The Mechanism of Life

u To this force, vi/. 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 precipitated membranes are hy drat eel 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 potas- sium and sulphate of copper. Blitschli also has recently described the microscopic appearance of precipitated mem- branes 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.

" Hartirig, Vogelsang, Hansen, Blitschli, 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 Hal-ting'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 crystal- lization 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 Famitzin, repeated and extended by Biitschli, show that sphero-crystals are produced by the reaction of chloride of calcium on carbonate of potassium without the presence of gelatine or albumen. Biitschli studied the spheroids of carbonate of lime by means of polarized light, and found that the layers were alternately positively and negatively polarized,"

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 Sehroen, 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 Scientlfique 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 Gottingen, Aus dent Liickengebiete zwischen Organischer und Anorganisclier Materie, 1906. In 1907, Dr. Luiz Razetti of Carracas published a magnifi- cent study of the subject under the title Qne es la vlda. 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. 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 Fliissige Krystalle und die Theonen 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 Recue'd (Feocperi- ences 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 crce 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 Pr ogres, 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

THE phenomenon of osmotic growth has doubtless presented itself to the eyes of every chemist ; but to discover a pheno- menon 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 gas in a balloon. This pressure increases the volume of the cell, and in consequence water rushes in through the permeable membrane ai;d 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 tran- sparent 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

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. 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 phos- phates and carbonates, to which we have already al- luded. 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 con- stitution 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 concentra- tions, we may obtain an immense variety of osmotic growths. Silicate of potash, sp. gr. 1-3 (33 Keaume) . . 60 gr. Saturated solution of sodium carbonate . . .60 gr. Saturated solution of dibasic sodium phosphate . 30 gr. Distilled water . . . make up to 1 litre.

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 BO 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 : (b] The growth broken by the upward pressure of the solution. (c] The wound having cicalri/cd, the stem continues to grow downwards.

In this solution we can obtain osmotic growths which may attain to a height of 40 centimetres or more, vegetable forms, roots, arborescent twigs, loaves, 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

stains used for microscopy, in the liquids used for fixing pre- parations. We now know that the physical force which builds up these growths is that of osmotic pressure, since the slightest considera- tion 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 milli- metres 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 &, 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 hydro- static 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 . . . Tribasic potassium phosphate, saturated solution . 4 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 im- prisoned in the upper cells. 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 experi- ment, 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 car-

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.) bonate, is transformed into calcium carbonate. CaCl 2 + K 2 CO :i Thus an osmotic rowth can make a FlG. 39. An osmotic growth photographed by transverse light to show the construction of the terminal organs. choice between the substances offered to it. rejecting the potassium of the nutrient liquid, and absorbing water and the radical C0 a , while at the same time it eliminates and excretes

FlG. 40. Osmotic growth in a solution of KNO-j, showing spine-like organs. chlorine, which may be found in the nutrient liquid after the reaction. Of all the ordinary physi- cal forces, osmotic pressure 1 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 unsus- pected. Oxmotic Growths. If we sow fragments of calcium chloride in solutions of the alkaline carbonates, phos- phates, or silicates, we obtain a wonderful variety of fili- form and linear growths which may attain to a height of 30 or 40 centimetres Some are so flexible that the sterns

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. 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

FIG. 41. Terminal organs like catkins, developing in a solution of ammonium chloride. terminal organs will then grow out from the ends of the stems, which may during their further growth become conical or pirifonu 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 sin-faces 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.

The preponderating influence in morphogenesis is osmotic pressure, the osmotic forms varying with its intensity, dis- tribution, 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.

Coralline growths may also be obtained by using appro- priate 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. 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 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 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