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+The Project Gutenberg EBook of The Mechanism of Life, by Stéphane Leduc
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: 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
+
+
+
+
+
+Transcriber's note: A few typographical errors have been corrected: they
+are listed at the end of the text.
+
+       *       *       *       *       *
+
+
+THE MECHANISM OF LIFE
+
+[Illustration: Osmotic Productions. [_Frontispiece_]
+
+THE
+
+MECHANISM OF LIFE
+
+BY
+
+DR. STÉPHANE LEDUC
+
+PROFESSEUR À L'ÉCOLE DE MÉDECINE DE NANTES
+
+TRANSLATED BY
+
+W. DEANE BUTCHER
+
+FORMERLY PRESIDENT OF THE RÖNTGEN SOCIETY, AND OF THE
+ELECTRO-THERAPEUTICAL SECTION OF THE ROYAL SOCIETY OF MEDICINE
+
+
+
+
+ "La nature a formé, et forme tous
+  les jours les êtres les plus simples par
+  génération spontanée." LAMARCK.
+
+
+
+
+[Illustration]
+
+NEW YORK
+
+REBMAN COMPANY
+
+HERALD SQUARE BUILDING
+141-145, WEST 36TH STREET
+
+  _First Impression    March  1911_
+
+  _Second Impression   January 1914_
+
+  _Printed in England_
+
+       *       *       *       *       *
+
+
+{vii}
+
+TRANSLATOR'S PREFACE
+
+Professor Leduc's _Théorie Physico-chimique de la Vie et Générations
+Spontanées_ 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 _Comptes Rendus_ the report of these experimental
+researches on diffusion and osmosis, because it touched too closely on the
+burning question of spontaneous generation.
+
+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.
+
+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.
+
+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 {viii} 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.
+
+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.
+
+
+
+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.
+
+  W. DEANE BUTCHER.
+
+  EALING.
+
+       *       *       *       *       *
+
+
+{ix}
+
+PREFACE TO THE ENGLISH EDITION
+
+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.
+
+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.
+
+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.
+
+  STÉPHANE LEDUC.
+
+  NANTES, 1911.
+
+       *       *       *       *       *
+
+
+{xi}
+
+TABLE OF CONTENTS
+
+                                                          PAGE
+
+  TRANSLATOR'S PREFACE                                     vii
+
+  AUTHOR'S PREFACE                                          ix
+
+  INTRODUCTION                                            xiii
+
+  I. LIFE AND LIVING BEINGS                                  1
+
+  II. SOLUTIONS                                             14
+
+  III. ELECTROLYTIC SOLUTIONS                               24
+
+  IV. COLLOIDS                                              36
+
+  V. DIFFUSION AND OSMOSIS                                  43
+
+  VI. PERIODICITY                                           67
+
+  VII. COHESION AND CRYSTALLIZATION                         78
+
+  VIII. KARYOKINESIS                                        89
+
+  IX. ENERGETICS                                            97
+
+  X. SYNTHETIC BIOLOGY                                     113
+
+  XI. OSMOTIC GROWTH: A STUDY IN MORPHOGENESIS             123
+
+  XII. THE PHENOMENA OF LIFE AND OSMOTIC PRODUCTIONS:
+  A STUDY IN PHYSIOGENESIS                                 147
+
+  XIII. EVOLUTION AND SPONTANEOUS GENERATION               160
+
+       *       *       *       *       *
+
+
+{xiii}
+
+INTRODUCTION
+
+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.
+
+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.
+
+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.
+
+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.
+
+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 {xiv} marked contrast to the perennial character of the
+matter and the energy which circulate within it.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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 {xv}
+possible by simple liquid diffusion to reproduce in ordered and regular
+succession complicated movements like those observed in the karyokinesis of
+the living cell.
+
+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.
+
+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.
+
+       *       *       *       *       *
+
+
+{1}
+
+THE MECHANISM OF LIFE
+
+CHAPTER I
+
+LIFE AND LIVING BEINGS
+
+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.
+
+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.
+
+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 [Greek: entelecheia]." This principle is itself
+in need of definition, and Aristotle only substitutes one unknown epithet
+for another.
+
+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. {2}
+
+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.
+
+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.
+
+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.
+
+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 {3} 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.
+
+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.
+
+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.
+
+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.
+
+The true definition of a living being is that it is a transformer of
+energy, receiving from its environment the energy {4} which it returns to
+that environment under another form. All living organisms are transformers
+of energy.
+
+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.
+
+Living beings are also transformers of form. They commence as a very simple
+form, which gradually develops and becomes more complicated.
+
+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.
+
+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.
+
+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.
+
+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. {5}
+
+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?"
+
+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.
+
+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.
+
+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.
+
+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.
+
+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.
+
+Phenomena succeed one another in time as consequences {6} 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.
+
+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.
+
+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.
+
+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.
+
+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.
+
+The phenomena of life may in certain cases slow down from their normal
+rapidity and intensity, as in hibernating {7} 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.
+
+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.
+
+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.
+
+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.
+
+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 {8} 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.
+
+Organic bodies may be divided into four principal groups. (1)
+_Carbohydrates_, including the sugars and the starches, all of which may be
+considered as formed of carbon and water. (2) _Fats_, 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) _Albuminoids_, 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) _Minerals_ 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.
+
+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.
+
+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 {9} 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.
+
+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.
+
+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.
+
+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.
+
+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_2O, by the combination of a molecule of water with an atom of carbon.
+
+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_2O = C_2H_4O_2. Three
+molecules of formol form a molecule of lactic acid, 3CH_2O = C_3H_6O_3. Six
+molecules of formol represent glucose and levulose, 6CH_2O = C_6H_{12}O_6.
+Twelve molecules of formol minus one molecule of water form saccharose,
+lactose, cane sugar, and sugar of milk, 12CH_2O = C_{12}H_{22}O_{11} +
+H_2O; _n_ times six {10} molecules of formol minus one molecule of water,
+_n_(C_6H_{10}O_5), form starch and cellulose.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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. {11} 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.
+
+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.e._ 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.
+
+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.
+
+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.
+
+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 {12} 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.
+
+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.
+
+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.
+
+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.
+
+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 {13} 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.
+
+       *       *       *       *       *
+
+
+{14}
+
+CHAPTER II
+
+SOLUTIONS
+
+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.
+
+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.
+
+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.
+
+Avogadro's law asserts that under similar conditions of temperature and
+pressure, equal volumes of various gases {15} 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.
+
+_Gramme-Molecule._--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.
+
+_Concentration._--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. (_a_) The weight of solute
+dissolved in 100 grammes of the solvent. (_b_) The weight of solute present
+in 100 grammes of the solution. (_c_) The weight of solute dissolved in a
+litre of the solvent. (_d_) 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.
+
+_Molecular Concentration._--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.e_. 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.
+
+_Normal Solution._--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, {16} contains 60 grammes of urea per litre, while a normal
+solution of sugar contains 342 grammes of sugar per litre.
+
+_The Dissolved Substance is a Gas._--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.e._ 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.
+
+_Osmotic Pressure._--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.
+
+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.
+
+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.
+
+_Boyle's Law_.--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.
+
+_Gay-Lussac's Law._--For a difference of temperature of a degree Centigrade
+all gases dilate or contract by 1 / 273 of their volume at 0° Centigrade.
+{17}
+
+_Dalton's Law._--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.
+
+_Pressure proportional to Molecular Concentration._--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.e._ 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.
+
+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.
+
+_Absolute Zero._--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 _t°_ indicates the
+Centigrade temperature above the freezing point of water, then the absolute
+temperature is equal to _t°_ + 273°.
+
+_The Gaseous Constant._--Consider a mass of gas at 0° C. under a pressure
+P_o, with volume V_o. At the absolute temperature T, if the pressure be
+unaltered, the volume of this gas will be V_oT / 273. Therefore the
+constant PV, the product of the pressure by the volume, will be represented
+by P_oV_oT / 273. {18}
+
+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_oV_o), it will still equal P_oV_oT / 273. Therefore P_oV_o / 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.
+
+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.
+
+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.
+
+_Pfeffer's Apparatus._--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 {19} 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.
+
+_Osmotic Pressure follows the Laws of Gaseous Pressure._--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.
+
+_Osmotic Pressure of Sugar._--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.
+
+_Isotonic Solutions._--Two solutions which have the same {20} 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.
+
+_Lowering of the Freezing Point._--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.
+
+_Cryoscopy of Blood._--In order to determine the osmotic pressure of the
+blood at 37° C., _i.e._ 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.
+
+_Rise of Boiling Point._--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.
+
+_Lowering of the Vapour Tension._--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
+{21} 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.
+
+_Corresponding Values._--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--
+
+  1. The Molecular Concentration.
+  2. The Osmotic Pressure.
+  3. The Diminution of Vapour Tension.
+  4. The Raising of the Boiling Point.
+  5. The Lowering of the Freezing Point.
+
+_Cryoscopy._--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 {22} the two freezing points is the required "lowering
+of the freezing point."
+
+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.
+
+_Molecular Lowering of the Freezing Point._--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.
+
+_Determination of the Molecular Concentration._--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 n be the number of
+gramme-molecules per litre, then n = A / 1.85.
+
+_Determination of the Osmotic Pressure._--The osmotic pressure P of a
+solution may be obtained by multiplying its molecular concentration n by
+22.35 atmospheres. P = n × 22.35 = A / 1.85 × 22.35.
+
+_Determination of Molecular Weight._--The lowering of the freezing point
+also enables us to calculate the molecular {23} 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
+_x_ 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 n, the number of gramme-molecules per litre. The molecular weight M may
+be determined by dividing the original weight x by n.
+
+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."
+
+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.
+
+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.
+
+       *       *       *       *       *
+
+
+{24}
+
+CHAPTER III
+
+ELECTROLYTIC SOLUTIONS
+
+_Solutions which conduct Electricity._--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 times the number of
+molecules of solute originally introduced into it. If n be the original
+number of molecules, then it will apparently contain n' = in 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 = n'/n, which is
+the ratio of the apparent number of the molecules present to the number
+originally introduced.
+
+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 {25} 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.
+
+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.
+
+_Coefficient of Dissociation._--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, which is called the
+Coefficient of Dissociation.
+
+This coefficient of dissociation, i, may be found by observing the lowering
+of the freezing point of a normal solution, and dividing it by 1.85. i =
+t/1.85.
+
+The coefficient of dissociation varies with the degree of concentration of
+the solution, rising to a maximum when the solution is sufficiently
+diluted.
+
+If we know i, the coefficient of dissociation for a given solute, contained
+in a solution of a definite concentration, we can find n', the number of
+particles present in a solution containing n gramme-molecules of the solute
+per litre, since n' = in. On the other hand, if from a consideration of its
+freezing point and other constants we find that an electrolytic solution
+appears to contain n' gramme-molecules per litre, the real number of
+chemical gramme-molecules in one litre of the solution will be only n' / i
+= n.
+
+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.
+
+_Electrolysis._--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 {26} 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.
+
+_Electrolytes._--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.
+
+_Arrhenius' Theory of Electrolysis._--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. {27}
+
+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.e._ 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^+ and Cl^- indicate the two ions of a salt
+solution; Cu^{++} and SO_4^{--} 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^. and Cl^,; Cu^{..} and SO_4^{,,}.
+
+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.
+
+_Degree of Dissociation._--The degree of dissociation is the fraction of
+the molecules in the solution which have undergone dissociation. Let n be
+the total number of molecules of the solute, and n" the number of
+dissociated molecules. Then n" / n = a will represent the degree of
+dissociation. Let k be the number of ions into which each molecule is
+split. Then a = n"k / nk, _i.e._ 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.
+
+Let n' be the total number of particles present in a solution {28}
+containing n molecules, each of which is composed of k ions. Then if a is
+the degree of dissociation,
+
+  n' = n - an + ank,
+  n' = n[1 + a (k - 1)],
+  n' / n = 1 + a (k - 1) = i.
+
+We thus obtain i the coefficient of dissociation, in terms of the degree of
+dissociation a and the number of ions in each molecule k.
+
+If there is no dissociation, _i.e._ if a = 0, then n' = n, and i = 1. If
+all the molecules are dissociated, a = 1, and i = k.
+
+_Faraday's Law._--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.
+
+_Electrochemical Equivalent._--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.
+
+_Electrolytic Conductivity._--The conductivity of an electrolyte is the
+inverse of its resistance. C = 1/R.
+
+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.
+
+_The specific conductivity_ [Delta] of an electrolyte is the conductivity
+of a cube of the solution, each face of which is one square centimetre in
+area. The _molecular conductivity_ 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
+[Delta], its specific conductivity. U = V[Delta]. Whence [Delta] = U / V,
+_i.e._ the specific {29} conductivity equals the molecular conductivity
+divided by the volume.
+
+The conductivity of an electrolyte is proportional to the number of ions in
+a volume of the solution containing one gramme-molecule. Let M_{[infinity]}
+be the conductivity for complete dissociation and M_v the molecular
+conductivity at the volume V. Then
+
+  M_v / M_{[infinity]} = n"k / nk = n" / n = a,
+
+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.
+
+    |         --    --    --     |  --    --    --                |
+    |         SO_4  SO_4  SO_4   |  SO_4  SO_4  SO_4              |
+    |                            |                                |
+    |         ++    ++    ++     |  ++    ++    ++                |
+    |         Cu    Cu    Cu     |  Cu    Cu    Cu                |
+    |                            |                                |
+    +----------------------------+--------------------------------+
+
+FIG. 1.--Before the passage of the current.
+
+    |                     --     |  --    --                      |
+    |                     SO_4   |  SO_4  SO_4  SO_4  SO_4  SO_4  |
+  - |                            |                                | +
+    |                     ++     |  ++    ++                      |
+    |   Cu    Cu    Cu    Cu     |  Cu    Cu                      |
+    |                            |                                |
+    +---------------------------+---------------------------------+
+
+FIG. 2.--After the passage of the current.
+
+_Velocity of the Ions._--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:-- {30}
+
+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 u be the
+velocity of the anions, and v the velocity of the cations. Let n be the
+loss of concentration at the cathode, and 1 - n the loss of concentration
+at the anode. Then
+
+  u / v = n / (1 - n),
+
+_i.e._ 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.
+
+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 _differences_ 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.e._ the difference of conductivity between potassium
+chloride and sodium chloride is the same as that between {31} potassium
+bromide and sodium bromide. Hence we may conclude that the conductivity of
+any salt is an ionic property.
+
+Kohlrausch's law may be expressed by the formula c = d(u + v), where c is
+the conductivity of the salt, d the degree of dissociation, _i.e._ the
+fraction of the electrolyte broken up into ions, and u and v the velocity
+of the anions and cations respectively. When all the molecules of the
+electrolyte are dissociated, d = 1, and the formula becomes c_{[infinity]}
+= u + v.
+
+As we have already seen, a salt is formed by the union of a metal M with an
+acid radical R. Potassium sulphate, K_2SO_4, consists of the metal K_2 and
+the acid radical SO_4. Ammonium chloride, NH_4Cl, consists of the basic
+radical NH_4 and the acid radical Cl. The various acids may be considered
+as salts of the metal hydrogen. Thus sulphuric acid, H_2SO_4, 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:--
+
+  Salts = MR.
+  Acids = HR.
+  Bases = MOH.
+
+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.e._ the degree of dissociation of its ions. The
+acidity of an electrolytic solution is due to the presence of the
+dissociated ion H^+, and its strength is determined by the concentration of
+these free hydrogen ions. Hence the greater the degree of dissociation the
+stronger the acid.
+
+The basic character of a solution is determined by the presence of the
+hydroxyl radical OH^-. The greater the concentration of the hydroxyl ions,
+_i.e._ the greater the dissociation, the stronger is the base.
+
+The ions H^+ and OH^- are of special importance, since they are the ions of
+water, H_2O = H^+ + OH^-. The degree of {32} 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^+ and OH^-, their diversity being due to variations in the relative
+proportions and grouping.
+
+_The Chemical, Therapeutic, and Toxic Actions of Ions._--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^-. 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_3 or C_2H_3ClO_2.
+
+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^{---}. The phosphates
+contain phosphorus in the same proportion as the phosphides, but this
+phosphorus is harmlessly entangled in the complex ion PO_4^{---}, whose
+properties are absolutely different from those of the ion 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. {33}
+
+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^{+++}, but rather those of the complex anion of which they form a part.
+
+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.
+
+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. {34}
+
+Since all chemical, toxic, and therapeutic actions are ionic, they are
+proportional to the degree of ionic concentration, _i.e._ 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^+. 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^+ is very concentrated;
+whereas the feeble acids are but slightly dissociated, so that the ion H^+
+is less concentrated.
+
+Paul and Krönig have shown that the bactericidal action of different salts
+also varies with their degree of dissociation, _i.e._ 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 _Bacillus anthracis_. 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^-
+would be more toxic than Cl^- or Br^-. 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^{++}. This ion is very {35} concentrated in the highly dissociated
+solution HgCl_2, less concentrated in the less ionized solution HgBr_2, and
+exceedingly dilute in the HgCy_2, which is hardly ionized at all.
+
+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.
+
+       *       *       *       *       *
+
+
+{36}
+
+CHAPTER IV
+
+COLLOIDS
+
+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.
+
+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.
+
+_Colloids._--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 {37} 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.
+
+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.
+
+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,
+
+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.
+
+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 {38} solution of similar strength of a
+crystalloid whose molecular weight was 40.
+
+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."
+
+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.
+
+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.
+
+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.
+
+Most colloidal substances are precipitated from their solutions by the
+addition of very small quantities of electrolytic {39} 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.
+
+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.
+
+_Metallic Colloids._--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.
+
+_Catalytic Properties of Colloids._--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.
+
+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.
+
+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 {40} 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.
+
+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.
+
+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.
+
+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.
+
+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. {41} 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.
+
+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.
+
+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.
+
+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.
+
+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 {42} 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.
+
+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.
+
+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.
+
+       *       *       *       *       *
+
+
+{43}
+
+CHAPTER V
+
+DIFFUSION AND OSMOSIS
+
+_Diffusion and Osmosis._--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.
+
+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.
+
+_Coefficient of Diffusion._--The coefficient of diffusion has {44} 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."
+
+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.
+
+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.
+
+_Osmosis._--In 1748, l'Abbé Nollet discovered that when a pig's bladder
+filled with alcohol was plunged into water, the {45} 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.
+
+_Precipitated Membranes._--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.
+
+_Osmotic Membranes._--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."
+
+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. {46}
+
+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.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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 {47} 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.
+
+A disregard of this fact, that a solute will always pass from a solution
+where its osmotic pressure is high, into one 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.
+
+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.
+
+_Plasmolysis._--We all know that a cut flower soon dries {48} 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 _Tradescantia
+discolor_. 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.e._ 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.
+
+_Red Blood Corpuscles as Indicators of Isotony._--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 {49} 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.
+
+_The Hæmatocrite._--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.
+
+_Action of Solutions of Different Degrees of Concentration on Living
+Cells_.--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 {50}
+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.
+
+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 {51} 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.
+
+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.
+
+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 {52} 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.
+
+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.e._ 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.
+
+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.
+
+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^+ of the salt in the stomach contents exchanges with
+an ion H^+ of the monobasic salts of the blood, NaHCO_3 + NaCl = HCl +
+Na_2CO_3. {53}
+
+_Influence of Muscular Contraction on the Intramuscular Osmotic
+Pressure._--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:--
+
+Change of weight of untired leg--
+
+  After  8 hours  -.000.
+  After 16 hours  -.000.
+  After 24 hours  -.006.
+
+Change of weight of stimulated leg--
+
+  After  8 hours  +.050.
+  After 16 hours  +.080.
+  After 24 hours  +.101.
+
+{54}
+
+This result shows that muscular work provoked by electric stimulation
+noticeably increases the osmotic pressure of the muscle.
+
+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:--
+
+Change of weight of untired leg--
+
+  After  8 hours  -.000.
+  After 16 hours  -.004.
+  After 24 hours  -.006.
+
+Change of weight of stimulated leg--
+
+  After  8 hours  +.039.
+  After 16 hours  +.072.
+  After 24 hours  +.099.
+
+Finally, in a solution freezing at -.72°, _i.e._ with an osmotic pressure
+at 15° C. of 9.176 atmospheres, we obtained the following mean values for
+the untired leg:--
+
+  After  8 hours  -.04.
+  After 16 hours  -.05.
+  After 24 hours  -.05.
+
+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.
+
+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.
+
+I made further experiments in order to discover whether the variation in
+osmotic pressure depended on the duration of {55} 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:--
+
+  Untired muscles.   Muscles stimulated once a second during
+                     2 Minutes.   4 Minutes.   6 Minutes.
+       .000             +.026        +.084        +.094
+      +.001             +.034        +.065        +.093
+      +.005             +.045        +.079        +.097
+       .000             +.037        +.070        +.095
+       .000             +.032        +.072        +.096
+
+Mean of all the observations--
+
+      +.0012            +.0348       +.074        +.095
+
+These experiments show clearly that the osmotic intramuscular pressure
+rises in proportion to the duration of the electrical stimulation.
+
+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.
+
+Briefly, then, the results of our experiments are as follow:--
+
+1. Muscular contraction electrically produced causes an increase of the
+osmotic pressure in a muscle.
+
+2. The intramuscular osmotic pressure may reach, or even exceed, 2.5
+atmospheres, or 2.6 kilogrammes per square centimetre of surface.
+
+3. When a muscle is made to contract once a second, the {56} elevation of
+the osmotic pressure increases with the number of contractions.
+
+4. The intramuscular osmotic pressure increases with the work done by the
+muscle.
+
+5. Fatigue is caused by the increase of osmotic pressure in a contracting
+muscle.
+
+[Illustration: FIG. 3.--Fields of diffusive force.
+
+(_a_) Monopolar field of diffusion. A drop of blood in a saline solution of
+higher concentration.
+
+(_b_) 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. ]
+
+_The Field of Diffusion._--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.
+
+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. {57}
+
+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 a. 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.
+
+[Illustration: FIG. 4.--Two drops of blood in a more concentrated solution,
+showing a field of diffusion between two poles of the same sign.]
+
+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
+_b_). 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.
+
+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.e._ 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. {58}
+
+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.
+
+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.
+
+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.
+
+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 {59} the current of water carries
+with it the blood globules which produce the redness.
+
+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.
+
+_Tactism and Tropism._--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.
+
+[Illustration: FIG. 5.--Liquid figures of diffusion.
+
+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_3
+solution.]
+
+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.
+
+_The Morphogenic Effects of Diffusion._--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 {60} 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.
+
+[Illustration: FIG. 6.--Pattern produced in gelatine by the diffusion of
+drops of concentrated solutions of nitrate of silver and bromide of
+ammonium.]
+
+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.
+
+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 {61} 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_4 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_4. 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.
+
+[Illustration: FIG. 7.--Pattern produced in gelatine by the diffusion of
+drops of silver nitrate and sodium carbonate.]
+
+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.
+
+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 {62} 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.
+
+[Illustration: FIG. 8.--Pattern produced in gelatine by the diffusion of
+drops of a solution of nitrate of silver and of citrate of potassium.]
+
+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 {63} 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.
+
+[Illustration: FIG. 9.--Tissue of artificial cells formed by the diffusion
+in gelatine of drops of potassium ferrocyanide.]
+
+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.
+
+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, {64} _i.e._ by
+continually repairing the loss of concentration at the centre of the cell.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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 {65} 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.
+
+[Illustration: FIG. 10.--Artificial liquid cells, formed by coloured drops
+of concentrated salt solution in a less concentrated salt solution.]
+
+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.
+
+[Illustration: FIG. 11.--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.]
+
+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.
+
+Similar cells may be produced in water. If we pour a thin layer of water on
+a horizontal plate, and with a pipette {66} 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.
+
+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).
+
+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.
+
+       *       *       *       *       *
+
+
+{67}
+
+CHAPTER VI
+
+PERIODICITY
+
+_Periodic Precipitation._--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.
+
+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.
+
+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 _On
+Stratification by Diffusion_.
+
+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 {68} sulphate. At the Congress of Rheims in 1907 I
+exhibited the result of some further experiments on the same subject.
+
+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.
+
+[Illustration: FIG. 12.--Lines of diffusion precipitate, showing the
+simultaneous propagation of "undulations of different wave-length.]
+
+_Circular Waves of Precipitation._--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 {69} give
+us a very beautiful representation of the simultaneous propagation of
+undulations of different wave-length in the same medium.
+
+[Illustration: FIG. 13.--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.]
+
+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.
+
+[Illustration: FIG. 14.--Transformation of a spherical wave-front into a
+plane wave-front by a convergent diopter.]
+
+These diffusion rings furnish us with most excellent diagrams of refraction
+at a "diopter," _i.e._ a spherical surface separating two media of
+different densities. Fig. 14 shows the refraction at a convergent diopter,
+_i.e_. 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.
+
+These periodic diffusion rings also illustrate the phenomena of colour
+diffraction. Diffusion waves of different {70} 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.e._ it will transform a
+divergent into a convergent beam. This is an illustration of what is called
+the aberration of refrangibility.
+
+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.
+
+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.
+
+[Illustration: FIG. 15.--Diffraction of diffusion waves on passing through
+a narrow aperture.]
+
+_Diffraction._--When light traverses a minute orifice, instead {71} 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.
+
+[Illustration: FIG. 16.--Interference of diffusion waves.]
+
+_Interference._--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. {72} 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.
+
+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.
+
+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.
+
+The phenomena associated with the pressure of light, the {73} 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.
+
+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.
+
+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.
+
+Diffusion waves differ greatly in length, varying from several millimetres
+to 2 [mu]. 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.
+
+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.
+
+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.
+
+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 {74} 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.
+
+[Illustration: FIG. 17.--Photomicrograph of striated structure of a
+periodic precipitate of carbonate and phosphate of lime (magnified 500
+times).]
+
+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 {75} 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_2CO_3)
+to one of dibasic sodium phosphate (Na_2HPO_4). 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.
+
+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.
+
+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.
+
+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.
+
+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 {76} 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."
+
+[Illustration: FIG. 18.--Articulate form produced by periodic
+precipitation.]
+
+A slight alkalinity of the liquid is necessary to start the phenomenon.
+This explains the retardation at the beginning {77} 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.
+
+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.
+
+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.
+
+       *       *       *       *       *
+
+
+{78}
+
+CHAPTER VII
+
+COHESION AND CRYSTALLIZATION
+
+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.
+
+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.
+
+[Illustration: FIG. 19.--Muriform cohesion figure formed by a drop of
+Indian ink in a solution of salt.]
+
+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 {79} 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).
+
+[Illustration: FIG. 20.--Seven similar drops of Indian ink diffusing in a
+salt solution. Two minutes after introducing the drops.]
+
+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 {80} 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.
+
+[Illustration: FIG. 21.--The same drops 15 minutes later, showing the
+granulation appearance.]
+
+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.
+
+[Illustration: FIG. 22.--The same drops after 30 minutes. The granulations
+have agglomerated at the centre of the drops.]
+
+It is otherwise, however, with the colouring matter of the {81} 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 {82} completely absorbed the six
+smaller ones, and only one large drop will remain.
+
+[Illustration: FIG. 23.--Attraction between coloured drops in an isotonic
+solution.]
+
+_Incubation._--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.
+
+_Artificial Parthenogenesis._--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.
+
+[Illustration: FIG. 24.--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.]
+
+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 {83} 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.
+
+[Illustration: FIG. 25.--The same preparation several hours later, showing
+a cellular gastrula-like structure.]
+
+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 {84} 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.
+
+[Illustration: FIG. 26.--Field of crystallization of sodium chloride
+(magnified 60 diameters).]
+
+_Crystallization._--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. {85}
+
+[Illustration: FIG. 27.--Field of crystallization around a crystal of
+sodium chloride in process of formation.]
+
+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 {86} 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.
+
+[Illustration: FIG. 28.--Three crystals of sodium chloride in process of
+formation, each in the centre of a field of crystallization.]
+
+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 _Applicacion de la crystalogenia experimental à la
+investigacion toxicologica de cas alcaloïdes_. {87}
+
+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.
+
+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.
+
+[Illustration: FIG. 29.--Crystallization of sodium chloride in a colloidal
+solution, giving a plant-like form.]
+
+[Illustration: FIG. 30.--Form produced by the crystallization of chloride
+of ammonium in a colloidal solution.]
+
+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."
+
+I should like here to recall to your notice the work of an English
+observer, Dr. E. Montgomery of St. Thomas's {88} 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.e._ 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.
+
+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."
+
+       *       *       *       *       *
+
+
+{89}
+
+CHAPTER VIII
+
+KARYOKINESIS
+
+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."
+
+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.
+
+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 {90}
+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.
+
+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.e._ 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
+karyokinesis. {91}
+
+[Illustration: FIG. 31.--Diffusion figure representing karyokinesis.
+Achromatin spindle between two similar poles of concentration.]
+
+"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.
+
+"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. {92}
+
+"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).
+
+[Illustration: FIG. 32.--Four successive stages in the production of
+artificial karyokinesis by diffusion.]
+
+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,
+{93} and as far as we know diffusion alone, is able to produce a spindle
+between homologous poles.
+
+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
+_vera causa_ 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.
+
+_Nuclear Division._--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 {94} 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.
+
+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).
+
+[Illustration: FIG. 33.--Equatorial crown produced by diffusion.]
+
+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. {95}
+
+[Illustration: FIG. 34.--A triaster produced by diffusion.]
+
+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.
+
+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.
+
+We may also produce diffusion figures of abnormal karyokinesis. Fig. 34
+represents such a form, a triaster produced by diffusion.
+
+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. {96}
+
+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.e._ 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.
+
+       *       *       *       *       *
+
+
+{97}
+
+CHAPTER IX
+
+ENERGETICS
+
+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 _Metamorphoses_: "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."
+
+The French poetess Mme. Ackermann has expressed the same idea in beautiful
+verse:--
+
+ "Ainsi, jamais d'arrêt. L'immortelle matière,
+  Un seul instant encore n'a pu se reposer.
+  La Nature ne fait, patiente ouvrière,
+  Que défaire et recomposer.
+  {98}
+  Tout se métamorphose entre ses mains actives;
+  Partout le mouvement incessant et divers,
+  Dans le cercle éternel des formes fugitives,
+  Agitant l'immense univers."
+
+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.
+
+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.
+
+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.
+
+The actual state of our knowledge with regard to the science of energy
+rests on two principles, that of Mayer and that of Carnot.
+
+The first principle was defined by J. R. Mayer, a medical practitioner of
+Heilbronn, whose work, _Bemerkungen ueber die Kräfte der unbelebten Natur_,
+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 {99}
+quantity of mechanical work represented by different modes of motion
+remains invariable."
+
+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.
+
+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."
+
+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.
+
+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.
+
+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.
+
+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. {100}
+
+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.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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 _vis viva_
+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 {101} energies, represents the total potential energy of the weight
+before it began to fall.
+
+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.
+
+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.
+
+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.
+
+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 {102} 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.
+
+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.
+
+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.e._ the anterior
+phenomena, which determined such transformation.
+
+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 {103}
+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.
+
+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.
+
+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.
+
+The second law of thermodynamics, Carnot's law, may therefore be enunciated
+thus: "Energy cannot be transformed without a fall of potential."
+
+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.
+
+  Efficiency = energy transformed / total energy absorbed
+
+The total energy is the product QI, _i.e._ 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
+
+  Q(I - I') / QI = (I - I') / I.
+
+ If I represents a temperature, then in order that the efficiency may be
+positive I' must be less than I, {104} there must be a fall of temperature
+in the machine. If I' were greater than I, _i.e._ 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.
+
+_Entropy._--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
+
+  (I - I') / I
+
+is also zero.
+
+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."
+
+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 {105} 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.
+
+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 {106} 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.
+
+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.
+
+Three conditions, then, are required for a transformation or displacement
+of energy:--
+
+1. _The cause_, the intervention of a stimulus which starts the
+transformation or displacement.
+
+2. _The possibility_, the necessary fall of potential.
+
+3. _The condition_, the conservation of the energy concerned, since being
+indestructible its total quantity cannot alter.
+
+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.
+
+Man obtains his supply of energy either directly from the {107} 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.
+
+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.
+
+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.
+
+The formula for the efficiency of a thermic transformer is
+
+  (T - T') / T,
+
+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.e._ it can transform 20 per cent. of the energy absorbed. The
+ordinary temperature of muscle is 38° C., or 311° absolute. We have {108}
+therefore (T - 311) / T = .20, or T = 388.75° absolute, _i.e._ 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.
+
+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.e._ 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 {109} 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.
+
+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.
+
+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.
+
+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.
+
+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.
+
+A muscle is doing positive work when it is raising a weight or moving a
+body from one point to another. {110}
+
+The fourth state of muscular contraction is when the muscle is doing
+negative work, _i.e._ 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.
+
+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.
+
+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, {111} 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.
+
+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."
+
+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 {112} 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.
+
+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.e._ the
+transformation of the potential energy already stored in the organism into
+the actual energy of motion and vital activity.
+
+       *       *       *       *       *
+
+
+{113}
+
+CHAPTER X
+
+SYNTHETIC BIOLOGY
+
+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.
+
+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.
+
+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 {114} unite and associate these, and to
+observe their development under various external influences.
+
+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.
+
+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."
+
+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.
+
+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. {115}
+
+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.
+
+In 1866, Moritz Traube of Breslau discovered the osmotic properties of
+certain chemical precipitates. As I pointed out in the _Revue Scientifique_
+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 (_Gesammelte Abhandlungen von Moritz Traube_, 1899).
+
+In 1867 there appeared in England a paper by Dr. E. Montgomery, of St.
+Thomas's Hospital, _On the Formation of so-called Cells in Animal Bodies_.
+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 {116} 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.
+
+"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."
+
+In 1871 there appeared a memoir by the Dutch savant Harting entitled
+_Recherche de Morphologie synthetique sur la production artificielle de
+quelques formations calcaires organiques_. 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."
+
+In the _Comptes Rendues_ of 1882 is the following note by D. Monnier and
+Karl Vogt:--
+
+"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. {117}
+
+"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.
+
+"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.
+
+"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.
+
+"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.
+
+"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.
+
+"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.
+
+"8. It is probable that the inorganic elements which are present in the
+natural protoplasm may play an important part {118} in determining the form
+which is assumed by the figured elements of the organism."
+
+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 _Annalen der Physik_ 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.
+
+"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.
+
+"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 {119} 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.
+
+"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.
+
+"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.
+
+"Later on Traube himself considered the precipitated membrane to be a thin,
+solid gelatinous layer in which the water was mechanically entangled.
+
+"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 {120} 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.
+
+"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.
+
+"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.
+
+"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.
+
+"I shall show later on that gelatine and albumen essentially modify the
+precipitate and do not merely act as catalytic substances. The researches
+of Famintzin, 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." {121}
+
+Such is the history of morphogenesis as described in 1902 by the authority
+most qualified for the task, Professor Quinke of Heidelberg.
+
+In 1904, Professor Moritz Benedikt of Vienna treated the whole question in
+his book, _Crystallization and Morphogenesis_, 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 _Revue Scientifique_ in 1905.
+
+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.
+
+One of the most active of the modern morphogenists is Professor Herrera of
+Mexico, whose work is illustrated in the _Atlas de Plasmogenie_ 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 _Memoirs of the Societé
+Alzate, Mexico_.
+
+A bibliography of the works which have appeared on this subject may be
+found in the book of Professor Rhumbler of Göttingen, _Aus dem
+Lückengebiete zwischen Organischer und Anorganischer Materie_, 1906.
+
+In 1907, Dr. Luiz Razetti of Carracas published a magnificent study of the
+subject under the title _Que es la vida_.
+
+In 1907, Dr. Martin Kuckuck of St. Petersburg repeated and extended the
+experiments of R. Dubois, and published his results under the title
+_Archigonia, Generatio Spontanea_, Leipzig, Ambrosius Barth.
+
+Butler Burke of Cambridge has also made a series of experiments with radium
+and barium salts analogous to those of Dubois.
+
+In 1909, Albert and Alexandre Mary of Beauvais published {122} an
+interesting study of this question under the title _Études expérimentales
+sur la génération primitive_, published by Jules Rousset.
+
+I should mention also among the works of synthetic biology the publications
+of Professor Otto Lehmann of Karlsruhe, and in particular _Flüssige
+Krystalle und die Theorien des Lebens_, Leipzig, Ambrosius Barth.
+
+Professor Ulenhuth of Berlin has published his study on the osmotic growth
+of iron in alkaline hypochlorites under the title _Untersuchungen ueber
+Antiformin_, Berlin, Julius Springer.
+
+Professor Gariel has made a series of researches on osmotic growth which
+are published in Abraham's _Recueil d'expériences de physique_.
+
+A. Lecha Marzo of Valladolid published his researches on the growth of
+aniline colours in the _Gaceta Medica Catalana_, 1909, under the title
+_Otra nueva flora artificiale_.
+
+Dr. Maurice d'Halluin of Lille has also published a volume on osmotic
+growths under the title, _Stéphane Leduc a-t-il créé la vie?_
+
+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 _Documents du Progrès_, Sept. 1909.
+
+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.
+
+       *       *       *       *       *
+
+
+{123}
+
+CHAPTER XI
+
+OSMOTIC GROWTH--A STUDY IN MORPHOGENESIS
+
+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.
+
+_Osmotic Membranes._--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.
+
+An osmotic membrane is not a semi-permeable membrane, as sometimes
+described, _i.e._ 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.
+
+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 {124} 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.
+
+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.
+
+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
+{125} 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.
+
+[Illustration: FIG. 35. FIG. 36.
+
+Osmotic growths of ferrocyanide of copper.]
+
+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.
+
+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.
+
+A good solution to commence with is the following:--
+
+  Silicate of potash, sp. gr. 1.3 (33° Beaumé)     60 gr.
+  Saturated solution of sodium carbonate           60 gr.
+  Saturated solution of dibasic sodium phosphate   30 gr.
+  Distilled water                     make up to 1 litre.
+
+{126}
+
+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.
+
+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:--
+
+  Ten per cent. solution of gelatine           10 to 20 c.c.
+  Saturated solution of potassium ferrocyanide  5 to 10 c.c.
+  Saturated solution of sodium chloride         5 to 10 c.c.
+  Warm water (32° to 40° C.)                        100 c.c.
+
+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).
+
+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 {127} stains used for microscopy, in the liquids used for fixing
+preparations.
+
+[Illustration: FIG. 37.--Osmotic vermiform growth.
+
+(_a_) The sickle-shaped growth.
+
+(_b_) The growth broken by the upward pressure of the solution.
+
+(_c_) The wound having cicatrized, the stem continues to grow downwards. ]
+
+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.
+
+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 _b_, 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.
+
+_Osmotic Growths in Air._--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_2 in a shallow flat-bottomed glass dish, just covering the fragment
+with liquid. The best solution is as follows:--
+
+  Potassium carbonate, saturated solution          76 parts.
+  Sodium sulphate, saturated solution              20   "
+  Tribasic potassium phosphate, saturated solution  4   "
+
+{128}
+
+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.
+
+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.
+
+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.
+
+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.
+
+[Illustration: FIG. 38.--Osmotic growth produced by sowing a mixture of
+CaCl_2 and MnCl_2 in a solution of alkaline carbonate, phosphate, and
+silicate. The stem and terminal organs are of different colours. (One-third
+of the natural size.)]
+
+[Illustration: FIG. 39.--An osmotic growth photographed by transverse light
+to show the construction of the terminal organs.]
+
+_Assimilation and Excretion._--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 {130} carbonate,
+is transformed into calcium carbonate. CaCl_2 + K_2CO_3 = CaCO_3 + 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_3, while at the same time it eliminates and excretes {131}
+chlorine, which may be found in the nutrient liquid after the reaction.
+
+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.
+
+[Illustration: FIG. 40.--Osmotic growth in a solution of KNO_3, showing
+spine-like organs.]
+
+_Osmotic Growths._--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.
+
+[Illustration: FIG. 41.--Terminal organs like catkins, developing in a
+solution of ammonium chloride.]
+
+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 {132} terminal organs will then grow out
+from the ends of the stems, which may during their further growth become
+conical or piriform in shape.
+
+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.
+
+[Illustration: FIG. 42.--An osmotic madrepore.]
+
+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. {133}
+
+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.
+
+[Illustration: FIG. 43.--An osmotic mushroom form.]
+
+[Illustration: FIG. 44.--Osmotic fungi.]
+
+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.
+
+Most remarkable fungus-like forms may be obtained by commencing the growth
+in a concentrated solution, and then {134} 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 {135} 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 {136} 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.
+
+[Illustration: FIG. 45.--A shell-like calcareous osmotic growth.]
+
+[Illustration: FIG. 46.--Osmotic growths in the form of shells.]
+
+[Illustration: FIG. 47.--Capsular osmotic growth. The capsule has been
+broken to show the interior structure.]
+
+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. {137}
+
+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.
+
+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.
+
+[Illustration: FIG. 48.--An osmotic growth in which the terminal organs are
+differently coloured from the stems, showing that the chemical evolution is
+different.]
+
+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.
+
+[Illustration: FIG. 49.--Osmotic capsular growth with figured belt.]
+
+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 {138} the internal osmotic
+pressure, showing the gelatinous contents through the opening.
+
+[Illustration: FIG. 50.--Amoeboid osmotic growth, floating free in the
+mother liquor.]
+
+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.
+
+[Illustration: FIG. 51.--Transparent osmotic cell, in which may be seen the
+white calcareous nucleus. The summit of the cell bears osmotic
+prolongations.]
+
+[Illustration: FIG. 52.--Amoeboid osmotic growth with long crystalline
+cilia swimming about in the mother liquor.]
+
+[Illustration: FIG. 53.--Osmotic growth swimming in mother liquor. The
+fin-like prolongation grew out between two liquid layers of different
+concentrations.]
+
+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 {139} 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 {140} 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.
+
+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.
+
+[Illustration: FIG. 54.--Capsular osmotic growth, the two valves separated
+showing the colloidal contents.]
+
+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 amoeba. The same
+phenomenon may be observed with vermiform growths, a single seed often
+giving {141} rise in this way to a whole series of amoebiform or vermiform
+productions.
+
+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.
+
+[Illustration: FIG. 55.--Microphotograph showing the structure of various
+osmotic stems. (Magnified 25 diameters.)
+
+(_a_) Sodium sulphite.
+
+(_b_) Potassium bichromate.
+
+(_c_) Sodium sulphide.
+
+(_d_) Sodium bisulphite. ]
+
+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. Similarly, 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.
+
+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. {142}
+
+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. {143}
+
+[Illustration: FIG. 56.--Microphotograph showing the structure of osmotic
+stems. (Magnified 40 diameters.)]
+
+[Illustration: FIG. 57.--Photograph of an osmotic leaf showing the veins.]
+
+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.
+
+[Illustration: FIG. 58.--Photomicrograph of an osmotic leaf showing the
+cellular structure.]
+
+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 {144} 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 {146} 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.
+
+[Illustration: FIG. 59.--Osmotic growth with nucleated terminal organs.
+(One-third of the natural size.)]
+
+[Illustration: FIG. 60.--A group of osmotic plants.]
+
+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?
+
+       *       *       *       *       *
+
+
+{147}
+
+CHAPTER XII
+
+THE PHENOMENA OF LIFE AND OSMOTIC PRODUCTIONS--A STUDY IN PHYSIOGENESIS
+
+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.
+
+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 {148} 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.
+
+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.
+
+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.
+
+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.e._ 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
+{149} 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.
+
+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.
+
+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 {150} of such
+marvellous results should have hitherto been almost entirely neglected.
+
+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.
+
+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.
+
+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 {151} corresponding weight. Thus
+growth, which has hitherto been considered an essential phenomenon of life,
+is also a phenomenon common to all osmotic productions.
+
+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.
+
+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.
+
+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 {152} 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.
+
+[Illustration: FIG. 61.--A group of osmotic forms.]
+
+Organization has long been considered as one of the principal
+characteristics of life, _i.e._ 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.
+
+The phenomena of osmotic growth show how ordinary mineral matter,
+carbonates, phosphates, silicates, nitrates, and chlorides, may imitate the
+forms of animated nature without {153} 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.
+
+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:--
+
+  Potassium carbonate            76 parts.
+  Potassium sulphate             16   "
+  Tribasic potassium phosphate   46   "
+
+During the whole period of growth there is an abundant liberation of
+bubbles of gas, which is accurately limited to a belt around the base of
+the growth, and sometimes also to a cap at the summit.
+
+Since morphological differentiations of different parts is but the result
+of differences of evolution, _i.e._ of functional differences of the
+various parts, we may consider that osmotic growths possess the faculty of
+organization like living beings.
+
+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.
+
+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 {154} 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.
+
+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.
+
+_Coagulation._--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.e._ 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, {155} 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.
+
+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.
+
+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.
+
+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.
+
+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 {156} being has as its
+ultimate cause a stimulus or excitation coming from without.
+
+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.
+
+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.
+
+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.
+
+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
+{157} 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.
+
+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.
+
+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.
+
+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.
+
+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. {158}
+
+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.
+
+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.
+
+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 force is able to aggregate matter under such and such a form,
+{159} 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."
+
+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.
+
+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.
+
+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.
+
+       *       *       *       *       *
+
+
+{160}
+
+CHAPTER XIII
+
+EVOLUTION AND SPONTANEOUS GENERATION
+
+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.
+
+In his _Philosophie Zoologique_, 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."
+
+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 {161} 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?"
+
+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."
+
+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."
+
+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 {162} been formed, and are still being formed to-day, by
+spontaneous generation."
+
+Lamarck himself gives a résumé of his doctrine in the following six
+propositions:--
+
+1. "All the organized bodies of our globe are veritable productions of
+Nature, which she has successively formed during the lapse of ages.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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."
+
+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. {163}
+Hilaire, but he too was soon reduced to silence under the weight of
+authority of his adversaries.
+
+[Illustration: FIG. 62.--Osmotic vegetation.]
+
+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 {164} to the milieu into which it was
+born. It was the environment that stifled the offspring of Lamarck.
+
+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.
+
+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 _Comptes Rendus_ the report of my researches on diffusion and osmosis,
+because it raised the question of spontaneous generation.
+
+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.
+
+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."
+
+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, {165} 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."
+
+In his expression of this law Lamarck insists on the fact that organization
+precedes function. He affirms only that function, _i.e._ 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.
+
+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.
+
+Evolutionists like Lamarck and Haeckel admit spontaneous generation, not as
+the most probable, but as the only possible explanation of the phenomenon
+of life.
+
+Lamarck shows us the apparition of living things at a certain epoch of the
+earth's evolution, and the gradual {166} 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.
+
+[Illustration: FIG. 63.--Marine forms of osmotic growth.]
+
+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 {167} 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.
+
+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.
+
+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.
+
+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 {168} 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."
+
+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.
+
+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 {169} 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.
+
+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.
+
+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
+{170} 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.
+
+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.
+
+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.e._ the external, internal, and molecular forms of the living being.
+
+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.
+
+[Illustration: FIG. 64.--Osmotic shells and corals.]
+
+We have already seen that the seas of the primary and {171} 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.
+
+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 {172} 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.
+
+_Printed by_ MORRISON & GIBB LIMITED, _Edinburgh_
+
+       *       *       *       *       *
+
+
+Corrections made to printed original.
+
+Page 47. "into one where its osmotic pressure is low": 'into on' in
+original.
+
+Page 90. "the achromatin spindle in karyokinesis.": 'karineyoksis' in
+original.
+
+Page 120. "The researches of Famintzin": 'Famitzin' in original,
+inconsistent with spelling 2 paragraphs earlier.
+
+Page 141. "Similarly, if we suddenly dilute": 'Simiarly' in original.
+
+Page 153. "which is accurately limited": 'acurately' in original.
+
+Page 158. "this force is able to aggregate matter": 'this orce' in
+original.
+
+
+
+
+
+
+End of the Project Gutenberg EBook of The Mechanism of Life, by Stéphane Leduc
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+
+<pre>
+
+The Project Gutenberg EBook of The Mechanism of Life, by Stéphane Leduc
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: 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>&nbsp;</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>&nbsp;</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">&nbsp;</span>E<span class="gsp">&nbsp;</span>B<span class="gsp">&nbsp;</span>M<span class="gsp">&nbsp;</span>A<span class="gsp">&nbsp;</span>N C<span class="gsp">&nbsp;</span>O<span class="gsp">&nbsp;</span>M<span class="gsp">&nbsp;</span>P<span class="gsp">&nbsp;</span>A<span class="gsp">&nbsp;</span>N<span class="gsp">&nbsp;</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,&mdash;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>&nbsp;</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&mdash;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&mdash;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&mdash;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,&mdash;having for its cause a principle
+  which has its end in itself, namely <span title="entelecheia" class="grk"
+  >&#x1F10;&nu;&tau;&epsilon;&lambda;&#x1F73;&chi;&epsilon;&iota;&alpha;</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,&mdash;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&mdash;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,&mdash;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&mdash;the juxtaposition of bricks, as
+  it were&mdash;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&mdash;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,"&mdash;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,&mdash;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&mdash;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,&mdash;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,&mdash;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&mdash;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&mdash;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&mdash;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&mdash;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&mdash;geometrical forms, bounded by straight lines, planes, and
+  regular angles. Living organisms, on the contrary, affect forms which are
+  less regular&mdash;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&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>.&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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&prime; the gas
+  will have a different volume V&prime;. Since, according to Boyle's law,
+  PV is constant (P&prime;V&prime; = 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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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&mdash;</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>&mdash;The usual method employed for the
+  determination of the molecular concentration and osmotic pressure of a
+  solution is by cryoscopy&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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&mdash;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>&mdash;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&prime; = 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&prime;/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>&mdash;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&prime;</i>, the number of particles present in a solution containing
+  <i>n</i> gramme-molecules of the solute per litre, since <i>n&prime;</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&prime;</i> gramme-molecules per litre, the real number of
+  chemical gramme-molecules in one litre of the solution will be only
+  <i>n&prime;</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>&mdash;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>&mdash;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,&mdash;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>&mdash;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>&mdash;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&Prime;</i> the number of dissociated molecules. Then
+  <i>n&Prime;</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&Prime;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&prime;</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&prime;</i> = <i>n</i> - <i>an</i> + <i>ank</i>,</p>
+      <p><i>n&prime;</i> = <i>n</i>[1 + <i>a</i> (<i>k</i> - 1)],</p>
+      <p><i>n&prime;</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&prime;</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>&mdash;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>&mdash;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>&mdash;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">&Delta;</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">&Delta;</span>, its specific conductivity.
+  U = V<span class="grk">&Delta;</span>. Whence <span
+  class="grk">&Delta;</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>&infin;</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>&infin;</sub> = <i>n&Prime;k</i> / <i>nk</i> = <i>n&Prime;</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>&mdash;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>&mdash;After the passage of the current.
+  </div>
+
+  <p><i>Velocity of the Ions.</i>&mdash;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:&mdash; <!-- 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>&infin;</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:&mdash;</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>&mdash;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&mdash;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>&mdash;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>&mdash;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>&mdash;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&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>.&mdash;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&mdash;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>&mdash;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:&mdash;</p>
+
+  <p>Change of weight of untired leg&mdash;</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&mdash;</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:&mdash;</p>
+
+  <p>Change of weight of untired leg&mdash;</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&mdash;</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:&mdash;</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. &nbsp;</td></tr>
+<tr><td class="spacsingle"> After 16 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.05. &nbsp;</td></tr>
+<tr><td class="spacsingle"> After 24 hours </td><td class="spacsingle" style="text-align:right; vertical-align:bottom;"> -.06. &nbsp;</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:&mdash;</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;"> &nbsp; .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;"> &nbsp; .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;"> &nbsp; .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&mdash;</td></tr>
+<tr><td class="spacsingle" style="text-align:center;"> &nbsp; +.0012 </td><td class="spacsingle" style="text-align:center;"> &nbsp; +.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:&mdash;</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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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&mdash;the life of the
+  artificial cell&mdash;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&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;Lines of diffusion precipitate,
+    showing the simultaneous propagation of "undulations of different
+    wave-length.
+  </div>
+
+  <p><i>Circular Waves of Precipitation.</i>&mdash;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>&mdash;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>&mdash;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>&mdash;Diffraction of diffusion waves
+    on passing through a narrow aperture.
+  </div>
+
+  <p><i>Diffraction.</i>&mdash;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>&mdash;Interference of diffusion waves.
+  </div>
+
+  <p><i>Interference.</i>&mdash;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">&mu;</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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;Attraction between coloured
+    drops in an isotonic solution.
+  </div>
+
+  <p><i>Incubation.</i>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;Field of crystallization of
+    sodium chloride (magnified 60 diameters).
+  </div>
+
+  <p><i>Crystallization.</i>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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&mdash;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>&mdash;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&mdash;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&mdash;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:&mdash;</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&mdash;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&prime;), 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&prime;) / QI = (I - I&prime;) / I.</p>
+    </div>
+  </div>
+
+  <p> If I represents a temperature, then in order that the efficiency may
+  be positive I&prime; 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&prime; 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>&mdash;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&prime; is now zero, and therefore the efficiency of
+  the machine</p>
+
+  <div class="poem">
+    <div class="stanza">
+      <p>(I - I&prime;) / 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:&mdash;</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&prime;) / 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&mdash;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&mdash;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&mdash;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&mdash;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&mdash;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 &amp; 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:&mdash;</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&mdash;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>&mdash;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&mdash;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 &amp; 36." title="Figs. 35 &amp; 36." /></a>
+    <span class="sc">Fig. 35.</span> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
+    &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
+    <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:&mdash;</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:&mdash;</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>&mdash;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>&mdash;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:&mdash;</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 &nbsp; &nbsp;,,</td></tr>
+<tr><td class="spacsingle"> Tribasic potassium phosphate, saturated solution </td><td class="spacsingle"> &nbsp; 4 &nbsp; &nbsp;,,</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>&mdash;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>&mdash;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>&mdash;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&mdash;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>&mdash;Osmotic growth in a solution of
+    KNO<sub>3</sub>, showing spine-like organs.
+  </div>
+
+  <p><i>Osmotic Growths.</i>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;Am&oelig;boid 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>&mdash;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>&mdash;Am&oelig;boid 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>&mdash;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>&mdash;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 am&oelig;ba. 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
+  am&oelig;biform 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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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>&mdash;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&mdash;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&mdash;water, carbon,
+  nitrogen, phosphorus, sulphur&mdash;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&mdash;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>&mdash;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:&mdash;</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 &nbsp; &nbsp;,,</td></tr>
+<tr><td class="spacsingle"> Tribasic potassium phosphate </td><td class="spacsingle"> 46 &nbsp; &nbsp;,,</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>&mdash;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&mdash;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&mdash;nutrition,
+  assimilation, sensibility, growth, and organization&mdash;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&mdash;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:&mdash;</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&mdash;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>&mdash;Osmotic vegetation.
+  </div>
+
+  <p>Before the doctrine of evolution could live and take its proper place,
+  it had to be reborn in England&mdash;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&mdash;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>&mdash;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&mdash;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&mdash;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&mdash;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>&mdash;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,&mdash;the soluble salts of calcium,
+  carbonates, phosphates, silicates, albuminoid matter, became organized as
+  osmotic productions,&mdash;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 &amp; Gibb Limited</span>,
+  <i>Edinburgh</i></p>
+
+
+
+
+
+
+
+
+<pre>
+
+
+
+
+
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@@ -0,0 +1,5951 @@
+The Project Gutenberg EBook of The Mechanism of Life, by Stephane Leduc
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: The Mechanism of Life
+
+Author: Stephane Leduc
+
+Translator: W Deane Butcher
+
+Release Date: October 15, 2010 [EBook #33862]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** 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
+
+
+
+
+
+Transcriber's note: A few typographical errors have been corrected: they
+are listed at the end of the text.
+
+       *       *       *       *       *
+
+
+THE MECHANISM OF LIFE
+
+[Illustration: Osmotic Productions. [_Frontispiece_]
+
+THE
+
+MECHANISM OF LIFE
+
+BY
+
+DR. STEPHANE LEDUC
+
+PROFESSEUR A L'ECOLE DE MEDECINE DE NANTES
+
+TRANSLATED BY
+
+W. DEANE BUTCHER
+
+FORMERLY PRESIDENT OF THE ROENTGEN SOCIETY, AND OF THE
+ELECTRO-THERAPEUTICAL SECTION OF THE ROYAL SOCIETY OF MEDICINE
+
+
+
+
+ "La nature a forme, et forme tous
+  les jours les etres les plus simples par
+  generation spontanee." LAMARCK.
+
+
+
+
+[Illustration]
+
+NEW YORK
+
+REBMAN COMPANY
+
+HERALD SQUARE BUILDING
+141-145, WEST 36TH STREET
+
+  _First Impression    March  1911_
+
+  _Second Impression   January 1914_
+
+  _Printed in England_
+
+       *       *       *       *       *
+
+
+{vii}
+
+TRANSLATOR'S PREFACE
+
+Professor Leduc's _Theorie Physico-chimique de la Vie et Generations
+Spontanees_ has excited a good deal of attention, and not a little
+opposition, on the Continent. As recently as 1907 the Academie des Sciences
+excluded from its _Comptes Rendus_ the report of these experimental
+researches on diffusion and osmosis, because it touched too closely on the
+burning question of spontaneous generation.
+
+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.
+
+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.
+
+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 {viii} 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.
+
+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.
+
+
+
+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.
+
+  W. DEANE BUTCHER.
+
+  EALING.
+
+       *       *       *       *       *
+
+
+{ix}
+
+PREFACE TO THE ENGLISH EDITION
+
+C'est par l'initiative du Dr. Deane Butcher que cette ouvrage est presente
+aux lecteurs anglais, a la race qui a dote l'humanite de tant de
+decouvertes originales, geniales et d'une portee tres generale.
+
+Comme un etre vivant, une idee exige pour naitre et se developper le germe
+et le milieu de developpement. Il est indeniable que le peuple
+anglo-americain constitue un milieu particulierement favorable a la
+naissance et au developpement des idees nouvelles.
+
+Pendant notre collaboration le Dr. Deane Butcher a ete un critique
+judicieux et eclaire, tous les changements dans l'edition anglaise sont dus
+a ses observations. Il s'est assimile l'ouvrage pour le traduire, et dans
+beaucoup de parties, il a mis plus de clarte et de concision qu'il n'y en
+avait dans le texte original.
+
+  STEPHANE LEDUC.
+
+  NANTES, 1911.
+
+       *       *       *       *       *
+
+
+{xi}
+
+TABLE OF CONTENTS
+
+                                                          PAGE
+
+  TRANSLATOR'S PREFACE                                     vii
+
+  AUTHOR'S PREFACE                                          ix
+
+  INTRODUCTION                                            xiii
+
+  I. LIFE AND LIVING BEINGS                                  1
+
+  II. SOLUTIONS                                             14
+
+  III. ELECTROLYTIC SOLUTIONS                               24
+
+  IV. COLLOIDS                                              36
+
+  V. DIFFUSION AND OSMOSIS                                  43
+
+  VI. PERIODICITY                                           67
+
+  VII. COHESION AND CRYSTALLIZATION                         78
+
+  VIII. KARYOKINESIS                                        89
+
+  IX. ENERGETICS                                            97
+
+  X. SYNTHETIC BIOLOGY                                     113
+
+  XI. OSMOTIC GROWTH: A STUDY IN MORPHOGENESIS             123
+
+  XII. THE PHENOMENA OF LIFE AND OSMOTIC PRODUCTIONS:
+  A STUDY IN PHYSIOGENESIS                                 147
+
+  XIII. EVOLUTION AND SPONTANEOUS GENERATION               160
+
+       *       *       *       *       *
+
+
+{xiii}
+
+INTRODUCTION
+
+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.
+
+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.
+
+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.
+
+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.
+
+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 {xiv} marked contrast to the perennial character of the
+matter and the energy which circulate within it.
+
+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.
+
+In this volume I have endeavoured to give as much of the science of
+energetics as can be treated without the use of mathematical formulae; the
+conception of entropy and Carnot's law of thermodynamics are also
+discussed.
+
+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.
+
+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.
+
+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 {xv}
+possible by simple liquid diffusion to reproduce in ordered and regular
+succession complicated movements like those observed in the karyokinesis of
+the living cell.
+
+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.
+
+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.
+
+       *       *       *       *       *
+
+
+{1}
+
+THE MECHANISM OF LIFE
+
+CHAPTER I
+
+LIFE AND LIVING BEINGS
+
+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.
+
+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.
+
+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 [Greek: entelecheia]." This principle is itself
+in need of definition, and Aristotle only substitutes one unknown epithet
+for another.
+
+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. {2}
+
+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.
+
+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.
+
+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.
+
+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 {3} 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.
+
+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.
+
+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.
+
+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.
+
+The true definition of a living being is that it is a transformer of
+energy, receiving from its environment the energy {4} which it returns to
+that environment under another form. All living organisms are transformers
+of energy.
+
+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.
+
+Living beings are also transformers of form. They commence as a very simple
+form, which gradually develops and becomes more complicated.
+
+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.
+
+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.
+
+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.
+
+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. {5}
+
+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?"
+
+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.
+
+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.
+
+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.
+
+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.
+
+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.
+
+Phenomena succeed one another in time as consequences {6} 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.
+
+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.
+
+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.
+
+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.
+
+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.
+
+The phenomena of life may in certain cases slow down from their normal
+rapidity and intensity, as in hibernating {7} 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.
+
+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 0deg C. and 100deg 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 44deg 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 0deg to 40deg, and then to
+diminish rapidly as the temperature rises above that point, becoming nearly
+extinct at 60deg C.
+
+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 anaerobic micro-organisms which apparently exist
+without oxygen, but these in reality obtain their oxygen from the medium in
+which they grow.
+
+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.
+
+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 {8} 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.
+
+Organic bodies may be divided into four principal groups. (1)
+_Carbohydrates_, including the sugars and the starches, all of which may be
+considered as formed of carbon and water. (2) _Fats_, 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) _Albuminoids_, 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 haemoglobin of the blood contains iron. (4) _Minerals_ 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.
+
+Woehler 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.
+
+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 {9} 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.
+
+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.
+
+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.
+
+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.
+
+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_2O, by the combination of a molecule of water with an atom of carbon.
+
+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_2O = C_2H_4O_2. Three
+molecules of formol form a molecule of lactic acid, 3CH_2O = C_3H_6O_3. Six
+molecules of formol represent glucose and levulose, 6CH_2O = C_6H_{12}O_6.
+Twelve molecules of formol minus one molecule of water form saccharose,
+lactose, cane sugar, and sugar of milk, 12CH_2O = C_{12}H_{22}O_{11} +
+H_2O; _n_ times six {10} molecules of formol minus one molecule of water,
+_n_(C_6H_{10}O_5), form starch and cellulose.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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. {11} 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.
+
+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.e._ 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.
+
+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.
+
+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.
+
+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 {12} 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.
+
+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.
+
+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.
+
+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.
+
+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 {13} 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.
+
+       *       *       *       *       *
+
+
+{14}
+
+CHAPTER II
+
+SOLUTIONS
+
+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.
+
+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.
+
+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.
+
+Avogadro's law asserts that under similar conditions of temperature and
+pressure, equal volumes of various gases {15} 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.
+
+_Gramme-Molecule._--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.
+
+_Concentration._--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. (_a_) The weight of solute
+dissolved in 100 grammes of the solvent. (_b_) The weight of solute present
+in 100 grammes of the solution. (_c_) The weight of solute dissolved in a
+litre of the solvent. (_d_) 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.
+
+_Molecular Concentration._--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.e_. 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.
+
+_Normal Solution._--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, {16} contains 60 grammes of urea per litre, while a normal
+solution of sugar contains 342 grammes of sugar per litre.
+
+_The Dissolved Substance is a Gas._--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.e._ 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.
+
+_Osmotic Pressure._--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.
+
+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.
+
+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.
+
+_Boyle's Law_.--When a gas is compressed its volume is diminished. If the
+pressure is doubled, the volume is reduced to one-half. The quantity V x P,
+that is the volume multiplied by the pressure, is constant.
+
+_Gay-Lussac's Law._--For a difference of temperature of a degree Centigrade
+all gases dilate or contract by 1 / 273 of their volume at 0deg Centigrade.
+{17}
+
+_Dalton's Law._--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.
+
+_Pressure proportional to Molecular Concentration._--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.e._ 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.
+
+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.
+
+_Absolute Zero._--According to Gay-Lussac's law, the volume of a gas
+diminishes by 1 / 273 of its volume at 0deg 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 -273deg 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 _tdeg_ indicates the
+Centigrade temperature above the freezing point of water, then the absolute
+temperature is equal to _tdeg_ + 273deg.
+
+_The Gaseous Constant._--Consider a mass of gas at 0deg C. under a pressure
+P_o, with volume V_o. At the absolute temperature T, if the pressure be
+unaltered, the volume of this gas will be V_oT / 273. Therefore the
+constant PV, the product of the pressure by the volume, will be represented
+by P_oV_oT / 273. {18}
+
+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_oV_o), it will still equal P_oV_oT / 273. Therefore P_oV_o / 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.
+
+Suppose, for instance, we have a gramme-molecule of a gas at 0deg C. in a
+space of 1 litre. It has a pressure of 22.35 atmospheres at 0deg C., or
+273deg absolute temperature. Since PV = RT, R = PV / T = 1 x 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.
+
+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.
+
+_Pfeffer's Apparatus._--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 {19} 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.
+
+_Osmotic Pressure follows the Laws of Gaseous Pressure._--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.
+
+_Osmotic Pressure of Sugar._--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.
+
+_Isotonic Solutions._--Two solutions which have the same {20} 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.
+
+_Lowering of the Freezing Point._--Pure water freezes at 0deg 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 1.85deg C. Thus a normal solution of any non-ionizable
+substance in water freezes at -1.85deg C. The measurement of this lowering
+of the freezing point is called Cryoscopy, a method which is becoming of
+great utility in medicine.
+
+_Cryoscopy of Blood._--In order to determine the osmotic pressure of the
+blood at 37deg C., _i.e._ 98.6deg F., the normal temperature, we proceed as
+follows. On freezing the blood, we find that it congeals at -.56deg. Its
+molecular concentration is therefore .56 / 1.85 = .30, or about one-third
+of a gramme-molecule per litre. Its osmotic pressure at 0deg C. is
+therefore .3 x 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 0deg for every degree rise of temperature. The increase of pressure at
+37deg is therefore .00367 x 37 x 6.7 = .9 atmospheres. The total osmotic
+pressure at 37deg is therefore 6.7 + .9 = 7.6 atmospheres.
+
+_Rise of Boiling Point._--Water under atmospheric pressure boils at a
+temperature of 100deg 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.
+
+_Lowering of the Vapour Tension._--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 100deg
+C., it is manifest that its vapour tension is then less than that of the
+{21} 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.
+
+_Corresponding Values._--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--
+
+  1. The Molecular Concentration.
+  2. The Osmotic Pressure.
+  3. The Diminution of Vapour Tension.
+  4. The Raising of the Boiling Point.
+  5. The Lowering of the Freezing Point.
+
+_Cryoscopy._--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 5deg
+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 0deg 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 {22} the two freezing points is the required "lowering
+of the freezing point."
+
+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.
+
+_Molecular Lowering of the Freezing Point._--For every substance whose
+solution is not ionized and therefore does not conduct electricity, the
+lowering of the freezing point is the same, viz. 1.85deg C. for each
+gramme-molecule of the solute per litre of the solution.
+
+_Determination of the Molecular Concentration._--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 n be the number of
+gramme-molecules per litre, then n = A / 1.85.
+
+_Determination of the Osmotic Pressure._--The osmotic pressure P of a
+solution may be obtained by multiplying its molecular concentration n by
+22.35 atmospheres. P = n x 22.35 = A / 1.85 x 22.35.
+
+_Determination of Molecular Weight._--The lowering of the freezing point
+also enables us to calculate the molecular {23} 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
+_x_ 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 n, the number of gramme-molecules per litre. The molecular weight M may
+be determined by dividing the original weight x by n.
+
+The study of osmotic pressure was begun by the Abbe 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."
+
+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.
+
+Osmotic pressure plays a most important role in the arena of life. It is
+found at work in all the phenomena of life. When osmotic pressure fails,
+life itself ceases.
+
+       *       *       *       *       *
+
+
+{24}
+
+CHAPTER III
+
+ELECTROLYTIC SOLUTIONS
+
+_Solutions which conduct Electricity._--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 1.85deg. 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 times the number of
+molecules of solute originally introduced into it. If n be the original
+number of molecules, then it will apparently contain n' = in 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 = n'/n, which is
+the ratio of the apparent number of the molecules present to the number
+originally introduced.
+
+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 {25} 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.
+
+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.
+
+_Coefficient of Dissociation._--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, which is called the
+Coefficient of Dissociation.
+
+This coefficient of dissociation, i, may be found by observing the lowering
+of the freezing point of a normal solution, and dividing it by 1.85. i =
+t/1.85.
+
+The coefficient of dissociation varies with the degree of concentration of
+the solution, rising to a maximum when the solution is sufficiently
+diluted.
+
+If we know i, the coefficient of dissociation for a given solute, contained
+in a solution of a definite concentration, we can find n', the number of
+particles present in a solution containing n gramme-molecules of the solute
+per litre, since n' = in. On the other hand, if from a consideration of its
+freezing point and other constants we find that an electrolytic solution
+appears to contain n' gramme-molecules per litre, the real number of
+chemical gramme-molecules in one litre of the solution will be only n' / i
+= n.
+
+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.
+
+_Electrolysis._--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 {26} 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.
+
+_Electrolytes._--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.
+
+_Arrhenius' Theory of Electrolysis._--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. {27}
+
+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.e._ 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^+ and Cl^- indicate the two ions of a salt
+solution; Cu^{++} and SO_4^{--} 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^. and Cl^,; Cu^{..} and SO_4^{,,}.
+
+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.
+
+_Degree of Dissociation._--The degree of dissociation is the fraction of
+the molecules in the solution which have undergone dissociation. Let n be
+the total number of molecules of the solute, and n" the number of
+dissociated molecules. Then n" / n = a will represent the degree of
+dissociation. Let k be the number of ions into which each molecule is
+split. Then a = n"k / nk, _i.e._ 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.
+
+Let n' be the total number of particles present in a solution {28}
+containing n molecules, each of which is composed of k ions. Then if a is
+the degree of dissociation,
+
+  n' = n - an + ank,
+  n' = n[1 + a (k - 1)],
+  n' / n = 1 + a (k - 1) = i.
+
+We thus obtain i the coefficient of dissociation, in terms of the degree of
+dissociation a and the number of ions in each molecule k.
+
+If there is no dissociation, _i.e._ if a = 0, then n' = n, and i = 1. If
+all the molecules are dissociated, a = 1, and i = k.
+
+_Faraday's Law._--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.
+
+_Electrochemical Equivalent._--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.
+
+_Electrolytic Conductivity._--The conductivity of an electrolyte is the
+inverse of its resistance. C = 1/R.
+
+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.
+
+_The specific conductivity_ [Delta] of an electrolyte is the conductivity
+of a cube of the solution, each face of which is one square centimetre in
+area. The _molecular conductivity_ 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
+[Delta], its specific conductivity. U = V[Delta]. Whence [Delta] = U / V,
+_i.e._ the specific {29} conductivity equals the molecular conductivity
+divided by the volume.
+
+The conductivity of an electrolyte is proportional to the number of ions in
+a volume of the solution containing one gramme-molecule. Let M_{[infinity]}
+be the conductivity for complete dissociation and M_v the molecular
+conductivity at the volume V. Then
+
+  M_v / M_{[infinity]} = n"k / nk = n" / n = a,
+
+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.
+
+    |         --    --    --     |  --    --    --                |
+    |         SO_4  SO_4  SO_4   |  SO_4  SO_4  SO_4              |
+    |                            |                                |
+    |         ++    ++    ++     |  ++    ++    ++                |
+    |         Cu    Cu    Cu     |  Cu    Cu    Cu                |
+    |                            |                                |
+    +----------------------------+--------------------------------+
+
+FIG. 1.--Before the passage of the current.
+
+    |                     --     |  --    --                      |
+    |                     SO_4   |  SO_4  SO_4  SO_4  SO_4  SO_4  |
+  - |                            |                                | +
+    |                     ++     |  ++    ++                      |
+    |   Cu    Cu    Cu    Cu     |  Cu    Cu                      |
+    |                            |                                |
+    +---------------------------+---------------------------------+
+
+FIG. 2.--After the passage of the current.
+
+_Velocity of the Ions._--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:-- {30}
+
+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 u be the
+velocity of the anions, and v the velocity of the cations. Let n be the
+loss of concentration at the cathode, and 1 - n the loss of concentration
+at the anode. Then
+
+  u / v = n / (1 - n),
+
+_i.e._ 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.
+
+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 _differences_ 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.e._ the difference of conductivity between potassium
+chloride and sodium chloride is the same as that between {31} potassium
+bromide and sodium bromide. Hence we may conclude that the conductivity of
+any salt is an ionic property.
+
+Kohlrausch's law may be expressed by the formula c = d(u + v), where c is
+the conductivity of the salt, d the degree of dissociation, _i.e._ the
+fraction of the electrolyte broken up into ions, and u and v the velocity
+of the anions and cations respectively. When all the molecules of the
+electrolyte are dissociated, d = 1, and the formula becomes c_{[infinity]}
+= u + v.
+
+As we have already seen, a salt is formed by the union of a metal M with an
+acid radical R. Potassium sulphate, K_2SO_4, consists of the metal K_2 and
+the acid radical SO_4. Ammonium chloride, NH_4Cl, consists of the basic
+radical NH_4 and the acid radical Cl. The various acids may be considered
+as salts of the metal hydrogen. Thus sulphuric acid, H_2SO_4, 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:--
+
+  Salts = MR.
+  Acids = HR.
+  Bases = MOH.
+
+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.e._ the degree of dissociation of its ions. The
+acidity of an electrolytic solution is due to the presence of the
+dissociated ion H^+, and its strength is determined by the concentration of
+these free hydrogen ions. Hence the greater the degree of dissociation the
+stronger the acid.
+
+The basic character of a solution is determined by the presence of the
+hydroxyl radical OH^-. The greater the concentration of the hydroxyl ions,
+_i.e._ the greater the dissociation, the stronger is the base.
+
+The ions H^+ and OH^- are of special importance, since they are the ions of
+water, H_2O = H^+ + OH^-. The degree of {32} 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^+ and OH^-, their diversity being due to variations in the relative
+proportions and grouping.
+
+_The Chemical, Therapeutic, and Toxic Actions of Ions._--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^-. 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_3 or C_2H_3ClO_2.
+
+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^{---}. The phosphates
+contain phosphorus in the same proportion as the phosphides, but this
+phosphorus is harmlessly entangled in the complex ion PO_4^{---}, whose
+properties are absolutely different from those of the ion 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. {33}
+
+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^{+++}, but rather those of the complex anion of which they form a part.
+
+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.
+
+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
+Menciere 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. {34}
+
+Since all chemical, toxic, and therapeutic actions are ionic, they are
+proportional to the degree of ionic concentration, _i.e._ 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^+. 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^+ is very concentrated;
+whereas the feeble acids are but slightly dissociated, so that the ion H^+
+is less concentrated.
+
+Paul and Kroenig have shown that the bactericidal action of different salts
+also varies with their degree of dissociation, _i.e._ 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 _Bacillus anthracis_. 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^-
+would be more toxic than Cl^- or Br^-. 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^{++}. This ion is very {35} concentrated in the highly dissociated
+solution HgCl_2, less concentrated in the less ionized solution HgBr_2, and
+exceedingly dilute in the HgCy_2, which is hardly ionized at all.
+
+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.
+
+       *       *       *       *       *
+
+
+{36}
+
+CHAPTER IV
+
+COLLOIDS
+
+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.
+
+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.
+
+_Colloids._--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 {37} 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.
+
+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.
+
+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,
+
+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.
+
+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 {38} solution of similar strength of a
+crystalloid whose molecular weight was 40.
+
+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."
+
+Similar phenomena of aggregation may be observed in the molecules of many
+inorganic substances. The molecule of iodine, for example, is monatomic at
+1200deg C., but becomes diatomic at the ordinary temperature. Sulphur at
+860deg C. is a gas with a vapour density of 2.2, while at 500deg 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.
+
+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 micellae, which absorb or abandon their extra
+molecules under the slightest influence. This mobility in the constitution
+of the micellae appears to be one of the principal causes of the peculiar
+properties of colloidal solutions.
+
+The phenomenon of polymerization appears to be reversible. The micellae 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 micellae. One may easily understand what an important role is played by
+this alternate polymerization and disintegration in the phenomena of life.
+
+Most colloidal substances are precipitated from their solutions by the
+addition of very small quantities of electrolytic {39} 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.
+
+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.
+
+_Metallic Colloids._--Carey Lea and afterwards Crede 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.
+
+_Catalytic Properties of Colloids._--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.
+
+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.
+
+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 {40} 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.
+
+A catalyzer is a stimulus which excites a transformation of energy. The
+catalyzer plays the same role 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.
+
+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.
+
+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.
+
+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. {41} 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 haemoglobin 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.
+
+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.
+
+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 Roentgen rays.
+
+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.
+
+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 {42} 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.
+
+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.
+
+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.
+
+       *       *       *       *       *
+
+
+{43}
+
+CHAPTER V
+
+DIFFUSION AND OSMOSIS
+
+_Diffusion and Osmosis._--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.
+
+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.
+
+_Coefficient of Diffusion._--The coefficient of diffusion has {44} 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."
+
+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.
+
+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.
+
+_Osmosis._--In 1748, l'Abbe Nollet discovered that when a pig's bladder
+filled with alcohol was plunged into water, the {45} 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.
+
+_Precipitated Membranes._--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.
+
+_Osmotic Membranes._--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."
+
+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. {46}
+
+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.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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 {47} 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.
+
+A disregard of this fact, that a solute will always pass from a solution
+where its osmotic pressure is high, into one 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.
+
+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.
+
+_Plasmolysis._--We all know that a cut flower soon dries {48} 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 _Tradescantia
+discolor_. 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.e._ 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.
+
+_Red Blood Corpuscles as Indicators of Isotony._--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 haemoglobin, 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 {49} 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 haemoglobin is dissolved.
+
+_The Haematocrite._--In 1891, Hedin devised an instrument for determining
+the influence of different solutions on the red blood corpuscles. This
+instrument, the haematocrite, 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.
+
+_Action of Solutions of Different Degrees of Concentration on Living
+Cells_.--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
+haemoglobin dissolving in the liquid and colouring it red. This is the
+phenomenon of haematolysis. According to Hamburger, the serum of blood may
+be considerably diluted with water before producing haematolysis.
+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
+haemoglobin 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 haematolysis. In mammals the blood corpuscles remain invariable
+in a salt solution of about .9 per cent., and begin to lose their {50}
+haemoglobin 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.
+
+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 {51} 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.
+
+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.
+
+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 -.6deg C.
+The dog was then drowned, when the freezing point of the blood in the left
+ventricle was increased to -.29deg C., and that in the right ventricle to
+-.42deg C. On the other hand, when a dog was killed before being thrown
+into the water, the {52} 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.
+
+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.e._ 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 x .76 x 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.
+
+Cryoscopy is also of great use in practical medicine, more especially for
+the examination of the urine. The freezing point of urine varies from
+-1.26deg C. to -2.35deg. 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.
+
+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^+ of the salt in the stomach contents exchanges with
+an ion H^+ of the monobasic salts of the blood, NaHCO_3 + NaCl = HCl +
+Na_2CO_3. {53}
+
+_Influence of Muscular Contraction on the Intramuscular Osmotic
+Pressure._--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 -.53deg C. At 15deg 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:--
+
+Change of weight of untired leg--
+
+  After  8 hours  -.000.
+  After 16 hours  -.000.
+  After 24 hours  -.006.
+
+Change of weight of stimulated leg--
+
+  After  8 hours  +.050.
+  After 16 hours  +.080.
+  After 24 hours  +.101.
+
+{54}
+
+This result shows that muscular work provoked by electric stimulation
+noticeably increases the osmotic pressure of the muscle.
+
+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 -.57deg, we obtained the
+following values:--
+
+Change of weight of untired leg--
+
+  After  8 hours  -.000.
+  After 16 hours  -.004.
+  After 24 hours  -.006.
+
+Change of weight of stimulated leg--
+
+  After  8 hours  +.039.
+  After 16 hours  +.072.
+  After 24 hours  +.099.
+
+Finally, in a solution freezing at -.72deg, _i.e._ with an osmotic pressure
+at 15deg C. of 9.176 atmospheres, we obtained the following mean values for
+the untired leg:--
+
+  After  8 hours  -.04.
+  After 16 hours  -.05.
+  After 24 hours  -.05.
+
+In this solution, freezing at -.72deg 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.
+
+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.
+
+I made further experiments in order to discover whether the variation in
+osmotic pressure depended on the duration of {55} the muscular contraction.
+For this purpose I used a solution freezing at -.53deg 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:--
+
+  Untired muscles.   Muscles stimulated once a second during
+                     2 Minutes.   4 Minutes.   6 Minutes.
+       .000             +.026        +.084        +.094
+      +.001             +.034        +.065        +.093
+      +.005             +.045        +.079        +.097
+       .000             +.037        +.070        +.095
+       .000             +.032        +.072        +.096
+
+Mean of all the observations--
+
+      +.0012            +.0348       +.074        +.095
+
+These experiments show clearly that the osmotic intramuscular pressure
+rises in proportion to the duration of the electrical stimulation.
+
+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 .53deg 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.
+
+Briefly, then, the results of our experiments are as follow:--
+
+1. Muscular contraction electrically produced causes an increase of the
+osmotic pressure in a muscle.
+
+2. The intramuscular osmotic pressure may reach, or even exceed, 2.5
+atmospheres, or 2.6 kilogrammes per square centimetre of surface.
+
+3. When a muscle is made to contract once a second, the {56} elevation of
+the osmotic pressure increases with the number of contractions.
+
+4. The intramuscular osmotic pressure increases with the work done by the
+muscle.
+
+5. Fatigue is caused by the increase of osmotic pressure in a contracting
+muscle.
+
+[Illustration: FIG. 3.--Fields of diffusive force.
+
+(_a_) Monopolar field of diffusion. A drop of blood in a saline solution of
+higher concentration.
+
+(_b_) 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. ]
+
+_The Field of Diffusion._--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.
+
+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. {57}
+
+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 a. 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.
+
+[Illustration: FIG. 4.--Two drops of blood in a more concentrated solution,
+showing a field of diffusion between two poles of the same sign.]
+
+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
+_b_). 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.
+
+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 role 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.e._ 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. {58}
+
+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.
+
+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.
+
+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.
+
+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 {59} the current of water carries
+with it the blood globules which produce the redness.
+
+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.
+
+_Tactism and Tropism._--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.
+
+[Illustration: FIG. 5.--Liquid figures of diffusion.
+
+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_3
+solution.]
+
+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.
+
+_The Morphogenic Effects of Diffusion._--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 {60} 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.
+
+[Illustration: FIG. 6.--Pattern produced in gelatine by the diffusion of
+drops of concentrated solutions of nitrate of silver and bromide of
+ammonium.]
+
+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.
+
+In order to cover a lantern slide 8-1/2 cm. x 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 {61}
+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_4 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_4. 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.
+
+[Illustration: FIG. 7.--Pattern produced in gelatine by the diffusion of
+drops of silver nitrate and sodium carbonate.]
+
+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.
+
+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 {62} 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.
+
+[Illustration: FIG. 8.--Pattern produced in gelatine by the diffusion of
+drops of a solution of nitrate of silver and of citrate of potassium.]
+
+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 {63} 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.
+
+[Illustration: FIG. 9.--Tissue of artificial cells formed by the diffusion
+in gelatine of drops of potassium ferrocyanide.]
+
+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.
+
+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, {64} _i.e._ by
+continually repairing the loss of concentration at the centre of the cell.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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 {65} 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.
+
+[Illustration: FIG. 10.--Artificial liquid cells, formed by coloured drops
+of concentrated salt solution in a less concentrated salt solution.]
+
+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.
+
+[Illustration: FIG. 11.--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.]
+
+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.
+
+Similar cells may be produced in water. If we pour a thin layer of water on
+a horizontal plate, and with a pipette {66} 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.
+
+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).
+
+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.
+
+       *       *       *       *       *
+
+
+{67}
+
+CHAPTER VI
+
+PERIODICITY
+
+_Periodic Precipitation._--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.
+
+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.
+
+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
+Duesseldorf, who in 1907 published a work on the subject, entitled _On
+Stratification by Diffusion_.
+
+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 {68} sulphate. At the Congress of Rheims in 1907 I
+exhibited the result of some further experiments on the same subject.
+
+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.
+
+[Illustration: FIG. 12.--Lines of diffusion precipitate, showing the
+simultaneous propagation of "undulations of different wave-length.]
+
+_Circular Waves of Precipitation._--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 {69} give
+us a very beautiful representation of the simultaneous propagation of
+undulations of different wave-length in the same medium.
+
+[Illustration: FIG. 13.--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.]
+
+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.
+
+[Illustration: FIG. 14.--Transformation of a spherical wave-front into a
+plane wave-front by a convergent diopter.]
+
+These diffusion rings furnish us with most excellent diagrams of refraction
+at a "diopter," _i.e._ a spherical surface separating two media of
+different densities. Fig. 14 shows the refraction at a convergent diopter,
+_i.e_. 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.
+
+These periodic diffusion rings also illustrate the phenomena of colour
+diffraction. Diffusion waves of different {70} 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.e._ it will transform a
+divergent into a convergent beam. This is an illustration of what is called
+the aberration of refrangibility.
+
+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.
+
+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.
+
+[Illustration: FIG. 15.--Diffraction of diffusion waves on passing through
+a narrow aperture.]
+
+_Diffraction._--When light traverses a minute orifice, instead {71} 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.
+
+[Illustration: FIG. 16.--Interference of diffusion waves.]
+
+_Interference._--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. {72} 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.
+
+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.
+
+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.
+
+The phenomena associated with the pressure of light, the {73} 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.
+
+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.
+
+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.
+
+Diffusion waves differ greatly in length, varying from several millimetres
+to 2 [mu]. 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 moire or mother-of-pearl.
+
+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.
+
+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.
+
+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 {74} 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.
+
+[Illustration: FIG. 17.--Photomicrograph of striated structure of a
+periodic precipitate of carbonate and phosphate of lime (magnified 500
+times).]
+
+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 {75} 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_2CO_3)
+to one of dibasic sodium phosphate (Na_2HPO_4). 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.
+
+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.
+
+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.
+
+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.
+
+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 {76} 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."
+
+[Illustration: FIG. 18.--Articulate form produced by periodic
+precipitation.]
+
+A slight alkalinity of the liquid is necessary to start the phenomenon.
+This explains the retardation at the beginning {77} 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.
+
+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.
+
+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.
+
+       *       *       *       *       *
+
+
+{78}
+
+CHAPTER VII
+
+COHESION AND CRYSTALLIZATION
+
+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.
+
+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.
+
+[Illustration: FIG. 19.--Muriform cohesion figure formed by a drop of
+Indian ink in a solution of salt.]
+
+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 {79} 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).
+
+[Illustration: FIG. 20.--Seven similar drops of Indian ink diffusing in a
+salt solution. Two minutes after introducing the drops.]
+
+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 {80} 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.
+
+[Illustration: FIG. 21.--The same drops 15 minutes later, showing the
+granulation appearance.]
+
+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.
+
+[Illustration: FIG. 22.--The same drops after 30 minutes. The granulations
+have agglomerated at the centre of the drops.]
+
+It is otherwise, however, with the colouring matter of the {81} 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 {82} completely absorbed the six
+smaller ones, and only one large drop will remain.
+
+[Illustration: FIG. 23.--Attraction between coloured drops in an isotonic
+solution.]
+
+_Incubation._--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.
+
+_Artificial Parthenogenesis._--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.
+
+[Illustration: FIG. 24.--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.]
+
+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 {83} 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.
+
+[Illustration: FIG. 25.--The same preparation several hours later, showing
+a cellular gastrula-like structure.]
+
+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 {84} 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.
+
+[Illustration: FIG. 26.--Field of crystallization of sodium chloride
+(magnified 60 diameters).]
+
+_Crystallization._--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. {85}
+
+[Illustration: FIG. 27.--Field of crystallization around a crystal of
+sodium chloride in process of formation.]
+
+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 {86} 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 45deg
+are clearly indicated.
+
+[Illustration: FIG. 28.--Three crystals of sodium chloride in process of
+formation, each in the centre of a field of crystallization.]
+
+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 Soles of Barcelona an interesting work on this
+subject, which he contributed to the International Congress of Medicine at
+Madrid in 1903, entitled _Applicacion de la crystalogenia experimental a la
+investigacion toxicologica de cas alcaloides_. {87}
+
+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.
+
+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 role 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.
+
+[Illustration: FIG. 29.--Crystallization of sodium chloride in a colloidal
+solution, giving a plant-like form.]
+
+[Illustration: FIG. 30.--Form produced by the crystallization of chloride
+of ammonium in a colloidal solution.]
+
+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."
+
+I should like here to recall to your notice the work of an English
+observer, Dr. E. Montgomery of St. Thomas's {88} 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.e._ 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.
+
+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."
+
+       *       *       *       *       *
+
+
+{89}
+
+CHAPTER VIII
+
+KARYOKINESIS
+
+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."
+
+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 Goettingen.
+
+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 {90}
+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.
+
+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.e._ 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
+karyokinesis. {91}
+
+[Illustration: FIG. 31.--Diffusion figure representing karyokinesis.
+Achromatin spindle between two similar poles of concentration.]
+
+"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.
+
+"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. {92}
+
+"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).
+
+[Illustration: FIG. 32.--Four successive stages in the production of
+artificial karyokinesis by diffusion.]
+
+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,
+{93} and as far as we know diffusion alone, is able to produce a spindle
+between homologous poles.
+
+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
+_vera causa_ 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.
+
+_Nuclear Division._--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 {94} 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.
+
+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).
+
+[Illustration: FIG. 33.--Equatorial crown produced by diffusion.]
+
+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. {95}
+
+[Illustration: FIG. 34.--A triaster produced by diffusion.]
+
+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.
+
+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.
+
+We may also produce diffusion figures of abnormal karyokinesis. Fig. 34
+represents such a form, a triaster produced by diffusion.
+
+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. {96}
+
+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.e._ 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.
+
+       *       *       *       *       *
+
+
+{97}
+
+CHAPTER IX
+
+ENERGETICS
+
+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 _Metamorphoses_: "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."
+
+The French poetess Mme. Ackermann has expressed the same idea in beautiful
+verse:--
+
+ "Ainsi, jamais d'arret. L'immortelle matiere,
+  Un seul instant encore n'a pu se reposer.
+  La Nature ne fait, patiente ouvriere,
+  Que defaire et recomposer.
+  {98}
+  Tout se metamorphose entre ses mains actives;
+  Partout le mouvement incessant et divers,
+  Dans le cercle eternel des formes fugitives,
+  Agitant l'immense univers."
+
+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.
+
+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.
+
+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.
+
+The actual state of our knowledge with regard to the science of energy
+rests on two principles, that of Mayer and that of Carnot.
+
+The first principle was defined by J. R. Mayer, a medical practitioner of
+Heilbronn, whose work, _Bemerkungen ueber die Kraefte der unbelebten
+Natur_, 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 {99} quantity of mechanical work represented by different modes of
+motion remains invariable."
+
+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.
+
+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."
+
+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.
+
+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.
+
+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.
+
+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. {100}
+
+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.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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 _vis viva_
+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 {101} energies, represents the total potential energy of the weight
+before it began to fall.
+
+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.
+
+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.
+
+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.
+
+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 {102} 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.
+
+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.
+
+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.e._ the anterior
+phenomena, which determined such transformation.
+
+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 {103}
+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.
+
+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.
+
+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.
+
+The second law of thermodynamics, Carnot's law, may therefore be enunciated
+thus: "Energy cannot be transformed without a fall of potential."
+
+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.
+
+  Efficiency = energy transformed / total energy absorbed
+
+The total energy is the product QI, _i.e._ 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
+
+  Q(I - I') / QI = (I - I') / I.
+
+ If I represents a temperature, then in order that the efficiency may be
+positive I' must be less than I, {104} there must be a fall of temperature
+in the machine. If I' were greater than I, _i.e._ 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.
+
+_Entropy._--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
+
+  (I - I') / I
+
+is also zero.
+
+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."
+
+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 {105} 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.
+
+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 {106} 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.
+
+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.
+
+Three conditions, then, are required for a transformation or displacement
+of energy:--
+
+1. _The cause_, the intervention of a stimulus which starts the
+transformation or displacement.
+
+2. _The possibility_, the necessary fall of potential.
+
+3. _The condition_, the conservation of the energy concerned, since being
+indestructible its total quantity cannot alter.
+
+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.
+
+Man obtains his supply of energy either directly from the {107} 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.
+
+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.
+
+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.
+
+The formula for the efficiency of a thermic transformer is
+
+  (T - T') / T,
+
+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.e._ it can transform 20 per cent. of the energy absorbed. The
+ordinary temperature of muscle is 38deg C., or 311deg absolute. We have
+{108} therefore (T - 311) / T = .20, or T = 388.75deg absolute, _i.e._
+115.75deg C. Thus, in order to obtain an efficiency of 20 per cent. with an
+ordinary thermic transformer, having a temperature of 38deg at the sink, we
+should need a temperature of over 115deg 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.
+
+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.e._ 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 {109} 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.
+
+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.
+
+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.
+
+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.
+
+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.
+
+A muscle is doing positive work when it is raising a weight or moving a
+body from one point to another. {110}
+
+The fourth state of muscular contraction is when the muscle is doing
+negative work, _i.e._ 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 Beclard. 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. Beclard'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.
+
+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.
+
+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, {111} 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.
+
+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."
+
+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 {112} 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.
+
+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.e._ the
+transformation of the potential energy already stored in the organism into
+the actual energy of motion and vital activity.
+
+       *       *       *       *       *
+
+
+{113}
+
+CHAPTER X
+
+SYNTHETIC BIOLOGY
+
+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.
+
+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.
+
+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 {114} unite and associate these, and to
+observe their development under various external influences.
+
+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.
+
+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."
+
+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.
+
+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. {115}
+
+The first experiment in physiogeny was the discovery of osmosis by the Abbe
+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.
+
+In 1866, Moritz Traube of Breslau discovered the osmotic properties of
+certain chemical precipitates. As I pointed out in the _Revue Scientifique_
+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 (_Gesammelte Abhandlungen von Moritz Traube_, 1899).
+
+In 1867 there appeared in England a paper by Dr. E. Montgomery, of St.
+Thomas's Hospital, _On the Formation of so-called Cells in Animal Bodies_.
+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 {116} 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.
+
+"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."
+
+In 1871 there appeared a memoir by the Dutch savant Harting entitled
+_Recherche de Morphologie synthetique sur la production artificielle de
+quelques formations calcaires organiques_. 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."
+
+In the _Comptes Rendues_ of 1882 is the following note by D. Monnier and
+Karl Vogt:--
+
+"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. {117}
+
+"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.
+
+"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.
+
+"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.
+
+"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.
+
+"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.
+
+"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.
+
+"8. It is probable that the inorganic elements which are present in the
+natural protoplasm may play an important part {118} in determining the form
+which is assumed by the figured elements of the organism."
+
+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 _Annalen der Physik_ under the
+title "Unsichtbare Fluessigkeitschichten": "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.
+
+"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.
+
+"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 {119} 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.
+
+"In 1867, R. Boettger 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; Boettger gives no explanation
+of the phenomenon.
+
+"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.
+
+"Later on Traube himself considered the precipitated membrane to be a thin,
+solid gelatinous layer in which the water was mechanically entangled.
+
+"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 {120} 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.
+
+"Graham had already obtained colourless jellies by the interaction of
+concentrated solutions of ferrocyanide of potassium and sulphate of copper.
+Buetschli also has recently described the microscopic appearance of
+precipitated membranes produced by ferrocyanide of potassium and acetate or
+chloride of iron.
+
+"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.
+
+"Harting, Vogelsang, Hansen, Buetschli, 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.
+
+"I shall show later on that gelatine and albumen essentially modify the
+precipitate and do not merely act as catalytic substances. The researches
+of Famintzin, repeated and extended by Buetschli, show that sphero-crystals
+are produced by the reaction of chloride of calcium on carbonate of
+potassium without the presence of gelatine or albumen. Buetschli studied
+the spheroids of carbonate of lime by means of polarized light, and found
+that the layers were alternately positively and negatively polarized."
+{121}
+
+Such is the history of morphogenesis as described in 1902 by the authority
+most qualified for the task, Professor Quinke of Heidelberg.
+
+In 1904, Professor Moritz Benedikt of Vienna treated the whole question in
+his book, _Crystallization and Morphogenesis_, 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 Schroen, who considers that crystals like living beings begin
+as a cell and grow by a process of intussusception. Professor Benedikt has
+made a complete resume of the question in an article, "The Origins of the
+Forms of Life," which appeared in the _Revue Scientifique_ in 1905.
+
+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.
+
+One of the most active of the modern morphogenists is Professor Herrera of
+Mexico, whose work is illustrated in the _Atlas de Plasmogenie_ by Dr.
+Jules Felix of Brussels, one of the most enthusiastic disciples of the new
+science. There is a resume of Herrera's work in the _Memoirs of the Societe
+Alzate, Mexico_.
+
+A bibliography of the works which have appeared on this subject may be
+found in the book of Professor Rhumbler of Goettingen, _Aus dem
+Lueckengebiete zwischen Organischer und Anorganischer Materie_, 1906.
+
+In 1907, Dr. Luiz Razetti of Carracas published a magnificent study of the
+subject under the title _Que es la vida_.
+
+In 1907, Dr. Martin Kuckuck of St. Petersburg repeated and extended the
+experiments of R. Dubois, and published his results under the title
+_Archigonia, Generatio Spontanea_, Leipzig, Ambrosius Barth.
+
+Butler Burke of Cambridge has also made a series of experiments with radium
+and barium salts analogous to those of Dubois.
+
+In 1909, Albert and Alexandre Mary of Beauvais published {122} an
+interesting study of this question under the title _Etudes experimentales
+sur la generation primitive_, published by Jules Rousset.
+
+I should mention also among the works of synthetic biology the publications
+of Professor Otto Lehmann of Karlsruhe, and in particular _Fluessige
+Krystalle und die Theorien des Lebens_, Leipzig, Ambrosius Barth.
+
+Professor Ulenhuth of Berlin has published his study on the osmotic growth
+of iron in alkaline hypochlorites under the title _Untersuchungen ueber
+Antiformin_, Berlin, Julius Springer.
+
+Professor Gariel has made a series of researches on osmotic growth which
+are published in Abraham's _Recueil d'experiences de physique_.
+
+A. Lecha Marzo of Valladolid published his researches on the growth of
+aniline colours in the _Gaceta Medica Catalana_, 1909, under the title
+_Otra nueva flora artificiale_.
+
+Dr. Maurice d'Halluin of Lille has also published a volume on osmotic
+growths under the title, _Stephane Leduc a-t-il cree la vie?_
+
+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 resume of my researches on osmotic growth has already
+appeared in the _Documents du Progres_, Sept. 1909.
+
+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.
+
+       *       *       *       *       *
+
+
+{123}
+
+CHAPTER XI
+
+OSMOTIC GROWTH--A STUDY IN MORPHOGENESIS
+
+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
+role which it plays in the scheme of nature.
+
+_Osmotic Membranes._--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.
+
+An osmotic membrane is not a semi-permeable membrane, as sometimes
+described, _i.e._ 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.
+
+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 {124} 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.
+
+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.
+
+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
+{125} 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.
+
+[Illustration: FIG. 35. FIG. 36.
+
+Osmotic growths of ferrocyanide of copper.]
+
+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.
+
+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.
+
+A good solution to commence with is the following:--
+
+  Silicate of potash, sp. gr. 1.3 (33deg Beaume)   60 gr.
+  Saturated solution of sodium carbonate           60 gr.
+  Saturated solution of dibasic sodium phosphate   30 gr.
+  Distilled water                     make up to 1 litre.
+
+{126}
+
+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.
+
+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:--
+
+  Ten per cent. solution of gelatine           10 to 20 c.c.
+  Saturated solution of potassium ferrocyanide  5 to 10 c.c.
+  Saturated solution of sodium chloride         5 to 10 c.c.
+  Warm water (32deg to 40deg C.)                    100 c.c.
+
+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).
+
+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 {127} stains used for microscopy, in the liquids used for fixing
+preparations.
+
+[Illustration: FIG. 37.--Osmotic vermiform growth.
+
+(_a_) The sickle-shaped growth.
+
+(_b_) The growth broken by the upward pressure of the solution.
+
+(_c_) The wound having cicatrized, the stem continues to grow downwards. ]
+
+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.
+
+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 _b_, 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.
+
+_Osmotic Growths in Air._--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_2 in a shallow flat-bottomed glass dish, just covering the fragment
+with liquid. The best solution is as follows:--
+
+  Potassium carbonate, saturated solution          76 parts.
+  Sodium sulphate, saturated solution              20   "
+  Tribasic potassium phosphate, saturated solution  4   "
+
+{128}
+
+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.
+
+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.
+
+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.
+
+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.
+
+[Illustration: FIG. 38.--Osmotic growth produced by sowing a mixture of
+CaCl_2 and MnCl_2 in a solution of alkaline carbonate, phosphate, and
+silicate. The stem and terminal organs are of different colours. (One-third
+of the natural size.)]
+
+[Illustration: FIG. 39.--An osmotic growth photographed by transverse light
+to show the construction of the terminal organs.]
+
+_Assimilation and Excretion._--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 {130} carbonate,
+is transformed into calcium carbonate. CaCl_2 + K_2CO_3 = CaCO_3 + 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_3, while at the same time it eliminates and excretes {131}
+chlorine, which may be found in the nutrient liquid after the reaction.
+
+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.
+
+[Illustration: FIG. 40.--Osmotic growth in a solution of KNO_3, showing
+spine-like organs.]
+
+_Osmotic Growths._--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.
+
+[Illustration: FIG. 41.--Terminal organs like catkins, developing in a
+solution of ammonium chloride.]
+
+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 {132} terminal organs will then grow out
+from the ends of the stems, which may during their further growth become
+conical or piriform in shape.
+
+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.
+
+[Illustration: FIG. 42.--An osmotic madrepore.]
+
+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. {133}
+
+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.
+
+[Illustration: FIG. 43.--An osmotic mushroom form.]
+
+[Illustration: FIG. 44.--Osmotic fungi.]
+
+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.
+
+Most remarkable fungus-like forms may be obtained by commencing the growth
+in a concentrated solution, and then {134} 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 {135} 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 lamellae, which are sometimes intersected by concentric
+layers parallel to the outer {136} 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.
+
+[Illustration: FIG. 45.--A shell-like calcareous osmotic growth.]
+
+[Illustration: FIG. 46.--Osmotic growths in the form of shells.]
+
+[Illustration: FIG. 47.--Capsular osmotic growth. The capsule has been
+broken to show the interior structure.]
+
+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. {137}
+
+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.
+
+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.
+
+[Illustration: FIG. 48.--An osmotic growth in which the terminal organs are
+differently coloured from the stems, showing that the chemical evolution is
+different.]
+
+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.
+
+[Illustration: FIG. 49.--Osmotic capsular growth with figured belt.]
+
+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 {138} the internal osmotic
+pressure, showing the gelatinous contents through the opening.
+
+[Illustration: FIG. 50.--Amoeboid osmotic growth, floating free in the
+mother liquor.]
+
+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.
+
+[Illustration: FIG. 51.--Transparent osmotic cell, in which may be seen the
+white calcareous nucleus. The summit of the cell bears osmotic
+prolongations.]
+
+[Illustration: FIG. 52.--Amoeboid osmotic growth with long crystalline
+cilia swimming about in the mother liquor.]
+
+[Illustration: FIG. 53.--Osmotic growth swimming in mother liquor. The
+fin-like prolongation grew out between two liquid layers of different
+concentrations.]
+
+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 {139} 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 {140} 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.
+
+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.
+
+[Illustration: FIG. 54.--Capsular osmotic growth, the two valves separated
+showing the colloidal contents.]
+
+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 amoeba. The same
+phenomenon may be observed with vermiform growths, a single seed often
+giving {141} rise in this way to a whole series of amoebiform or vermiform
+productions.
+
+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.
+
+[Illustration: FIG. 55.--Microphotograph showing the structure of various
+osmotic stems. (Magnified 25 diameters.)
+
+(_a_) Sodium sulphite.
+
+(_b_) Potassium bichromate.
+
+(_c_) Sodium sulphide.
+
+(_d_) Sodium bisulphite. ]
+
+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. Similarly, 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.
+
+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. {142}
+
+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. {143}
+
+[Illustration: FIG. 56.--Microphotograph showing the structure of osmotic
+stems. (Magnified 40 diameters.)]
+
+[Illustration: FIG. 57.--Photograph of an osmotic leaf showing the veins.]
+
+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 lacunae, but all these lacunae
+are closed cavities, the appearance being due to the transparency of the
+cell walls.
+
+[Illustration: FIG. 58.--Photomicrograph of an osmotic leaf showing the
+cellular structure.]
+
+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 {144} 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 role osmotic
+growth may have played in the formation of the various rocks, siliceous,
+calcareous, barytic, magnesian, the fibrous and nodular rocks and atolls.
+The palaeontologist 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 {146} 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.
+
+[Illustration: FIG. 59.--Osmotic growth with nucleated terminal organs.
+(One-third of the natural size.)]
+
+[Illustration: FIG. 60.--A group of osmotic plants.]
+
+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?
+
+       *       *       *       *       *
+
+
+{147}
+
+CHAPTER XII
+
+THE PHENOMENA OF LIFE AND OSMOTIC PRODUCTIONS--A STUDY IN PHYSIOGENESIS
+
+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.
+
+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 {148} 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.
+
+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.
+
+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.
+
+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.e._ 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
+{149} 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.
+
+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.
+
+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 {150} of such
+marvellous results should have hitherto been almost entirely neglected.
+
+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.
+
+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.
+
+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 {151} corresponding weight. Thus
+growth, which has hitherto been considered an essential phenomenon of life,
+is also a phenomenon common to all osmotic productions.
+
+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.
+
+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.
+
+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 {152} 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.
+
+[Illustration: FIG. 61.--A group of osmotic forms.]
+
+Organization has long been considered as one of the principal
+characteristics of life, _i.e._ 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.
+
+The phenomena of osmotic growth show how ordinary mineral matter,
+carbonates, phosphates, silicates, nitrates, and chlorides, may imitate the
+forms of animated nature without {153} 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.
+
+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:--
+
+  Potassium carbonate            76 parts.
+  Potassium sulphate             16   "
+  Tribasic potassium phosphate   46   "
+
+During the whole period of growth there is an abundant liberation of
+bubbles of gas, which is accurately limited to a belt around the base of
+the growth, and sometimes also to a cap at the summit.
+
+Since morphological differentiations of different parts is but the result
+of differences of evolution, _i.e._ of functional differences of the
+various parts, we may consider that osmotic growths possess the faculty of
+organization like living beings.
+
+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.
+
+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 {154} 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.
+
+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.
+
+_Coagulation._--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.e._ 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, {155} 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.
+
+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.
+
+Finally, Arthus and Pages 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.
+
+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.
+
+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 {156} being has as its
+ultimate cause a stimulus or excitation coming from without.
+
+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.
+
+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.
+
+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.
+
+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
+{157} 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.
+
+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 ephemeridae who have
+but a brief existence, this change of substance is even more rapid than
+that in an osmotic growth.
+
+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.
+
+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.
+
+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. {158}
+
+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.
+
+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.
+
+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 force is able to aggregate matter under such and such a form,
+{159} 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."
+
+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.
+
+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.
+
+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.
+
+       *       *       *       *       *
+
+
+{160}
+
+CHAPTER XIII
+
+EVOLUTION AND SPONTANEOUS GENERATION
+
+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.
+
+In his _Philosophie Zoologique_, 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: "A leur source le physique et le moral ne sont sans
+doute qu'une seule et meme chose. Il faut rechercher dans la consideration
+de l'organisation les causes memes de la vie."
+
+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 {161} 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?"
+
+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."
+
+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."
+
+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 {162} been formed, and are still being formed to-day, by
+spontaneous generation."
+
+Lamarck himself gives a resume of his doctrine in the following six
+propositions:--
+
+1. "All the organized bodies of our globe are veritable productions of
+Nature, which she has successively formed during the lapse of ages.
+
+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.
+
+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.
+
+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.
+
+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.
+
+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."
+
+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. {163}
+Hilaire, but he too was soon reduced to silence under the weight of
+authority of his adversaries.
+
+[Illustration: FIG. 62.--Osmotic vegetation.]
+
+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 {164} to the milieu into which it was
+born. It was the environment that stifled the offspring of Lamarck.
+
+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.
+
+The spirit of opposition does not seem to have much changed in France since
+Lamarck's time. In 1907 the Academie des Sciences de Paris excluded from
+its _Comptes Rendus_ the report of my researches on diffusion and osmosis,
+because it raised the question of spontaneous generation.
+
+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.
+
+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."
+
+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, {165} 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."
+
+In his expression of this law Lamarck insists on the fact that organization
+precedes function. He affirms only that function, _i.e._ 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.
+
+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.
+
+Evolutionists like Lamarck and Haeckel admit spontaneous generation, not as
+the most probable, but as the only possible explanation of the phenomenon
+of life.
+
+Lamarck shows us the apparition of living things at a certain epoch of the
+earth's evolution, and the gradual {166} 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.
+
+[Illustration: FIG. 63.--Marine forms of osmotic growth.]
+
+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 {167} 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.
+
+The morphogenic action of diffusion produces osmotic growths of extreme
+variety. Most of these forms recall those of living things--shells, fungi,
+corals, and algae. 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.
+
+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.
+
+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 {168} 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 animalculae 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."
+
+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.
+
+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 {169} 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. Lenicque 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.
+
+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.
+
+At a later period, that of the primary and secondary rocks, there was a
+uniform and constant temperature of about 40deg 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 {170} 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.
+
+Palaeontology 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.
+
+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.e._ the external, internal, and molecular forms of the living being.
+
+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.
+
+[Illustration: FIG. 64.--Osmotic shells and corals.]
+
+We have already seen that the seas of the primary and {171} 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.
+
+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 {172} that
+osmosis has played a predominant role 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.
+
+_Printed by_ MORRISON & GIBB LIMITED, _Edinburgh_
+
+       *       *       *       *       *
+
+
+Corrections made to printed original.
+
+Page 47. "into one where its osmotic pressure is low": 'into on' in
+original.
+
+Page 90. "the achromatin spindle in karyokinesis.": 'karineyoksis' in
+original.
+
+Page 120. "The researches of Famintzin": 'Famitzin' in original,
+inconsistent with spelling 2 paragraphs earlier.
+
+Page 141. "Similarly, if we suddenly dilute": 'Simiarly' in original.
+
+Page 153. "which is accurately limited": 'acurately' in original.
+
+Page 158. "this force is able to aggregate matter": 'this orce' in
+original.
+
+
+
+
+
+
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