. A weight <i>x</i> of the substance is dissolved in a litre of + water, and the lowering of the freezing point is observed. The value thus + found divided by 1.85 gives us <i>n</i>, the number of gramme-molecules + per litre. The molecular weight M may be determined by dividing the + original weight <i>x</i> by <i>n</i>.</p> + + <p>The study of osmotic pressure was begun by the Abbé Nollet; and one of + his disciples, Parrot, at an early date thus described its importance: + "It is a force analogous in all respects to the mechanical forces, a + force able to set matter in motion, or to act as a static force in + producing pressure. It is this force which causes the circulation of + heterogeneous matter in the liquids which serve as its vehicle. It is + this force which produces those actions which escape our notice by their + minuteness and bewilder us by their results. It is for the infinitely + small particles of matter what gravitation is for heavy masses. It can + displace matter in solution upwards against gravity as easily as + downwards or in a horizontal direction."</p> + + <p>Thus the recognition of the fact that a substance in solution is + really a gas, has at a single stroke put us in possession of the laws of + osmotic pressure—laws slowly and laboriously discovered by the long + series of investigations on the pressure of gases.</p> + + <p>Osmotic pressure plays a most important rôle in the arena of life. It + is found at work in all the phenomena of life. When osmotic pressure + fails, life itself ceases.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 24 --><span class="pagenum"><a name="page24"></a>{24}</span></p> + +<h3>CHAPTER III</h3> + +<p class="cenhead">ELECTROLYTIC SOLUTIONS</p> + + <p><i>Solutions which conduct Electricity.</i>—The laws of solution + which we have studied in the previous chapter apply only to those + solutions, chiefly of organic origin, which do not conduct electricity. + Solutions of electrolytes such as the ordinary salts, acids, and bases, + which are ionized on solution, give values for the various constants of + solution which do not accord with those required by theory. If, for + instance, we take a gramme-molecule of an electrolyte such as chloride of + sodium, and dissolve it in a litre of water, we find that the lowering of + the freezing point is nearly double the theoretical value of 1.85°. The + same holds good for the osmotic pressure, and for all the constants which + are proportional to the molecular concentration of the solute. The + solution behaves, in each case, as if it contained more than one + gramme-molecule of sodium chloride per litre. It behaves, in fact, as if + it contained <i>i</i> times the number of molecules of solute originally + introduced into it. If <i>n</i> be the original number of molecules, then + it will apparently contain <i>n′ = in</i> molecules. This law is + universal for all electrolytic solutions; the theoretical value for their + concentration, osmotic pressure, and all the proportional physical + constants must be multiplied by this quantity, <i>i = n′/n</i>, + which is the ratio of the apparent number of the molecules present to the + number originally introduced.</p> + + <p>A similar dissociation of the molecule is observed in the case of many + gases. The vapour of chloride of ammonium, for instance, is decomposed by + heat, and it may be shown experimentally that the increase of pressure on + heating above <!-- Page 25 --><span class="pagenum"><a + name="page25"></a>{25}</span>that which theory demands, is due to an + increase in the number of the gaseous molecules present. Some of the + vapour particles are dissociated into two or more fragments, each of + which plays the part of a single molecule.</p> + + <p>Arrhenius, in 1885, advanced the hypothesis that the apparent increase + in the number of molecules of an electrolytic solution was also due to + dissociation. This interpretation at once threw a flood of light on a + number of phenomena hitherto obscure.</p> + + <p><i>Coefficient of Dissociation.</i>—We have seen that in order + to obtain values which accord with experiment we have to multiply the + number of gramme-molecules of the solute by the coefficient <i>i</i>, + which is called the Coefficient of Dissociation.</p> + + <p>This coefficient of dissociation, <i>i</i>, may be found by observing + the lowering of the freezing point of a normal solution, and dividing it + by 1.85. <i>i</i> = <i>t</i>/1.85.</p> + + <p>The coefficient of dissociation varies with the degree of + concentration of the solution, rising to a maximum when the solution is + sufficiently diluted.</p> + + <p>If we know <i>i</i>, the coefficient of dissociation for a given + solute, contained in a solution of a definite concentration, we can find + <i>n′</i>, the number of particles present in a solution containing + <i>n</i> gramme-molecules of the solute per litre, since <i>n′</i> + = <i>in</i>. On the other hand, if from a consideration of its freezing + point and other constants we find that an electrolytic solution appears + to contain <i>n′</i> gramme-molecules per litre, the real number of + chemical gramme-molecules in one litre of the solution will be only + <i>n′</i> / <i>i</i> = <i>n</i>.</p> + + <p>Very concentrated solutions do not conform to these laws. In this they + resemble gases, which as they approach their point of condensation tend + less and less to conform to the laws of gaseous pressure.</p> + + <p><i>Electrolysis.</i>—If we take a solution of an acid, a salt, + or a base, and dip into it two metallic rods, one connected to the + positive and the other to the negative pole of a battery, we <!-- Page 26 + --><span class="pagenum"><a name="page26"></a>{26}</span>find that the + metals or metallic radicals of the solution are liberated at the negative + pole, while the acid radicals of the salts and acids and the hydroxyl of + the bases are liberated at the positive pole. The liberated substances + may either be discharged unchanged, or they may enter into new + combinations, causing a series of secondary reactions.</p> + + <p><i>Electrolytes.</i>—Solutions which conduct electricity are + called Electrolytes, and the conducting metallic rods dipping into the + solution are the Electrodes. Faraday gave the names of Ions to the atoms + or atom-groups liberated at either electrode. The ions liberated at the + positive electrode are the Anions, and those at the negative electrode + are the Cations. The only solutions which possess any notable degree of + electrical conductivity are the aqueous solutions of the various salts, + acids, and bases, and in these solutions only do we meet with those + phenomena of dissociation which are evidenced by anomalies of osmotic + pressure, freezing point and the like,—anomalies which show that + the solution contains a greater number of molecules than that indicated + by its molecular concentration. These anomalies are due to dissociation, + the division of some of the molecules into fragments, each of which plays + the part of a separate molecule, contributing its quota to the osmotic + tension and vapour pressure of the solution, in fact to all the phenomena + which are dependent on the degree of molecular concentration. The + electrical conductivity of a solution is therefore proved to be dependent + on its molecular dissociation.</p> + + <p><i>Arrhenius' Theory of Electrolysis.</i>—In 1885, Arrhenius + brought forward his theory of the transport of electricity by an + electrolyte. According to this hypothesis, the electric current is + carried by the ions, the positive charges by the cations, and the + negative charges by the anions. In virtue of the attraction between + charges of different sign, and repulsion between charges of like sign, + the cations are repelled by the positive charge on the anode, and + attracted by the negative charge on the cathode. Similarly the anions are + repelled by the cathode and attracted by the anode. <!-- Page 27 --><span + class="pagenum"><a name="page27"></a>{27}</span></p> + + <p>An electrolytic solution contains three varieties of particles, + positive ions or cations, negative ions or anions, and undissociated + neutral molecules. The molecular concentration of such a solution, with + the corresponding constants, depends on the total number of these + particles, <i>i.e.</i> the sum of the ions and the undissociated neutral + molecules. We may indicate an ion by placing above it the sign of its + electrical charge, one sign for each valency. Thus Na<sup>+</sup> and + Cl<sup>-</sup> indicate the two ions of a salt solution; Cu<sup>++</sup> + and SO<sub>4</sub><sup>--</sup> the two ions of a solution of sulphate + of copper. A point is sometimes substituted for the + sign, and a comma + for the - sign. Thus Na<sup>.</sup> and Cl<sup>,</sup>; Cu<sup>..</sup> + and SO<sub>4</sub><sup>,,</sup>.</p> + + <p>My friend Dr. Lewis Jones has given a very vivid picture of the + processes which go on in an electrolytic solution when an electric + current is passing. He compares an electrolytic cell to a ballroom, in + which are gyrating a number of dancing couples, representing the neutral + molecules, and a number of isolated ladies and gentlemen representing the + anions and cations respectively. If we suppose a mirror at one end of the + ballroom and a buffet at the other, the ladies will gradually accumulate + around the mirror, and the gentlemen around the buffet. Moreover, the + dancing couples will gradually be dissociated in order to follow this + movement.</p> + + <p><i>Degree of Dissociation.</i>—The degree of dissociation is the + fraction of the molecules in the solution which have undergone + dissociation. Let <i>n</i> be the total number of molecules of the + solute, and <i>n″</i> the number of dissociated molecules. Then + <i>n″</i> / <i>n</i> = <i>a</i> will represent the degree of + dissociation. Let <i>k</i> be the number of ions into which each molecule + is split. Then <i>a</i> = <i>n″k</i> / <i>nk</i>, <i>i.e.</i> the + degree of dissociation is the ratio of the number of ions actually + present in a solution to the number which would be present if all the + molecules of the solute were dissociated.</p> + + <p>Let <i>n′</i> be the total number of particles present in a + solution <!-- Page 28 --><span class="pagenum"><a + name="page28"></a>{28}</span>containing <i>n</i> molecules, each of which + is composed of <i>k</i> ions. Then if <i>a</i> is the degree of + dissociation,</p> + + <div class="poem"> + <div class="stanza"> + <p><i>n′</i> = <i>n</i> - <i>an</i> + <i>ank</i>,</p> + <p><i>n′</i> = <i>n</i>[1 + <i>a</i> (<i>k</i> - 1)],</p> + <p><i>n′</i> / <i>n</i> = 1 + <i>a</i> (<i>k</i> - 1) = <i>i</i>.</p> + </div> + </div> + + <p>We thus obtain <i>i</i> the coefficient of dissociation, in terms of + the degree of dissociation <i>a</i> and the number of ions in each + molecule <i>k</i>.</p> + + <p>If there is no dissociation, <i>i.e.</i> if <i>a</i> = 0, then + <i>n′</i> = <i>n</i>, and <i>i</i> = 1. If all the molecules are + dissociated, <i>a</i> = 1, and <i>i</i> = <i>k</i>.</p> + + <p><i>Faraday's Law.</i>—Faraday found that the quantity of + electricity required to liberate one gramme-molecule of any radical is + 96.537 coulombs for each valency of the radical.</p> + + <p><i>Electrochemical Equivalent.</i>—The electrochemical + equivalent of a radical is the weight liberated by one coulomb of + electricity. It is equal to the molecular weight of the ion, divided by + 96.537 times its valency.</p> + + <p><i>Electrolytic Conductivity.</i>—The conductivity of an + electrolyte is the inverse of its resistance. C = 1/R.</p> + + <p>For a given difference of potential the conductivity of an electrolyte + is proportional to the number of ions in unit volume, the electrical + charge on each ion, and the velocity of the ions.</p> + + <p><i>The specific conductivity</i> <span class="grk">Δ</span> of + an electrolyte is the conductivity of a cube of the solution, each face + of which is one square centimetre in area. The <i>molecular + conductivity</i> of an electrolyte is the conductivity of a solution + containing one gramme-molecule of the substance placed between two + parallel conducting plates, one centimetre apart. The molecular + conductivity is independent of the volume occupied by the gramme-molecule + of the solute, depending only on the degree of dissociation. The + molecular conductivity U is equal to the product of V, the volume of the + molecule, by <span class="grk">Δ</span>, its specific conductivity. + U = V<span class="grk">Δ</span>. Whence <span + class="grk">Δ</span> = U / V, <i>i.e.</i> the specific <!-- Page 29 + --><span class="pagenum"><a name="page29"></a>{29}</span>conductivity + equals the molecular conductivity divided by the volume.</p> + + <p>The conductivity of an electrolyte is proportional to the number of + ions in a volume of the solution containing one gramme-molecule. Let + M<sub>∞</sub> be the conductivity for complete dissociation and + M<sub>v</sub> the molecular conductivity at the volume V. Then</p> + + <div class="poem"> + <div class="stanza"> + <p>M<sub>v</sub> / M<sub>∞</sub> = <i>n″k</i> / <i>nk</i> = <i>n″</i> / <i>n</i> = <i>a</i>,</p> + </div> + </div> + + <p>the degree of dissociation. This is Ostwald's law, which says that the + degree of dissociation is equal to the ratio of conductivity when the + gramme-molecule occupies a volume V, to its conductivity when the + solution is so dilute that dissociation is complete. Hence the degree of + dissociation may also be determined by comparing the electrical + conductivities of two solutions of different degrees of + concentration.</p> + + <div class="figcenter" style="width:47%;"> + <a href="images/Fig1.jpg"><img style="width:100%" src="images/Fig1.jpg" + alt="Fig. 1." title="Fig. 1." /></a> + <span class="sc">Fig. 1.</span>—Before the passage of the + current. + </div> + + <div class="figcenter" style="width:46%;"> + <a href="images/Fig2.jpg"><img style="width:100%" src="images/Fig2.jpg" + alt="Fig. 2." title="Fig. 2." /></a> + <span class="sc">Fig. 2.</span>—After the passage of the current. + </div> + + <p><i>Velocity of the Ions.</i>—If the electrolytic cell is divided + into two segments by means of a porous diaphragm, we shall find after a + time an unequal distribution of the solute on the two sides. For + instance, with a solution of sulphate of copper, after the current has + passed for some time there will be a diminution of concentration in the + liquid on both sides of the diaphragm, but the loss will be very + unequally divided. Two-thirds of the loss of concentration will be on the + side of the negative electrode and only one-third on the positive side. + In 1853, Hittorf gave the following ingenious explanation of this + phenomenon:— <!-- Page 30 --><span class="pagenum"><a + name="page30"></a>{30}</span></p> + + <p>Fig. 1 represents an electrolytic vessel containing a solution of + sulphate of copper, the vertical line indicating a porous partition + separating the vessel into two parts. Fig. 2 shows the same vessel after + the passage of the current. The acid radical has travelled twice as fast + as the metal. For each copper ion which has passed through the porous + plate towards the cathode two acid radicals have passed through it + towards the anode. Three ions have been liberated at either electrode, + but in consequence of the difference of velocity with which the positive + and the negative ions have travelled, the negative side of the vessel + contains only one molecule of copper sulphate and has lost two-thirds of + its molecular concentration, while the positive side contains two + molecules of copper sulphate and has only lost one-third of its + concentration. This proves clearly that the ions move in different + directions with different velocities. Let <i>u</i> be the velocity of the + anions, and <i>v</i> the velocity of the cations. Let <i>n</i> be the + loss of concentration at the cathode, and 1 - <i>n</i> the loss of + concentration at the anode. Then</p> + + <div class="poem"> + <div class="stanza"> + <p><i>u</i> / <i>v</i> = <i>n</i> / (1 - <i>n</i>),</p> + </div> + </div> + + <p><i>i.e.</i> the loss of concentration at the cathode is to the loss of + concentration at the anode as the velocity of the anions is to that of + the cations. Hence by measuring the loss of concentration at the two + electrodes, we have an easy means of determining the comparative velocity + of different ions.</p> + + <p>In 1876, Kohlrausch compared the conductivity of the chlorides, + bromides, and iodides of potassium, sodium, and ammonium respectively. He + found that altering the cation did not affect the <i>differences</i> of + conductivity between the three salts, thus showing that these differences + of conductivity were dependent on the nature of the anion only, and not + on the particular base with which it was combined. The difference of + conductivity between an iodide and a bromide, for example, is the same + whether potassium, sodium, or ammonium salts are compared. A similar + experiment has been made with a series of cations combined with various + anions. The difference of conductivity of the salts in the series is the + same whichever anion is used, <i>i.e.</i> the difference of conductivity + between potassium chloride and sodium chloride is the same as that + between <!-- Page 31 --><span class="pagenum"><a + name="page31"></a>{31}</span>potassium bromide and sodium bromide. Hence + we may conclude that the conductivity of any salt is an ionic + property.</p> + + <p>Kohlrausch's law may be expressed by the formula <i>c</i> = + <i>d</i>(<i>u</i> + <i>v</i>), where <i>c</i> is the conductivity of the + salt, <i>d</i> the degree of dissociation, <i>i.e.</i> the fraction of + the electrolyte broken up into ions, and <i>u</i> and <i>v</i> the + velocity of the anions and cations respectively. When all the molecules + of the electrolyte are dissociated, <i>d</i> = 1, and the formula becomes + <i>c</i><sub>∞</sub> = <i>u</i> + <i>v</i>.</p> + + <p>As we have already seen, a salt is formed by the union of a metal M + with an acid radical R. Potassium sulphate, K<sub>2</sub>SO<sub>4</sub>, + consists of the metal K<sub>2</sub> and the acid radical SO<sub>4</sub>. + Ammonium chloride, NH<sub>4</sub>Cl, consists of the basic radical + NH<sub>4</sub> and the acid radical Cl. The various acids may be + considered as salts of the metal hydrogen. Thus sulphuric acid, + H<sub>2</sub>SO<sub>4</sub>, is the sulphate of hydrogen. Bases may be + considered as salts with the hydroxyl group, OH, replacing the acid + radical. Thus potash, KOH, is the hydroxyl of potassium. The various + electrolytic combinations may be represented by the following + symbols:—</p> + + <div class="poem"> + <div class="stanza"> + <p>Salts = MR.</p> + <p>Acids = HR.</p> + <p>Bases = MOH.</p> + </div> + </div> + + <p>The various chemical reactions of an electrolyte are all ionic + reactions, the chemical activity of an electrolytic solution being + proportional to its electric conductivity, <i>i.e.</i> the degree of + dissociation of its ions. The acidity of an electrolytic solution is due + to the presence of the dissociated ion H<sup>+</sup>, and its strength is + determined by the concentration of these free hydrogen ions. Hence the + greater the degree of dissociation the stronger the acid.</p> + + <p>The basic character of a solution is determined by the presence of the + hydroxyl radical OH<sup>-</sup>. The greater the concentration of the + hydroxyl ions, <i>i.e.</i> the greater the dissociation, the stronger is + the base.</p> + + <p>The ions H<sup>+</sup> and OH<sup>-</sup> are of special importance, + since they are the ions of water, H<sub>2</sub>O = H<sup>+</sup> + + OH<sup>-</sup>. The degree of <!-- Page 32 --><span class="pagenum"><a + name="page32"></a>{32}</span>dissociation of pure water is but small. + Water is, however, the most important of all the various agents in the + chemical reactions of life, since a large number of organic substances + are decomposed by water by a process of hydrolysis, and a vast number of + organic substances are but combinations of carbon with the ions + H<sup>+</sup> and OH<sup>-</sup>, their diversity being due to variations + in the relative proportions and grouping.</p> + + <p><i>The Chemical, Therapeutic, and Toxic Actions of Ions.</i>—The + chemical, therapeutic, antiseptic, and toxic actions of electrolytic + solutions are almost exclusively due to ionization. Take, for instance, a + solution of nitrate of silver in which the addition of chlorine produces + a white precipitate of chloride of silver. This precipitate occurs only + when the solution added is one such as NaCl, where the chlorine is + present as the free ion Cl<sup>-</sup>. No such precipitate is produced + in a solution of chlorate of potassium or chloracetic acid, where the + chlorine is entangled in the complex ion ClO<sub>3</sub> or + C<sub>2</sub>H<sub>3</sub>ClO<sub>2</sub>.</p> + + <p>Since, then, the toxic and pharmacological properties of an + electrolyte depend entirely on the ionic grouping, it behoves the + physician and the biologist to study the structure and grouping of the + ions in a molecule, rather than that of the atoms. Consider for a moment + the totally different properties of the phosphides and the phosphates. + The former are extremely toxic, while the latter are perfectly harmless. + There is not the slightest analogy between their actions on the living + organism. On the other hand, all the phosphides produce the same toxic + and therapeutic effects, whatever the cation with which they are united. + Their toxic properties are derived from the presence of the free + phosphorus ion P<sup>---</sup>. The phosphates contain phosphorus in + the same proportion as the phosphides, but this phosphorus is harmlessly + entangled in the complex ion PO<sub>4</sub><sup>---</sup>, whose + properties are absolutely different from those of the ion + P<sup>---</sup>.</p> + + <p>The above considerations apply equally to the chlorides and chlorates, + the iodides and iodates, the sulphides and sulphates, and in general to + all chemical salts. <!-- Page 33 --><span class="pagenum"><a + name="page33"></a>{33}</span></p> + + <p>The question has an intimate bearing on practical pharmacology. When + we prescribe a cacodylate or an amylarsinate, we are not prescribing an + arsenical treatment whose effects can be compared with those of an + arsenide, an arsenite, or an arsenate. This fact is sufficiently + indicated by the difference in the toxic doses of the different salts. + Each variety of arsenical ion has its own special physiological and + therapeutic properties. We do not expect to obtain the results of a + ferruginous treatment from the administration of a ferrocyanide or a + ferricyanide. Both contain iron, it is true, but neither possess the + properties of the cation Fe<sup>+++</sup>, but rather those of the + complex anion of which they form a part.</p> + + <p>We have already said that most of the therapeutic, toxic, and caustic + actions of an electrolyte are due to ionic action, and the substances can + therefore have no toxic action unless they are dissociated. Many of the + solvents employed in medicine, such as alcohol, glycerine, vaseline, and + chloroform dissolve the electrolytes but do not dissociate them into + ions, and these solutions therefore do not conduct electricity. Such + solutions have no therapeutic action. With the absence of dissociation + all the ionic toxic and caustic effects also disappear entirely, and only + re-appear as the water of the tissue is able slowly to effect the + necessary dissociation.</p> + + <p>Carbolic acid dissolved in glycerine is hardly caustic and but very + slightly toxic. We have met with several instances in which a + tablespoonful of carbolized glycerine, in equal parts, has been swallowed + without any ill effect, either caustic or toxic, whereas the same dose + dissolved in water would have been fatal. This absence of dissociation + has enabled the surgeon Mencière to inject carbolic and glycerine in + equal proportions into the larger joints, the part being subsequently + washed out with pure alcohol. Thus by employing vaseline, oil, or + glycerine as a solvent, and avoiding the access of water, we are able to + use electrolytic antiseptics in very concentrated form. Their action is + brought out very slowly, as the water of the organism effects the + necessary dissociation of the electrolyte. <!-- Page 34 --><span + class="pagenum"><a name="page34"></a>{34}</span></p> + + <p>Since all chemical, toxic, and therapeutic actions are ionic, they are + proportional to the degree of ionic concentration, <i>i.e.</i> to the + number of ions in a given volume. The only point of importance, that + which determines their activity, whether chemical or therapeutic, is the + degree of ionization or dissociation. For example, all acids have the + same cation H<sup>+</sup>. They have all identical properties, but they + differ widely in the intensity of their action. There are weak acids such + as acetic acid, and strong acids like sulphuric acid. The stronger acids + are those which are more thoroughly dissociated, and in which the ion + H<sup>+</sup> is very concentrated; whereas the feeble acids are but + slightly dissociated, so that the ion H<sup>+</sup> is less + concentrated.</p> + + <p>Paul and Krönig have shown that the bactericidal action of different + salts also varies with their degree of dissociation, <i>i.e.</i> with the + concentration of the active ions. They made a series of observations on + the bactericidal action of various salts of mercury, the bichloride, the + bibromide, and the bicyanide, on the spores of <i>Bacillus anthracis</i>. + The following results were obtained from a comparison of solutions + containing 1 gramme-molecule of the salt in 64 litres of water. With the + bichloride solution, after exposure to the solution for twenty minutes, + only 7 colonies of the bacillus were developed. After exposure to a + similar solution of the bibromide the number of colonies was 34. The + antiseptic action of the bichloride was therefore five times as great as + that of the bibromide. The bicyanide of mercury, however, even when four + times as concentrated, permitted the growth of an enormous number of + colonies, showing that it had no appreciable antiseptic action whatever. + Nevertheless, the proportion of Hg is the same in all the solutions, and + if there were any difference one would naturally expect that the ion + Cy<sup>-</sup> would be more toxic than Cl<sup>-</sup> or Br<sup>-</sup>. + The real condition which varies in these solutions and determines their + activity is the degree of dissociation. The whole of the antiseptic + property resides in the ion Hg<sup>++</sup>. This ion is very <!-- Page + 35 --><span class="pagenum"><a name="page35"></a>{35}</span>concentrated + in the highly dissociated solution HgCl<sub>2</sub>, less concentrated in + the less ionized solution HgBr<sub>2</sub>, and exceedingly dilute in the + HgCy<sub>2</sub>, which is hardly ionized at all.</p> + + <p>What is true of the bactericidal action of the salts of mercury is + equally true of their therapeutic effect. It is a great mistake to + estimate the medicinal activity of a solution of a salt of mercury, or + indeed of any electrolytic solution, simply by its degree of molecular + concentration. The important point is the degree of dissociation, which + is the only true measure of its activity. In the intramuscular injection + of mercury salts it is by no means a matter of indifference what salt we + employ. A salt should be used such as the bichloride or the biniodide, + which is easily dissociated. Other salts are often employed because they + occasion less pain at the site of injection; but the pain is a sign of + the degree of activity of the preparation. The pain, it is true, may be + avoided by using a salt which is less easily dissociated, or in which the + mercury is bound up in a complex ion, but by so doing we diminish the + efficacy of the remedy. It is moreover quite easy to diminish, or even + entirely to suppress, the pain, by using a very dilute solution of an + active ionized salt. A one-half per cent. or even one-quarter per cent. + solution of the bichloride or biniodide of mercury may be injected very + slowly in sufficient quantity without producing the slightest discomfort. + Local action depends entirely on ionic concentration. One drop of pure + sulphuric acid will destroy the skin, whereas the same amount if diluted + in a tumblerful of water will furnish a refreshing drink.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 36 --><span class="pagenum"><a name="page36"></a>{36}</span></p> + +<h3>CHAPTER IV</h3> + +<p class="cenhead">COLLOIDS</p> + + <p>As we have already seen, living organisms are formed essentially of + liquids. These liquids are solutions of crystallizable substances or + crystalloids, and non-crystallizable substances or colloids—a + classification which we owe to Graham.</p> + + <p>The liquids are the most important constituents of a living organism, + since they are the seat of all the chemical and physical phenomena of + life. The junction of two liquids of different concentration is the arena + in which takes place both the chemical transformation of matter and the + correlative transformation of energy. In a former chapter we have passed + in review the class of crystalloids, we will now turn our attention to + the characteristic properties of colloids.</p> + + <p><i>Colloids.</i>—Colloids differ from crystalloids in that they + do not form crystals from solution, being completely amorphous when in + the solid state. The solution of a colloid solidifies in the same form + which it possessed in the liquid state, the solvent being enclosed in the + meshes of a sort of network formed by the solute. This form is + approximately retained even after the water has evaporated by drying, the + passage from the liquid state of solution to the solid state being + effected through a series of intermediary states, such as a clot, + coagulum, or jelly. This passage from the state of solution into a state + of jelly is called coagulation. Some colloids, such as gelatine, + coagulate with cold; while others, such as egg-albumin, coagulate with + heat. Some, like the caseine of milk, require the addition of certain + chemical substances to set up coagulation; while still others, such as + the fibrin of blood, appear to coagulate spontaneously. The physical + phenomena of <!-- Page 37 --><span class="pagenum"><a + name="page37"></a>{37}</span>coagulation are still but little understood. + In some cases it is a reversible phenomenon, thus gelatine coagulated by + cold is redissolved by heat; whereas with other colloids the process is + irreversible, albumin coagulated by heat is not redissolved on + cooling.</p> + + <p>Colloids in a state of coagulation have a vacuolar or sponge-like + structure. The solvent is imprisoned in the vacuoles of the clot, and is + expelled little by little by its retraction. Colloids diffused in water + are usually called colloidal solutions, but they are not true solutions. + Such a pseudo-solution of a colloid is called a "sol," while a colloid in + a state of coagulation is called a "gel." Colloidal solutions spread but + little, diffuse very slowly in the liquids of the body, and cannot + penetrate organic membranes.</p> + + <p>Colloidal solutions diffuse light, unlike crystalloid solutions, which + are transparent. We all know how the trajectory of a beam of sunlight + through a darkened room is rendered visible by the particles of dust. In + the same way if a colloidal solution is illuminated by a transverse ray + of light, the light is diffused by the molecules of the colloid in + semi-solution, and the liquid appears faintly illuminated on a dark + background. The light diffused by a colloidal solution is polarized, + which shows that it is reflected light,</p> + + <p>Siedentopf and Sigmondy have applied this principle of lateral + illumination on a dark background to the construction of the + ultra-microscope. With the aid of this instrument we may not only see, + but count the particles in a colloidal solution, which is in reality + merely a pseudo-solution or suspension, in contradistinction to the true + solution of a crystalloid.</p> + + <p>Colloidal solutions possess only a very feeble osmotic pressure. The + lowering of the freezing point and the other corresponding constants are + also quite insignificant. This arises from the fact that the molecules of + a colloid are extremely large when compared with those of a crystalloid. + For example let us take colloidal substance whose molecular weight is + 2000. A solution containing 40 grammes per litre would have an osmotic + pressure only one-fiftieth of that of a <!-- Page 38 --><span + class="pagenum"><a name="page38"></a>{38}</span>solution of similar + strength of a crystalloid whose molecular weight was 40.</p> + + <p>Not only so, but on measuring the molecular concentration, the osmotic + pressure, and the other constants of a colloidal solution, we find values + even lower than those which we should expect from a consideration of its + molecular weight. This is probably due to the tendency of a colloid to + polymerization, i.e. to form groups or associations of molecules. + Suppose, for instance, that the molecules of a colloidal solution are + aggregated into groups of ten. Since each group plays the part of a + simple molecule, the osmotic pressure will be ten times less than that + corresponding to the quantity of the solute present. Such a group of + molecules is called by Naegeli a "micella."</p> + + <p>Similar phenomena of aggregation may be observed in the molecules of + many inorganic substances. The molecule of iodine, for example, is + monatomic at 1200° C., but becomes diatomic at the ordinary temperature. + Sulphur at 860° C. is a gas with a vapour density of 2.2, while at 500° + C. its vapour density rises to 6.6. In both of these cases two or more + molecules of the element have been condensed into one as a result of the + fall of temperature.</p> + + <p>We frequently find that two successive cryoscopic observations on the + freezing point of the same colloidal solution will vary. This is due to + the extreme sensitiveness of the micellæ, which absorb or abandon their + extra molecules under the slightest influence. This mobility in the + constitution of the micellæ appears to be one of the principal causes of + the peculiar properties of colloidal solutions.</p> + + <p>The phenomenon of polymerization appears to be reversible. The micellæ + are formed under certain conditions, and are disintegrated when these + conditions are removed. The osmotic pressure varies in the same manner, + diminishing with polymerization and augmenting with the disintegration of + the micellæ. One may easily understand what an important rôle is played + by this alternate polymerization and disintegration in the phenomena of + life.</p> + + <p>Most colloidal substances are precipitated from their solutions by the + addition of very small quantities of electrolytic <!-- Page 39 --><span + class="pagenum"><a name="page39"></a>{39}</span>solutions. + Non-electrolytic solutions do not appear to provoke this precipitation. + This is not a chemical action, for an exceedingly small quantity of an + electrolyte is able to precipitate an indefinite quantity of the colloid. + The precipitation is probably due to the electric charges carried by the + dissociated ions of the electrolytes.</p> + + <p>When an electric current is passed through a colloid solution, the + course of the molecules of the colloid is sometimes towards the cathode + and sometimes towards the anode, according to the nature of the colloid + and of the solvent. This displacement would appear to indicate a + difference of electric potential between the molecules of the colloid and + those of the solvent. Hardy has shown that in an alkaline solution the + molecules of albumin travel towards the anode, while in an acid solution + they travel towards the cathode.</p> + + <p><i>Metallic Colloids.</i>—Carey Lea and afterwards Credé + succeeded in obtaining silver in colloidal solution by ordinary chemical + means. Professor Bredig has introduced a more general method of obtaining + a number of metals in colloidal solutions in a state of great purity. He + causes an electric arc to pass between two rods of the metal immersed in + distilled water. The cathode is thus pulverized into a very fine powder + which rests in suspension in the liquid, constituting a colloidal + solution. Bredig has in this way prepared sols of platinum, palladium, + iridium, silver, and cadmium.</p> + + <p><i>Catalytic Properties of Colloids.</i>—Catalysis is the + property possessed by certain bodies of initiating chemical reaction. The + mass of the catalyzing body has no definite proportion to that of the + substances entering into the reaction, and the appearance of the + catalyzer is in no way altered by the reaction.</p> + + <p>Ostwald has shown that catalysis consists essentially in the + acceleration or retardation of chemical reactions which would take place + without the action of the catalyzer, but more slowly.</p> + + <p>Catalytic reactions are very numerous in chemistry. The inversion of + sugar by acids, the etherization of alcohol by sulphuric acid, the + decomposition of hydrogen peroxide by <!-- Page 40 --><span + class="pagenum"><a name="page40"></a>{40}</span>platinum black are all + instances of catalysis. Fermentation by means of a soluble ferment or + diastase, a phenomenon which may almost be called vital, is also a + catalytic action. The action of pepsin, of the pancreatic ferment, of + zymase, and of other similar ferments has a great analogy with the purely + physical phenomenon of catalysis. The diastases are all colloids, and so + are many other catalyzers.</p> + + <p>A catalyzer is a stimulus which excites a transformation of energy. + The catalyzer plays the same rôle in a chemical transformation as does + the minimal exciting force which sets free the accumulation of potential + energy previous to its transformation into kinetic energy. A catalyzer is + the friction of the match which sets free the chemical energy of the + powder magazine.</p> + + <p>Bredig has studied the catalytic decomposition of hydrogen peroxide by + metallic colloids prepared by his electric method. He found that 1 + atom-gramme of colloidal platinum gives a sensible catalytic effect when + diluted with 70 million litres of water. Caustic soda and other chemical + substances inhibit the catalytic action of colloidal platinum in the same + way as they inhibit the fermenting action of diastase. The curve of + decomposition of hydrogen peroxide by colloidal platinum may be compared + with the curve of fermentation by emulsin. Both are equally affected by + the addition of an alkali. Many other chemical and physical agents have a + similar inhibitory action on the catalysis of colloidal metals and on + diastasic fermentation. Thus a mere trace of sulphuretted hydrogen or + hydrocyanic acid will paralyse the action of a colloidal metal, just as + it does that of a ferment. This is what Bredig calls the poisoning of + metallic ferments.</p> + + <p>We may hope that the further study of catalysis, a purely + physico-chemical phenomenon, may throw more light on the mechanism of + diastasic fermentation, which is essentially a vital reaction.</p> + + <p>It must not be forgotten that all classification is artificial and + arbitrary, and only to be used as long as it facilitates study. This + observation is particularly applicable to the classification of + substances into crystalloids and colloids. <!-- Page 41 --><span + class="pagenum"><a name="page41"></a>{41}</span>There is no sharp line + between the two groups, the passage is gradual, and it is impossible to + say where one group ends and the other begins. Many colloids such as + hæmoglobin are crystallizable, and many crystallizable substances are + coagulable. Many substances appear at one time in the crystalloid state + and at another time in the colloidal state, so that instead of dividing + substances into colloids and crystalloids, we should rather consider + these expressions as denoting different phases assumed by the same + substance.</p> + + <p>In order to define clearly our various classes and divisions, we are + apt to exaggerate slight differences of properties or composition. We say + that colloids have no osmotic pressure, whereas in fact the osmotic + pressure of the colloids though feeble plays a very important part in the + phenomena of life.</p> + + <p>So in other departments of science—a factor which is almost + infinitesimal may yet exercise a vast influence on the results. It is by + infinitesimal variations of pressure, a thousandth of a millimetre or + less, that we obtain the various degrees of penetration in the Röntgen + rays.</p> + + <p>The division into solutions and pseudo-solutions or suspensions is + also an arbitrary one. A true solution is also a suspension of the + molecules of the solute. There is no essential difference between a + solution and a suspension, but only a difference in the size of the + molecules, or agglomerations of molecules, in one case so small as to be + transparent, and in the other case just big enough to diffuse light. + There are moreover many properties common to colloidal solutions and + suspensions of fine powders, such as kaolin, mastic, charcoal, or Indian + ink. These particles in suspension are precipitated by solutions of + electrolytes in a manner similar to the coagulation of colloids.</p> + + <p>The surface of every liquid is covered by a very thin layer, a sort of + membrane slightly differentiated from the rest of the liquid. This + membrane may be a chemical one, a pellicular precipitate like that which + is formed by the contact of two membranogenous liquids. On the other + hand, the membrane may not differ from the subjacent liquid in chemical + composition, but only in physical properties. If we <!-- Page 42 --><span + class="pagenum"><a name="page42"></a>{42}</span>consider the molecules in + the middle of a liquid, each molecule is subjected to the cohesive + attraction of molecules on every side, attractions which neutralize one + another. At the surface of the liquid, however, there are quite other + conditions of equilibrium. There each molecule is drawn downwards towards + the centre of the liquid, and there is no compensating attraction in an + opposite direction. The resultant pressure is normal to the surface of + the liquid, and is mechanically equivalent to an elastic membrane which + tends to diminish the surface, and hence the volume of the liquid. We may + therefore regard this surface tension as acting the part of a veritable + physical membrane.</p> + + <p>There is a still further differentiation of the surface of a liquid. + When the liquid is not a simple one, but complex as in a solution, we + find that the concentration of the solute is greater at the surface than + in the interior. This is the so-called phenomenon of "adsorption," which + is another cause for the production of a physical membrane covering the + surface of a liquid.</p> + + <p>Substances in a colloidal state have a great tendency to form these + chemical or physical membranes at the point of contact between the + colloidal solute and the solvent. This is probably the reason why the + coagulum of a colloidal liquid usually presents a vacuolar or spongy + structure.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 43 --><span class="pagenum"><a name="page43"></a>{43}</span></p> + +<h3>CHAPTER V</h3> + +<p class="cenhead">DIFFUSION AND OSMOSIS</p> + + <p><i>Diffusion and Osmosis.</i>—If we place a lump of sugar in the + bottom of a glass of water, it will dissolve, and spread by slow degrees + equally throughout the whole volume of the liquid. If we pour a + concentrated solution of sulphate of copper into the bottom of a glass + vessel, and carefully pour over it a layer of clear water, the liquids, + at first sharply separated by their difference of density, will gradually + mix, so as to form a solution having exactly the same composition in all + parts of the jar. The process whereby the sugar and the copper sulphate + spread uniformly through the whole mass of the liquid in opposition to + gravity is called Diffusion. This diffusion of the solute is a phenomenon + exactly analogous to the expansion of a gas. It is the expression of + osmotic pressure, or rather of the difference of the osmotic pressure of + the solute in different parts of the vessel. The molecules of the solute + move from a place where the osmotic pressure is greater towards a + position where the osmotic pressure is less. The water molecules on the + other hand pass from positions where the osmotic pressure of the solute + is less towards positions where it is greater. As a consequence of this + double circulation the osmotic pressure tends to become equalized in all + parts of the vessel.</p> + + <p>Diffusion appears to be the fundamental physical phenomenon of life. + It is going on continually in the tissues of all living beings, and a + study of the laws of diffusion and osmosis is therefore absolutely + necessary for a just conception of vital phenomena.</p> + + <p><i>Coefficient of Diffusion.</i>—The coefficient of diffusion + has <!-- Page 44 --><span class="pagenum"><a + name="page44"></a>{44}</span>been defined by Fick as the quantity of a + solute which in one second traverses each square centimetre of the cross + section of a column of liquid 1 centimetre long, between the opposite + sides of which there is unit difference of concentration. Nernst in his + definition substitutes "unit difference of osmotic pressure" for "unit + difference of concentration."</p> + + <p>Until recently it was generally believed that diffusion took place in + colloids and plasmas just as in pure water. This is, however, by no means + the case: the differences are considerable. When a solute is introduced + into a colloidal solution, the greater the concentration of the colloid + the slower will be the diffusion. This may be shown by a simple + experiment. Several glass plates are prepared, by spreading on each a + solution of gelatine of different concentration, to which a few drops of + phenol phthalein have been added. If now a drop of an alkaline solution + be placed on each plate, we can see that the drop diffuses more slowly + through the more concentrated gelatine solution, since the presence of + the alkali is rendered visible by the coloration of the phenol phthalein. + A similar demonstration may be made by allowing drops of acid to diffuse + through solutions of gelatine made slightly alkaline and coloured with + phenol phthalein. In general, we find on experiment that when similar + drops of any coloured or colouring solution are left for an equal time on + plates of gelatine of different degrees of concentration, the greater the + concentration of the gelatine the smaller will be the circle of + coloration obtained.</p> + + <p>We may show that the rapidity of diffusion diminishes as the + gelatinous concentration increases, by another experiment. If we put side + by side on our gelatine plate a drop of sulphate of copper and another of + ferrocyanide of potassium, the point of contact of the two fluids will be + sharply marked by a line of precipitate. We find that under similar + conditions the time between the sowing of the drops and the formation of + this line of precipitate is longer when the gelatine is more + concentrated.</p> + + <p><i>Osmosis.</i>—In 1748, l'Abbé Nollet discovered that when a + pig's bladder filled with alcohol was plunged into water, the <!-- Page + 45 --><span class="pagenum"><a name="page45"></a>{45}</span>water passed + into the bladder more rapidly than the alcohol passed out; the bladder + became distended, the internal pressure increased, and the liquid spirted + out when the bladder was pricked by a pin. This passage of certain + substances in solution through an animal membrane is called Osmosis, and + membranes which exhibit this property are called osmotic membranes.</p> + + <p><i>Precipitated Membranes.</i>—In 1867, Traube of Breslau + discovered that osmotic membranes could be made artificially. Certain + chemical precipitates such as copper ferrocyanide can form membranes + having properties analogous to those of osmotic membranes. With these + precipitated membranes Traube made a number of interesting experiments. + These have lately been collected in the volume of his memoirs published + by his son.</p> + + <p><i>Osmotic Membranes.</i>—Osmotic membranes were formerly called + semi-permeable membranes, being regarded as membranes which allow water + to pass through them, but arrest the passage of the solute. This + definition is inexact, since no membrane permeable to water is absolutely + impermeable to the solutes. All we can say is that certain membranes are + more permeable to water than to the substances in solution, and are + moreover very unequally permeable to the various substances in solution. + As a rule a membrane is much more permeable to a solute whose molecule is + of small dimensions. Molecules of salt, for instance, pass through such a + membrane much more quickly than do those of sugar. The term "osmotic + membrane" should therefore in all cases replace that of "semi-permeable + membrane."</p> + + <p>Osmotic membranes behave exactly like colloids. The resistance which + they oppose to the passage of different substances varies with the nature + of the liquid or solute concerned. There is no real difference between + the passage of a solution through an osmotic membrane and its diffusion + through a colloid. The protoplasm of a living organism, being a colloid, + acts exactly like an osmotic membrane so far as regards the distribution + of solutions and substances in solution. <!-- Page 46 --><span + class="pagenum"><a name="page46"></a>{46}</span></p> + + <p>The diffusion of molecules through a colloid, a plasma, or a membrane + is governed by laws precisely analogous to Ohm's law, which governs the + transport of electricity. The intensity or rapidity of diffusion is + proportional to the difference of osmotic pressure, and varies inversely + with the resistance.</p> + + <p>In the case of molecular diffusion, however, the rapidity of diffusion + depends also on the size and nature of the molecules of the diffusing + substance. The theory of the resistance of the various plasmas and + membranes to diffusion has been but little understood; we can discover + hardly any reference to it in the literature of the subject.</p> + + <p>The laws of diffusion apply equally to the diffusion of ions. Nernst + has shown that there is a difference of electric potential at the surface + of contact of two electrolytic solutions of different degrees of + concentration. Both the positive and negative ions of the more + concentrated solution pass into the less concentrated solution, but the + ions of one sign will pass more rapidly than those of the other sign, + because being smaller, they meet with less resistance.</p> + + <p>The resistance of the medium plays a most important part in all the + phenomena of diffusion. When two solutions of different concentration + come into contact, the interchange of molecules and ions which occurs is + unequal owing to the differences in resistance. Hence both solutions + become modified not only in concentration but also in composition. It has + long been known that diffusion can cause the decomposition of certain + easily decomposed substances, and it would appear probable that diffusion + is also capable of producing new chemical combinations.</p> + + <p>The separation of the liberated ions in consequence of the unequal + resistance which they meet with in the medium they traverse often + determines chemical reaction. This ionic separation is a fertile agent of + chemical transformation in the living organism, and may be the + determinant cause in those chemical reactions which constitute the + phenomena of nutrition.</p> + + <p>When different liquids come into contact there are two distinct series + of phenomena, those due to osmotic pressure and those due to differences + of chemical composition. Even <!-- Page 47 --><span class="pagenum"><a + name="page47"></a>{47}</span>with isotonic solutions there will be a + transfer of the solutes if these are of different chemical constitution. + Take, for instance, two isotonic solutions, one of salt and another of + sugar. When these are brought into contact there is no transference of + water from one solution to the other, but there is a transference of the + solutes. In the salt solution the osmotic pressure of the sugar is zero. + Hence the difference of osmotic pressure of the sugar in the two + solutions will cause the molecules of sugar to diffuse into the salt + solution. For the same reason the salt will diffuse into the sugar + solution.</p> + + <p>A disregard of this fact, that a solute will always pass from a + solution where its osmotic pressure is high, into <span + class="correction" title="Original reads 'on'.">one</span> where its + osmotic pressure is low, is a frequent source of error. Thus it is said + to be contrary to the laws of osmosis that solutes should pass from the + blood, with its low osmotic pressure, into the urine, where the general + osmotic pressure is higher; the more so because in consequence of the + exchange the osmotic pressure of the urine is still further increased. + Such an exchange, it is argued, is contrary to the ordinary laws of + physics, and can therefore only be accomplished by some occult vital + action. This, however, is not the fact, as is proved by experiment.</p> + + <p>Consider an inextensible osmotic cell containing a solution of sugar, + the walls of the cell being impermeable to sugar but permeable to salt. + Let us plunge such a cell into a solution of salt, which has a lower + osmotic pressure than the sugar solution. Since the walls of the cell are + inextensible, the quantity of water in the cell cannot increase. The + salt, however, will pass into the cell, since the osmotic pressure of the + salt is greater on the outside than on the inside, and the walls are + permeable to the molecules of salt. This passage will continue until the + osmotic pressure of the salt is equal inside and outside the cell; at the + same time the total osmotic pressure within the cell will have increased, + in spite of its being originally greater than the osmotic pressure + outside.</p> + + <p><i>Plasmolysis.</i>—We all know that a cut flower soon dries + <!-- Page 48 --><span class="pagenum"><a name="page48"></a>{48}</span>up + and fades. When, however, we place the shrivelled flower in water, the + contracted protoplasm swells up again and refills the cells, which become + turgid, and the flower revives. This phenomenon is due to the fact that + vegetable protoplasm holds in solution substances like sugars and salts + which have a high osmotic pressure. Consequently water has a tendency to + penetrate the cellular walls of plants, to distend the cells and render + them turgescent. De Vries has used this phenomenon for the measurement of + osmotic tension. He employs for this purpose the turgid cells of the + plant <i>Tradescantia discolor</i>. The cells are placed under the + microscope and irrigated with a solution of nitrate of soda. On gradually + increasing the concentration of the solution there comes a moment when + the protoplasmic mass is seen to contract and to detach itself from the + walls of the cell. This phenomenon, which is known as plasmolysis, occurs + at the moment when the solution of nitrate of soda begins to abstract + water from the protoplasmic juice, <i>i.e.</i> when the osmotic tension + of the nitrate of soda becomes greater than that of the protoplasmic + liquid. So long as the osmotic tension of the soda solution is less than + that of the protoplasm, there will be a tendency for water to penetrate + the cell wall and swell the protoplasm. When the osmotic tension of the + solution which bathes the cell is identical with that of the cellular + juice, there is no change in the volume of the protoplasm. In this way we + are able to determine the osmotic pressure of any solution. We have only + to dilute the solution till it has no effect on the protoplasm of the + vegetable cells. Since the osmotic tension of this protoplasm is known, + we can easily calculate the osmotic tension of the solution from the + degree of dilution required.</p> + + <p><i>Red Blood Corpuscles as Indicators of Isotony.</i>—In 1886, + Hamburger showed that the weakest solutions of various substances which + would allow the deposition of the red blood cells, without being dilute + enough to dissolve the hæmoglobin, were isotonic to one another, and also + to the blood serum, and to the contents of the blood corpuscles. This is + Hamburger's method of determining the osmotic <!-- Page 49 --><span + class="pagenum"><a name="page49"></a>{49}</span>tension of a liquid. The + diluted solution is gradually increased in strength until, when a drop of + blood is added to it, the corpuscles are just precipitated, and no + hæmoglobin is dissolved.</p> + + <p><i>The Hæmatocrite.</i>—In 1891, Hedin devised an instrument for + determining the influence of different solutions on the red blood + corpuscles. This instrument, the hæmatocrite, is a graduated pipette, + designed to measure the volume of the globules separated by + centrifugation from a given volume of blood under the influence of the + liquid whose osmotic pressure is to be measured. The method depends on + the principle that solutions isotonic to the blood corpuscles and to the + blood serum will not alter the volume of the blood corpuscles, whereas + hypertonic solutions decrease that volume.</p> + + <p><i>Action of Solutions of Different Degrees of Concentration on Living + Cells</i>.—We have just seen that a living cell, whether vegetable + or animal, is not altered in volume when immersed in an isotonic solution + that does not act upon it chemically. When immersed in a hypertonic + solution, it retracts; in a slightly hypotonic solution it absorbs water + and becomes turgescent, while in a very hypotonic solution it swells up + and bursts. In a hypertonic solution the red blood cells retract and fall + to the bottom of the glass, the rapidity with which they are deposited + depending on the amount of retraction. In a hypotonic solution they swell + up and burst, the hæmoglobin dissolving in the liquid and colouring it + red. This is the phenomenon of hæmatolysis. According to Hamburger, the + serum of blood may be considerably diluted with water before producing + hæmatolysis. Experimenting with the blood of the frog, he found that the + globules remained intact in size and shape when irrigated with a salt + solution containing .64 per cent. of salt, this solution being isotonic + with the frog's blood serum. On the other hand, they did not begin to + lose their hæmoglobin till the proportion of salt was reduced to below + .22 per cent. Thus frog's serum may be diluted with 200 per cent. of + water before producing hæmatolysis. In mammals the blood corpuscles + remain invariable in a salt solution of about .9 per cent., and begin to + lose their <!-- Page 50 --><span class="pagenum"><a + name="page50"></a>{50}</span>hæmoglobin approximately in a .6 per cent. + solution. A solution of .9 per cent. of NaCl is therefore isotonic to the + contents of the red blood corpuscles, to the serum of the blood, and to + the cells of the tissues. It by no means follows that the cells of the + blood and tissues undergo no change when irrigated with a .9 per cent. + solution of chloride of sodium. They do not lose or gain water, it is + true, and they retain their volume and their specific gravity. But they + do undergo a chemical alteration, by the exchange of their electrolytes + with those of the solution. Hamburger has pointed out that in mammals the + shape of the red corpuscles is altered in every liquid other than the + blood serum; even in the lymph of the same animal there is a diminution + of the long diameter, and an increase of the shorter diameter, while the + concave discs become more spherical.</p> + + <p>All the cells of a living organism are extremely sensitive to slight + differences of osmotic pressure—the cells of epithelial tissue and + of the nervous system as well as the blood cells. For instance, the + introduction of too concentrated a saline solution into the nasal cavity + will set up rhinitis and destroy the terminations of the olfactory + nerves. Pure water, on the other hand, is itself a caustic. There is a + spring at Gastein, in the Tyrol, which is called the poison spring, the + "Gift-Brunnen." The water of this spring is almost absolutely pure, hence + it has a tendency to distend and burst the epithelium cells of the + digestive tract, and thus gives rise to the deleterious effects which + have given it its name. Ordinary drinking water is never pure, it + contains in solution salts from the soil and gases from the atmosphere. + These give it an osmotic pressure which prevents the deleterious effects + of a strongly hypotonic liquid. During a surgical operation it is of the + first importance not to injure the living surfaces by flooding them with + strongly hypertonic or hypotonic solutions. This precaution becomes still + more important when foreign liquids are brought into contact with the + delicate cells of the large surfaces of the serous membranes. Gardeners + are well aware of the noxious influence of a low osmotic pressure. They + water the soil around the roots of a plant, so that the water may take up + <!-- Page 51 --><span class="pagenum"><a + name="page51"></a>{51}</span>some of the salts from the soil before being + absorbed by the plant. Pure water poured over the heart of a delicate + plant may burst its cells owing to its low osmotic pressure. In many + medical and surgical applications, on the other hand, a low osmotic + pressure is of advantage. Thus, in order to remove the dry crusts of + eczema and impetigo, the most efficacious application is a compress of + cotton wool soaked in warm distilled water. Under the influence of such a + hypotonic solution the dry cells rapidly swell up, burst, and are + dissolved.</p> + + <p>Cooking is also very much a question of osmotic pressure. If salt is + put into the water in which potatoes and other vegetables are boiled, + osmosis is set up and a current of water passes from the vegetable cells + to the salt water. The cellular tissue of the vegetable becomes + contracted and dried, and the membranes become adherent, the vegetable + loses weight and becomes difficult of digestion, in consequence of its + hard and waxy consistency, which prevents the action of the digestive + juices. Vegetables should be cooked in soft water, and should be salted + after cooking. When so treated, a potato absorbs water, the cells swell + up, the skin bursts, the grains of starch also swell up and burst, and + the pulp becomes more friable. The digestive juice is thus able to + penetrate the different parts of the vegetable rapidly, and digestion is + facilitated. Any one can easily prove for himself that a potato boiled in + salt water diminishes in weight, whilst its weight increases when it is + cooked in soft water.</p> + + <p>The method of cryoscopy is also of considerable service in forensic + medicine. As shown by Carrara, the cryoscopy of the blood is an important + aid in determining the question whether a body found in the water was + thrown in before or after death. In the former case the concentration of + the blood will be much diminished. In certain experiments on dogs the + cryoscopic examination of the blood showed a freezing point of -.6° C. + The dog was then drowned, when the freezing point of the blood in the + left ventricle was increased to -.29° C., and that in the right ventricle + to -.42° C. On the other hand, when a dog was killed before being thrown + into the water, the <!-- Page 52 --><span class="pagenum"><a + name="page52"></a>{52}</span>osmotic pressure of the blood was hardly + decreased even after an immersion of 72 hours. In the case of persons or + animals drowned in sea water, a similar alteration of the point of + congelation is observed, but in the reverse direction. In this case the + osmotic pressure is raised considerably in those who are drowned, whereas + no such rise is observed in those who are thrown into the sea after + death.</p> + + <p>The circulation of the sap in plants and trees is also in great part + due to osmotic pressure. The aspiration of the water from the soil is due + to the intracellular osmotic pressure in the roots, which causes the sap + to rise in the stem of a plant as it would in the tube of a manometer. + From a knowledge of the osmotic pressure of the intracellular liquid of + the roots, we may calculate the height to which the sap can be raised in + the trunk of a tree, <i>i.e.</i> the maximum height to which the tree can + possibly grow. Suppose, for instance, the plasma of the rootlets has an + osmotic pressure of six atmospheres, corresponding to that of a 9 per + cent. solution of sugar. A pressure of six atmospheres is equal to the + weight of a column of water 6 × .76 × 13.596 = 61.95 metres high. This, + then, is the maximum height to which this osmotic pressure is able to + lift the sap. That is to say, a tree whose rootlets contain a solution of + sugar of 9 per cent. concentration, or its equivalent, can grow to a + height of 62 metres.</p> + + <p>Cryoscopy is also of great use in practical medicine, more especially + for the examination of the urine. The freezing point of urine varies from + -1.26° C. to -2.35°. Koryani has studied the ratio of the point of + congelation of urine to that of a solution containing an equal quantity + of chloride of sodium. He finds that the ratio (freezing point of urine) + / (freezing point of NaCl) increases when the circulation through the + tubules of the kidney is diminished.</p> + + <p>Hans Koeppe has shown that the hydrochloric acid of the gastric juice + is produced by the osmotic exchanges between the blood and the gastric + contents. The ion Na<sup>+</sup> of the salt in the stomach contents + exchanges with an ion H<sup>+</sup> of the monobasic salts of the blood, + NaHCO<sub>3</sub> + NaCl = HCl + Na<sub>2</sub>CO<sub>3</sub>. <!-- Page + 53 --><span class="pagenum"><a name="page53"></a>{53}</span></p> + + <p><i>Influence of Muscular Contraction on the Intramuscular Osmotic + Pressure.</i>—When a muscle is immersed in an isotonic salt + solution it does not change in weight. In a hypertonic solution it loses + weight in consequence of a loss of water, which passes from the muscle + into the solution to equalize the osmotic pressure. It gains weight in a + hypotonic solution, the water current setting towards the point of higher + concentration. It is easy, therefore, to tell whether the osmotic + pressure in a muscle is above or below that of a given solution, by + observing whether the muscle gains or loses weight when immersed in it. + Thus we may measure the osmotic pressure in a muscle by finding a salt + solution in which the muscle neither gains nor loses weight. In this way + we have been able to prove that the osmotic pressure of a tired muscle is + higher than that of the normal muscle. Our experiments were carried out + on the muscles of frogs. After having pithed the frog, one of the hind + legs is removed by a single stroke of the scissors. The leg is skinned, + dried with blotting paper, and weighed. It is then placed in a salt + solution whose freezing point is -.53° C. At 15° C. such a solution has + an osmotic pressure of 6.6 atmospheres. We next proceed to determine the + osmotic pressure of the corresponding leg after it has been tired by + muscular work. For this it is stimulated by an intermittent faradic + current passing once a second for five minutes. The leg is then skinned, + dried, weighed, and placed in the same salt solution. After eight hours' + immersion the legs are weighed again. The following are the results of + six experiments, the numbers representing fractions of the original + weight:—</p> + + <p>Change of weight of untired leg—</p> + +<table class="nob" summary="Change of weight of untired leg." title="Change of weight of untired leg."> +<tr><td class="spacsingle"> After 8 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.000.</td></tr> +<tr><td class="spacsingle"> After 16 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.000.</td></tr> +<tr><td class="spacsingle"> After 24 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.006.</td></tr> +</table> + + <p>Change of weight of stimulated leg—</p> + +<table class="nob" summary="Change of weight of stimulated leg." title="Change of weight of stimulated leg."> +<tr><td class="spacsingle"> After 8 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> +.050.</td></tr> +<tr><td class="spacsingle"> After 16 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> +.080.</td></tr> +<tr><td class="spacsingle"> After 24 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> +.101.</td></tr> +</table> + +<p><!-- Page 54 --><span class="pagenum"><a name="page54"></a>{54}</span></p> + + <p>This result shows that muscular work provoked by electric stimulation + noticeably increases the osmotic pressure of the muscle.</p> + + <p>In order to discover the exact osmotic pressure in the stimulated + muscles we repeated the series of experiments, using more and more + concentrated solutions. In a solution whose freezing point was -.57°, we + obtained the following values:—</p> + + <p>Change of weight of untired leg—</p> + +<table class="nob" summary="Change of weight of untired leg." title="Change of weight of untired leg."> +<tr><td class="spacsingle"> After 8 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.000.</td></tr> +<tr><td class="spacsingle"> After 16 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.004.</td></tr> +<tr><td class="spacsingle"> After 24 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.006.</td></tr> +</table> + + <p>Change of weight of stimulated leg—</p> + +<table class="nob" summary="Change of weight of stimulated leg." title="Change of weight of stimulated leg."> +<tr><td class="spacsingle"> After 8 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> +.039.</td></tr> +<tr><td class="spacsingle"> After 16 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> +.072.</td></tr> +<tr><td class="spacsingle"> After 24 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> +.099.</td></tr> +</table> + + <p>Finally, in a solution freezing at -.72°, <i>i.e.</i> with an osmotic + pressure at 15° C. of 9.176 atmospheres, we obtained the following mean + values for the untired leg:—</p> + +<table class="nob" summary="Change of weight of untired leg." title="Change of weight of untired leg."> +<tr><td class="spacsingle"> After 8 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.04. </td></tr> +<tr><td class="spacsingle"> After 16 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.05. </td></tr> +<tr><td class="spacsingle"> After 24 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.06. </td></tr> +</table> + + <p>In this solution, freezing at -.72° C., some of the stimulated muscles + showed no diminution in weight, while others showed a very small + diminution, and others again a slight augmentation, the maximum increase + being .085 of the initial weight. The solution is therefore practically + isotonic with the stimulated muscle.</p> + + <p>In this case the elevation of the intramuscular osmotic pressure + produced by the electrical excitation and the muscular contractions was + therefore 2.5 atmospheres, or more than 2.6 kilogrammes per square + centimetre of surface.</p> + + <p>I made further experiments in order to discover whether the variation + in osmotic pressure depended on the duration of <!-- Page 55 --><span + class="pagenum"><a name="page55"></a>{55}</span>the muscular contraction. + For this purpose I used a solution freezing at -.53° C. and immersed in + it untired muscles, and muscles which had been electrically excited for + two, four, and six minutes respectively. The following are the + results:—</p> + +<table class="nob" summary="Effect of simulation time." title="Effect of simulation time."> +<tr><td class="spacsingle" style="text-align:center;"> Untired muscles. </td><td class="spacsingle" style="text-align:center;" colspan="3"> Muscles stimulated once a second during</td></tr> +<tr><td class="spacsingle" style="text-align:center;"> </td><td class="spacsingle" style="text-align:center;"> 2 Minutes. </td><td class="spacsingle" style="text-align:center;"> 4 Minutes. </td><td class="spacsingle" style="text-align:center;"> 6 Minutes.</td></tr> +<tr><td class="spacsingle" style="text-align:center;"> .000 </td><td class="spacsingle" style="text-align:center;"> +.026 </td><td class="spacsingle" style="text-align:center;"> +.084 </td><td class="spacsingle" style="text-align:center;"> +.094</td></tr> +<tr><td class="spacsingle" style="text-align:center;"> +.001 </td><td class="spacsingle" style="text-align:center;"> +.034 </td><td class="spacsingle" style="text-align:center;"> +.065 </td><td class="spacsingle" style="text-align:center;"> +.093</td></tr> +<tr><td class="spacsingle" style="text-align:center;"> +.005 </td><td class="spacsingle" style="text-align:center;"> +.045 </td><td class="spacsingle" style="text-align:center;"> +.079 </td><td class="spacsingle" style="text-align:center;"> +.097</td></tr> +<tr><td class="spacsingle" style="text-align:center;"> .000 </td><td class="spacsingle" style="text-align:center;"> +.037 </td><td class="spacsingle" style="text-align:center;"> +.070 </td><td class="spacsingle" style="text-align:center;"> +.095</td></tr> +<tr><td class="spacsingle" style="text-align:center;"> .000 </td><td class="spacsingle" style="text-align:center;"> +.032 </td><td class="spacsingle" style="text-align:center;"> +.072 </td><td class="spacsingle" style="text-align:center;"> +.096</td></tr> + +<tr><td class="spacsingle" style="text-align:left;" colspan="4"> Mean of all the observations—</td></tr> +<tr><td class="spacsingle" style="text-align:center;"> +.0012 </td><td class="spacsingle" style="text-align:center;"> +.0348 </td><td class="spacsingle" style="text-align:center;"> +.074 </td><td class="spacsingle" style="text-align:center;"> +.095</td></tr> +</table> + + <p>These experiments show clearly that the osmotic intramuscular pressure + rises in proportion to the duration of the electrical stimulation.</p> + + <p>In order to determine the influence of the work accomplished by the + muscle on the elevation of the osmotic pressure, I made the following + experiment. The two hind legs of a frog were submitted to the same + electrical excitation, one leg being left at liberty, and the other being + stretched by a hundred-gramme weight, acting by a cord and pulley. After + exciting them electrically for five minutes, the legs were immersed for + twenty-four hours in a saline solution freezing at .53° C. The free limb + showed an augmentation of .085 of the initial weight, and the stretched + limb an increase of .106 of the initial weight. It is evident, therefore, + that the osmotic pressure increases with the amount of work done by a + muscle.</p> + + <p>Briefly, then, the results of our experiments are as + follow:—</p> + + <p>1. Muscular contraction electrically produced causes an increase of + the osmotic pressure in a muscle.</p> + + <p>2. The intramuscular osmotic pressure may reach, or even exceed, 2.5 + atmospheres, or 2.6 kilogrammes per square centimetre of surface.</p> + + <p>3. When a muscle is made to contract once a second, the <!-- Page 56 + --><span class="pagenum"><a name="page56"></a>{56}</span>elevation of the + osmotic pressure increases with the number of contractions.</p> + + <p>4. The intramuscular osmotic pressure increases with the work done by + the muscle.</p> + + <p>5. Fatigue is caused by the increase of osmotic pressure in a + contracting muscle.</p> + + <div class="figright" style="width:39%;"> + <a href="images/Fig3.jpg"><img style="width:100%" src="images/Fig3.jpg" + alt="Fig. 3." title="Fig. 3." /></a> + <span class="sc">Fig. 3.</span>—Fields of diffusive force. + + <p class="poem">(<i>a</i>) Monopolar field of diffusion. A drop of + blood in a saline solution of higher concentration.</p> + + <p class="poem">(<i>b</i>) Bipolar field of diffusion. Two poles of + opposite signs. On the right a grain of salt forming a hypertonic pole + of concentration, on the left a drop of blood forming a hypotonic pole + of dilution. </p> + </div> + + <p><i>The Field of Diffusion.</i>—Just as Faraday introduced the + conception of a field of magnetic force and a field of electric force to + explain magnetic and electrical phenomena, so we may elucidate the + phenomena of diffusion by the conception of a field of diffusion, with + centres or poles of diffusive force. If we consider a solution as a field + of diffusion, any point where the concentration is greater than that of + the rest may be considered as a centre of force, attractive for the + molecules of water, and repulsive for the molecules of the solute. In the + same way any point of less concentration may be regarded as a centre of + attraction for the molecules of the solute, and a centre of repulsion for + the molecules of water.</p> + + <p>A field of diffusion may be monopolar or bipolar. A bipolar field has + a hypertonic pole or centre of concentration, and a hypotonic pole or + centre of dilution. By analogy with the magnetic and electric fields we + may designate the hypertonic pole as the positive pole of diffusion, and + the hypotonic as the negative pole. <!-- Page 57 --><span + class="pagenum"><a name="page57"></a>{57}</span></p> + + <p>The positive and negative poles and the lines of force in the field of + diffusion may be illustrated by the following experiment. A thin layer of + salt water is spread over an absolutely horizontal plate of glass. If now + we take a drop of blood, or of Indian ink, and drop it carefully into the + middle of the salt solution, we shall find that the coloured particles + will travel along the lines of diffusive force, and thus map out for us a + monopolar field of diffusion, as in Fig. 3 <i>a</i>. Again, if we place + two similar drops side by side in a salt solution, their lines of + diffusion will repel one another, as in Fig. 4.</p> + + <div class="figright" style="width:26%;"> + <a href="images/Fig4.jpg"><img style="width:100%" src="images/Fig4.jpg" + alt="Fig. 4." title="Fig. 4." /></a> + <span class="sc">Fig. 4.</span>—Two drops of blood in a more + concentrated solution, showing a field of diffusion between two poles + of the same sign. + </div> + + <p>Now let us put into the solution, side by side, one drop of less + concentration and another of greater concentration than the solution. The + lines of diffusion will pass from one drop to the other, diverging from + the centre of one drop and converging towards the centre of the other + (Fig. 3 <i>b</i>). In this manner we are able to obtain diffusion fields + analogous to the magnetic fields between poles of the same sign and poles + of opposite signs.</p> + + <p>The conception of poles of diffusion is of the greatest importance in + biology, throwing a flood of light on a number of phenomena, such as + karyokinesis, which have hitherto been regarded as of a mysterious + nature. It also enables us to appreciate the rôle played by diffusion in + many other biological phenomena. Consider, for example, a centre of + anabolism in a living organism. Here the molecules of the living + protoplasm are in process of construction, simpler molecules being united + and built up to form larger and more complex groups. As a result of this + aggregation the number of molecules in a given area is diminished, + <i>i.e.</i> the concentration and the osmotic pressure fall, producing a + hypotonic centre of diffusion. We may thus regard every centre of + anabolism as a negative pole of diffusion. <!-- Page 58 --><span + class="pagenum"><a name="page58"></a>{58}</span></p> + + <p>Consider, on the other hand, a centre of catabolism, where the + molecules are being broken up into fragments or smaller groups. The + concentration of the solution is increased, the osmotic pressure is + raised, and we have a hypertonic centre of diffusion. Every centre of + catabolism is therefore a positive pole of diffusion. Similar + considerations as to the formation and breaking up of the molecules in + anabolism and catabolism apply to polymerization.</p> + + <p>The diffusion field has similar properties to the magnetic and the + electric field. Thus there is repulsion between poles of similar sign, + and attraction between poles of different signs. A simple experiment will + show this. A field of diffusion is made by pouring on a horizontal glass + plate a 10 per cent. solution of gelatine to which 5 per cent. of salt + has been added. The gelatine being set, we place side by side on its + surface two drops, one of water, and one of a salt solution of greater + concentration than 5 per cent. We have thus two poles of diffusion of + contrary signs, a hypotonic pole at the water drop, and a hypertonic pole + at the salt drop. Diffusion immediately begins to take place through the + gelatine, the drops become elongated, advance towards one another, touch, + and unite. If, on the contrary, the two neighbouring drops are both more + concentrated or both less concentrated than the medium, they exhibit + signs of repulsion as in Fig. 4.</p> + + <p>Diffusion not only sets up currents in the water and in the solutes, + but it also determines movements in any particles that may be in + suspension, such as blood corpuscles, particles of Indian ink, and the + like. These particles are drawn along with the water stream which passes + from the hypotonic centres or regions toward those which are + hypertonic.</p> + + <p>These considerations suggest a vast field of inquiry in biology, + pathology, and therapeutics. Inflammation, for example, is characterized + by tumefaction, turgescence of the tissues, and redness. The essence of + inflammation would appear to be destructive dis-assimilation with intense + catabolism. We have seen that a centre of catabolism is a hypertonic + focus of diffusion. Hence the osmotic pressure in an inflamed region is + increased, turgescence is produced, and <!-- Page 59 --><span + class="pagenum"><a name="page59"></a>{59}</span>the current of water + carries with it the blood globules which produce the redness.</p> + + <p>The phenomenon of agglutination may also possibly be due to osmotic + pressure, a positive centre of diffusion attracting and agglomerating the + particles held in suspension.</p> + + <p><i>Tactism and Tropism.</i>—The phenomena of tactism and tropism + may also be partly explained by the action of these diffusion currents of + particles in suspension, these polar attractions and repulsions. In all + experiments on this subject we should take into account the possible + influence of osmotic pressure, since many of the causes of tactism or + tropism also modify the osmotic pressure at the point of action, and it + is possible that this modification is the true cause of the phenomenon. + Osmotactism and osmotropism have not as yet been sufficiently + studied.</p> + + <div class="figright" style="width:28%;"> + <a href="images/Fig5.jpg"><img style="width:100%" src="images/Fig5.jpg" + alt="Fig. 5." title="Fig. 5." /></a> + <span class="sc">Fig. 5.</span>—Liquid figures of diffusion. + + <p class="poem">The six negative poles of diffusion are coloured with + Indian ink. The positive pole in the centre is uncoloured and is formed + by a drop of KNO<sub>3</sub> solution.</p> + </div> + + <p>Thus it may be said that osmotic pressure dominates all the kinetic + and dynamic phenomena of life, all those at least which are not purely + mechanical, like the movements of respiration and circulation. The study + of these vital phenomena is greatly facilitated by the conception of the + field of diffusion and poles of diffusion, and of the lines of force, + which are the trajectories of the molecules of the solutes, and the + particles and globules in suspension.</p> + + <p><i>The Morphogenic Effects of Diffusion.</i>—Many interesting + experiments may be made showing variations of the lines of force in a + field of diffusion, and how liquids subjected only to differences of + osmotic pressure diffuse and mix with one <!-- Page 60 --><span + class="pagenum"><a name="page60"></a>{60}</span>another in definite + patterns. When a liquid diffuses in another undisturbed by the influence + of gravity, it produces figures of geometric regularity, and we may thus + obtain figures and forms of infinite variety. The following is our method + of procedure. A glass plate is placed absolutely horizontal and is + covered with a thin layer of water or of saline solution. Then with a + pipette we introduce into the solution, in a regular pattern, a number of + drops of liquid coloured with Indian ink. A wonderful variety of patterns + and figures may be obtained by employing solutions of different + concentration and varying the position of the drops.</p> + + <div class="figleft" style="width:29%;"> + <a href="images/Fig6.jpg"><img style="width:100%" src="images/Fig6.jpg" + alt="Fig. 6." title="Fig. 6." /></a> + <span class="sc">Fig. 6.</span>—Pattern produced in gelatine by + the diffusion of drops of concentrated solutions of nitrate of silver + and bromide of ammonium. + </div> + + <p>Instead of the water or salt solution, we may spread on the plate a 5 + or 10 per cent. solution of gelatine, containing various salts in + solution. If now we sow on this gelatine drops of various solutions which + give colorations with the salts in the gelatine, we may obtain forms of + perfect regularity, presenting most beautiful colours and contrasts. The + drops, of course, must be placed in a symmetrical pattern. In this way we + may obtain an endless number of ornamental figures.</p> + + <p>In order to cover a lantern slide 8½ cm. × 10 cm., about 5 c.c. of + gelatine is required. To this amount of gelatine we add a single drop of + a saturated solution of salicylate of sodium, and spread the liquid + gelatine evenly over the plate. When the gelatine has set, we put the + plate over a diagram, a hexagon for instance, and place a drop of ferrous + sulphate solution at each of the six angles. The drops immediately + diffuse <!-- Page 61 --><span class="pagenum"><a + name="page61"></a>{61}</span>through the gelatine, and the result after a + time is the production of a beautiful purple rosette. The gelatine must + be carefully covered to prevent its drying until the diffusion is + complete. The preparation may then be dried and mounted as a lantern + slide, and will give the most brilliant effect on projection. If the + gelatine has been treated with a drop of potassium ferrocyanide solution + instead of salicylate of sodium, a few drops of FeSO<sub>4</sub> will + give a blue pattern. Or we may treat the gelatine with ferrocyanide of + potassium and salicylate of sodium mixed, and thus obtain an intermediary + colour on the addition of FeSO<sub>4</sub>. We may, indeed, vary + indefinitely the nature and concentration of the solution, as well as the + number and position of the drops. The results have all the charm of the + unexpected, which adds greatly to the interest of the experiment.</p> + + <div class="figright" style="width:32%;"> + <a href="images/Fig7.jpg"><img style="width:100%" src="images/Fig7.jpg" + alt="Fig. 7." title="Fig. 7." /></a> + <span class="sc">Fig. 7.</span>—Pattern produced in gelatine by + the diffusion of drops of silver nitrate and sodium carbonate. + </div> + + <p>These experiments are not merely a scientific toy. They show us the + possibility, hitherto unsuspected, that a vast number of the forms and + colours of nature may be the result of diffusion. Thus many of the + phenomena of life, hitherto so mysterious, present themselves to us as + merely the consequences of the diffusion of one liquid into another. One + cannot help hoping that the study of diffusion will throw still further + light on the subject.</p> + + <p>If a number of spheres, each capable of expansion and deformation, are + produced simultaneously in a liquid, they will form polyhedra when they + expand by growth. This is the <!-- Page 62 --><span class="pagenum"><a + name="page62"></a>{62}</span>precise architecture of a vast number of + living organisms and tissues, which are formed by the union of + microscopic polyhedra or cells. A section of such a polyhedral structure + would appear as a tissue of polygons. It is interesting to note that the + simple process of diffusion will produce such structures under conditions + closely allied to those which govern the development of the tissues of a + living organism.</p> + + <div class="figleft" style="width:37%;"> + <a href="images/Fig8.jpg"><img style="width:100%" src="images/Fig8.jpg" + alt="Fig. 8." title="Fig. 8." /></a> + <span class="sc">Fig. 8.</span>—Pattern produced in gelatine by + the diffusion of drops of a solution of nitrate of silver and of + citrate of potassium. + </div> + + <p>We may obtain this cellular structure by a simple experiment. On a + glass plate we spread a 5 per cent. solution of pure gelatine, and when + set sow on it a number of drops of a 5 to 10 per cent. solution of + ferrocyanide of potassium. The drops must be placed at regular intervals + of 5 mm. all over the plate. When these have been allowed to diffuse and + the gelatine has dried, we obtain a preparation which exactly resembles + the section of a vegetable cellular tissue (Fig. 9). The drops have by + mutual pressure formed polygons, which appear in section as cells, with a + membranous envelope, a <!-- Page 63 --><span class="pagenum"><a + name="page63"></a>{63}</span>nucleus, and a cytoplasm, which is in many + cases entirely separated from the membrane. These cells when united form + a veritable tissue, in all respects similar to the cellular structure of + a living organism.</p> + + <div class="figright" style="width:35%;"> + <a href="images/Fig9.jpg"><img style="width:100%" src="images/Fig9.jpg" + alt="Fig. 9." title="Fig. 9." /></a> + <span class="sc">Fig. 9.</span>—Tissue of artificial cells formed + by the diffusion in gelatine of drops of potassium ferrocyanide. + </div> + + <p>In the preparation showing artificial cells the cellular structure is + not directly visible until the gelatine has dried. One sees only a + gelatinous mass analogous to the protoplasm of a living organism. This + mass is nevertheless organized, or at least in process of organization, + as we may see by the refraction when its image is projected on the + screen.</p> + + <p>During the cell-formation, and as long as there is any difference of + concentration in the gelatine, each cell is the arena of active molecular + movement. There is a double current, as in the living cell, a stream of + water from the periphery to the centre, and of the solute from the centre + to the periphery. This molecular activity—the life of the + artificial cell—may be prolonged by appropriate nourishment, <!-- + Page 64 --><span class="pagenum"><a + name="page64"></a>{64}</span><i>i.e.</i> by continually repairing the + loss of concentration at the centre of the cell.</p> + + <p>The life of the artificial cell may also be prolonged by maintaining + around it an appropriate medium. If we prematurely dry such a preparation + of artificial cells, the molecular currents will cease, to recur again + when we restore the necessary humidity to the preparation. This to my + mind gives us a most vivid picture of the conditions of latent life in + seeds and many rotifera.</p> + + <p>These artificial cells, like living organisms, have an evolutionary + existence. The first stage corresponds to the process of organization, + the gelatine representing the blastema, and the drop the nucleus. Thus + the cell becomes organized, forming its own cytoplasm and its own + enveloping membrane.</p> + + <p>The second stage in the life of this artificial cell is the period + during which the metabolism of the cell is active and tends to equalize + the concentration of the liquid in the cell and in the surrounding + medium.</p> + + <p>The third stage is the period of decline. The double molecular current + gradually slows down as the difference of concentration decreases between + the cell contents and its entourage. When this equality of concentration + has become complete the molecular currents cease, the cell has terminated + its existence; it is dead. The currents of substance and of energy have + ceased to flow—the form only remains.</p> + + <p>These artificial cells are sensible to most of the influences which + affect living organisms. Like living cells they are influenced both in + their organization and in their development by humidity, dryness, + acidity, or alkalinity. They are also greatly affected by the addition of + minute quantities of chemical substances either to the gelatinous + blastema or to the drops which represent the primary nuclei. We may in + this way obtain endless varieties, nuclei which are opaque or + transparent, with or without a nucleolus, and cells containing + homogeneous cytoplasm without a nucleus. We may also obtain cells with + cytoplasm filling the whole of the cellular cavity or separated from the + cell-membrane. We may obtain <!-- Page 65 --><span class="pagenum"><a + name="page65"></a>{65}</span>cells imitating all the natural tissues, + cells without a membranous envelope, cells with thick walls adhering to + one another, or cells with wide intracellular spaces.</p> + + <div class="figright" style="width:28%;"> + <a href="images/Fig10.jpg"><img style="width:100%" src="images/Fig10.jpg" + alt="Fig. 10." title="Fig. 10." /></a> + <span class="sc">Fig. 10.</span>—Artificial liquid cells, formed + by coloured drops of concentrated salt solution in a less concentrated + salt solution. + </div> + + <p>The forms of these artificial cells depend on the number and relative + position of the drops which represent the nuclei, and on the molecular + concentration or osmotic tension of the solution. The number of the + cellular polyhedra is determined by the number of centres of diffusion. + The magnitude of the dihedral angles, from which radiate three and + occasionally four walls, depends on the position of the hypertonic poles + of diffusion. The curvature of a surface is determined by the differences + of concentration on either side. Between isotonic solutions the surface + is plane, whilst it is curved between solutions of different osmotic + pressures, the convexity being directed towards the hypertonic + solution.</p> + + <div class="figleft" style="width:21%;"> + <a href="images/Fig11.jpg"><img style="width:100%" src="images/Fig11.jpg" + alt="Fig. 11." title="Fig. 11." /></a> + <p class="poem"><span class="sc">Fig. 11.</span>—Liquid cells + with a fringe of cilia, obtained by sowing coloured drops of + concentrated salt solution in a weaker salt solution. The contents of + the cells have undergone segmentation.</p> + </div> + + <p>The time required for these artificial cells to grow varies from two + to twenty-four hours, according to the concentration of the gelatine, the + growth being most rapid in dilute solutions.</p> + + <p>Similar cells may be produced in water. If we pour a thin layer of + water on a horizontal plate, and with a pipette <!-- Page 66 --><span + class="pagenum"><a name="page66"></a>{66}</span>sow in it a number of + drops of salt water coloured with Indian ink, we may obtain artificial + cells composed entirely of liquid, having the same characters as those + produced in a gelatinous solution.</p> + + <p>It is possible by liquid diffusion to produce not only ordinary cells + but ciliated cells. If we spread a layer of salt water on a horizontal + glass plate, and sow in it drops of Indian ink, artificial cells are + produced by diffusion. At the edge of the preparation there is often to + be seen a sort of fringe, analogous to the cilia of living cells (Fig. + 11).</p> + + <p>These tissues of artificial cells demonstrate the fact that inorganic + matter is able to organize itself into forms and structures analogous to + those of living organisms under the action of the simple physical forces + of osmotic pressure and diffusion. The structures thus produced have + functions which are also analogous to those of living beings, a double + current of diffusion, an evolutionary existence, and a latent vitality + when desiccated or congealed.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 67 --><span class="pagenum"><a name="page67"></a>{67}</span></p> + +<h3>CHAPTER VI</h3> + +<p class="cenhead">PERIODICITY</p> + + <p><i>Periodic Precipitation.</i>—A phenomenon is said to be + periodic when it varies in time and space and is identically reproduced + at equal intervals. We are surrounded on all sides by periodic phenomena; + summer and winter, day and night, sleep and waking, rhythm and rhyme, + flux and reflux, the movements of respiration and the beating of the + heart, all are periodic. Our first sorrows were appeased by the periodic + rhythm of the cradle, and in our later years the periodic swing of the + rocking-chair and the hammock still soothe the infirmities of old + age.</p> + + <p>Sound is a periodic movement of the atmosphere which brings to us + harmony and melody. Light consists of periodic undulations of the ether + which convey to us the beauty of form and colour. Periodic ethereal waves + waft to us the wireless message through terrestrial space and the radiant + energy of the sun and stars.</p> + + <p>It is therefore not to be wondered at that the phenomena of diffusion + are also periodic. According to Professor Quinke of Heidelberg, the first + mention of the periodic formation of chemical precipitates must be + attributed to Runge in 1885. Since that time these precipitates have been + studied by a number of authors, and particularly by R. Liesegang of + Düsseldorf, who in 1907 published a work on the subject, entitled <i>On + Stratification by Diffusion</i>.</p> + + <p>In 1901 I presented to the Congress of Ajaccio a number of + preparations showing concentric rings, alternately transparent and + opaque, obtained by diffusing a drop of potassium ferrocyanide solution + in gelatine containing a trace of ferric <!-- Page 68 --><span + class="pagenum"><a name="page68"></a>{68}</span>sulphate. At the Congress + of Rheims in 1907 I exhibited the result of some further experiments on + the same subject.</p> + + <p>These periodic precipitates may be obtained from a great number of + different chemical substances. The following is the best method of + demonstrating the phenomenon. A glass lantern slide is carefully cleaned + and placed absolutely level. We then take 5 c.c. of a 10 per cent. + solution of gelatine and add to it one drop of a concentrated solution of + sodium arsenate. This is poured over the glass plate whilst hot, and as + soon as it is quite set, but before it can dry, we allow a drop of silver + nitrate solution containing a trace of nitric acid to fall on it from a + pipette. The drop slowly spreads in the gelatine, and we thus obtain + magnificent rings of periodic precipitates of arsenate of silver, with + which any one may easily repeat the experiments detailed in this + chapter.</p> + + <div class="figright" style="width:29%;"> + <a href="images/Fig12.jpg"><img style="width:100%" src="images/Fig12.jpg" + alt="Fig. 12." title="Fig. 12." /></a> + <span class="sc">Fig. 12.</span>—Lines of diffusion precipitate, + showing the simultaneous propagation of "undulations of different + wave-length. + </div> + + <p><i>Circular Waves of Precipitation.</i>—The wave-front of the + periodic rings of precipitates is always perpendicular to the rays of + diffusion. The distance between the rings depends on the concentration of + the diffusing solution. The greater the fall of concentration, the less + is the interval between the rings. Each ring represents an equipotential + line in the field of diffusion. These equipotential lines of diffusion + give us the best and most concrete reproduction of the mode of + propagation of periodic waves in space. They are, in fact, a visible + diagram of the propagation of the waves of light and sound. Occasionally + we may observe in the gelatine the simultaneous propagation of + undulations of different wave-length, just as we have them in the ether + and the air. These diffusion wavelets <!-- Page 69 --><span + class="pagenum"><a name="page69"></a>{69}</span>give us a very beautiful + representation of the simultaneous propagation of undulations of + different wave-length in the same medium.</p> + + <div class="figleft" style="width:27%;"> + <a href="images/Fig13.jpg"><img style="width:100%" src="images/Fig13.jpg" + alt="Fig. 13." title="Fig. 13." /></a> + <p class="poem"><span class="sc">Fig. 13.</span>—Waves of + diffusion refracted at a plane surface on passing from a less + concentrated into a more concentrated solution. The refracted + wave-front is flattened, the wave-length being less in the denser + medium.</p> + </div> + + <p>Like waves of light and sound, these waves of diffusion are refracted + when they pass from one medium into another of a different density, where + they have a different velocity. When, for instance, a diffusion wave + passes from a 5 per cent. solution of gelatine into a 10 per cent. + solution, the wave-front is retarded, the retardation being proportional + to the length of the path through the denser medium. Hence the wave-front + is flattened, the curvature of the refracted wave being less than that of + the original wave of diffusion. The contrary is the case when the + wave-front passes into a medium where its velocity is greater. The middle + of the wave-front now travels faster than the flanks, and the curvature + is increased.</p> + + <div class="figright" style="width:25%;"> + <a href="images/Fig14.jpg"><img style="width:100%" src="images/Fig14.jpg" + alt="Fig. 14." title="Fig. 14." /></a> + <span class="sc">Fig. 14.</span>—Transformation of a spherical + wave-front into a plane wave-front by a convergent diopter. + </div> + + <p>These diffusion rings furnish us with most excellent diagrams of + refraction at a "diopter," <i>i.e.</i> a spherical surface separating two + media of different densities. Fig. 14 shows the refraction at a + convergent diopter, <i>i.e</i>. a surface where the denser medium is + convex. The diffusion waves in this case emanate from the principal focus + of the diopter, and therefore become plane on passing through the convex + surface of the denser gelatine.</p> + + <p>These periodic diffusion rings also illustrate the phenomena of colour + diffraction. Diffusion waves of different <!-- Page 70 --><span + class="pagenum"><a name="page70"></a>{70}</span>wavelength are unequally + refracted by a gelatine lens. Hence rings of different wave-length which, + originating at the same spot, are at first concentric, are no longer + parallel after passing through a gelatine lens. A convergent lens which + will change the long spherical incident waves into shorter plane waves, + will transform the short incident waves into concave waves whose + curvature is opposite to that of the original waves, <i>i.e.</i> it will + transform a divergent into a convergent beam. This is an illustration of + what is called the aberration of refrangibility.</p> + + <p>In the same way we may demonstrate the course of diffusion waves + through a gelatine prism, showing the refraction on their incidence and + again on emergence. The prism is made of a stronger gelatine solution, + which is more refractive than the gelatine around it. The waves of + diffusion whilst traversing the prism are retarded, and this retardation + is greatest at the base where the passage is longer. Hence the wave-front + is tilted towards the base of the prism, and this tilting is repeated + when the wave-front leaves the prism.</p> + + <p>If we examine diffusion waves of different wave-length on their + emergence from the gelatine prism, we shall see that they cut one + another. With a dense prism, the wave-front of the shorter waves is more + tilted towards the base than the wave-front of the longer waves. For + diffusion as for light the shorter waves are the most refracted. Both + refraction and dispersion are due to the unequal resistances of the + medium to undulatory movements of different periodicity.</p> + + <div class="figright" style="width:28%;"> + <a href="images/Fig15.jpg"><img style="width:100%" src="images/Fig15.jpg" + alt="Fig. 15." title="Fig. 15." /></a> + <span class="sc">Fig. 15.</span>—Diffraction of diffusion waves + on passing through a narrow aperture. + </div> + + <p><i>Diffraction.</i>—When light traverses a minute orifice, + instead <!-- Page 71 --><span class="pagenum"><a + name="page71"></a>{71}</span>of passing on in a straight line, it spreads + out like a fan, forming a diverging cone of light, just as if the orifice + were itself a luminous point. This is the phenomenon of diffraction which + has hitherto been considered incompatible with the emission theory of + light. Diffusion waves may also be made to pass through a narrow orifice, + when they will behave exactly like the waves of light. The new waves + radiate from the orifice like a fan, instead of giving a cone of waves + bounded by lines passing through the circumference of the orifice and the + original centre of radiation. Thus on passing through a small orifice + diffusion waves exhibit the phenomenon of diffraction just as light waves + do.</p> + + <div class="figleft" style="width:23%;"> + <a href="images/Fig16.jpg"><img style="width:100%" src="images/Fig16.jpg" + alt="Fig. 16." title="Fig. 16." /></a> + <span class="sc">Fig. 16.</span>—Interference of diffusion waves. + </div> + + <p><i>Interference.</i>—The phenomenon of interference may also be + illustrated by waves of diffusion. If on a gelatine plate we produce two + series of diffusion waves from two separate centres, we get at certain + points an appearance corresponding to the interference of two sets of + light waves. This appearance is best shown by sowing on the gelatine film + a straight row of drops equidistant from one another. It should be + remarked that this phenomenon of the production of circles of precipitate + separated by transparent spaces, although periodic, is not of necessity + vibratory or undulatory. It would thus appear that periodic phenomena may + be propagated through space without vibratory or oscillatory motion. If + we submit to a critical examination the various experiments which have + established the undulatory theory of light, we find that they do indeed + demonstrate the periodic nature of light, but in no wise prove that light + is a vibratory movement of the ether. <!-- Page 72 --><span + class="pagenum"><a name="page72"></a>{72}</span>On the contrary, the + hypothesis that light is propagated by vibratory movements is open to + many objections. Even the Zeeman effect, although it may tend to + establish the fact that light is produced by vibratory movement, by no + means proves that it is propagated in the same manner. When the theory + was accepted that the transmission of light was periodic it was supposed + that this periodic transmission could only be vibratory or undulatory in + character, since waves or vibrations were the only periodic phenomena + known at that time. We now know that there are other means of periodic + transmission which are apparently not undulatory. The periodic + precipitates produced by diffusion show us the transmission of spherical + waves through space, which follow the laws of light, although the + periodic phenomenon is apparently emissive rather than vibratory.</p> + + <p>It will be remembered that Newton considered light to be produced by + projectile-like particles emanating from a centre, and proceeding in + straight lines in all directions. This emission theory of light was + abandoned in favour of Huygens' undulatory theory.</p> + + <p>It was said that the phenomena of interference and diffraction could + not be explained by the theory of emission, while the undulatory theory + gave a simple explanation. The scientific mind was unable to conceive the + idea of emission and periodicity as taking part in the same phenomenon. + The savants and thinkers who have meditated on this question have always + considered the theory of emission and that of periodicity as + incompatible. Nevertheless, we are here in presence of a phenomenon in + which emission and periodicity exist simultaneously. The molecules + emanating from our drop are diffused in straight radiating lines, and yet + produce periodic precipitates which are subject to interference and + diffraction like the undulations of Huygens.</p> + + <p>The phenomena associated with the pressure of light, the <!-- Page 73 + --><span class="pagenum"><a name="page73"></a>{73}</span>discovery of the + cathode rays and the radiations of radium, together with the introduction + of the electron theory of electricity, all seem to have brought again + into greater prominence Newton's original conception of the emissionary + nature of light.</p> + + <p>Some of the phenomena of radiation can be explained only by the + emission theory, and others by the undulatory theory of light. All these + difficulties would be solved if we admitted the hypothesis that radiating + bodies project electrons, which produce in the ether periodic waves + similar to those formed in our gelatine films by the molecules of + diffusion.</p> + + <p>These diffusion films are of the greatest possible service in the + practical teaching of optics. They place before the eye of the student a + working model as it were of the undulations of light. When projected on + the screen, they give excellent pictures of the phenomena of refraction, + diffraction, and interference, and the simultaneous propagation of + undulation of different wave-lengths, and they show in a visible manner + the changes of wave-length in media of different densities.</p> + + <p>Diffusion waves differ greatly in length, varying from several + millimetres to 2 <span class="grk">μ</span>. Many are even shorter + than this, too short to be separately distinguished even under the + highest power of the microscope, when they give the effect of moiré or + mother-of-pearl.</p> + + <p>It is easy to construct a spectroscopic grating in this way with fine + lines whose distance apart is of the order of a micron, separated by + clear spaces. Every physical laboratory may thus produce its own + spectroscopic gratings, rectilinear, circular, or of any desired + form.</p> + + <p>The most beautiful colour effects may be produced with these diffusion + gratings, as we have shown at the Congress of Rheims in 1907. We have a + considerable collection of these diffusion gratings, some with very fine + lines, giving a very extended spectrum, and others with coarser + striations which give a large number of small spectra.</p> + + <p>This study of periodic precipitates is of the highest interest when we + come to investigate the production of colour in natural objects, such as + the wings of insects or the plumage of <!-- Page 74 --><span + class="pagenum"><a name="page74"></a>{74}</span>birds. Many tissues have + this lined or striated structure and exhibit interference colours like + those of the periodic precipitates, their structure showing alternate + transparent and opaque lines, whose width is of the order of a micron. + This is the structure of muscle, and to this striated surface is also + attributable many of the most beautiful colours of nature, the gleam of + tendon and aponeurosis, the fire of scarab and beetle, the colours of the + peacock, and the iridescence of the mollusc and the pearl. The study of + liquid diffusion has given us an idea of the physical mechanism by which + these striated tissues are produced, a mechanism which up to the present + time has not been even suspected. Our experiments show how readily such + striped or ruled structures may be produced in a colloidal solution by + the simple diffusion of salts such as are found in every living + organism.</p> + + <div class="figright" style="width:35%;"> + <a href="images/Fig17.jpg"><img style="width:100%" src="images/Fig17.jpg" + alt="Fig. 17." title="Fig. 17." /></a> + <span class="sc">Fig. 17.</span>—Photomicrograph of striated + structure of a periodic precipitate of carbonate and phosphate of lime + (magnified 500 times). + </div> + + <p>To make a spectroscopic grating by diffusion we proceed as follows. We + take 5 c.c. of a 10 per cent. solution of gelatine, and add to it one + drop of a concentrated solution <!-- Page 75 --><span class="pagenum"><a + name="page75"></a>{75}</span>of calcium nitrate. We spread the gelatine + evenly over a plain glass lantern slide and allow it to set. After it is + set, but before it dries, we place in the centre of the slide a drop of + concentrated solution containing two parts of sodium carbonate + (Na<sub>2</sub>CO<sub>3</sub>) to one of dibasic sodium phosphate + (Na<sub>2</sub>HPO<sub>4</sub>). Tribasic sodium phosphate alone without + the addition of the carbonate will also give good results. If the + phosphate solution is placed on the gelatine in the form of a drop, we + obtain circular periodic precipitates. If it is desired to make a + rectilineal grating, we deposit the phosphate solution on the gelatine in + a straight line by means of two parallel glass plates. In this way we may + obtain lines of periodic precipitation to the number of 500 to 1000 per + millimetre, forming gratings which produce most beautiful spectra.</p> + + <p>Pearls and mother-of-pearl both owe their iridescence to a similar + ruled structure, which is developed in the living tissue of a mollusc. + They are, in fact, periodic precipitates of phosphate and carbonate of + lime deposited in the colloidal organic substance of the mollusc. They + have the same structure and the same chemical composition; they have the + same physical properties, the glow, the fire, and the brilliancy of our + spectroscopic gratings. In these experiments, indeed, we have realized + the synthesis of the pearl, not only a chemical synthesis, but the + synthesis of its structure and organism.</p> + + <p>We have been able to make these periodic precipitates by the reaction + of a great number of chemical substances, giving a bewildering variety of + form and structure. Some of these recall the form of various organisms, + and especially of insects, as may be seen in Fig. 18.</p> + + <p>All the phenomena of life are periodic. The movement of heart and + lungs, sleep and waking, all nervous phenomena, have a regular + periodicity. It is possible that the study of these purely physical + phenomena of periodic precipitation may give us the key to the causation + of rhythm and periodicity in living beings.</p> + + <p>Besides this periodic precipitation there appear to be other chemical + reactions which are periodic. Professor Bredig of Heidelberg has lately + described a curious phenomenon, the <!-- Page 76 --><span + class="pagenum"><a name="page76"></a>{76}</span>periodic catalysis of + peroxide of hydrogen by mercury. He thus describes his experiment: "We + place in a perfectly clean test tube a few cubic centimetres of perfectly + pure mercury. Upon this we pour 10 c.c. of a 10 per cent. solution of + hydrogen peroxide. The mercury speedily becomes covered with a thin, + brilliant bronze-coloured pellicle which reflects light. Then little by + little catalysis of the hydrogen peroxide begins, with liberation of + oxygen. After some time, from five to twenty minutes, the liberation of + gas at the surface of the mercury ceases, the cloud formed by the gas + bubbles disappears, and the bronze mirror at the surface of the mercury + lights up with the glint of silver. There is a pause of one or more + seconds, and then the catalytic action begins afresh, commencing at the + edges of the mirror. The cloud is again formed and again disappears. This + beautiful and surprising rhythmic phenomenon may continue at regular + intervals for an hour or more."</p> + + <div class="figright" style="width:37%;"> + <a href="images/Fig18.jpg"><img style="width:100%" src="images/Fig18.jpg" + alt="Fig. 18." title="Fig. 18." /></a> + <span class="sc">Fig. 18.</span>—Articulate form produced by + periodic precipitation. + </div> + + <p>A slight alkalinity of the liquid is necessary to start the + phenomenon. This explains the retardation at the beginning <!-- Page 77 + --><span class="pagenum"><a name="page77"></a>{77}</span>of the + experiment, since the rhythmic catalysis cannot begin until the hydrogen + peroxide has dissolved a little of the glass so as to render it slightly + alkaline. The catalytic process may, however, be set going at once by + adding a trace of potassium acetate to the solution.</p> + + <p>We may even obtain a curve giving an automatic record of the + periodicity of this catalytic action. For this purpose the oxygen given + off is led to a manometer, which registers on a revolving drum the + periodic variation in pressure. The curve thus obtained presents a + remarkable resemblance to a tracing of the pulse. The frequency and + character of the undulatory curve is modified by physical and chemical + influences. Like circulation or respiration, periodic catalysis has its + poisons, and exhibits signs of fatigue, and of paralysis by cold.</p> + + <p>The rhythmic catalysis of Bredig produces an electrical current of + action between the mercury and the water just like that produced by the + rhythmic contraction of the heart, and this current may be registered in + a similar way by means of the Einthoven galvanometer. Thus the heart-beat + may be but an instance of rhythmic catalysis, since both produce the same + phenomena, movement, chemical action, and periodic currents. In the + chapter on physiogenesis we shall return to the study of this question + and consider another rhythmic phenomenon which is the result of osmotic + growth.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 78 --><span class="pagenum"><a name="page78"></a>{78}</span></p> + +<h3>CHAPTER VII</h3> + +<p class="cenhead">COHESION AND CRYSTALLIZATION</p> + + <p>Chemical affinity is the force which holds together the different + atoms in a molecule. Cohesion is the force which holds together molecules + which are chemically similar. Although physical science distinguishes + three states of matter, solid, liquid, and gaseous, yet here as elsewhere + there are no sharp dividing lines, but rather an absolute continuity. We + have in fact many intermediate states; between liquids and gases there + are the various conditions of vapour, and between liquids and solids we + get viscous, gelatinous, and paste-like conditions. The only real + difference between solids, liquids, and gases is the intensity of the + force of cohesion, which is considerable in solids, feeble in liquids, + and absent in gases.</p> + + <p>A living organism is the arena in which are brought into play the + opposing forces of cohesion and disintegration. The study of cohesion is + therefore a vital one for the biologist, and especially cohesion under + the conditions which obtain in living beings, viz. in liquids of + heterogeneous constitution. The forces of cohesion brought into play + under these conditions may be beautifully illustrated by a simple + experiment. We take a plate of glass, well cleaned and absolutely + horizontal. On it we pour a layer of salt water, and in the middle we + carefully drop a spot of Indian ink. The drop at once begins to diffuse, + and we obtain a circular figure, like the monopolar field of diffusion + already described, the rays of diffusion radiating from the centre in all + directions.</p> + + <div class="figright" style="width:19%;"> + <a href="images/Fig19.jpg"><img style="width:100%" src="images/Fig19.jpg" + alt="Fig. 19." title="Fig. 19." /></a> + <span class="sc">Fig. 19.</span>—Muriform cohesion figure formed + by a drop of Indian ink in a solution of salt. + </div> + + <p>If we keep the plate carefully protected from all disturbing + influences, after some ten to twenty minutes we shall see the coloured + particles returning on their path, and the centre of <!-- Page 79 + --><span class="pagenum"><a name="page79"></a>{79}</span>the drop + becoming more and more black. Each line of force becomes segmented into + granules, which gradually increase in size, and approach nearer to one + another and to the centre of the drop, until it assumes the mulberry + appearance shown in the photograph (Fig. 19).</p> + + <div class="figleft" style="width:34%;"> + <a href="images/Fig20.jpg"><img style="width:100%" src="images/Fig20.jpg" + alt="Fig. 20." title="Fig. 20." /></a> + <span class="sc">Fig. 20.</span>—Seven similar drops of Indian + ink diffusing in a salt solution. Two minutes after introducing the + drops. + </div> + + <p>If we sow a number of drops of Indian ink in regular order on the + surface of a salt solution, we obtain most beautiful patterns formed by + the mutual repulsion of the drops. Figs. 20, 21, and 22 represent the + successive aspects of seven drops of Indian ink thus sown on a layer of + salt solution, and kept undisturbed long enough to allow of their + evolution. Fig. 20 shows the aspect after two minutes, when the diffusion + is almost complete. In Fig. 21, photographed after fifteen <!-- Page 80 + --><span class="pagenum"><a name="page80"></a>{80}</span>minutes, the + colouring matter has almost entirely reunited to form separate + granulations; whilst in Fig. 22, taken after thirty minutes, these + granulations are rearranged to form an agglomeration around the centre of + each drop.</p> + + <div class="figright" style="width:33%;"> + <a href="images/Fig21.jpg"><img style="width:100%" src="images/Fig21.jpg" + alt="Fig. 21." title="Fig. 21." /></a> + <span class="sc">Fig. 21.</span>—The same drops 15 minutes later, + showing the granulation appearance. + </div> + + <p>The following experiment, which is more difficult, will show the + cohesive attraction of one drop for another. A plate of glass is adjusted + absolutely horizontal, and covered as before with a layer of salt + solution. On this we sow a number of drops of the same salt solution + coloured with Indian ink. The drops must be of exactly the same + concentration as the salt medium, so as to avoid any difference of + osmotic pressure between the drops and the medium, otherwise the drops + would not remain intact but would diffuse into the solution. Since under + these conditions the liquid of the medium around the drops is perfectly + symmetrical and homogeneous, it cannot exercise any influence on the + liquid of the drops.</p> + + <div class="figleft" style="width:31%;"> + <a href="images/Fig22.jpg"><img style="width:100%" src="images/Fig22.jpg" + alt="Fig. 22." title="Fig. 22." /></a> + <span class="sc">Fig. 22.</span>—The same drops after 30 minutes. + The granulations have agglomerated at the centre of the drops. + </div> + + <p>It is otherwise, however, with the colouring matter of the <!-- Page + 81 --><span class="pagenum"><a name="page81"></a>{81}</span>drops. The + particles of Indian ink may be seen passing from one drop to another, the + coloured circles become elongated towards one another, touch, and finally + unite. If, as in Fig. 23, the drops are of different size, the larger one + will have a preponderating attractive action and eat up the smaller + drops. In the figure, six small drops are placed around a large one, and + the smaller drops have begun to be deformed and to move towards the + larger drop. This central drop is also deformed, and has assumed a more + or less hexagonal form, under the influence of the attraction of the six + smaller ones. It may be noticed that the least prominent angle of the + hexagon is opposite the small drop which is farthest away from it, whilst + one of the smaller drops has already begun to be swallowed up by the + large one. This cohesion phenomenon is very slow in its action, but after + an hour or two the central drop will be found to have <!-- Page 82 + --><span class="pagenum"><a name="page82"></a>{82}</span>completely + absorbed the six smaller ones, and only one large drop will remain.</p> + + <div class="figright" style="width:14%;"> + <a href="images/Fig23.jpg"><img style="width:100%" src="images/Fig23.jpg" + alt="Fig. 23." title="Fig. 23." /></a> + <span class="sc">Fig. 23.</span>—Attraction between coloured + drops in an isotonic solution. + </div> + + <p><i>Incubation.</i>—In the living organism we frequently find + conditions similar to those realized in this experiment, viz. very slow + movements of diffusion in liquids containing particles in suspension. In + such cases the consequences must be the same, viz. granulation and + segmentation. Consider for a moment the incubation of an egg. The heat of + incubation determines a certain amount of evaporation through the shell, + with a concentration of the liquid near the surface. As a consequence of + this superficial concentration we get segmentation of the vitellus, with + the production of a morula.</p> + + <p><i>Artificial Parthenogenesis.</i>—The experimental + parthenogenesis of Loeb and Delage consists in plunging the egg into a + liquid other than sea water, and returning it again to its original + medium. This operation will necessarily determine slow movements of + diffusion in the egg, which will give rise to segmentation. It may be + objected that segmentation is also produced by a solution which is + isotonic with sea water. Such a solution would not indeed produce an + exchange of water with the egg, but it would set up an exchange of + electrolytes, since there would be a difference of their osmotic pressure + in the egg and in the new isotonic medium. The extremely slow movements + of diffusion thus produced would be very favourable to the action of the + cohesive force on the particles in suspension, and hence to the + segmentation of the egg.</p> + + <div class="figleft" style="width:34%;"> + <a href="images/Fig24.jpg"><img style="width:100%" src="images/Fig24.jpg" + alt="Fig. 24." title="Fig. 24." /></a> + <span class="sc">Fig. 24.</span>—A circle of eight drops of + Indian ink 30 minutes after they have been sown in a salt solution. The + drops have undergone diffusion and subsequent cohesion, resulting in a + reticulate structure. + </div> + + <p>Few physical phenomena give us a deeper insight into the phenomena of + life than those which we here contemplate. There is still another + experiment which is even more convincing. On the surface of our + horizontal salt solution we sow a number of drops of a more concentrated + salt solution at equal distances around the circumference of a circle. + Movements of diffusion are thus set up in the interior of the circle, and + after a time, when this diffusion has become so slow as to be almost + imperceptible, a furrow begins to appear in the coloured mass. Then a + second and third appear, and others crossing the former break up the mass + <!-- Page 83 --><span class="pagenum"><a + name="page83"></a>{83}</span>into segments. Finally the segmentation + becomes complete, and the preparation presents a muriform appearance, + looking in fact something like a mulberry (Fig. 24). If the preparation + is preserved for several hours longer, we may see the cells formed by + segmentation unite around the circumference so as to form a hollow bag + corresponding to a gastrula, as shown in Fig. 25.</p> + + <div class="figright" style="width:30%;"> + <a href="images/Fig25.jpg"><img style="width:100%" src="images/Fig25.jpg" + alt="Fig. 25." title="Fig. 25." /></a> + <span class="sc">Fig. 25.</span>—The same preparation several + hours later, showing a cellular gastrula-like structure. + </div> + + <p>These preparations are extremely sensitive to external influences, + which renders the demonstration of cohesion phenomena difficult. I have + nevertheless on several occasions been able to project the experiment on + the screen during a lecture. The segmentation is influenced by very + slight currents of diffusion, and I have many preparations showing the + segmentation regularly distributed in various ways along radial diffusion + lines. We may in this way produce many varieties of structure lamellar, + vacuolate, or cellular, in fact <!-- Page 84 --><span class="pagenum"><a + name="page84"></a>{84}</span>all the tissue structures which are met with + in living organisms. All these structures are retractile, the retraction + going on very slowly for a long time, as if the force of cohesion + continued to act in the web of the structure even after its formation was + complete. The phenomenon is a purely physical synthetic reproduction of + the phenomenon of coagulation, the cohesion figure being in fact a + retractile clot.</p> + + <div class="figleft" style="width:32%;"> + <a href="images/Fig26.jpg"><img style="width:100%" src="images/Fig26.jpg" + alt="Fig. 26." title="Fig. 26." /></a> + <span class="sc">Fig. 26.</span>—Field of crystallization of + sodium chloride (magnified 60 diameters). + </div> + + <p><i>Crystallization.</i>—When we evaporate a solution of a + crystalloid it becomes more concentrated, slow movements of diffusion are + set up, and at a given moment agglomeration occurs, the agglomerates + taking the form of crystals. Thus crystallization may be regarded as a + particular case of conglomeration by cohesion, differing only in the + regularity of the arrangement of the molecules, which gives the + geometrical form of the crystal. Hence we can easily understand how the + presence of a crystalline fragment may facilitate the process of + crystallization. Consider a liquid in which extremely slow movements of + diffusion are taking place. If the liquid is perfectly homogeneous there + will be no centre of attraction to which the molecules may become + attached. <!-- Page 85 --><span class="pagenum"><a + name="page85"></a>{85}</span></p> + + <div class="figright" style="width:30%;"> + <a href="images/Fig27.jpg"><img style="width:100%" src="images/Fig27.jpg" + alt="Fig. 27." title="Fig. 27." /></a> + <span class="sc">Fig. 27.</span>—Field of crystallization around + a crystal of sodium chloride in process of formation. + </div> + + <p>If, however, a crystal or other heterogeneous structure is present, it + forms a centre of cohesion which will attach any molecules that are + brought by diffusion into its sphere of attraction. We have succeeded in + photographing the arrangement of the molecules of a liquid around a + crystal in the act of formation (Fig. 26). For this purpose we add to the + solution traces of some colloidal substance, such as gelatine or gum, so + as to delay the crystallization. It may thus be shown that the molecules + of the surrounding liquid are already arranged in crystalline order for + some distance from the crystal, forming a sort of field of + crystallization. The arrangement of this regular field varies in + different cases, and is more or less complicated according to + circumstances. One of the most frequent forms is that shown in Fig. 27, + which is the field around a crystal of sodium chloride. In the centre + <!-- Page 86 --><span class="pagenum"><a name="page86"></a>{86}</span>of + the crystal is a square with well-marked outline. At each corner of this + square there is a straight line at right angles to the diagonal, which + will form the sides of the crystal in process of formation. From the + middle of each side arise yet other perpendiculars, which in their turn + bear other cross lines, each new line being set at right angles to its + predecessor. A later stage of crystallization is shown in Fig. 27, where + the two squares one inside the other at an angle of 45° are clearly + indicated.</p> + + <div class="figright" style="width:41%;"> + <a href="images/Fig28.jpg"><img style="width:100%" src="images/Fig28.jpg" + alt="Fig. 28." title="Fig. 28." /></a> + <span class="sc">Fig. 28.</span>—Three crystals of sodium + chloride in process of formation, each in the centre of a field of + crystallization. + </div> + + <p>Every crystallizable substance gives a different characteristic field + of crystallization. In 1903, at the Congress of Angers, I terminated my + address by these words: "The field of crystallization may serve to + determine the character of a substance in solution." I have subsequently + received from Carbonell y Solès of Barcelona an interesting work on this + subject, which he contributed to the International Congress of Medicine + at Madrid in 1903, entitled <i>Applicacion de la crystalogenia + experimental à la investigacion toxicologica de cas alcaloïdes</i>. <!-- + Page 87 --><span class="pagenum"><a name="page87"></a>{87}</span></p> + + <p>Six years ago I received from Australia an exceedingly beautiful + photograph of a thin pellicle found in a rain gauge. My correspondent + supposed that this strange figure might have been produced under the + influence of an electric or magnetic field. I was able to assure him by + return of post that the figure was the result of the crystallization of + copper sulphate in a colloidal medium. In return I received a letter + verifying this fact, and saying that there were copper works in the + neighbourhood, and the air was filled with the dust of copper + sulphate.</p> + + <p>Living beings are but solutions of colloids and crystalloids, and + their tissues are built up by the aggregation of these solutes. We have + already seen how the forces of crystallization are modified in colloid + solutions. This force of crystallization must play an important rôle in + the metamorphoses of the living organism, and influence their morphology. + It may therefore be of interest to investigate some of the numberless + forms of crystallization in colloidal solutions.</p> + + <div class="figleft" style="width:32%;"> + <a href="images/Fig29.jpg"><img style="width:100%" src="images/Fig29.jpg" + alt="Fig. 29." title="Fig. 29." /></a> + <span class="sc">Fig. 29.</span>—Crystallization of sodium + chloride in a colloidal solution, giving a plant-like form. + </div> + + <div class="figright" style="width:37%;"> + <a href="images/Fig30.jpg"><img style="width:100%" src="images/Fig30.jpg" + alt="Fig. 30." title="Fig. 30." /></a> + <span class="sc">Fig. 30.</span>—Form produced by the + crystallization of chloride of ammonium in a colloidal solution. + </div> + + <p>Figs. 29 and 30 represent the forms produced by chloride of sodium and + chloride of ammonium respectively, in solutions of gelatine of different + degrees of concentration. Their resemblance to vegetable growth is so + remarkable that several observers on first seeing them have called them + "Fern-crystals."</p> + + <p>I should like here to recall to your notice the work of an English + observer, Dr. E. Montgomery of St. Thomas's <!-- Page 88 --><span + class="pagenum"><a name="page88"></a>{88}</span>Hospital, which was + published as long ago as 1865. This work was recently brought to my + notice by the kindness of Professor Baumler of Freiburg. He says: + "Crystals are not strangers in the organic world. Many organic compounds + are able to assume crystalline forms under certain conditions. Rainey has + shown that many shells consist of globular crystals <i>i.e.</i> of + mineral substances made to crystallize by the influence of viscid + material." In this connection I may also mention the interesting work of + Otto Lehmann of Karlsruhe on liquid crystals.</p> + + <p>In conclusion, we may recall the words of Schwann himself, the + originator of the cell theory: "The formation of the elementary shapes of + an organism is but a crystallization of substances capable of imbibition. + The organism is but an aggregate of such imbibing crystals."</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 89 --><span class="pagenum"><a name="page89"></a>{89}</span></p> + +<h3>CHAPTER VIII</h3> + +<p class="cenhead">KARYOKINESIS</p> + + <p>In 1873, Hermann Fol, writing of the eggs of Geryonia, thus describes + the phenomenon of karyokinesis: "On either side of the residue of the + nucleus there appears a concentration of plasma, thus forming two + perfectly regular star-like figures, whose rays are straight lines of + granulations. There are other curved rays which pass from one star or + centre of attraction to the other. The whole figure is extraordinarily + distinct, recalling in a striking manner the arrangement of iron filings + surrounding the poles of a magnet. Sachs' theory is that the division of + the nucleus is caused by centres of attraction, and I agree with him, not + on theoretical grounds, but because I have actually seen these centres of + attraction."</p> + + <p>Since the discovery of Hermann Fol, a great number of explanations + have been given, all of them theoretical, to account for the figures and + phenomena of karyokinesis. Many of these so-called explanations are + mechanical, while others invoke the aid of magnetism or electricity to + account for the resemblance of the figures of karyokinesis to the + magnetic or electric phantom or spectre. Among the authors who have dealt + with this question we may mention Hartog of Cork, Gallardo of Buenos + Ayres, and Rhumbler of Göttingen.</p> + + <p>In 1904 I presented to the Grenoble Congress, and in 1906 to the Lyons + Congress, a series of photographs and preparations of experimental + karyokinesis. I showed how, in a solution analogous to that found in the + natural cell, the simple processes of liquid diffusion, without the + intervention of magnetism or electricity, may reproduce with perfect + accuracy and in their normal sequence the whole of the movements and <!-- + Page 90 --><span class="pagenum"><a name="page90"></a>{90}</span>figures + which characterize the phenomenon of karyokinesis. This experiment + consists not merely in the production of a certain figure, such as is + obtained in the magnetic spectre, but in the reproduction of the movement + itself, and of all the successive forms which are seen in the natural + phenomenon. These are evolved before the eyes of the spectator in their + regular order and sequence.</p> + + <p>I may here reproduce the text of my communication at Grenoble: "Until + I introduced the conception of a field of diffusion, there was no proper + means of studying the phenomena of diffusion, which obey the laws of a + field of force as expounded by Faraday. Moreover, no one suspected the + possibility of reproducing by liquid diffusion a spectre analogous to the + electro-magnetic phantom. Guided by this theory of a diffusion field of + force, I have been able to reproduce experimentally the figures of + karyokinesis by simple diffusion. With regard to the achromatin spindle, + Professor Hartog has shown that the two poles of the spindle are of the + same sign, and not of opposite signs as was at first supposed. In the + process of karyokinesis the two centrosomes, <i>i.e.</i> the two poles of + the achromatin spindle, repel one another. They must therefore be poles + of the same sign. An electric or magnetic spectre showing a spindle + between two poles of the same sign is unknown; such a thing would appear + to be an absolute impossibility. What is impossible in electricity and + magnetism, however, is quite possible in the artificial diffusion field; + we can here have a spindle between two poles which repel one + another—that is, between poles of the same sign. Fig. 31 is a + photograph of such a spindle produced by diffusion. On either side are + two poles of concentration, which represent the centrosomes, each pole + being surrounded by a star-like radiation. These poles being alike, repel + one another. In the preparation one may see the distance between the two + poles slowly increase, the poles gradually separating from one another + just as do the centrosomes of an ovum during karyokinesis. This + preparation, then, which is produced entirely by diffusion, presents a + perfect resemblance to the achromatin spindle in <span class="correction" + title="Original reads 'karineyoksis'.">karyokinesis</span>. <!-- Page 91 + --><span class="pagenum"><a name="page91"></a>{91}</span></p> + + <div class="figright" style="width:39%;"> + <a href="images/Fig31.jpg"><img style="width:100%" src="images/Fig31.jpg" + alt="Fig. 31." title="Fig. 31." /></a> + <span class="sc">Fig. 31.</span>—Diffusion figure representing + karyokinesis. Achromatin spindle between two similar poles of + concentration. + </div> + + <p>"The spindle of which we give a photograph in Fig. 31 was made by + placing in salt water a drop of the same solution pigmented with blood or + Indian ink, and placing on either side of this central drop a hypertonic + drop of salt solution more lightly coloured. After diffusion had gone on + for some minutes, we obtained the figure which we have photographed. I + would draw your attention to the equatorial plane, which shows that the + spindle is not formed by lines of force passing from one pole to the + other, as would be the case between two poles of contrary sign, but by + two forces acting in opposite directions. On either side the pigment of + the central drop has been drawn towards the hypertonic centre nearest to + it. In the median line, however, the pigment is attracted in opposite + directions by equal forces, and therefore remains undisturbed, marking + the position of the equatorial plane. This observation applies equally to + the equatorial plane in natural karyokinesis, whose existence is thus + readily explained.</p> + + <p>"It is hardly necessary to insist on the fact that liquid preparations + like these are of extreme delicacy and sensitiveness, and require for + their production, and still more for their photography, the greatest care + and skill, which can only be acquired by long practice. <!-- Page 92 + --><span class="pagenum"><a name="page92"></a>{92}</span></p> + + <p>"We are able to produce by diffusion not only the achromatin spindle, + but also the segmentation of the chromatin, and the division of the + nucleus. If in the saline solution we place a coloured isotonic drop + between two coloured hypertonic drops, all the figures and movements of + karyokinesis appear successively in their due order. The central drop, + representing the nucleus between the two lateral drops or centrosomes, + first becomes granular. Next we see what appears to be a rolled-up ribbon + analogous to the chromatin band, which soon breaks into fragments + analogous to the chromosomes. These arrange themselves around, and are + gradually attracted towards the centrosomes, where they accumulate to + form two pigmented nuclear masses. A partition then makes its appearance + in the median line, and this partition becomes continuous with the + boundary of the spheres around the centrosomes. Finally we have two cells + in juxtaposition, each with its nucleus, its protoplasm, and its + enveloping membrane. I have been able to photograph these successive + stages of the segmentation of the chromatin just as I have those of the + achromatin spindle" (Fig. 32).</p> + + <div class="figright" style="width:24%;"> + <a href="images/Fig32.jpg"><img style="width:100%" src="images/Fig32.jpg" + alt="Fig. 32." title="Fig. 32." /></a> + <span class="sc">Fig. 32.</span>—Four successive stages in the + production of artificial karyokinesis by diffusion. + </div> + + <p>This memoir, written in 1904, clearly asserts the homopolarity of the + centrosomes, and shows that the nuclear division is the result of a + bipolar action, two poles of the same sign exerting their influence on + opposite sides of the nucleus. It also emphasizes the important fact that + diffusion, <!-- Page 93 --><span class="pagenum"><a + name="page93"></a>{93}</span>and as far as we know diffusion alone, is + able to produce a spindle between homologous poles.</p> + + <p>A glance at the photograph is enough to show that the spindle is + formed between poles of the same sign. The lines of diffusion radiate + from one centre and converge towards the other centre in curves, giving + the double convergence characteristic of a spindle. The central drop + merely supplies the necessary material, and should have a concentration + but slightly less than that of the plasma, so as not to set up its own + lines of diffusion. The photograph shows clearly that the rays of the + spindle traverse the equator without any break. It has been objected that + these lines form not so much a spindle as two hemi-spindles, but it is + clear that these two hemi-spindles are continuous and form a single sheaf + of rays uniting the two poles of concentration. This is a phenomenon + entirely unknown in the magnetic or electric fields, where two poles of + the same sign, one on either side of a pole of the contrary sign, give + two separate spindles. In a magnetic field it is impossible to make the + lines emanating from one pole converge, except to a pole of opposite + sign. Hence if we admit the homopolarity of the centrosomes, we must also + admit that diffusion is the <i>vera causa</i> of karyokinesis, since, as + I showed at the Grenoble Congress in 1904, diffusion and diffusion alone + is capable of producing a spindle between two poles of the same sign.</p> + + <p><i>Nuclear Division.</i>—In order to reproduce artificially the + phenomena attending the division of the nucleus, we may proceed as + follows. We cover a perfectly horizontal glass plate with a + semi-saturated solution of potassium nitrate to represent the cytoplasm + of the cell. The nucleus in the centre is reproduced by a drop of the + same solution coloured by a trace of Indian ink, the solid particles of + which will represent the chromatin granules of the nucleus. The addition + of the Indian ink will have slightly lowered the concentration of the + central drop, and this is in accordance with nature, since the osmotic + pressure of the nucleus is somewhat less than that of the plasma. We next + place on either side of the drop which represents the <!-- Page 94 + --><span class="pagenum"><a name="page94"></a>{94}</span>nucleus a + coloured drop of solution more concentrated than the cytoplasm solution. + The particles of Indian ink in the central drop arrange themselves in a + long coloured ribbon, apparently rolled up in a coil, the edges of the + ribbon having a beaded appearance. After a short time the ribbon loses + its beaded appearance and becomes smooth, with a double outline, as is + shown in A, Fig. 32. This coil or skein of ribbon subsequently divides, + forming a nuclear spindle, while the chromatin substance collects + together in the equatorial plane as in B, Fig. 32.</p> + + <p>A more advanced stage of the nuclear division is shown at C, Fig. 32, + where the chromatin bands of artificial chromosomes are grouped in two + conical sheafs converging towards the two centrosomes. For some + considerable time these conical bundles remain united by fine filaments, + the last vestiges of the nuclear spindle. The final stage is that of two + artificial cells in juxtaposition, whose nuclei are formed by the + original centrosomes augmented by the chromatin bands or chromosomes + (Fig. 32, D).</p> + + <div class="figright" style="width:27%;"> + <a href="images/Fig33.jpg"><img style="width:100%" src="images/Fig33.jpg" + alt="Fig. 33." title="Fig. 33." /></a> + <span class="sc">Fig. 33.</span>—Equatorial crown produced by + diffusion. + </div> + + <p>The resemblance of these successive phenomena to those of natural + karyokinesis is of the closest. The experiment shows that diffusion is + quite sufficient to produce organic karyokinesis, and that the only + physical force required is that of osmotic pressure. If in the cytoplasm + of a cell there are two points of molecular concentration greater than + that of the general mass, the nucleus must necessarily divide with all + the phenomena which accompany karyokinesis. In nature these two centres + of positive concentration are introduced into the protoplasm of the cell + by fecundation—that is, by the entrance of the centrosomes of the + sperm cell. In certain abnormal cases the concentration may be produced + in the cell itself by the formation of two centres of catabolism or + molecular disintegration, since, as we have seen, molecular + disintegration raises the osmotic pressure. This phenomenon, namely the + production of karyokinesis from centres of catabolism, may account for + the abnormal karyokinesis of cancer cells and the like. The subject is + one which would well repay further investigation. <!-- Page 95 --><span + class="pagenum"><a name="page95"></a>{95}</span></p> + + <div class="figleft" style="width:35%;"> + <a href="images/Fig34.jpg"><img style="width:100%" src="images/Fig34.jpg" + alt="Fig. 34." title="Fig. 34." /></a> + <span class="sc">Fig. 34.</span>—A triaster produced by + diffusion. + </div> + + <p>It has been found in our experiments that in order to obtain the + regular division of the artificial nucleus represented by the + intermediary drop, the latter must have an osmotic pressure slightly + below that of the plasma. This leads to the supposition that a similar + condition must obtain in the natural cell. It may be noticed, moreover, + that the grains of pigment follow the direction of the flow of water, + being carried along by the stream. This would appear to show that the + nucleus of a natural cell has also a molecular concentration less than + that of the plasma—a result either of dehydration of the plasma, or + of some diminution in the molecular concentration of the nucleus.</p> + + <p>Other phenomena of karyokinesis may also be closely imitated by + diffusion. For instance, in the diffusion preparation we notice at each + extremity of the equator a V-shaped figure with its apex towards the + centre, corresponding exactly to what in natural karyokinesis is called + the equatorial crown.</p> + + <p>We may also produce diffusion figures of abnormal karyokinesis. Fig. + 34 represents such a form, a triaster produced by diffusion.</p> + + <p>Artificial karyokinesis may also be produced by hypotonic poles of + concentration—that is to say, when the central drop representing + the ovum is positive and the lateral drops representing the centrosomes + are negative with respect to the plasma. In this case, however, the + resemblance to natural karyokinesis is less perfect. <!-- Page 96 + --><span class="pagenum"><a name="page96"></a>{96}</span></p> + + <p>Without attaching to it an importance which is not warranted by + experimental results, it is interesting to note that we have here two + methods of fertilization, hypertonic and hypotonic, <i>i.e.</i> by + centrosomes of greater concentration and by centrosomes of less + concentration than that of the plasma of the ovum, and that we have in + nature two corresponding results, viz. two different sexes. It is + possible that we have in these two methods of producing nuclear division + the secret of the difference of sex.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 97 --><span class="pagenum"><a name="page97"></a>{97}</span></p> + +<h3>CHAPTER IX</h3> + +<p class="cenhead">ENERGETICS</p> + + <p>Movement is everywhere; there is no such thing as immobility; the very + idea of rest is itself an illusion. Immobility is only apparent and + relative, and disappears under closer examination. All terrestrial + objects are driven with prodigious velocity around the sun, and the + dwellers on the earth's equator travel each day around the 40,000 + kilometres of its circumference. All objects on the globe are in motion, + the inanimate as well as the living. The waters rise in vapour from the + sea, float over mountain and valley, and return down the rivers to the + sea again. Still more marvellous is the current of water which flows + eternally from dew and rain, through the sap of plants and the blood of + animals to the mineral world again. The very mountains crumble and their + substance is washed down into the plains; the winds move the air and + raise the waves of the sea, whilst the strong ocean currents are produced + by variations of temperature in different parts. This agitation, this + incessant and universal motion, has been a favourite subject of poetic + contemplation. Heraclitus writes: "There is a perpetual flow, all is one + universal current; nothing remains as it was, change alone is eternal." + Ovid writes in his <i>Metamorphoses</i>: "Believe me, nothing perishes in + this vast universe, but all varies, and changes its figure. I think that + nothing endures long under the same appearance. What was solid earth has + become sea, and solid ground has issued from the bosom of the + waters."</p> + + <p>The French poetess Mme. Ackermann has expressed the same idea in + beautiful verse:—</p> + + <div class="poem"> + <div class="stanza"> + <p class="hg3">"Ainsi, jamais d'arrêt. L'immortelle matière,</p> + <p>Un seul instant encore n'a pu se reposer.</p> + <p>La Nature ne fait, patiente ouvrière,</p> + <p>Que défaire et recomposer.</p> +<!-- Page 98 --><span class="pagenum"><a name="page98"></a>{98}</span> + <p>Tout se métamorphose entre ses mains actives;</p> + <p>Partout le mouvement incessant et divers,</p> + <p>Dans le cercle éternel des formes fugitives,</p> + <p>Agitant l'immense univers."</p> + </div> + </div> + + <p>It was only towards the middle of last century that mankind in the + long search after unity in nature began to realize that all the movements + of the universe are the manifestations of a single agent, which we call + energy. In reality all the phenomena of nature may be conceived as + diverse forms of motion, and the word "energy" is the common expression + applied to all the various modes of motion in the universe. It was by the + study of heat, and more especially of thermodynamics, that we obtained + our conceptions of the science of energetics.</p> + + <p>It was in Munich in 1798 that the English engineer Count Rumford first + observed that in the operation of boring a cannon the copper was heated + to such a degree that the shavings became red-hot. This suggested his + famous experiment, in which a heavy iron pestle was turned by horse power + in a metal mortar filled with water. The water boiled, and when more + water was added this also became heated to ebullition, and so on + indefinitely. Rumford argued that the heat thus obtained in an indefinite + quantity could not be a material substance; that motion was the only + thing added to the water without limit, and that therefore heat must be + motion.</p> + + <p>While Rumford's experiment showed the transformation of motion into + heat, the steam engine was soon afterwards to demonstrate the opposite + transformation, viz. that of heat into motion.</p> + + <p>The actual state of our knowledge with regard to the science of energy + rests on two principles, that of Mayer and that of Carnot.</p> + + <p>The first principle was defined by J. R. Mayer, a medical practitioner + of Heilbronn, whose work, <i>Bemerkungen ueber die Kräfte der unbelebten + Natur</i>, was published in 1842. "All physical phenomena," says Mayer, + "whether vital or chemical, are forms of motion. All these forms of + motion are susceptible of change into one another, and in all the + transformations the <!-- Page 99 --><span class="pagenum"><a + name="page99"></a>{99}</span>quantity of mechanical work represented by + different modes of motion remains invariable."</p> + + <p>The energy of a given body is the amount of transferable motion stored + up in that body, and is measured by its capacity of producing mechanical + work.</p> + + <p>Ostwald thus defines energy: "Energy is work, all that can be obtained + from work, and all that can be changed into work." Different forms of + energy may be measured in different ways, but all forms of energy can be + measured either in units of mechanical work or in units of heat, in + kilogramme-metres or foot-pounds or in calories, according as the energy + in question is transformed into mechanical work or into heat. The first + principle of energetics, the conservation of energy, may be thus + expressed: "Energy is eternal; none is ever created, and none is ever + lost. The quantity of energy in the universe is invariable, and is + conserved for ever in its integrity."</p> + + <p>The unit by which we measure quantities of heat is the calory, the + amount of heat required to raise the temperature of one kilogramme of + water one degree Centigrade.</p> + + <p>The practical unit of mechanical work is the kilogramme-metre, the + work required to raise the weight of one kilogramme to the height of one + metre. The theoretical unit of work is one erg, the work required to move + a mass of one gramme through one centimetre against a force of one + dyne.</p> + + <p>Joule of Manchester was the first to verify Mayer's law + quantitatively. By an experiment analogous to that of Rumford, he + transformed work into heat, arranging his apparatus so that he might + measure the amount of heat produced and the work expended. On dividing + the quantity of work that had disappeared by the quantity of heat which + had been disengaged, he found that 424 kilogramme-metres of work had been + expended for each calory of heat produced.</p> + + <p>Hirn of Colmar measured the ratio of work to heat in the steam engine. + He found that for each calory of heat which had disappeared there were + produced 425 kilogramme-metres of work. <!-- Page 100 --><span + class="pagenum"><a name="page100"></a>{100}</span></p> + + <p>This number 425 has therefore been accepted as representing in + calories and kilogramme-metres the transformation of work into heat, and + of heat into work.</p> + + <p>Further measurements on the transformations of other forms of energy, + chemical energy and electrical energy, have shown that Joule's law of + equivalents is general, and that the quantity of mechanical work + represented by any form of energy remains undiminished after + transformation, whatever the nature of that transformation.</p> + + <p>Energy presents itself to us under two forms, potential and actual. + Potential energy is slumbering energy, energy localized or locked up in + the body. In order to transform potential energy into actual energy, + there is required the intervention of an additional awakening, + stimulating, or exciting energy from without. This stimulating energy may + be almost infinitesimal in amount and bears no quantitative relation to + the amount of energy transformed. It is the small amount of work required + to turn the key which liberates an indeterminate quantity of potential + energy.</p> + + <p>Actual energy, on the other hand, is energy in movement, awake and + alert, ready to be transformed into any other form of energy without the + intervention of any such external stimulating force.</p> + + <p>The passage of a given quantity of energy from the potential into the + actual state is effected gradually, and during the time of transformation + the sum of the actual and the potential energy remains constant.</p> + + <p>A weight suspended by a cord possesses a quantity of potential energy + equal to the product of its weight into the height through which it can + fall. This energy is locked up in a certain space, it cannot be + transformed without the intervention of some external energy to cut the + cord. During the falling of the weight, at the middle of its path, half + of this slumbering energy has become kinetic, and is represented by the + <i>vis viva</i> of the weight, while the other half is still potential + and is equivalent to the work which the weight will accomplish during the + second half of its fall. At any moment the sum of these two energies, the + sleeping and the waking <!-- Page 101 --><span class="pagenum"><a + name="page101"></a>{101}</span>energies, represents the total potential + energy of the weight before it began to fall.</p> + + <p>So with the powder in a gun. The potential energy of the powder cannot + become actual without some stimulus, some exciting force from without to + set it free. It is the external work of pressing the trigger that + liberates the potential energy of the powder, transforming it into the + actual energy of combustion, and the kinetic energy of the + projectile.</p> + + <p>Since energy is work, and work is a function of motion, there is in + reality no such thing as energy in repose. Matter according to our modern + conception is a complex of molecules, atoms, and electrons; we conceive + the molecules of matter as always in movement, animated with cyclic or + vibratory motion, these oscillatory or rotatory movements representing + the potential energy of the body in question. Potential energy is thus + the expression of molecular motion without translation of the molecules + as a whole in space.</p> + + <p>When this potential energy is transformed into actual energy by the + intervention of some external force, we get a current of energy, a + transference of the molecules in space. Thus, when an external force has + released the weight, the molecular orbits in the falling body change in + form, and the potential energy of the molecular motion becomes the + kinetic energy of the falling body. Similarly in the conduction of heat, + the energy of the hot body is transferred to a colder body by + transmission of the vibratory motion from molecule to molecule. So again + with chemical energy, the molecular motion of combustion may be + transformed into the radiant energy of the ethereal waves.</p> + + <p>Actual energy may be regarded as a current of molecular motion. To + make the matter clearer, let a mass of matter be represented by a + regiment of soldiers. Then each soldier will represent an electron, a + company will be an atom, and a battalion will be a molecule. As long as + the soldiers mark time, turn, or otherwise exercise without advancing, we + have simply an accumulation of potential energy. The word of command, + "March," is the exciting force which suddenly transforms this potential + into kinetic energy. The marching <!-- Page 102 --><span + class="pagenum"><a name="page102"></a>{102}</span>regiment is a + representation of a body possessing kinetic energy. Potential energy is + energy confined to a certain point in space, whereas actual energy is a + current of energy, continually changing its place or form. Energy is like + water-power—potential in the lake, actual in the waterfall or + river.</p> + + <p>Any mechanism capable of causing one form of energy to pass into + another is a transformer of energy. A steam engine is a transformer of + energy, changing caloric energy into mechanical work. An electrical + machine is a transformer of energy, converting mechanical motion into a + current of electricity, whilst an electro-motor changes the movement of + electrons into mechanical movement. Every living being, and even man + himself, is but a transformer of energy, changing the energy derived from + the earth and air and sun into mechanical motion, nervous energy, and + heat.</p> + + <p>The first law of energetics, that of the conservation of energy, is + analogous to Lavoisier's principle in chemistry, the conservation of + matter. The sign of equality which unites the terms of a chemical + equation expresses the fact that after every chemical reaction the same + total mass of matter is present as before the transformation. This is + also true of energy; after every transformation we find exactly the same + total quantity of energy as before it. This, however, tells us nothing as + to the conditions of the transformation, or the causes, <i>i.e.</i> the + anterior phenomena, which determined such transformation.</p> + + <p>The second principle of energetics, that of Carnot, enunciated in + 1824, deals with the conditions under which a transformation of energy is + possible. A mass of water at a certain height represents a quantity of + potential energy equal to the product of its weight by its height; but + this energy cannot produce mechanical work unless the water is allowed to + fall. Consider two lakes at the same altitude and of the same capacity, + one of which is entirely landlocked, while the other has an open channel + leading to the sea. Each lake represents the same quantity of potential + energy, but the energy of the landlocked lake is useless, it cannot be + <!-- Page 103 --><span class="pagenum"><a + name="page103"></a>{103}</span>transformed; whereas the other lake whose + water can run into the sea realizes the conditions necessary for + utilization, viz. the transformability of its energy. The same may be + said of all forms of energy; a heat engine can only act as a transformer, + change heat into work, if there is a difference of temperature between + its source and its sink; an electric motor can only work if there is a + fall of potential between the entrance and the exit of the electric + current.</p> + + <p>Energy presents itself to us as the product of two factors, weight and + height in the waterfall, quantity and temperature in the heat engine, + current intensity and potential in the electric motor.</p> + + <p>In considering these two factors we may note that one factor is always + a quantity (Q) and the other an intensity (I). This latter expresses some + sort of difference of position or condition, the height of the weight, a + difference of temperature in the heat engine, of pressure in the gas + engine, or of electric potential in the dynamo or electric furnace. There + can be no current of energy without this difference of potential, and + therefore no transformation from one form of energy to another.</p> + + <p>The second law of thermodynamics, Carnot's law, may therefore be + enunciated thus: "Energy cannot be transformed without a fall of + potential."</p> + + <p>We may also derive this principle from a consideration of the formula + of efficiency, the ratio of the work done by the transformer to the work + done on the transformer.</p> + + <div class="poem"> + <div class="stanza"> + <p>Efficiency = energy transformed / total energy absorbed</p> + </div> + </div> + + <p>The total energy is the product QI, <i>i.e.</i> the product of the + total quantity by the total intensity at our disposal. The transformed + energy is Q(I - I′), the product of the total quantity by the + difference of intensity at the inlet and at the outlet of the machine. + The formula for efficiency thus becomes</p> + + <div class="poem"> + <div class="stanza"> + <p>Q(I - I′) / QI = (I - I′) / I.</p> + </div> + </div> + + <p> If I represents a temperature, then in order that the efficiency may + be positive I′ must be less than I, <!-- Page 104 --><span + class="pagenum"><a name="page104"></a>{104}</span>there must be a fall of + temperature in the machine. If I′ were greater than I, <i>i.e.</i> + if the temperature at the outlet were greater than that at the inlet, the + efficiency would be a negative one, and the transformer would have to + borrow heat from some external source.</p> + + <p><i>Entropy.</i>—In every transformation of energy a certain + portion of the energy is transformed into heat: a lamp gives out useless + heat as well as light, a machine gives out useless heat as well as + mechanical work. This loss of useful energy as heat occurs in every + transference or transformation of energy; it is only in the case of heat + passing from a hotter to a colder body that there is no such + transformation. When equality of temperature is established there has + been no loss of energy, but the whole of the energy has become + unutilizable, i.e. untransformable. In the formula of efficiency the fall + of intensity I - I′ is now zero, and therefore the efficiency of + the machine</p> + + <div class="poem"> + <div class="stanza"> + <p>(I - I′) / I</p> + </div> + </div> + + <p>is also zero.</p> + + <p>Since in all its transformations a certain fraction of the energy is + changed into heat, there is a tendency in nature for all differences of + temperature to become equalized. Hence the quantity of utilizable energy + in the universe tends to diminish. Clausius called this unutilizable + energy enmeshed in the substance of a body its entropy, and showed that + in every transformation the amount of this unutilizable energy tended to + increase. "The entropy of a system always tends towards a maximum + value."</p> + + <p>If this gradual incessant increase of entropy is universal in nature, + and if there is no compensatory mechanism, the universe must be tending + towards a definite end, when the whole of its energy shall have been + transformed into unutilizable heat with a uniform temperature. There is, + however, reason to suppose that some such compensatory mechanism does in + fact exist. Behind us stretches an infinite past, and in the future we + believe that the phenomena of nature will be unrolled in a cycle which + has no end. But the arguments derived from a study of entropy apply only + to the facts and phenomena actually under our notice, the supposed <!-- + Page 105 --><span class="pagenum"><a + name="page105"></a>{105}</span>impossibility, without borrowing energy + from without, of re-establishing the differences of temperature by + drawing heat from a colder in order to concentrate it in a hotter body, + and may not be absolutely identical with those obtaining in other ages. + Our ignorance of such a phenomenon and our powerlessness to produce it in + no way argue that it is impossible. It may exist for aught we know in + some other region of space, or in another time than ours. We may perhaps + some day obtain artificially the conditions which would render possible + such a phenomenon, since it may be possible to produce in the + experimental laboratory conditions which are not spontaneously realized + in nature under present conditions. The future may perchance reveal to us + absolutely new phenomena which have not hitherto been realized. In his + work on the evolution of matter and of energy Gustave le Bon gives + expression to some interesting and original ideas on this subject.</p> + + <p>The laws of Mayer and Carnot alone are not sufficient to explain the + phenomena of life, without some consideration of the laws of stimulus. + Mayer's principle asserts the conservation of energy, and Carnot's the + conditions necessary for its transformation, but these alone cannot + account for the transformation of potential into actual energy. A weight + suspended by a cord does not fall merely because there is room for its + descent. We need the intervention of some outside force to cut the cord. + In every transformation of energy this external force is required to cut + the cord, or pull the trigger, some external force of excitation or + liberation, an energy which may be infinitesimal in amount, and which + bears no proportion to the quantity of potential energy it sets free. + This intervention of an excitatory, stimulating, or liberating energy is + universal. Every phenomenon of nature is but a transformation or a + transference of energy, determined by the intervention of a minimal + quantity of energy from without. This liberation of large quantities of + potential energy by an exceedingly small external stimulus has not + hitherto received the consideration it demands. Certain phenomena, such + as those of chemical catalysis or the action of soluble ferments, excite + our astonishment because such extremely small quantities of <!-- Page 106 + --><span class="pagenum"><a name="page106"></a>{106}</span>certain + substances will determine the chemical transformations of large + quantities of matter, there being no proportion between the amount of the + catalytic substance and of the matter transformed. These phenomena are, + however, only particular cases of the general law of energetics that + transformation requires a stimulus. The catalyzer, or ferment, does not + contribute matter to the reaction, but only the minimal energy necessary + to liberate the chemical potential energy stored in the fermenting + substance.</p> + + <p>We must therefore add a third to the two laws of energetics, Mayer's + law of conservation, and Carnot's law of fall of potential. This third + law is the law of stimulus, the necessity of the intervention of an + external excitatory force capable of setting in motion the current of + energy required for a transformation. This stimulus is the primary + phenomenon, the determinant cause of such transformation.</p> + + <p>Three conditions, then, are required for a transformation or + displacement of energy:—</p> + + <p>1. <i>The cause</i>, the intervention of a stimulus which starts the + transformation or displacement.</p> + + <p>2. <i>The possibility</i>, the necessary fall of potential.</p> + + <p>3. <i>The condition</i>, the conservation of the energy concerned, + since being indestructible its total quantity cannot alter.</p> + + <p>Every living being is a transformer of energy. The lower animals and + man himself receive from food and air the potential energy which becomes + actual under the process of oxydation. This chemical combustion is the + source of all vital energy; the ancients aptly compared life to a flame, + and Lavoisier has shown that life, like the flame, is maintained by a + process of oxydation. The energy derived from food and air is restored by + the organism to the external world in the form of heat and mechanical + motion. The celebrated experiments of Atwater show that there is an + absolute equality between the energy obtained from the oxydation of the + various aliments and the sum of the calorific and mechanical energy + liberated by a living being.</p> + + <p>Man obtains his supply of energy either directly from the <!-- Page + 107 --><span class="pagenum"><a name="page107"></a>{107}</span>vegetable + world, or indirectly from vegetables which have passed through the flesh + of animals. Vegetables in their turn obtain their substance from the + mineral world and their energy from the sun. The salts, the water, and + the carbonic acid absorbed by plants possess no store of potential + energy. Whence then can they obtain the potential energy which they + transmit to animals and man, if not from the sun? The energy of the solar + radiations is absorbed by the chlorophyll of the leaves, and stored up in + the organic carbohydrates formed by the synthesis of water and carbon. + Chlorophyll has the peculiar property of reducing carbonic acid, and + uniting the carbon with water in different proportions to form sugar and + starch, whilst fats and vegetable albumens are also formed by an + analogous reaction. All these complex bodies are stores of energy; the + vital processes of oxydation do but liberate in the human body the energy + which the chlorophyll of plants has absorbed from the solar rays.</p> + + <p>We must look, then, to the sun as the direct source of all the energy + which animates the surface of the earth. The sun looses the winds, and + raises the waters of the sea to the mountain-tops, to form the rivers and + torrents which return again to the sea; the sun warms our hearths, drives + our ships, and works our steam engines. There is no sign of life or + movement on our planet which does not come directly or indirectly from + the solar rays.</p> + + <p>It may be asked by what path does the chemical energy of the living + organism pass into the mechanical energy of motion. It would appear that + the intermediary step cannot be heat, as in the steam engine, since the + necessary temperature would be quite incompatible with life.</p> + + <p>The formula for the efficiency of a thermic transformer is</p> + + <div class="poem"> + <div class="stanza"> + <p>(T - T′) / T,</p> + </div> + </div> + + <p>the ratio of the difference of the absolute temperatures at the source + and at the sink, to the absolute temperature at the source. Calorimetric + measurements have shown that the efficiency of the human machine is about + one-fifth, <i>i.e.</i> it can transform 20 per cent. of the energy + absorbed. The ordinary temperature of muscle is 38° C., or 311° absolute. + We have <!-- Page 108 --><span class="pagenum"><a + name="page108"></a>{108}</span>therefore (T - 311) / T = .20, or T = + 388.75° absolute, <i>i.e.</i> 115.75° C. Thus, in order to obtain an + efficiency of 20 per cent. with an ordinary thermic transformer, having a + temperature of 38° at the sink, we should need a temperature of over 115° + C. at the source. Such a temperature would be quite incompatible with the + integrity of living tissues, and we may therefore conclude that the human + organism is not a heat engine.</p> + + <p>We are indeed completely ignorant of the mode of transformation of + chemical into kinetic energy in the living organism; we know only that + muscular contraction is accompanied by a change of form; at the moment of + transformation the combustion of the muscle is increased, and during + contraction the stretched muscular fibre tends to acquire a spherical + shape. It is this shortening of the muscular fibre which produces the + mechanical movement. The step which we do not as yet fully understand is + the physical phenomenon which intervenes between the disengagement of + chemical energy and the occurrence of muscular contraction. Professor + d'Arsonval supposes that this missing step is a variation in the surface + tension of the liquid in the muscular fibre. The surface tension of a + liquid is due to the unbalanced forces of cohesion acting on the surface + layer of molecules. Under the attraction of cohesion the molecules within + the liquid are in a state of equilibrium, being equally attracted in all + directions, but those at the surface of the liquid are drawn towards the + centre. The resultant of these attractive forces is a pressure normal to + the surface, which is mechanically equivalent to an elastic tension + tending to diminish the surface. In consequence of this surface tension + the liquid has a tendency to assume the form in which its surface area is + a minimum, <i>i.e.</i> the spherical form. If such a sphere is stretched + into a cylinder or fibre by mechanical tension, it will shorten itself + when released; and if by any means we increase the surface tension of + such a liquid fibre it will tend to assume a spherical form and contract + just as a muscular fibre does. The surface tension of a liquid varies + with its chemical composition; the slightest chemical modification of a + liquid alters the force of <!-- Page 109 --><span class="pagenum"><a + name="page109"></a>{109}</span>this tension. We may therefore explain the + mechanism of muscular contraction by supposing that a nervous impulse + alters in some way the rate of combustion in a muscular fibre, that this + alteration produces a momentary change in the chemical composition of the + muscular cell, and that this change of chemical composition increases the + surface tension of the cell sufficiently to provoke its contraction into + a more spherical form.</p> + + <p>Ostwald has introduced a very useful conception for the study of this + question of surface energy. A liquid surface contains a quantity of + energy equal to its surface tension multiplied by its area, hence any + variation either of area or of tension corresponds to a variation of its + energy. This novel conception constitutes a valuable addition to the + experimental study of the physiology of muscular action, since it gives + us some idea of the mechanism by which chemical energy may be transformed + into muscular contraction.</p> + + <p>Whatever the mechanism of transformation in the animal machine, we + have to consider the same quantities as in other motor machines. These + are: (1) the efficiency; (2) the potential energy; (3) the power; (4) the + energy given up to the medium under the form of heat; (5) the + temperature.</p> + + <p>Muscles, then, are merely transformers which change chemical energy + into mechanical work, the diminution of stored-up energy in a muscle + being expressed by the sensation of fatigue. A muscle may be studied in + four different phases: (1) in repose; (2) in a state of tension; (3) when + doing positive work; (4) when work is being done on it.</p> + + <p>When a muscle is in a state of tension, as when a weight is sustained + by the outstretched arm, the muscle is producing no external work. The + entire work done is converted into heat; just as it is in a dynamo or + steam engine which is prevented from turning by a brake. Muscular + contraction produces fatigue even when it does no external work. It is + impossible for the muscle to support even the weight of the outstretched + arm itself for any considerable time.</p> + + <p>A muscle is doing positive work when it is raising a weight or moving + a body from one point to another. <!-- Page 110 --><span + class="pagenum"><a name="page110"></a>{110}</span></p> + + <p>The fourth state of muscular contraction is when the muscle is doing + negative work, <i>i.e.</i> when work is being done on it, as for instance + when we go downstairs, or when a descending weight forces down the + opposing arm which attempts to support it. In this case the muscles + receive a portion of the energy lost by the descending weight, and this + energy shows itself in the muscle in the form of heat. This increase of + heat in a muscle doing negative work has been clearly demonstrated by the + calorimetric experiments of Hirn and the thermometric experiments of + Béclard. Hirn's observations on muscular calorimetry show a production of + heat corresponding to 150 calories per hour when in repose, 248 calories + per hour during positive work, and 287 during negative work. Béclard's + thermometric measurements also show that the temperature of a muscle + rises each time that it contracts, and that the rise of temperature is + greatest when the muscle is doing negative work, least during positive + work, and intermediate when in a state of tension.</p> + + <p>It is of the greatest importance in medical practice to distinguish + between these different forms of muscular activity. There is a vast + physiological difference between muscular contraction with the production + of positive work, and muscular contraction without the production of + work, or with negative work. To climb a flight of stairs is to contract + the muscles with the production of work equal to the weight of the body + multiplied by the height of the stairs. To descend the stairs is to + contract the same muscles, but with the production of negative work, and + consequently a maximum of heat. To walk on level ground is to contract + the muscles with the production of little or no external work; as in a + machine turning without friction in a vacuum.</p> + + <p>We have seen that a fall of potential and a current of energy are the + necessary conditions for the production of any natural phenomenon. Hence + we may assume that the phenomenon of sensation is also accompanied by a + fall of potential and a current of energy. When we touch a hot body, + there is a flow of energy from the hot body to the hand. When we touch a + cold body, there is a current of energy in the opposite direction, <!-- + Page 111 --><span class="pagenum"><a name="page111"></a>{111}</span>from + the hand to the body. It was formerly held, and is still held by some + physiologists, that the chief characteristic of life is the disproportion + between an excitation and the response which it invokes from the + organism. Such a doctrine can only be held by one who believes, at least + implicitly, that the phenomena of life are supernatural, or at all events + different in their nature from all other phenomena; for the disproportion + between an excitation and the response it evokes is by no means confined + to living things. This disproportion is universal in nature, and quite in + conformity with the physical laws which govern the transformation of + energy. The energy of living things is potential energy—a fact + which has been too little recognized. In the case of reflex actions it is + self-evident, because the response is immediate, and always the same for + the same stimulus. As in all other transformations, the stimulus consists + in the intervention of a minimal quantity of external energy.</p> + + <p>Long before the discovery of the laws of energy, Lamarck had + recognized and formulated this fact. He writes: "What would vegetable + life be without excitations from without, what would be the life even of + the lower animals without this cause?" In another passage, seeking for a + power capable of exciting the action of the organism, he says: "The lower + animal forms, without nervous system, live only by the aid of excitations + which they receive from without. In the lowest forms of life this + exciting force is borrowed directly from the environment, while in the + higher forms the external exciting force is transferred to the interior + of the living being and placed at the disposal of the individual."</p> + + <p>This remark, that the movements of living things are not communicated + but excited, that the external excitation only sets free latent or + potential energy in the organism, shows that Lamarck had penetrated more + deeply than many of the modern physiologists into the secrets of + biological energy. We seek in vain in the text-books of physiology for + any conception of potential energy in living beings, or the notion of an + exciting force as the cause of sensation. All action of a living organism + is reflex action. Every action has a cause, and <!-- Page 112 --><span + class="pagenum"><a name="page112"></a>{112}</span>the cause of an organic + action is an exciting energy from without, either immediate, or stored up + in the nervous system from an external impression made at some previous + epoch. Actions which are not evidently reflex are merely delayed + reflexes; we have acquired the power of inhibiting, delaying, or + modifying the response to an external stimulus, so that the same + excitation may determine responses of very different kinds according to + the mood produced by previous impressions. When carefully investigated, + no action of ours is automatic; every movement is determined by + impressions derived from without. An action without a motive, that is + without an external determining cause, would be an action without + reason.</p> + + <p>In conclusion, we may formulate this general principle: The energy of + a living being is potential energy; sensations represent the intervention + of an external exciting energy which provokes the response, <i>i.e.</i> + the transformation of the potential energy already stored in the organism + into the actual energy of motion and vital activity.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 113 --><span class="pagenum"><a name="page113"></a>{113}</span></p> + +<h3>CHAPTER X</h3> + +<p class="cenhead">SYNTHETIC BIOLOGY</p> + + <p>The course of development of every branch of natural science has been + the same. It begins by the observation and classification of the objects + and phenomena of nature. The next step is to decompose the more complex + phenomena in order to determine the physical mechanism underlying + them—the science has become analytical. Finally, when the mechanism + of a phenomenon is understood, it becomes possible to reproduce it, to + repeat it by directing the physical forces which are its cause—the + science has now become synthetical.</p> + + <p>Modern biology admits that the phenomena of life are physico-chemical + in their nature. Although we have not as yet been able to define the + exact nature of the physical and chemical processes which underlie all + vital phenomena, yet every further discovery confirms our belief that the + physical laws of life are identical with those of the mineral world, and + modern research tends more and more to prove that life is produced by the + same forces and is subject to the same laws that regulate inanimate + matter.</p> + + <p>The evolution of biology has been the same as that of the other + sciences; it has been successively descriptive, analytical, and + synthetic. Just as synthetic chemistry began with the artificial + formation of the simplest organic products, so biological synthesis must + content itself at first with the fabrication of forms resembling those of + the lowest organisms. Like other sciences, synthetic biology must proceed + from the simpler to the more complex, beginning with the reproduction of + the more elementary vital phenomena. Later on we may hope to <!-- Page + 114 --><span class="pagenum"><a name="page114"></a>{114}</span>unite and + associate these, and to observe their development under various external + influences.</p> + + <p>The synthesis of life, should it ever occur, will not be the + sensational discovery which we usually associate with the idea. If we + accept the theory of evolution, then the first dawn of the synthesis of + life must consist in the production of forms intermediate between the + inorganic and the organic world—forms which possess only some of + the rudimentary attributes of life, to which other attributes will be + slowly added in the course of development by the evolutionary action of + the environment.</p> + + <p>Long ago, the penetrating genius of Lamarck seized on the idea that a + knowledge of life could only be obtained by the comparison of organic + with inorganic phenomena. He writes: "If we would acquire a real + knowledge of what constitutes life, of what it consists, what are the + causes and the laws which give rise to this wonderful phenomenon of + nature, and how life can be the source of the multitude of forms + presented to us by living organisms, we must before all consider with + great attention the differences which exist between inorganic and living + bodies; and for this purpose we must compare side by side the essential + characters of these two classes of bodies."</p> + + <p>Synthetic biology includes morphogeny, physiogeny, and synthetic + organic chemistry, which is also a branch of synthetic biology, since it + deals with the composition of the constituents of living organisms. + Synthetic organic chemistry is already a well-organized science, + important by reason of the triumphs which it has already gained. The + other two branches of biological synthesis, morphogeny, the synthesis of + living forms and structures, and physiogeny, the synthesis of functions, + can hardly as yet be said to exist as sciences. They are, however, no + less legitimate and no less important than the sister science of + synthetic chemistry.</p> + + <p>Although morphogeny and physiogeny do not exist as well-organized and + recognized sciences, there are already a number of works on the subject + by enthusiastic pioneers—independent seekers, who have not feared + to abandon the paths of official science to wander in new and hitherto + unexplored domains. <!-- Page 115 --><span class="pagenum"><a + name="page115"></a>{115}</span></p> + + <p>The first experiment in physiogeny was the discovery of osmosis by the + Abbé Nollet in 1748. He filled a pig's bladder with alcohol, and plunged + it into water. He noticed that the bladder gradually increased in volume + and became distended, the water penetrating into the interior of the + bladder more quickly than the alcohol could escape. This was the first + recorded experiment in the physics of nutrition and growth.</p> + + <p>In 1866, Moritz Traube of Breslau discovered the osmotic properties of + certain chemical precipitates. As I pointed out in the <i>Revue + Scientifique</i> of March 1906, Traube made the first artificial cell, + and studied the osmotic properties of membranes and their mode of + production. This remarkable research should have been the starting-point + of synthetic biology. The only result, however, was to give rise to + numberless objections, and it soon fell into complete oblivion. "There + are," says Traube, "a number of persons quite blind to all progress, who + in the presence of a new discovery think only of the objections which may + be brought against it." The works of Traube have been collected and + published by his son (<i>Gesammelte Abhandlungen von Moritz Traube</i>, + 1899).</p> + + <p>In 1867 there appeared in England a paper by Dr. E. Montgomery, of St. + Thomas's Hospital, <i>On the Formation of so-called Cells in Animal + Bodies</i>. This paper, published by Churchill & Sons, is a most + interesting contribution and one of great originality. The author says: + "There can be no compromise between the tenets of the cell theory and the + conclusions arrived at in this paper; the distinction is thorough. Either + the units of which an organism is composed owe their origin to some kind + or other of procreation, a mysterious act of that mysterious entity life, + by which, in addition to their material properties, they become endowed + with those peculiar metaphysical powers constituting vitality. Or, on the + other hand, the organic units, like the crystalline units of inorganic + bodies, form the organism by dint of similar inherent qualities, form in + fact a living being possessed of all its inherent properties, as soon as + certain chemical compounds are placed under certain physical conditions. + If the former opinion be <!-- Page 116 --><span class="pagenum"><a + name="page116"></a>{116}</span>true, then we must clearly understand that + there exists naturally a break in the sequence of evolution, a chasm + between the organic and the inorganic world never to be bridged over. If, + on the contrary, the latter view be correct, then it strongly argues for + a continuity of development, a gradual chemical elaboration, which + culminates in those high compounds which, under surrounding influences, + manifest those complex changes called vital.</p> + + <p>"Surely it is not a matter of indifference or of mere words, if the + extreme aim of physiology avowedly be the detection of the different + functions dependent on the vital exertions of a variety of ultimate + organisms, and the discovery of the specific stimulants which naturally + incite these functions into play. Or, on the other hand, if it be + understood to consist rather in the careful investigation of the + succession of chemical differentiations and their accompanying physical + changes, which give rise to the formation of a variety of tissues that + are found to possess certain specific properties, to display certain + definite actions due to a further flow of chemical and physical + modifications."</p> + + <p>In 1871 there appeared a memoir by the Dutch savant Harting entitled + <i>Recherche de Morphologie synthetique sur la production artificielle de + quelques formations calcaires organiques</i>. This memoir, says Professor + R. Dubois, had cost Harting more than thirty years of work. "Synthetic + morphology is yet only in its infancy, let us hope that in a time equal + to that which has already expired since the first artificial production + of urea, it will have made a progress equal to that of its older sister, + synthetic chemistry."</p> + + <p>In the <i>Comptes Rendues</i> of 1882 is the following note by D. + Monnier and Karl Vogt:—</p> + + <p>"1. Figured forms presenting all the characteristics of organic + growth, cells, porous canals, tubes with partition walls, and + heterogeneous granules, may be produced artificially in appropriate + liquids by the mutual action of two salts which form one or more + insoluble salts by double decomposition. One of the component salts + should be in solution, while the other salt must be introduced in the + solid form. <!-- Page 117 --><span class="pagenum"><a + name="page117"></a>{117}</span></p> + + <p>"2. Such forms of organic elements, cells, tubes, etc., may be + produced either in an organic liquid or a semi-organic liquid such as + sucrate of lime, or in an absolutely inorganic liquid such as silicate of + soda. Thus there can no longer be any question of distinctive forms as + characterizing organic bodies in contradistinction to inorganic + bodies.</p> + + <p>"3. The figured elements of these pseudo-organic forms depend on the + nature, the viscosity, and the concentration of the liquids in which they + are produced. Certain viscous liquids such as solutions of gum arabic or + chloride of zinc do not produce these forms.</p> + + <p>"4. The form of these artificial pseudo-organic products is constant, + as constant as that of the crystalline forms of mineral salts. This form + is so characteristic that it may often serve for the recognition of a + minimal proportion of a substance in a mixture. The observation of these + forms is a means of analysis as sensitive as that of the spectrum. We + may, for example, differentiate in this way the alkaline bicarbonates + from the sesqui-carbonates or the carbonates.</p> + + <p>"5. The form of these artificial pseudo-organic elements depends + principally on the nature of the acid radical of the solid salt. Thus the + sulphates and the phosphates generally produce tubes, while the + carbonates form cells.</p> + + <p>"6. As a rule these pseudo-organic forms are engendered only by + substances which are found in the living organism. Thus sucrate of + calcium will engender organic forms, whereas sucrate of strontium or + barium does not do so. There are, however, some exceptions to this rule, + such as the sulphates of copper, cadmium, zinc, and nickel.</p> + + <p>"7. These artificial pseudo-organic elements are surrounded by + veritable membranes, dializing membranes which allow only liquids to pass + through them. These artificial cells have heterogeneous cell-contents, + and produce in their interior granulations which are disposed in a + regular order. Thus they are both in constitution and in form absolutely + similar to the cellular elements which constitute living organisms.</p> + + <p>"8. It is probable that the inorganic elements which are present in + the natural protoplasm may play an important part <!-- Page 118 --><span + class="pagenum"><a name="page118"></a>{118}</span>in determining the form + which is assumed by the figured elements of the organism."</p> + + <p>In 1902, Professor Quinke of Heidelberg, who has consecrated his life + with such distinction to the physics of liquids, writes thus of the + organogenic power of liquids in a paper published in the <i>Annalen der + Physik</i> under the title "Unsichtbare Flüssigkeitschichten": "In 1837, + Gustav Rose obtained organic forms by precipitation from inorganic + solutions. By precipitating chloride of calcium with the carbonates of + ammonium and other alkaline carbonates, he obtained small spheres which + grew and were transformed into calcic rhombohedra. He also obtained a + flocculent precipitate which later became granular and showed under the + microscope forms like the starfish, and discs with undulated borders. At + Freiberg, in certain stalactites, Rose also discovered forms consisting + of six pyramidal cells around a spherical nucleus.</p> + + <p>"In 1839, Link obtained spherical granulations by the precipitation of + calcic or plumbic solutions by potash, soda, or carbonic acid. These + spherical granulations united after a time to form crystals. Sulphate of + iron, ammoniated sulphate of zinc, sulphate of copper precipitated by + sulphuretted hydrogen, and saline solutions precipitated by ferrocyanide + of potash, all give granular precipitates or discs, of which the granular + origin is quite perceptible.</p> + + <p>"Runge in 1855 was the first to describe the formation of periodic + chemical precipitates. He used blotting paper as the medium in which + various chemical substances met by diffusion. In this way he studied the + mutual reactions of solutions of ferrocyanide of potash, chloride of + iron, and the sulphates of copper, iron, manganese, and zinc. The + coloured precipitates appeared at different positions in the paper, and + disappeared periodically at greater or longer intervals. The designs + formed by these coloured precipitates change with the concentration of + the saline solutions, or on the addition of oxalic acid, salts of potash + or ammonia, and other substances. These designs are shown in a number of + beautiful illustrations which accompany the work. In this <!-- Page 119 + --><span class="pagenum"><a name="page119"></a>{119}</span>case the + capillarity of the paper necessarily exerts a certain influence on the + formation of the figures, but in addition to this, Runge admits the + intervention of another force hitherto unknown, which he calls + 'Bildungstrieb,' the formative impulse, which he considers to be the + elementary vital force in the formation of plants and animals.</p> + + <p>"In 1867, R. Böttger obtained arborescent forms and ramifications of + metallic vegetation by sowing fragments the size of a pea of crystals of + the iron chlorides, chloride of cobalt, sulphate of manganese, nitrate + and chloride of copper, etc., in an aqueous solution of silicate of + sodium of specific gravity 1.18. These forms are due, as I shall show + later on, to the surface tension of the oily precipitate; Böttger gives + no explanation of the phenomenon.</p> + + <p>"To this force, viz. that of surface tension, is also due the cellular + forms obtained by Traube in 1866. These were obtained from gelatine and + tannin, from acetate of copper or lead, and from nitrate of mercury in an + aqueous solution of ferrocyanide of potassium. These cells and + precipitated membranes have also been studied by Reinke, F. Cohn, H. de + Vries, and myself, who all observed the regression of these membranes, + which although colloidal at the beginning of the reaction speedily become + friable. This entirely refutes the opinion of Traube as to the + constitution of the precipitated membranes. He supposed them to consist + of masses of solid substance, with smaller orifices which do not permit + the passage of the membranogenous substance, whilst the larger orifices + through which it can pass are soon closed by the precipitate, the + membrane itself thus growing by a process of intussusception.</p> + + <p>"Later on Traube himself considered the precipitated membrane to be a + thin, solid gelatinous layer in which the water was mechanically + entangled.</p> + + <p>"Tamman has also made a number of experiments with solutions of the + chlorides and sulphates of the heavy metals, and solutions of phosphates, + silicates, ferrocyanides, and other salts. He found that most of these + membranes were permeable to the membranogenous solution. According to + Tamman, all <!-- Page 120 --><span class="pagenum"><a + name="page120"></a>{120}</span>precipitated membranes are hydrated + substances, and some of them, like the ferrocyanide of copper and the + tannate of gelatine are, when first formed, entirely comparable to liquid + membranes in all their properties.</p> + + <p>"Graham had already obtained colourless jellies by the interaction of + concentrated solutions of ferrocyanide of potassium and sulphate of + copper. Bütschli also has recently described the microscopic appearance + of precipitated membranes produced by ferrocyanide of potassium and + acetate or chloride of iron.</p> + + <p>"Like Linke and Gustav Rose, Famintzin has obtained spheroidal + precipitates by the reciprocal action of concentrated solutions of + chloride of calcium and carbonate of potassium. These grow rapidly and + suddenly, with concentric layers showing a spherical or flattened + nucleus. He also obtained forms resembling sphero-crystals and starch + grains.</p> + + <p>"Harting, Vogelsang, Hansen, Bütschli, and others have studied the + structures which are formed by the reciprocal action of chloride of + calcium and the alkaline carbonates. Vogelsang has found small calcareous + bodies in the amorphous and globular precipitate formed by chloride of + calcium and carbonate of ammonium. He describes spheres attached to one + another, vesicles, and muriform structures. The number of these spheroids + is increased by the addition of gelatine. Hansen has also studied + Harting's method for the formation of sphero-crystals by the action of + the alkaline carbonates and phosphates on the salts of calcium in + presence of albumen and gelatine. He considers that the latter retard the + crystallization and assist the formation of the sphero-crystals.</p> + + <p>"I shall show later on that gelatine and albumen essentially modify + the precipitate and do not merely act as catalytic substances. The + researches of <span class="correction" title="Original reads 'Famitzin'." + >Famintzin</span>, repeated and extended by Bütschli, show that + sphero-crystals are produced by the reaction of chloride of calcium on + carbonate of potassium without the presence of gelatine or albumen. + Bütschli studied the spheroids of carbonate of lime by means of polarized + light, and found that the layers were alternately positively and + negatively polarized." <!-- Page 121 --><span class="pagenum"><a + name="page121"></a>{121}</span></p> + + <p>Such is the history of morphogenesis as described in 1902 by the + authority most qualified for the task, Professor Quinke of + Heidelberg.</p> + + <p>In 1904, Professor Moritz Benedikt of Vienna treated the whole + question in his book, <i>Crystallization and Morphogenesis</i>, of which + a French translation appeared in the Maloine Library. This book is full + of original and suggestive ideas; it describes the work of Harting, and + more especially that of Van Schroën, who considers that crystals like + living beings begin as a cell and grow by a process of intussusception. + Professor Benedikt has made a complete résumé of the question in an + article, "The Origins of the Forms of Life," which appeared in the + <i>Revue Scientifique</i> in 1905.</p> + + <p>In 1904, Professor Dubois of Lyons presented a report to the Society + of Biology on his interesting experiments on mineral cytogenesis. The + same year he gave a discourse at the university of Lyons on "The Creation + of Living Beings," which has been published by A. Storck of Lyons.</p> + + <p>One of the most active of the modern morphogenists is Professor + Herrera of Mexico, whose work is illustrated in the <i>Atlas de + Plasmogenie</i> by Dr. Jules Félix of Brussels, one of the most + enthusiastic disciples of the new science. There is a résumé of Herrera's + work in the <i>Memoirs of the Societé Alzate, Mexico</i>.</p> + + <p>A bibliography of the works which have appeared on this subject may be + found in the book of Professor Rhumbler of Göttingen, <i>Aus dem + Lückengebiete zwischen Organischer und Anorganischer Materie</i>, + 1906.</p> + + <p>In 1907, Dr. Luiz Razetti of Carracas published a magnificent study of + the subject under the title <i>Que es la vida</i>.</p> + + <p>In 1907, Dr. Martin Kuckuck of St. Petersburg repeated and extended + the experiments of R. Dubois, and published his results under the title + <i>Archigonia, Generatio Spontanea</i>, Leipzig, Ambrosius Barth.</p> + + <p>Butler Burke of Cambridge has also made a series of experiments with + radium and barium salts analogous to those of Dubois.</p> + + <p>In 1909, Albert and Alexandre Mary of Beauvais published <!-- Page 122 + --><span class="pagenum"><a name="page122"></a>{122}</span>an interesting + study of this question under the title <i>Études expérimentales sur la + génération primitive</i>, published by Jules Rousset.</p> + + <p>I should mention also among the works of synthetic biology the + publications of Professor Otto Lehmann of Karlsruhe, and in particular + <i>Flüssige Krystalle und die Theorien des Lebens</i>, Leipzig, Ambrosius + Barth.</p> + + <p>Professor Ulenhuth of Berlin has published his study on the osmotic + growth of iron in alkaline hypochlorites under the title + <i>Untersuchungen ueber Antiformin</i>, Berlin, Julius Springer.</p> + + <p>Professor Gariel has made a series of researches on osmotic growth + which are published in Abraham's <i>Recueil d'expériences de + physique</i>.</p> + + <p>A. Lecha Marzo of Valladolid published his researches on the growth of + aniline colours in the <i>Gaceta Medica Catalana</i>, 1909, under the + title <i>Otra nueva flora artificiale</i>.</p> + + <p>Dr. Maurice d'Halluin of Lille has also published a volume on osmotic + growths under the title, <i>Stéphane Leduc a-t-il créé la vie?</i></p> + + <p>The subjects of the numerous memoirs that I have myself published + during the last ten years upon the question are treated anew in the pages + of this volume, and a résumé of my researches on osmotic growth has + already appeared in the <i>Documents du Progrès</i>, Sept. 1909.</p> + + <p>We have thus shown that synthetic morphogenesis has already attracted + the attention of a certain number of ardent investigators. Morphogeny has + now its methods and its results, and physiogeny is also developing side + by side with it, since function is but the result of form. The field of + research is opened, and workers alone are needed in order to reap an + abundant harvest.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 123 --><span class="pagenum"><a name="page123"></a>{123}</span></p> + +<h3>CHAPTER XI</h3> + +<p class="cenhead">OSMOTIC GROWTH—A STUDY IN MORPHOGENESIS</p> + + <p>The phenomenon of osmotic growth has doubtless presented itself to the + eyes of every chemist; but to discover a phenomenon it is not enough + merely to have it under our eyes. Before Newton many a mathematician had + seen a spectrum, if only in the rainbow; many an observer before Franklin + had watched the lightning. To discover a phenomenon is to understand it, + to give it its due interpretation, and to comprehend the importance of + the rôle which it plays in the scheme of nature.</p> + + <p><i>Osmotic Membranes.</i>—Certain substances in concentrated + solution have the property of forming osmotic membranes when they come in + contact with other chemical solutions. When a soluble substance in + concentrated solution is immersed in a liquid which forms with it a + colloidal precipitate, its surface becomes encased in a thin layer of + precipitate which gradually forms an osmotic membrane round it.</p> + + <p>An osmotic membrane is not a semi-permeable membrane, as sometimes + described, <i>i.e.</i> a membrane permeable to water but impermeable to + the solute. It is a membrane which opposes different resistances to the + passage of water and of the various substances in solution, being very + permeable to water, but much less so to the different solutes.</p> + + <p>A soluble substance thus surrounded by an osmotic membrane represents + what Traube has called an artificial cell. In such a cell the dissolved + substances have a very high osmotic pressure, an expansive force like + that of steam in a boiler; the molecules of the solute exerting pressure + on the walls of the extensible cell, and distending it like the <!-- Page + 124 --><span class="pagenum"><a name="page124"></a>{124}</span>gas in a + balloon. This pressure increases the volume of the cell, and in + consequence water rushes in through the permeable membrane and still + further distends the cell. Most beautiful osmotic cells may be produced + by dropping a fragment of fused calcium chloride into a saturated + solution of potassium carbonate or tribasic potassium phosphate, the + calcium chloride becoming surrounded by an osmotic membrane of calcium + carbonate or calcium phosphate. This mineral membrane is beautifully + transparent and perfectly extensible. It is astonishing to contemplate + the contrast between the hard crystalline forms of ordinary chalk and + these soft transparent elastic membranes which have the same chemical + constitution. These osmotic cells of carbonate of lime or phosphate of + lime consist of a transparent membrane enclosing liquid contents and a + solid nucleus of chloride of calcium. Their form is that of an ovoid or + flattened sphere, and they may attain a diameter of seven centimetres or + more.</p> + + <p>More frequently the osmotic growth consists of a number of cells + instead of one large cell. The first cell gives birth to a second cell or + vesicle, and this to a third, and so on, so that we finally obtain an + association of microscopic cellular cavities, separated by osmotic + walls—a structure completely analogous to that which we meet with + in a living organism.</p> + + <p>We may easily picture to ourselves the mechanism by which an osmotic + cell gives birth to such a colony of microscopic vesicles. The + membranogenous substance, the chloride of calcium, diffuses uniformly on + all sides from the solid nucleus, and forms an osmotic membrane where it + comes into contact with the solution. This spherical membrane is extended + by osmotic pressure, and grows gradually larger. Since the area of the + surface of a sphere increases as the square of its radius, when the cell + has grown to twice its original diameter, each square centimetre of the + membrane will receive by diffusion but a quarter as much of the + membranogenous substance. Hence, after a time, the membrane will not be + sufficiently nourished by the membranogenous substance, it will break + down, and an aperture will occur through which the interior liquid oozes + out, forming in its turn a new <!-- Page 125 --><span class="pagenum"><a + name="page125"></a>{125}</span>membranous covering for itself. This is + the explanation of the fact that all living organisms are formed by + colonies of microscopical elements, although we must not forget that + Nature often produces similar results in different ways.</p> + + <div class="figright" style="width:24%;"> + <a href="images/Fig35.jpg"><img style="width:100%" src="images/Fig35.jpg" + alt="Figs. 35 & 36." title="Figs. 35 & 36." /></a> + <span class="sc">Fig. 35.</span> + + <span class="sc">Fig. 36.</span> + + <p class="cenhead">Osmotic growths of ferrocyanide of copper.</p> + </div> + + <p>Osmotic growths may be obtained from a great number of chemical + substances. The most easily grown are the soluble salts of calcium in + solutions of alkaline phosphates and carbonates, to which we have already + alluded. We may also reverse the phenomenon by growing phosphates and + carbonates in solutions of calcium salts, but in this case the osmotic + growths are not so beautiful.</p> + + <p>The various silicates play an important part in the constitution of + shells and of the skeletons of marine animals. Most of the metallic + salts, and more especially the soluble salts of calcium, give rise to the + phenomenon of osmotic growth when sown in solutions of the alkaline + silicates. In this way, by using different silicates and varying the + proportions and the concentrations, we may obtain an immense variety of + osmotic growths.</p> + + <p>A good solution to commence with is the following:—</p> + +<table class="nob" summary="Good solution to commence with." title="Good solution to commence with."> +<tr><td class="spacsingle"> Silicate of potash, sp. gr. 1.3 (33° Beaumé) </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> 60 gr.</td></tr> +<tr><td class="spacsingle"> Saturated solution of sodium carbonate </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> 60 gr.</td></tr> +<tr><td class="spacsingle"> Saturated solution of dibasic sodium phosphate </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> 30 gr.</td></tr> +<tr><td class="spacsingle"> Distilled water </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> make up to 1 litre.</td></tr> +</table> + +<p><!-- Page 126 --><span class="pagenum"><a name="page126"></a>{126}</span></p> + + <p>A fragment of fused calcium chloride dropped into this solution will + produce a rapid growth of slender osmotic forms which may attain a height + of 20 or 30 centimetres.</p> + + <p>Small pellets may also be made of one part of sugar and two of copper + sulphate and sown in the following solution, which must be kept warm + until the growth is complete:—</p> + +<table class="nob" summary="Gelatine solution." title="Gelatine solution."> +<tr><td class="spacsingle"> Ten per cent. solution of gelatine </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> 10 to 20 c.c.</td></tr> +<tr><td class="spacsingle"> Saturated solution of potassium ferrocyanide </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> 5 to 10 c.c.</td></tr> +<tr><td class="spacsingle"> Saturated solution of sodium chloride </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> 5 to 10 c.c.</td></tr> +<tr><td class="spacsingle"> Warm water (32° to 40° C.) </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> 100 c.c.</td></tr> +</table> + + <p>In this solution we can obtain osmotic growths which may attain to a + height of 40 centimetres or more, vegetable forms, roots, arborescent + twigs, leaves, and terminal organs. These growths are stable as soon as + the gelatine has cooled and set, and may be carried about without fear of + injury (Fig. 35).</p> + + <p>Precipitated osmotic membranes are very widely distributed in nature. + Professor Ulenhuth has seen iron growths in alkaline sodium hypochlorite + (Javelle water), and Lecha-Marzo has demonstrated the osmotic growth of + the various <!-- Page 127 --><span class="pagenum"><a + name="page127"></a>{127}</span>stains used for microscopy, in the liquids + used for fixing preparations.</p> + + <div class="figright" style="width:47%;"> + <a href="images/Fig37.jpg"><img style="width:100%" src="images/Fig37.jpg" + alt="Fig. 37." title="Fig. 37." /></a> + <span class="sc">Fig. 37.</span>—Osmotic vermiform growth. + + <p class="poem">(<i>a</i>) The sickle-shaped growth.</p> + + <p class="poem">(<i>b</i>) The growth broken by the upward pressure of + the solution.</p> + + <p class="poem">(<i>c</i>) The wound having cicatrized, the stem + continues to grow downwards. </p> + </div> + + <p>We now know that the physical force which builds up these growths is + that of osmotic pressure, since the slightest consideration will show the + inadequacy of the usual explanation that the growth is due to mere + differences of density, or to amorphous precipitation around bubbles of + gas. These may indeed affect the phenomenon, but can in no way be + regarded as its cause.</p> + + <p>One of our experiments throws considerable light on this question. In + a glass vessel we placed a concentrated solution of carbonate of + potassium, to which had been added 4 per cent. of a saturated solution of + tribasic potassium phosphate. Into this solution we dropped a fragment of + fused calcium chloride, and obtained a vermiform growth some 6 + millimetres in diameter. This growth was curved, at first growing + upwards, then for a short distance horizontally, and finally downwards. + The upward pressure of the solution, which was heavier than the growth, + ultimately broke it at the top of the curve, as shown at <i>b</i>, Fig. + 37. The liquid contents of the growth began to ooze out through the + wound, but this after a time became cicatrized, and the stem continued to + grow obstinately downwards once more, in opposition to the hydrostatic + pressure. In consequence of this pressure the growth is sinuous, tacking + as it were from side to side like a boat against the wind. We give three + successive photographs of this growth, which attained a length of over 10 + inches. We have frequently obtained these vermiform growths forming a + series of such loops, growing upwards and falling again many times in + succession.</p> + + <p><i>Osmotic Growths in Air.</i>—Certain of these artificial cells + may be made to grow out of the solution into the air. For this purpose we + place a fragment of CaCl<sub>2</sub> in a shallow flat-bottomed glass + dish, just covering the fragment with liquid. The best solution is as + follows:—</p> + +<table class="nob" summary="Solution for growth into air." title="Solution for growth into air."> +<tr><td class="spacsingle"> Potassium carbonate, saturated solution </td><td class="spacsingle"> 76 parts.</td></tr> +<tr><td class="spacsingle"> Sodium sulphate, saturated solution </td><td class="spacsingle"> 20 ,,</td></tr> +<tr><td class="spacsingle"> Tribasic potassium phosphate, saturated solution </td><td class="spacsingle"> 4 ,,</td></tr> +</table> + +<p><!-- Page 128 --><span class="pagenum"><a name="page128"></a>{128}</span></p> + + <p>The calcium chloride surrounds itself with an osmotic membrane; water + penetrates into the interior of the cell thus formed, and a beautiful + transparent spherical cell is the result, the summit of which soon + emerges from the shallow liquid. The cell continues to increase by + absorption of the liquid at its base, and may grow up out of the liquid + into the air for as much as one or two centimetres.</p> + + <p>This is a most impressive spectacle, an osmotic production, half + aquatic and half aerial, absorbing water and salts by its base, and + losing water and volatile products by evaporation from its summit, while + at the same time it absorbs and dissolves the gases of the + atmosphere.</p> + + <p>The aerial portion of an osmotic growth will sometimes become + specialized in form. The summit of the growth develops a sort of crown or + cup surrounded by a circular wall. This cup contains liquid, and + continues to grow up into the air like the stem of a plant, carrying with + it the liquid which has been absorbed by the base of the growth.</p> + + <p>The preceding experiments give us an explanation of the curious + phenomena exhibited by so-called creeping salts. A saline solution left + at the bottom of a vessel will sometimes be found after some months to + have crept up to the top of the vessel. Cellular partitions formed in + this way will be found extending from the bottom to the top of the + vessel, and not only so, but the whole of the remaining liquid will be + imprisoned in the upper cells.</p> + + <div class="figleft" style="width:37%;"> + <a href="images/Fig38.jpg"><img style="width:100%" src="images/Fig38.jpg" + alt="Fig. 38." title="Fig. 38." /></a> + <span class="sc">Fig. 38.</span>—Osmotic growth produced by + sowing a mixture of CaCl<sub>2</sub> and MnCl<sub>2</sub> in a solution + of alkaline carbonate, phosphate, and silicate. The stem and terminal + organs are of different colours. (One-third of the natural size.) + </div> + + <div class="figright" style="width:40%;"> + <a href="images/Fig39.jpg"><img style="width:100%" src="images/Fig39.jpg" + alt="Fig. 39." title="Fig. 39." /></a> + <span class="sc">Fig. 39.</span>—An osmotic growth photographed + by transverse light to show the construction of the terminal organs. + </div> + +<div style="clear: right"></div> + <p><i>Assimilation and Excretion.</i>—Like a living being, an + osmotic growth absorbs nutriment from the medium in which it grows, and + this nutriment it assimilates and organizes. If we compare the weight of + an osmotic growth with that of the mineral fragment which produced it, we + shall find that the mineral seed has increased many hundred times in + weight. Similarly, if we weigh the liquid before and after the + experiment, we shall find that it has lost an equivalent weight. The + absorbed substance of an osmotic production must also undergo chemical + transformation before it can be assimilated—that is, before it can + form part of the growth. Calcium chloride, for example, growing in a + solution of potassium <!-- Page 130 --><span class="pagenum"><a + name="page130"></a>{130}</span>carbonate, is transformed into calcium + carbonate. CaCl<sub>2</sub> + K<sub>2</sub>CO<sub>3</sub> = + CaCO<sub>3</sub> + 2KCl. Thus an osmotic growth can make a choice between + the substances offered to it, rejecting the potassium of the nutrient + liquid, and absorbing water and the radical CO<sub>3</sub>, while at the + same time it eliminates and excretes <!-- Page 131 --><span + class="pagenum"><a name="page131"></a>{131}</span>chlorine, which may be + found in the nutrient liquid after the reaction.</p> + + <p>Of all the ordinary physical forces, osmotic pressure and osmosis + alone appear to possess this remarkable power of organization and + morphogenesis. It is a matter of surprise that this peculiar faculty has + hitherto remained almost unsuspected.</p> + + <div class="figright" style="width:27%;"> + <a href="images/Fig40.jpg"><img style="width:100%" src="images/Fig40.jpg" + alt="Fig. 40." title="Fig. 40." /></a> + <span class="sc">Fig. 40.</span>—Osmotic growth in a solution of + KNO<sub>3</sub>, showing spine-like organs. + </div> + + <p><i>Osmotic Growths.</i>—If we sow fragments of calcium chloride + in solutions of the alkaline carbonates, phosphates, or silicates, we + obtain a wonderful variety of filiform and linear growths which may + attain to a height of 30 or 40 centimetres. Some are so flexible that the + stems bend, falling in curves around the centre of growth, like leaves of + grass. If we dilute this same liquid, as it becomes less concentrated the + growths are more curved, ramified, dendritic, like those of trees or + corals.</p> + + <div class="figleft" style="width:25%;"> + <a href="images/Fig41.jpg"><img style="width:100%" src="images/Fig41.jpg" + alt="Fig. 41." title="Fig. 41." /></a> + <span class="sc">Fig. 41.</span>—Terminal organs like catkins, + developing in a solution of ammonium chloride. + </div> + + <p>In the culture of osmotic growths we may also by appropriate means + produce terminal organs resembling flowers and seed-capsules. To do this + we wait till the growth is considerably advanced, and then add a large + quantity of liquid to the nutrient solution so as to diminish the + concentration a hundredfold or more. Spherical <!-- Page 132 --><span + class="pagenum"><a name="page132"></a>{132}</span>terminal organs will + then grow out from the ends of the stems, which may during their further + growth become conical or piriform in shape.</p> + + <p>By superposing layers of liquid of different concentration and + decreasing density, one may obtain knots and swellings in the osmotic + growths marking the surfaces of separation of the liquid. When a young + growth in the vigour of its youth reaches the surface of the water, it + spreads out horizontally over the surface of the liquid in thin leaves or + foliaceous expansions of different forms.</p> + + <div class="figright" style="width:48%;"> + <a href="images/Fig42.jpg"><img style="width:100%" src="images/Fig42.jpg" + alt="Fig. 42." title="Fig. 42." /></a> + <span class="sc">Fig. 42.</span>—An osmotic madrepore. + </div> + + <p>The preponderating influence in morphogenesis is osmotic pressure, the + osmotic forms varying with its intensity, distribution, and mode of + application. Whatever the chemical composition of the liquid, similar + osmotic forces, modified in the same manner, give rise to forms which + have a family resemblance. The chemical nature of the liquid, however, is + not entirely without influence on the form. Thus the presence of a + nitrate in the mother liquor tends to produce points or thorns. Ammonium + chloride in a potassium ferrocyanide solution produces growths shaped + like catkins, and the alkaline chlorides tend to produce vermiform + growths. <!-- Page 133 --><span class="pagenum"><a + name="page133"></a>{133}</span></p> + + <p>Coralline growths may also be obtained by using appropriate chemical + solutions. For this purpose the solution of silicate, carbonate, and + dibasic phosphate should be diluted to half strength, with the addition + of 2 to 4 per cent. of a concentrated solution of sodium sulphate or + potassium nitrate.</p> + + <div class="figleft" style="width:45%;"> + <a href="images/Fig43.jpg"><img style="width:100%" src="images/Fig43.jpg" + alt="Fig. 43." title="Fig. 43." /></a> + <span class="sc">Fig. 43.</span>—An osmotic mushroom form. + </div> + + <div class="figright" style="width:43%;"> + <a href="images/Fig44.jpg"><img style="width:100%" src="images/Fig44.jpg" + alt="Fig. 44." title="Fig. 44." /></a> + <span class="sc">Fig. 44.</span>—Osmotic fungi. + </div> + +<div style="clear: right"></div> + <p>Coral-like forms may also be grown from a semi-saturated solution of + silicate, carbonate, and dibasic phosphate, to which has been added 4 per + cent. of a concentrated solution of sodium sulphate or potassium nitrate. + In this we may obtain beautiful growths like madrepores or corals, formed + by a central nucleus from which radiate large leaves like the petals of a + flower. The presence of nitrate of potassium produces pointed leaves with + thorn-like processes recalling the forms of the aloe and the agave.</p> + + <p>Most remarkable fungus-like forms may be obtained by commencing the + growth in a concentrated solution, and then <!-- Page 134 --><span + class="pagenum"><a name="page134"></a>{134}</span>carefully pouring a + layer of distilled water over the surface of the liquid. The resemblance + is so perfect that some of our productions have been taken for fungi even + by experts. The <!-- Page 135 --><span class="pagenum"><a + name="page135"></a>{135}</span>stem of these osmotic fungi is formed of + bundles of fine hollow fibres, while the upper surface of the cap is + sometimes smooth, and sometimes covered with small scales. The lower + surface of the cap shows traces of radiating lamellæ, which are sometimes + intersected by concentric layers parallel to the outer <!-- Page 136 + --><span class="pagenum"><a name="page136"></a>{136}</span>surface of the + cap. In this case the lower surface of the cap shows a number of orifices + or canals similar to those seen in many varieties of fungus.</p> + + <div class="figcenter" style="width:57%;"> + <a href="images/Fig45.jpg"><img style="width:100%" src="images/Fig45.jpg" + alt="Fig. 45." title="Fig. 45." /></a> + <span class="sc">Fig. 45.</span>—A shell-like calcareous osmotic + growth. + </div> + + <div class="figleft" style="width:47%;"> + <a href="images/Fig46.jpg"><img style="width:100%" src="images/Fig46.jpg" + alt="Fig. 46." title="Fig. 46." /></a> + <span class="sc">Fig. 46.</span>—Osmotic growths in the form of + shells. + </div> + + <div class="figright" style="width:47%;"> + <a href="images/Fig47.jpg"><img style="width:100%" src="images/Fig47.jpg" + alt="Fig. 47." title="Fig. 47." /></a> + <span class="sc">Fig. 47.</span>—Capsular osmotic growth. The + capsule has been broken to show the interior structure. + </div> + + <p>Shell-like osmotic productions may be grown by sowing the mineral in a + very shallow layer of concentrated solution, a centimetre or less in + depth, and pouring over this a less concentrated layer of solution. By + varying the solution or concentration we may thus grow an infinite + variety of shell forms. <!-- Page 137 --><span class="pagenum"><a + name="page137"></a>{137}</span></p> + + <p>Capsules or closed shells may be produced in the same way by + superimposing a layer of somewhat greater concentration. These capsules + consist of two valves joined together at their circumference. The lower + valve is thick and strong, while the upper valve may be transparent, + translucent, or opaque, but is always thinner and more fragile than the + lower one.</p> + + <p>Ferrous sulphate sown in a silicate solution gives rise to growths + which are green in colour, climbing, or herbaceous, twining in spirals + round the larger and more solid calcareous growths.</p> + + <div class="figcenter" style="width:47%;"> + <a href="images/Fig48.jpg"><img style="width:100%" src="images/Fig48.jpg" + alt="Fig. 48." title="Fig. 48." /></a> + <span class="sc">Fig. 48.</span>—An osmotic growth in which the + terminal organs are differently coloured from the stems, showing that + the chemical evolution is different. + </div> + + <p>With salts of manganese, the chloride, citrate or sulphate, the stages + of evolution of the growth are distinguished not only by diversities of + form, but also by modifications of colour. We may thus obtain terminal + organs black or golden yellow in colour on a white stalk. In a similar + way we may obtain fungi with a white stalk and a yellow cap, of which the + lower surface is black.</p> + + <div class="figright" style="width:28%;"> + <a href="images/Fig49.jpg"><img style="width:100%" src="images/Fig49.jpg" + alt="Fig. 49." title="Fig. 49." /></a> + <span class="sc">Fig. 49.</span>—Osmotic capsular growth with + figured belt. + </div> + + <p>Very beautiful growths may be obtained by sowing calcium chloride in a + solution of potassium carbonate, with the addition of 2 per cent. of a + saturated solution of tribasic potassium phosphate. This will give + capsules with figured belts, vertical lines at regular intervals, or + transverse stripes composed of projecting dots such as may be seen in + many sea-urchins. These capsules are closed at the summit by a cap, + forming an operculum, so that they sometimes appear as if formed of two + valves. Now and again we may see the upper valve raised by <!-- Page 138 + --><span class="pagenum"><a name="page138"></a>{138}</span>the internal + osmotic pressure, showing the gelatinous contents through the + opening.</p> + + <div class="figleft" style="width:35%;"> + <a href="images/Fig50.jpg"><img style="width:100%" src="images/Fig50.jpg" + alt="Fig. 50." title="Fig. 50." /></a> + <span class="sc">Fig. 50.</span>—Amœboid osmotic growth, + floating free in the mother liquor. + </div> + + <p>The calcareous capsules grown in a saturated solution of potassium + carbonate or phosphate often take a regular ovoid form. If these are + allowed to thicken, they may be taken out of the water without breaking, + and then present the aspect of veritable ooliths.</p> + + <div class="figleft" style="width:30%;"> + <a href="images/Fig51.jpg"><img style="width:100%" src="images/Fig51.jpg" + alt="Fig. 51." title="Fig. 51." /></a> + <span class="sc">Fig. 51.</span>—Transparent osmotic cell, in + which may be seen the white calcareous nucleus. The summit of the cell + bears osmotic prolongations. + </div> + + <div class="figright" style="width:44%;"> + <a href="images/Fig52.jpg"><img style="width:100%" src="images/Fig52.jpg" + alt="Fig. 52." title="Fig. 52." /></a> + <span class="sc">Fig. 52.</span>—Amœboid osmotic growth + with long crystalline cilia swimming about in the mother liquor. + </div> + + <div class="figright" style="width:46%;"> + <a href="images/Fig53.jpg"><img style="width:100%" src="images/Fig53.jpg" + alt="Fig. 53." title="Fig. 53." /></a> + <span class="sc">Fig. 53.</span>—Osmotic growth swimming in + mother liquor. The fin-like prolongation grew out between two liquid + layers of different concentrations. + </div> + + <p>Osmotic productions may be divided into two groups. Some like the + silicate growths are fixed. Like vegetables, they develop, become + organized, grow, decline, die, and are disintegrated at the spot where + they are sown. Others, especially those which are grown in alkaline + carbonates and phosphates, have two periods of evolution, the first a + fixed period, and the second a wandering <!-- Page 139 --><span + class="pagenum"><a name="page139"></a>{139}</span>one. During the first + period their specific gravity is greater than that of the surrounding + medium, and they rest immobile at the bottom of the vessel in which they + are sown. As they grow, they absorb water and their specific gravity + diminishes. Little by little they rise up in the liquid, and finally + acquire a considerable amount of mobility, being readily displaced by + every current. Hence it is very difficult to photograph these <!-- Page + 140 --><span class="pagenum"><a name="page140"></a>{140}</span>mobile + osmotic growths, which swim about in the mother liquor and are often + provided with prolongations in the forms of cilia, and sometimes with + fins, which undulate as they move. Some of these ciliary hairs are + evidently osmotic in their origin, being localized as a tuft at the + summit of the growth. Others are apparently crystalline in structure, and + are spread over the whole surface of the swimming vesicle. An osmotic + growth increases by the absorption of water from a concentrated solution. + When the solution is originally saturated it thus becomes supersaturated, + and deposits these long ciliary crystals on the surface of the + growth.</p> + + <p>When a capsule splits in two under the influence of the internal + osmotic pressure, it may happen that the operculum or upper valve floats + away in the liquid. We thus obtain a free swimming organism, a + transparent bell-like form with an undulating fringe, like a Medusa.</p> + + <div class="figleft" style="width:29%;"> + <a href="images/Fig54.jpg"><img style="width:100%" src="images/Fig54.jpg" + alt="Fig. 54." title="Fig. 54." /></a> + <span class="sc">Fig. 54.</span>—Capsular osmotic growth, the two + valves separated showing the colloidal contents. + </div> + + <p>Frequently a single seed or stock will give rise to a whole series of + osmotic growths. A vesicle is first produced, and then a contraction + appears around the vesicle, and this contraction increases till a portion + of the vesicle is cut off and swims away free like an amœba. The + same phenomenon may be observed with vermiform growths, a single seed + often giving <!-- Page 141 --><span class="pagenum"><a + name="page141"></a>{141}</span>rise in this way to a whole series of + amœbiform or vermiform productions.</p> + + <p>It must be remembered that in an osmotic growth the active growing + portion is the gelatinous contents in the interior, the external visible + growth being only a skeleton or shell. We may sometimes succeed in + hooking up one of these long vermiform growths, breaking the calcareous + sheath, and drawing out a long undulating translucid gelatinous cylinder. + The outline of this cylinder is so well defined as to make us doubt + whether the fine colloidal membrane which separates it clearly from the + liquid can have been formed so rapidly, or if it may not perhaps exist + already formed in the interior of its calcareous sheath.</p> + + <div class="figright" style="width:25%;"> + <a href="images/Fig55.jpg"><img style="width:100%" src="images/Fig55.jpg" + alt="Fig. 55." title="Fig. 55." /></a> + <span class="sc">Fig. 55.</span>—Microphotograph showing the + structure of various osmotic stems. (Magnified 25 diameters.) + + <p class="poem">(<i>a</i>) Sodium sulphite.</p> + + <p class="poem">(<i>b</i>) Potassium bichromate.</p> + + <p class="poem">(<i>c</i>) Sodium sulphide.</p> + + <p class="poem">(<i>d</i>) Sodium bisulphite. </p> + </div> + + <p>When a large capsular shell such as we have described bursts, it + expels a part or the whole of its contents as a gelatinous mass which + retains the form of the cavity. <span class="correction" title="Original reads 'Simiarly'." + >Similarly</span>, if we suddenly dilute the mother liquor around an + osmotic cell, it bursts by a process of dehiscence, and projects into the + liquid a part of its contents, which may thus become an independent + vesicle. In this way a single osmotic cell may produce a whole series of + independent vesicles.</p> + + <p>It is even possible to rejuvenate an osmotic growth that has become + degenerate through age. An osmotic production grows old and dies when it + has expended the osmotic force contained in the interior of its capsule. + A calcium osmotic growth which has thus become exhausted may be + rejuvenated by transferring it to a concentrated solution of calcium + chloride. It will absorb this, and thus be enabled to renew its evolution + and growth when put back again into the original mother liquor. <!-- Page + 142 --><span class="pagenum"><a name="page142"></a>{142}</span></p> + + <p>The structure of osmotic growths is no less varied than their form. + Their stems are formed of cells or vesicles juxtaposed, showing cavities + separated by osmotic walls. Sometimes the component vesicles have kept + their original form, so that the stem has the appearance of a row of + beads. Or the cells may be more or less flattened, the divisions being + widely separated. Or again, by the absorption of the divisions, a tube + may be formed, a veritable vessel or canal in which liquids can + circulate. <!-- Page 143 --><span class="pagenum"><a + name="page143"></a>{143}</span></p> + + <div class="figcenter" style="width:48%;"> + <a href="images/Fig56.jpg"><img style="width:100%" src="images/Fig56.jpg" + alt="Fig. 56." title="Fig. 56." /></a> + <span class="sc">Fig. 56.</span>—Microphotograph showing the + structure of osmotic stems. (Magnified 40 diameters.) + </div> + + <div class="figright" style="width:33%;"> + <a href="images/Fig57.jpg"><img style="width:100%" src="images/Fig57.jpg" + alt="Fig. 57." title="Fig. 57." /></a> + <span class="sc">Fig. 57.</span>—Photograph of an osmotic leaf + showing the veins. + </div> + + <p>The foliaceous expansions, or osmotic leaves, also present great + varieties both of appearance and of structure. The veins may be + longitudinal, fan-shaped, or penniform. We have occasionally met with + leaves having a lined or ruled surface, giving most beautiful diffraction + colours. The usual structure, however, is vesicular or cellular, as in + Fig. 58. In photographs we often get the appearance of lacunæ, but all + these lacunæ are closed cavities, the appearance being due to the + transparency of the cell walls.</p> + + <div class="figleft" style="width:30%;"> + <a href="images/Fig58.jpg"><img style="width:100%" src="images/Fig58.jpg" + alt="Fig. 58." title="Fig. 58." /></a> + <span class="sc">Fig. 58.</span>—Photomicrograph of an osmotic + leaf showing the cellular structure. + </div> + + <p>In conclusion we may say that osmotic growths are formed of an + ensemble of closed cavities of various forms, containing liquids and + separated by osmotic membranes, constituting veritable tissues. This + structure offers the closest <!-- Page 144 --><span class="pagenum"><a + name="page144"></a>{144}</span>resemblance to that of living organisms. + Is it possible to doubt that the simple conditions which produce an + osmotic growth have frequently been realized during the past ages of the + earth? What part has osmotic growth played in the evolution of living + forms, and what traces of its action may we hope to find to-day? Osmotic + growth gives us fibrous silicates, phosphatic nodules, corals, and + madrepores; it also gives us formations which remind one of the "atolls," + calcareous growths rising like a crown out of the water. The geologist + may well consider what rôle osmotic growth may have played in the + formation of the various rocks, siliceous, calcareous, barytic, + magnesian, the fibrous and nodular rocks and atolls. The palæontologist + relies on the different forms found in his rocks to classify his + specimens; from the existence of a shell, he concludes the presence of + life. Since, however, forms which are apparently organic may be merely + the product of osmotic growth, it is evident that he must reconsider his + conclusions. The same may be said of the various forms of coral or of + fungoid growths. In the <!-- Page 146 --><span class="pagenum"><a + name="page146"></a>{146}</span>presence of a calcified or silicated + fungus we can no longer argue with certainty as to the existence of life, + without taking into consideration the possibility that the specimen in + question may be an osmotic production.</p> + + <div class="figleft" style="width:37%;"> + <a href="images/Fig59.jpg"><img style="width:100%" src="images/Fig59.jpg" + alt="Fig. 59." title="Fig. 59." /></a> + <span class="sc">Fig. 59.</span>—Osmotic growth with nucleated + terminal organs. (One-third of the natural size.) + </div> + + <div class="figright" style="width:46%;"> + <a href="images/Fig60.jpg"><img style="width:100%" src="images/Fig60.jpg" + alt="Fig. 60." title="Fig. 60." /></a> + <span class="sc">Fig. 60.</span>—A group of osmotic plants. + </div> + +<div style="clear: right"></div> + <p>Whatever our opinion as to its signification, osmotic growth demands + the attention of every mind devoted to the study of nature. It is a + marvellous spectacle to see a formless fragment of calcium salt grow into + a shell, a madrepore, or a fungus, and this as the result of a simple + physical force. Why should the study of osmotic growth attract less + attention than the formation of crystals, on which so much time and + labour has been bestowed in the past?</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 147 --><span class="pagenum"><a name="page147"></a>{147}</span></p> + +<h3>CHAPTER XII</h3> + +<p class="cenhead">THE PHENOMENA OF LIFE AND OSMOTIC PRODUCTIONS—A +STUDY IN PHYSIOGENESIS</p> + + <p>It is impossible to define life, not only because it is complex, but + because it varies in different living beings. The phenomena which + constitute the life of a man are far other than those which make up the + life of a polyp or a plant; and in the more simple forms life is so + greatly reduced that it is often a matter of difficulty to decide whether + a given form belongs to the animal, vegetable, or mineral kingdom. + Considering the impossibility of defining the exact line of demarcation + between animate and inanimate matter, it is astonishing to find so much + stress laid on the supposed fundamental difference between vital and + non-vital phenomena. There is in fact no sharp division, no precise limit + where inanimate nature ends and life begins; the transition is gradual + and insensible, for just as a living organism is made of the same + substances as the mineral world, so life is a composite of the same + physical and chemical phenomena that we find in the rest of nature. All + the supposed attributes of life are found also outside living organisms. + Life is constituted by the association of physico-chemical phenomena, + their harmonious grouping and succession. Harmony is a condition of + life.</p> + + <p>We are quite unable to separate living beings from the other + productions of nature by their composition, since they are formed of the + same mineral elements. All the aliments of plants—water, carbon, + nitrogen, phosphorus, sulphur—before their absorption and + assimilation belonged to the mineral kingdom. The carbon and the water + are transformed into <!-- Page 148 --><span class="pagenum"><a + name="page148"></a>{148}</span>sugar and fat, the nitrogen and the + sulphur into albumen, and the compounds so formed are then said to belong + to the organic world. These organic bodies are returned once again to the + mineral world by the action of animals and microbes, which transform the + carbon into carbonates, and the nitrogen, sulphur, and phosphorus into + nitrates, sulphates, and phosphates. Hence life is but a phase in the + animation of mineral matter; all matter may be said to have within itself + the essence of life, potential in the mineral, actual in the animal and + the vegetable. The flux and reflux of matter is alternate and incessant, + from the mineral world to the living, and back again from the living to + the mineral world.</p> + + <p>At the same time there is a continuous flux of energy. Organic matter + contains potential energy, the energy of chemical combination; and during + its passage through the living being it is gradually stripped of this + energy and returned to the mineral world. The first step in synthetic + biology is the addition of potential energy to matter, the reduction of + an oxide, the separation of a salt into its radicals, the production of + some endothermic chemical combination. The energy stored up by such + processes can be again liberated as heat, that fire which the ancients + with wonderful prescience long ago recognized as the symbol of life.</p> + + <p>Attempts have been made to differentiate a living being by the nature + of its chemical combinations, the so-called organic compounds. It was + supposed that life alone could realize these and cause the production of + the various substances which form the structure of living beings. Of late + years, however, a large number of these organic substances have been + artificially produced in the laboratory, and the synthetic problems which + remain are of the same order as those which have been already solved.</p> + + <p>As one learns to know the mineral kingdom and the living world more + intimately the differences between them disappear. Thus a living being + was supposed to be characterized by its sensibility, <i>i.e.</i> its + faculty of reaction against external impressions. But this reaction is a + general phenomenon of nature; there is no action without reaction. + Neither can the <!-- Page 149 --><span class="pagenum"><a + name="page149"></a>{149}</span>reaction to internal impressions, + immediate or deferred, be considered as the characteristic of life, since + osmotic growths exhibit a most exquisite sensibility in this direction. + Since, then, the faculty of reaction is a general property of matter, the + characteristics of life in the lower organisms are only three in number, + viz. nutrition, growth, and reproduction by fission or budding. But + crystals are also nourished and grow in the water of crystallization. + They have moreover a specific form, and every biologist who wishes to + establish a parallel between the phenomena of the living and the mineral + world is wont to compare living beings with crystals. Crystals, it is + said, affect regular geometric forms, salient angles, and rectilinear + edges, while living beings have rounded forms without any geometric + regularity. Another supposed distinction is that living beings are + nourished by intussusception, whereas crystals increase by apposition. + Again, living beings are said to assimilate and transform the aliment + they absorb, whereas crystals do not transform the matter which is added + externally to their structure. Another supposed difference is that living + things eliminate and discharge their products of combustion, while the + evolution of a crystal is accompanied by no such elimination. Finally, + the phenomenon of reproduction is said to be the exclusive characteristic + of a living being; but crystals may also be reproduced and multiplied by + the introduction of fragments of crystalline matter into a supersaturated + solution.</p> + + <p>The resemblance between an osmotic growth and a living organism is + much closer than that between a living being and a crystal, there being + not only an analogy of form, but also of structure and of function. In + order to find the physical parallel to life, we must turn to osmosis and + osmotic growth rather than to crystals and crystallization.</p> + + <p>The first and most striking analogy between living beings and osmotic + growths is that of form. The morphogenic power of osmosis gives rise to + an infinite variety of forms. An osmotic growth, even at the first sight, + suggests the idea of a living thing. One need only glance at the + photographs of osmotic productions to recognize the forms of madrepore, + fungus, alga, and shell. It is wonderful that a force capable <!-- Page + 150 --><span class="pagenum"><a name="page150"></a>{150}</span>of such + marvellous results should have hitherto been almost entirely + neglected.</p> + + <p>A second analogy between vital and osmotic growths is to be found in + their structure, both being formed by groups of cells or vesicles + separated by osmotic membranes. An osmotic stem, formed by a row of + cellular cavities separated by osmotic membranes, has a great structural + resemblance to the knotted stems of bamboos, reeds, and the like. The + foliaceous expansions of osmotic growths are formed by colonies of cells + or vesicles disposed in regular lines, which may present various patterns + of innervation, parallel, palmate, or pennate. Many of the lamellar + osmotic growths are striped in parallel lines alternately opaque and + transparent. The terminal organs have also their enveloping membranes, + their pulp and nucleus, just like vegetable forms.</p> + + <p>The analogies of function are no less remarkable than those of form + and structure. Nutrition is perhaps the most elementary and essential + vital phenomenon, since without nutrition life cannot exist. Nutrition + consists in the absorption of alimentary substances from the surrounding + medium, the chemical transformation of such substances, their fixation by + intussusception in every part of the organism, and the ejection of the + products of combustion into the surrounding medium. Osmotic growths + absorb material from the medium in which they grow, submit it to chemical + metamorphosis, and eject the waste products of the reaction into the + surrounding medium. An osmotic growth moreover exercises choice in the + selection of the substances which are offered for its consumption, + absorbing some greedily and entirely rejecting others. Thus osmotic + growths present all the phenomena of nutrition, the fundamental + characteristic of life.</p> + + <p>In the living organism nutrition results in growth, development, and + evolution. Growth and development also follow the absorption and fixation + of aliment by an osmotic production. An osmotic production grows, its + form develops and becomes more complicated, and its weight increases. An + osmotic growth may weigh many hundred times as much as the mineral sown + in the solution, the mother liquor losing a <!-- Page 151 --><span + class="pagenum"><a name="page151"></a>{151}</span>corresponding weight. + Thus growth, which has hitherto been considered an essential phenomenon + of life, is also a phenomenon common to all osmotic productions.</p> + + <p>Osmotic growths like living things may be said to have an evolutionary + existence, the analogy holding good down to the smallest detail. In their + early youth, at the beginning of life, the phenomena of exchange, of + growth, and of organization are very intense. As they grow older, these + exchanges gradually slow down, and growth is arrested. With age the + exchanges still continue, but more slowly, and these then gradually fail + and are finally completely arrested. The osmotic growth is dead, and + little by little it decays, losing its structure and its form.</p> + + <p>The membranes of an osmotic growth thicken with age, and thus oppose + to the osmotic exchanges a steadily increasing resistance. Young osmotic + cells appear swollen and turgescent, whereas old ones become flaccid, + relaxed, and wrinkled. Analogous phenomena are met with in living + organisms, the calcareous infiltration of the vessels representing the + thickening and hardening of the osmotic membranes. The plumpness of a + child and the turgescence of young cells are but the expression of high + osmotic tension, while relaxation and flaccidity of the tissues in old + age betrays the fall of osmotic pressure in the intracellular + tissues.</p> + + <p>Circulation of the nutrient fluid may also be observed in an osmotic + growth as in a living organism. If we take a calcareous growth with long + ramified stems and dilute the mother liquor considerably, we may see + currents of liquid issuing from the summit of the growth—currents + which are made visible by the cloudy precipitates which they cause. The + same current is also rendered visible in the stems themselves by the + motion of the granulations and gas bubbles in the interior of the osmotic + cells. It is plain that some such circulation must exist, for how could a + membrane be formed 30 centimetres from the seed if the membranogenous + substance did not circulate through the stem? A moment's consideration + will show that the propulsion is due to osmotic pressure and not to mere + differences of density, for the liquid <!-- Page 152 --><span + class="pagenum"><a name="page152"></a>{152}</span>which rises in the stem + is a concentrated solution of calcium salt much denser than the mother + liquor, and the current of liquid after rising in the stem may be seen to + fall back again through the liquid.</p> + + <div class="figright" style="width:47%;"> + <a href="images/Fig61.jpg"><img style="width:100%" src="images/Fig61.jpg" + alt="Fig. 61." title="Fig. 61." /></a> + <span class="sc">Fig. 61.</span>—A group of osmotic forms. + </div> + + <p>Organization has long been considered as one of the principal + characteristics of life, <i>i.e.</i> the arrangement of matter so as to + produce an animated and evolutionary form accompanied by transformation + of energy. But osmotic growths are also organizations endowed with the + same faculties, and the physical mechanism which is at the basis of their + formation is the same as that which determines the organization of living + matter.</p> + + <p>The phenomena of osmotic growth show how ordinary mineral matter, + carbonates, phosphates, silicates, nitrates, and chlorides, may imitate + the forms of animated nature without <!-- Page 153 --><span + class="pagenum"><a name="page153"></a>{153}</span>the intervention of any + living organism. Ordinary physical forces are quite sufficient to produce + forms like those of living beings, closed cavities containing liquids + separated by osmotic membranes, with tissues similar to those of the + vital organs in form, colour, evolution, and function.</p> + + <p>It is only necessary to glance at the photographs of these osmotic + growths to appreciate the wonderful variety of form. The variety of + function is not less evident, and in many instances, especially with + manganese salts, the difference of function of various regions is marked + by differences of colour. When a large osmotic cell projects beyond the + mother liquor and grows up into the air, it is evident that the function + of liquid absorption must be localized in the submerged part. In other + cases we have a local evolution of gas, which may be demonstrated by + growing a fragment of calcium chloride in a mother liquor composed of the + following saturated solutions:—</p> + +<table class="nob" summary="Solution for evolution of gas." title="Solution for evolution of gas."> +<tr><td class="spacsingle"> Potassium carbonate </td><td class="spacsingle"> 76 parts.</td></tr> +<tr><td class="spacsingle"> Potassium sulphate </td><td class="spacsingle"> 16 ,,</td></tr> +<tr><td class="spacsingle"> Tribasic potassium phosphate </td><td class="spacsingle"> 46 ,,</td></tr> +</table> + + <p>During the whole period of growth there is an abundant liberation of + bubbles of gas, which is <span class="correction" title="Original reads 'acurately'." + >accurately</span> limited to a belt around the base of the growth, and + sometimes also to a cap at the summit.</p> + + <p>Since morphological differentiations of different parts is but the + result of differences of evolution, <i>i.e.</i> of functional differences + of the various parts, we may consider that osmotic growths possess the + faculty of organization like living beings.</p> + + <p>An osmotic growth may be wounded, and a wound delays its growth and + development like a disease or an accident in a living being. A wound in + an osmotic production may also become cicatrized and covered with a + membrane, when the growth will recommence exactly as in a living + being.</p> + + <p>An osmotic growth is a transformer of energy. It increases in bulk, + pushing aside the mother liquor, and thus doing external work. An osmotic + growth has a temperature above its medium, since the chemical reaction of + which it is the seat is accompanied by the production of heat. We know + <!-- Page 154 --><span class="pagenum"><a + name="page154"></a>{154}</span>but little of the transformation of energy + which takes place in an osmotic production, but we may say with certainty + that it is capable of transforming both chemical energy and osmotic + energy into heat and mechanical motion.</p> + + <p>An osmotic production is the arena of complicated chemical phenomena + which produce a veritable metabolism. It has long been known that + diffusion and osmosis may determine various chemical transformations. H. + St. Clair Deville has demonstrated that certain unstable salts are + partially decomposed by diffusion. Thus during the diffusion of alum, the + sulphate of potash is separated from the sulphate of aluminium. + Similarly, when the chloride or acetate of aluminium is caused to + diffuse, the acids become separated from the aluminia. This decomposition + is the result of the different resistance which the medium offers to the + diffusion of different ions. This difference of resistance may even cause + a difference of potential between two media, similar to the differences + of potential in living organisms. Frequently also a difference of + hydration in the chemical substances on either side of an osmotic + membrane will determine a chemical reaction, which like all other + chemical reactions is accompanied by a corresponding transformation of + energy. The study of these chemical metamorphoses and the transformations + of energy in osmotic growths has opened up a new subject for experimental + investigation in the field of organic chemistry.</p> + + <p><i>Coagulation.</i>—There is a most remarkable analogy between + the phenomena of coagulation as seen in living beings and the phenomena + which occur when the liquid in the interior of an osmotic growth comes + into contact with the mother liquor. When the sap of a plant or the blood + of an animal escapes into the air or water of the surrounding medium, it + coagulates, <i>i.e.</i> it changes from a liquid to a gelatinous + consistency. In the same way, when the liquid in the interior of an + osmotic growth leaks out into the mother liquor it forms a gelatinous + precipitate. This gelatinous precipitation is a physico-chemical + phenomenon of the same nature as coagulation. It is by the study of + coagulation in liquids less complex than blood that we may hope to + elucidate the mechanism of the process, <!-- Page 155 --><span + class="pagenum"><a name="page155"></a>{155}</span>which is simply a + physico-chemical phenomenon exactly analogous to gelatinous + precipitation. Calcium phosphate is always prone to coagulate; it has + been called the gelatinous phosphate of lime, and we have already seen + how readily tribasic calcium phosphate takes the form of beautiful + transparent colloidal membranes which are gelatinous in texture.</p> + + <p>We may obtain colloidal precipitates exactly analogous to coagulated + albumin by mixing a weak solution of chloride of calcium with potassium + carbonate or tribasic phosphate. Like albumin this precipitate forms + flakes, and is deposited slowly as a gelatinous colloidal mass. Like + albumin also this calcic solution is coagulated by heat; a solution of a + calcic salt of a volatile acid on heating forms a precipitate which has + all the appearance of albumin coagulated by heat.</p> + + <p>Finally, Arthus and Pagès have shown that blood does not coagulate + when deprived of its calcium salts by the addition of alkaline oxalates, + fluorides, or citrates, and that the blood thus treated recovers its + coagulability on the addition of a soluble salt of calcium. The + coagulation of milk is also a calcium salt precipitation. Coagulation + therefore would seem to be merely the colloidal precipitation of a salt + of calcium.</p> + + <p>Diffusion and osmosis are the elementary phenomena of life. All vital + phenomena result from the contact of two colloidal solutions, or of two + liquids separated by an osmotic membrane. Hence the study of the physics + of diffusion and osmosis is the very basis of synthetic biology.</p> + + <p>A living being exhibits two sorts of movements, those which are the + result of stimulus from without, and those which are determined by an + excitation arising from within. In the higher animals the stimulus or + exciting energy coming from the entourage may be infinitely small when + compared with the amount of energy transformed. Moreover, the response to + an identical excitation may so vary as to give to these different + responses an appearance of spontaneity. There is in reality no + spontaneity, since the difference in response is governed by previous + external impressions which have left their record on the machinery. There + is in fact no such thing as a spontaneous action, since every action of a + living <!-- Page 156 --><span class="pagenum"><a + name="page156"></a>{156}</span>being has as its ultimate cause a stimulus + or excitation coming from without.</p> + + <p>The movements of the second category are also conditioned by an + excitation, but the stimulus comes from within the organism. These + movements consist principally of changes of nutrition, or movements of + the circulation and respiration; they are rhythmic in character and are + probably produced by the same chemico-physical causes which determine + rhythmic movements outside the living body.</p> + + <p>Just in the same way osmotic growths present two sorts of movements, + external movements and those which are connected with their nutrition. A + free osmotic growth swimming in the mother liquor will alter its position + and form under the influence of the slightest exterior excitation or + vibration. It responds to every variation of temperature, or to a slight + difference of concentration produced by adding a single drop of water, + and reacts to every exterior influence by displacement or + deformation.</p> + + <p>An osmotic growth also shows indications of movements which are + connected with its nutrition, and these movements are rhythmic, like + those of respiration or circulation in a living organism. The growth of + an osmotic production shows itself not as a continuous process but + periodically. The water traverses the membrane, raises the pressure, and + distends the cell; at first the cell wall resists by reason of its + elasticity, it then suddenly relaxes, yielding to the osmotic pressure + and bulging out at a thinner spot on the surface; the internal pressure + falls suddenly, and there is a pause in the growth.</p> + + <p>This rhythmic growth may be best observed by sowing in a solution of a + tribasic alkaline phosphate, pellets composed of powdered calcium + chloride moistened with glycerine, to which has been added 1 per cent. of + monobasic calcium phosphate. The experiment is so arranged as to bend or + incline the growing stems which shoot out from these grains. This may be + done by carefully pouring above the mother liquor a layer of water, or a + less concentrated solution. As the internal osmotic pressure rises, the + drooping extremity of the twig will become turgescent and gradually lift + itself <!-- Page 157 --><span class="pagenum"><a + name="page157"></a>{157}</span>up, and then suddenly fall again for + several millimetres. We have frequently watched this rhythmic movement + for an hour or more—a slow gradual elevation of the extremity of + the twig and a rapid fall recurring every four seconds or so.</p> + + <p>It may be objected that the substance of an osmotic growth is + continually undergoing change, whereas a living organism transforms into + its own substance the extraneous matter which it borrows from its + environment. The distinction, however, is only an apparent one. The + substance of a living being is also continually undergoing chemical + change; it does not remain the same for a single instant. We see an + evidence of this change in the evolution of age; the substance of the + adult is not that of the infant. In some living organisms such as + insects, especially the ephemeridæ who have but a brief existence, this + change of substance is even more rapid than that in an osmotic + growth.</p> + + <p>It has been objected that osmotic productions cannot be compared with + living organisms since they contain no albuminoid matter. This is to + consider life as a substance, and to confound the synthesis of life with + that of albumin. If albumin is ever produced by synthesis in the + laboratory it will probably be dead albumin. All living organisms contain + albumin; this is probably due to the fact that albuminoid matter is + particularly adapted for the formation of osmotic membranes. Our osmotic + productions are composed of the same elements as those which constitute + living beings; an osmotic growth obtained by sowing calcium nitrate in a + solution of potassium carbonate with sodium phosphate and sulphate + contains all the principal elements of a living organism, viz. carbon, + oxygen, hydrogen, nitrogen, sulphur, and phosphorus.</p> + + <p>The whole of the vegetable world is produced by the osmotic growth of + mineral substances, if we except the small amount of organic matter + contained in the seeds.</p> + + <p>The most important problem of synthetic biology is not so much the + synthesis of the albuminoids as the reduction of carbonic acid. In nature + this reduction is accomplished by the radiant energy of the sun, by the + agency of the catalytic action of chlorophyll. <!-- Page 158 --><span + class="pagenum"><a name="page158"></a>{158}</span></p> + + <p>The physico-chemical study of osmotic growth is as yet hardly begun; + we have but indicated the method, the way is open, and the problems + awaiting solution are legion. Only work and ever more work and workers + are required. Experiments should be made with substances which are + chemically unstable like the albuminoids, substances which readily + combine and dissociate again, alternately absorbing and giving up the + potential energy which is the essence of life. Experiments should also be + made with substances which readily unite or decompose under the influence + of water, since hydration and hydrolysis appear to be the dominant + mechanism in all vital reaction, as they undoubtedly are in osmotic + growth, which consists of an increase of hydration on one side of an + osmotic membrane and a diminution on the other side.</p> + + <p>Life is not a substance but a mechanical phenomenon; it is a dynamic + and kinetic transference of energy determined by physico-chemical + reactions; and the whole trend of modern research leads to the belief + that these reactions are of the same nature as those met with in the + organic world. It is the grouping of physical reactions and their mode of + association and succession, their harmony in fact, which constitutes + life. The problem we have to solve in the synthesis of life is the proper + attuning and harmonizing of these physical phenomena, as they exist in + living beings, and there should be no absolute impossibility in our some + day realizing this harmony in whole or in part.</p> + + <p>Albert Gaudry says: "I cannot conceive why in determining the + connecting links of the animal world the fact that an organic body is + formed of such and such elements should be of greater importance than the + manner in which these elements are grouped. Descartes regarded extension + as the essential property of an organized being; he supposed it to be + inert of itself, and that it had the Deity for its motive force. To-day + the hypothesis of Descartes has given way to that of Leibnitz, who + regards force as the essential property of the living being, the visible + and tangible matter being only of secondary importance. If we regard the + living being as a force, this <span class="correction" title="Original reads 'orce'." + >force</span> is able to aggregate matter under such and such a form, + <!-- Page 159 --><span class="pagenum"><a + name="page159"></a>{159}</span>with such or such a structure, and such or + such a chemical essence. It does not seem that the classification + depending on differences of substance are any more important than those + which depend on differences of form."</p> + + <p>The biological interest of osmotic productions is quite independent of + the chemical nature of the substances which enter into their growth. All + substances which produce osmotic membranes by the contact of their + solutions exhibit phenomena analogous to those of nutrition. Osmotic + morphogenesis is a physical phenomenon resulting from the contact of the + most diverse substances. It has given us our first glimpse of the manner + in which a living being may be supposed to have been formed according to + the ordinary physical laws of nature. We cannot at present produce + osmotic growths with all the combinations found in living beings, but + that is only because chemistry still lags far behind physics in the + synthesis of organic forms.</p> + + <p>We are often told "not to force the analogy." But error is equally + produced by the exaggeration of unimportant differences. We have already + seen that nutrition, absorption, transformation, and excitation are not + the characteristics of living organisms alone; nor is reaction to + external impressions the appanage only of animate beings. To insist on + the resemblance between an osmotic production and a living being is not + to force an analogy but to demonstrate a fact.</p> + + <p>Let us briefly recapitulate. An osmotic growth has an evolutionary + existence; it is nourished by osmosis and intussusception; it exercises a + selective choice on the substances offered to it; it changes the chemical + constitution of its nutriment before assimilating it. Like a living thing + it ejects into its environment the waste products of its function. + Moreover, it grows and develops structures like those of living + organisms, and it is sensitive to many exterior changes, which influence + its form and development. But these very phenomena—nutrition, + assimilation, sensibility, growth, and organization—are generally + asserted to be the sole characteristics of life.</p> + + <p><br style="clear:both" /></p> +<hr class="full" /> + +<p><!-- Page 160 --><span class="pagenum"><a name="page160"></a>{160}</span></p> + +<h3>CHAPTER XIII</h3> + +<p class="cenhead">EVOLUTION AND SPONTANEOUS GENERATION</p> + + <p>By many biologists, even at the present day, the origin and evolution + of living beings is considered to be outside the domain of natural + phenomena, and hence beyond the reach of experimental research. The + change in our views on this subject is due to a Frenchman, Jean Lamarck, + who was the true originator of the scientific doctrine of evolution. At a + time when the miraculous origin of every living being was regarded as an + unchangeable verity, and was defended like a sacred dogma, Lamarck boldly + formulated his theory of evolution, with all its attendent consequences, + from spontaneous generation to the genealogy of man.</p> + + <p>In his <i>Philosophie Zoologique</i>, which appeared in 1809, Lamarck + put forth his claim to regard all the phenomena of life, of living + beings, and of man himself as pertaining to the domain of natural + phenomena. According to him, all bodies which are met with in nature, + organic and inorganic alike, are subject to the same laws. Life is a + physical phenomenon, and all the processes of life are due to mechanical + causes, either physical or chemical. He writes: "À leur source le + physique et le moral ne sont sans doute qu'une seule et même chose. Il + faut rechercher dans la considération de l'organisation les causes mêmes + de la vie."</p> + + <p>In the intellectual evolution of the human mind perhaps no advance has + been more important than that of Lamarck—the conquest of the domain + of life by human intelligence. In conformity with the true scientific + method, he founds his doctrine on the facts and phenomena of nature. "I + confine myself," he says, "within the bounds of a simple contemplation + <!-- Page 161 --><span class="pagenum"><a + name="page161"></a>{161}</span>of nature." It was this observation of the + gradual perfecting of living organisms from the simplest to the most + complicated that inspired Lamarck with the idea of evolution and + transformation. "How," he says, "can we help searching for the cause of + such wonderful results? Are we not compelled to admit that nature has + produced successively bodies endowed with life, proceeding from the + simplest to the most complex?"</p> + + <p>The various products of nature have been divided into classes, genera, + and species, simply to facilitate their study. Modern research tends to + show that there is no definite line of demarcation even between the + animal, vegetable, and mineral kingdoms. All our classification is + artificial, and the passage from one division to another is gradual and + insensible. Lamarck expresses this idea very clearly: "We must remember + that classes, orders, and families, and all such nomenclature, are + methods of our own invention. In nature there are no such things as + classes or orders or families, but only individuals. As we become better + acquainted with the productions of nature, and as the number of specimens + in our collections increases, we see the intervals between the classes + gradually fill up, and the lines of separation become effaced."</p> + + <p>Lamarck also raises his voice against the supposed immutability of + species. "Species have only a relative constancy, depending on the + circumstances of the individuals. The individuals of a given species + perpetuate themselves without variation only so long as there is no + variation in the circumstances which influence their existence. + Numberless facts prove that when an individual of a given species changes + its locality, it is subjected to a number of influences which little by + little alter, not only the consistency and proportions of its parts, but + also its form, its faculty, and even its organization; so that in time + every part will participate in the mutations which it has undergone."</p> + + <p>Lamarck also clearly affirms the fact of spontaneous generation. "I + hope to prove," he says, "that nature possesses means and faculties for + the production of all the forms which we so much admire. Rudimentary + animals and plants have <!-- Page 162 --><span class="pagenum"><a + name="page162"></a>{162}</span>been formed, and are still being formed + to-day, by spontaneous generation."</p> + + <p>Lamarck himself gives a résumé of his doctrine in the following six + propositions:—</p> + + <p>1. "All the organized bodies of our globe are veritable productions of + Nature, which she has successively formed during the lapse of ages.</p> + + <p>2. "Nature began, and still recommences day by day, with the + production of the simplest organic forms. These so-called spontaneous + generations are her direct work, the first sketches as it were of + organization.</p> + + <p>3. "The first sketches of an animal or a vegetable growth being begun + under favourable conditions, the faculties of commencing life and of + organic movement thus established have gradually developed little by + little the various parts and organs, which in process of time have become + diversified.</p> + + <p>4. "The faculty of growth is inherent in every part of an organized + body; it is the primary effect of life. This faculty of growth has given + rise to the various modes of multiplication and regeneration of the + individual, and by its means any progress which may have been acquired in + the composition and forms of the organism has been preserved.</p> + + <p>5. "All living things which exist at the present day have been + successively formed by this means, aided by a long lapse of time, by + favourable conditions, and by the changes on the surface of the + globe—in a word, by the power which new situations and new habits + have of modifying the organs of a body which is endowed with life.</p> + + <p>6. "Since all living things have undergone more or less change in + their organization, the species which have been thus insensibly and + successively produced can have but a relative constancy, and can be of no + very great antiquity."</p> + + <p>The admirable work of Lamarck was absolutely neglected in France, + where it was treated as unworthy even of consideration. This neglect + profoundly afflicted Lamarck, who gradually sank a victim to the + opposition of his contemporaries. He left, however, one disciple, Etienne + Jeoffroy St. <!-- Page 163 --><span class="pagenum"><a + name="page163"></a>{163}</span>Hilaire, but he too was soon reduced to + silence under the weight of authority of his adversaries.</p> + + <div class="figright" style="width:46%;"> + <a href="images/Fig62.jpg"><img style="width:100%" src="images/Fig62.jpg" + alt="Fig. 62." title="Fig. 62." /></a> + <span class="sc">Fig. 62.</span>—Osmotic vegetation. + </div> + + <p>Before the doctrine of evolution could live and take its proper place, + it had to be reborn in England—the country of liberty. This + resuscitation was due to Darwin, who added to it his illuminating + doctrine of natural selection. But apart from this and a perfecting of + its various details, Lamarck had already formulated the doctrine of + evolution with perfect precision. Lamarck's work was still-born, whereas + that of Darwin lived and grew to its full development. This was due, not + to any imperfection or insufficiency in Lamarck's work, but <!-- Page 164 + --><span class="pagenum"><a name="page164"></a>{164}</span>to the milieu + into which it was born. It was the environment that stifled the offspring + of Lamarck.</p> + + <p>In 1868, Ernest Haeckel speaks of the genius of Lamarck in these + words: "The chief of the natural philosophers of France is Jean Lamarck, + who takes his place beside Goethe and Darwin in the history of evolution. + To him belongs the imperishable glory of being the first to formulate the + theory of descent, and of founding the philosophy of nature on the solid + basis of biology," and adds, "There is no country in Europe where + Darwin's doctrine has had so little influence as in France." Haeckel has + but done tardy justice in his discovery of and testimony to the genius of + Lamarck.</p> + + <p>The spirit of opposition does not seem to have much changed in France + since Lamarck's time. In 1907 the Académie des Sciences de Paris excluded + from its <i>Comptes Rendus</i> the report of my researches on diffusion + and osmosis, because it raised the question of spontaneous + generation.</p> + + <p>The majority of scientists seem to consider that the question of + spontaneous generation was definitely settled once for all when Pasteur's + experiments showed that a sterilized liquid, kept in a closed tube, + remained sterile.</p> + + <p>Without the idea of spontaneous generation and a physical theory of + life, the doctrine of evolution is a mutilated hypothesis without unity + or cohesion. On this point Lamarck speaks most clearly: "Although it is + customary when one speaks of the members of the animal or vegetable + kingdom to call them products of nature, it appears that no definite + conception is attached to the expression. Our preconceived notions hinder + us from recognising the fact that Nature herself possesses all the + faculties and all the means of producing living beings in any variety. + She is able to vary, very slowly but without cessation, all the different + races and all the different forms of life, and to maintain the general + order which we see in all her works."</p> + + <p>The doctrine of Lamarck is frequently misinterpreted. We often hear it + expressed as "Function makes the organ," or even "Function creates the + organ." This is equivalent to saying, "Life makes the living being," + which is incomprehensible, <!-- Page 165 --><span class="pagenum"><a + name="page165"></a>{165}</span>making of function a sort of immaterial + and independent entity which constructs a material organ in order to + lodge within it. No such idea is to be found in all the works of Lamarck. + He formulates his law in the following terms: "In every animal which is + still undergoing development, the frequent and sustained use of any one + organ increases its size and power, whereas the constant neglect of the + use of such organ weakens and deteriorates it, so that it finally + disappears."</p> + + <p>In his expression of this law Lamarck insists on the fact that + organization precedes function. He affirms only that function, + <i>i.e.</i> action and reaction, modifies the organ; or, in other words, + that organisms are modelled by the action of exterior forces acting upon + them. It is in this sense only that function may be said to make an + organ, but this mode of expression should be avoided, as it is apt to be + misunderstood.</p> + + <p>Astronomy teaches us that our globe was detached from the sun in an + incandescent state, and geology asserts that this earth has passed + through a period of long ages when its temperature was incompatible with + the existence of life. It was only with the cooling of the earth crust + that it was possible for living beings to make their appearance. Hence + they must of necessity have been produced spontaneously from terrestrial + material under the influences of chemical and physical forces. This + opinion imposes itself on all who reflect and judge freely. In the same + way the doctrine of evolution necessitates as a corollary the doctrine of + spontaneous generation. The doctrine of evolution should reconstitute + every link in the chain of beings from the simplest to the most + complicated; it cannot afford to leave out the most important of all, + viz. the missing link between the inorganic and the organic kingdoms. If + there is a chain, it must be continuous in all its parts, there can be no + solution of continuity.</p> + + <p>Evolutionists like Lamarck and Haeckel admit spontaneous generation, + not as the most probable, but as the only possible explanation of the + phenomenon of life.</p> + + <p>Lamarck shows us the apparition of living things at a certain epoch of + the earth's evolution, and the gradual <!-- Page 166 --><span + class="pagenum"><a name="page166"></a>{166}</span>development of more + complicated forms as the conditions changed on the surface of the globe. + Darwin shows how heredity and natural selection tend to accentuate the + variations which are favourable to existence. Haeckel demonstrates the + parallelism between ontogenesis and philogenesis—between the + successive forms in the evolution of the embryo and the successive forms + of the individual in the evolution of a race. These are great and + admirable conquests of the human intelligence, they have demonstrated the + first appearance and the progressive evolution of living beings; it now + only remains for us to explain them.</p> + + <div class="figright" style="width:46%;"> + <a href="images/Fig63.jpg"><img style="width:100%" src="images/Fig63.jpg" + alt="Fig. 63." title="Fig. 63." /></a> + <span class="sc">Fig. 63.</span>—Marine forms of osmotic growth. + </div> + + <p>The doctrine of evolution, while enforcing the fact of spontaneous + generation and progressive evolution, gives us no hint as to the physical + mechanism of such generation. It does not tell us by what forces, or + according to what laws, the simpler forms of life have been produced, or + in what manner differences of environment have acted in order to modify + them. The doctrine asserts the simultaneous variations in organic forms + and in the physical influences which produce them, but says <!-- Page 167 + --><span class="pagenum"><a name="page167"></a>{167}</span>nothing as to + their mode of action. The Darwinian theory shows how acquired variations + are transmitted and accentuated by natural selection, but it says nothing + as to how these variations may be acquired. In the same way we are in + entire ignorance as to the physical mechanism of ontogenetic development, + the evolution of the embryo.</p> + + <p>The morphogenic action of diffusion produces osmotic growths of + extreme variety. Most of these forms recall those of living + things—shells, fungi, corals, and algæ. The analogy of function is + quite as close as the resemblance of form. The study of osmosis, however, + is as yet in its infancy, and osmotic productions vary with the physical + conditions of chemical constitution, temperature, concentration, and the + like. The study of the organizing action of osmosis on organic material + has as yet been hardly attempted.</p> + + <p>Osmosis produces growths of great complexity, much more complicated + indeed than the more simple forms of living organisms. This marvellous + complexity of an osmotic growth may be compared with another fact, the + ontogenetic development of the ovum, a single cell which under favourable + conditions of environment may evolve into a most complicated organism. + These considerations lead to the belief that the beginning of life has + not been the production of a simple primitive form from which all others + are descended, but that a number of such primitive forms may have been + produced, forms which by a rapid physical development attained a high + degree of complexity. Osmotic morphogenesis shows us that the ordinary + physical forces have in fact a power of organization infinitely greater + than has been hitherto supposed by the boldest imagination.</p> + + <p>When we consider the ignorance in which we still remain as to the + phenomena which pass before our very eyes, how can we expect to + understand those which occurred in past ages, when the physical and + chemical conditions were so immensely different from those which obtain + in our own time? What do we know even now of the physical and chemical + phenomena which take place in the unfathomed depths of the ocean, where + for aught we know even at the present time the same <!-- Page 168 + --><span class="pagenum"><a name="page168"></a>{168}</span>process may be + going on—the genesis of life, and the emergence of living beings + out of the inanimate mineral world? "Even now," says Albert Gaudry, + "polyps and oceanic animalculæ are building up vast coral reefs and + rocks. The oxygen and hydrogen which existed once was water, the oxygen + and nitrogen which once made air, the carbon, the phosphorus, the silica + and the lime which once were solid rock, now form the substance of living + beings. The silica is deposited in the skeleton of a sponge or a + radiolaria, the shell of a foraminifera or the carapace of a crustacean, + or unites with phosphorus to form the bones of a vertebrate. A very + tumult of life has succeeded to the primitive silence of inert matter. + Life has invaded the earth, and we see on all sides the inanimate mineral + kingdom being changed into a living world."</p> + + <p>The admission that life may have appeared on the earth under the + influence of natural forces and according to physical laws and conditions + different from those of the present era throws a vivid light on the study + of biogenesis, spontaneous generation, and evolution. The means of + research are now indicated, and we have only to study the documents + already in our possession in order to know the conditions which obtained + when life first appeared on the globe. We must endeavour to reproduce + these conditions and to study their effects.</p> + + <p>Since all living beings are formed of the same elements as those of + the mineral world, the term "organic" as applied to combinations can only + be used in order to emphasize the complexity of their constitution. It + was formerly believed that these organic combinations were the result of + life, and could not be reproduced except by living organisms. To-day many + of these organic substances are produced in the laboratory from inorganic + materials. In the past history of the globe it is easy to imagine + conditions which would facilitate the synthesis of organic substances + without the interposition of life. At the temperature of the electric + furnace, which was that of the earth at an early period of its evolution, + chemical combinations are possible quite other than those obtaining under + the present conditions of temperature and pressure. At the higher + temperature of the early <!-- Page 169 --><span class="pagenum"><a + name="page169"></a>{169}</span>geological era, silicides, carbides, + phosphides, and nitrides were formed in stable combinations instead of + the oxides, silicates, carbonates, phosphates, and nitrates of the + present time. These combinations existed on the earth at a time when the + conditions of temperature precluded the existence of water in a liquid + state. As the temperature cooled, and the water vapour became condensed, + it entered into chemical combination with the various rocks, producing + organic compounds like acetylene, which results from the action of water + on calcium carbide. H. Lénicque has developed a theory as to the + formation of various rocks under these conditions, which he communicated + in 1903 to the French Society of Civil Engineers.</p> + + <p>The chemical evolution of the globe has undergone great changes as the + temperature gradually fell and the constitution of its crust altered. As + long as the temperature was higher than that at which water can exist, + all chemical reactions must have taken place between anhydric substances, + elements and salts in a state of fusion. These conditions are very + different from those of the present-day chemistry, which is the chemistry + of aqueous solutions. We may hope to be able to reproduce the earlier + conditions by the experimental study of anhydric substances in a state of + fusion.</p> + + <p>At a later period, that of the primary and secondary rocks, there was + a uniform and constant temperature of about 40° C. The atmosphere was + charged with water vapour, and all the conditions were present for the + production of storms and tempests. The atmosphere during long ages must + have been the seat of formidable and incessant electric discharges; these + discharges are the most powerful of all physical agents of chemical + synthesis, and will cause nitrogen to combine directly to form various + compounds—nitrates, cyanides, and ammonia. Carbonic acid would also + be present in abundance and would enter into combination with these + nitrogenous compounds. In this way we may imagine that compounds were + formed which by some process of physical synthesis subsequently gave rise + to vast quantities of albuminoid matter. At that time the seas and oceans + contained all those substances which have <!-- Page 170 --><span + class="pagenum"><a name="page170"></a>{170}</span>since been fixed by the + metamorphism of the primitive rocks, or deposited in the sedimentary + strata. Most of the elements in our minerals were formerly in a state of + solution in these primeval seas, which contained carbonates, silicates, + and soluble phosphates in great abundance. As the crust gradually cooled, + the terrestrial atmosphere of necessity altered in composition, and the + slow evolution of the atmosphere no doubt also exercised an influence on + the development of living beings.</p> + + <p>Palæontology teaches us that the earliest living organism appeared in + the sea. The most ancient of living things, those of the primary ages, + which were of greater duration than all other ages put together, were all + aquatic. We find moreover that every living organism consists of liquids, + solutions of crystalloids and colloids separated by osmotic membranes; + and it is significant that the ocean, that vast laboratory of life, is + also a solution of crystalloids and colloids. It is evident, then, that + we must look to the study of solutions if we would hope to discover the + nature and origin of life.</p> + + <p>Life is an ensemble of functions and of energy-transformations, an + ensemble which is conditioned by the form, the structure, and the + composition of the living being. Life, therefore, may be said to be + conditioned by form, <i>i.e.</i> the external, internal, and molecular + forms of the living being.</p> + + <p>All living things consist of closed cavities, which are limited by + osmotic membranes, and filled with solutions of crystalloids and + colloids. The study of synthetic biology is therefore the study of the + physical forces and conditions which can produce cavities surrounded by + osmotic membranes, which can associate and group such cavities, and + differentiate and specialize their functions. Such forces are precisely + those which produce osmotic growths, having the forms and exhibiting many + of the functions of living beings. Of all the theories as to the origin + of life, that which attributes it to osmosis and looks on the earliest + living beings as products of osmotic growths is the most probable and the + most satisfying to the reason.</p> + + <div class="figright" style="width:47%;"> + <a href="images/Fig64.jpg"><img style="width:100%" src="images/Fig64.jpg" + alt="Fig. 64." title="Fig. 64." /></a> + <span class="sc">Fig. 64.</span>—Osmotic shells and corals. + </div> + + <p>We have already seen that the seas of the primary and <!-- Page 171 + --><span class="pagenum"><a name="page171"></a>{171}</span>secondary ages + presented in a high degree the particular conditions favourable for the + production of osmotic growths. During these long ages an exuberant growth + of osmotic vegetation must have been produced in these primeval seas. All + the substances which were capable of producing osmotic membranes by + mutual contact sprang into growth,—the soluble salts of calcium, + carbonates, phosphates, silicates, albuminoid matter, became organized as + osmotic productions,—were born, developed, evolved, dissociated, + and died. Millions of ephemeral forms must have succeeded one another in + the natural evolution of that age, when the living world was represented + by matter thus organized by osmosis.</p> + + <p>The experimental study of osmotic morphogeny adds its weight of + evidence in the same direction. When we see under our own eyes the cells + of calcium become organized, develop and grow in close imitation of the + forms of life, we cannot doubt that such a transformation has often + occurred in the past history of our planet, and the conviction becomes + irresistible <!-- Page 172 --><span class="pagenum"><a + name="page172"></a>{172}</span>that osmosis has played a predominant rôle + in the history of our earth and its inhabitants. It is a matter of + astonishment that the scientist has taken no notice of the active part + which osmosis has played in the evolution of our earth. On the effects of + this most important physical phenomenon science has hitherto remained + entirely mute.</p> + + <p><i>Printed by</i> <span class="sc">Morrison & Gibb Limited</span>, + <i>Edinburgh</i></p> + + + + + + + + +<pre> + + + + + +End of the Project Gutenberg EBook of The Mechanism of Life, by Stéphane Leduc + +*** END OF THIS PROJECT GUTENBERG EBOOK THE MECHANISM OF LIFE *** + +***** This file should be named 33862-h.htm or 33862-h.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/3/3/8/6/33862/ + +Produced by David Garcia, James Nugen, Keith Edkins and +the Online Distributed Proofreading Team at +http://www.pgdp.net + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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