The Mechanism of Life

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 locali/ed 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 :

During the whole period of growth there is an abundant liberation of bubbles of gas, which is acurately 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 I ; ke 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 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,

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 trans- parent 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

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 wry 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

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. 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 associa- tion 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 determin- ing 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 orce is able to aggregate matter under such and such a form,

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 morpho- genesis 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 resem- blance 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 intus- susception ; 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 pheno- mena nutrition, assimilation, sensibility, growth, and organization are generally asserted to be the sole character- istics of life.

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 attendant consequences, from spontaneous generation to the genealogy of man.

In his Philosophic Zooloffique, 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\me seule et mem* chose. II faut rechercher dans la consideration de Torganisation 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 of nature. 11 It was this observation of the gradual perfecting of living organisms from the simplest to the most com- plicated 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 com- pelled 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 in- creases, we see the intervals between the classes gradually fill up, and the lines of separation become effaced. 11

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 with- out 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 organiza- tion ; so that in time every part will participate in the mutations which it has undergone. 11

generation. " I hope to prove,"he says, " that nature possesses means and faculties for the production of all the forms which 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. 3. " 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 estab- lished 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 situa- tions 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 consider- ation. This neglect profoundly afflicted Lamarck, who gradually sank a victim to the opposition of his contem- poraries. He left, however, one disciple, Etienne Jeoffroy St. Hilaire, but he too was soon reduced to silence under the weight of authority of his adversaries. 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 the milieu into which it was born. It was the environment hat stifled the offspring of Lamarck.