Creative Evolution

by Henri Bergson

The "harmony" of the two kingdoms, the complementary characters they display, might then be due to the fact that they develop two tendencies which at first were fused in one. The more the single original tendency grows, the harder it finds it to keep united in the same living being those two elements which in the rudimentary state implied each other. Hence a parting in two, hence two divergent evolutions; hence also two series of characters opposed in certain points, complementary in others, but, whether opposed or complementary, always preserving an appearance of kinship. While the animal evolved, not without accidents along the way, toward a freer and freer expenditure of discontinuous energy, the plant perfected rather its system of accumulation without moving. We shall not dwell on this second point. Suffice it to say that the plant must have been greatly benefited, in its turn, by a new division, analogous to that between plants and animals. While the primitive vegetable cell had to fix by itself both its carbon and its nitrogen, it became able almost to give up the second of these two functions as soon as microscopic vegetables came forward which leaned in this direction exclusively, and even specialized diversely in this still complicated business. The microbes that fix the nitrogen of the air and those which convert the ammoniacal compounds into nitrous ones, and these again into nitrates, have, by the same splitting up of a tendency primitively one, rendered to the whole vegetable world the same kind of service as the vegetables in general have rendered to animals. If a special kingdom were to be made for these microscopic vegetables, it might be said that in the microbes of the soil, the vegetables and the animals, we have before us the analysis, carried out by the matter that life found at its disposal on our planet, of all that life contained, at the outset, in a state of reciprocal implication. Is this, properly speaking, a "division of labor"? These words do not give the exact idea of evolution, such as we conceive it. Wherever there is division of labor, there is association and also convergence of effort. Now, the evolution we are speaking of is never achieved by means of association, but by dissociation; it never tends toward convergence, but toward divergence of efforts. The harmony between terms that are mutually complementary in certain points is not, in our opinion, produced, in course of progress, by a reciprocal adaptation; on the contrary, it is complete only at the start. It arises from an original identity, from the fact that the evolutionary process, splaying out like a sheaf, sunders, in proportion to their simultaneous growth, terms which at first completed each other so well that they coalesced.

Now, the elements into which a tendency splits up are far from possessing the same importance, or, above all, the same power to evolve. We have just distinguished three different kingdoms, if one may so express it, in the organized world. While the first comprises only microorganisms which have remained in the rudimentary state, animals and vegetables have taken their flight toward very lofty fortunes. Such, indeed, is generally the case when a tendency divides. Among the divergent developments to which it gives rise, some go on indefinitely, others come more or less quickly to the end of their tether. These latter do not issue directly from the primitive tendency, but from one of the elements into which it has divided; they are residual developments made and left behind on the way by some truly elementary tendency which continues to evolve. Now, these truly elementary tendencies, we think, bear a mark by which they may be recognized.

This mark is like a trace, still visible in each, of what was in the original tendency of which they represent the elementary directions. The elements of a tendency are not like objects set beside each other in space and mutually exclusive, but rather like psychic states, each of which, although it be itself to begin with, yet partakes of others, and so virtually includes in itself the whole personality to which it belongs. There is no real manifestation of life, we said, that does not show us, in a rudimentary or latent state, the characters of other manifestations. Conversely, when we meet, on one line of evolution, a recollection, so to speak, of what is developed along other lines, we must conclude that we have before us dissociated elements of one and the same original tendency. In this sense, vegetables and animals represent the two great divergent developments of life. Though the plant is distinguished from the animal by fixity and insensibility, movement and consciousness sleep in it as recollections which may waken. But, beside these normally sleeping recollections, there are others awake and active, just those, namely, whose activity does not obstruct the development of the elementary tendency itself. We may then formulate this law: When a tendency splits up in the course of its development, each of the special tendencies which thus arise tries to preserve and develop everything in the primitive tendency that is not incompatible with the work for which it is specialized. This explains precisely the fact we dwelt on in the preceding chapter, viz., the formation of identical complex mechanisms on independent lines of evolution. Certain deep-seated analogies between the animal and the vegetable have probably no other cause: sexual generation is perhaps only a luxury for the plant, but to the animal it was a necessity, and the plant must have been driven to it by the same impetus which impelled the animal thereto, a primitive, original impetus, anterior to the separation of the two kingdoms. The same may be said of the tendency of the vegetable towards a growing complexity. This tendency is essential to the animal kingdom, ever tormented by the need of more and more extended and effective action. But the vegetable, condemned to fixity and insensibility, exhibits the same tendency only because it received at the outset the same impulsion. Recent experiments show that it varies at random when the period of "mutation" arrives; whereas the animal must have evolved, we believe, in much more definite directions. But we will not dwell further on this original doubling of the modes of life. Let us come to the evolution of animals, in which we are more particularly interested.

What constitutes animality, we said, is the faculty of utilizing a releasing mechanism for the conversion of as much stored-up potential energy as possible into "explosive" actions. In the beginning the explosion is haphazard, and does not choose its direction. Thus the amoeba thrusts out its pseudopodic prolongations in all directions at once. But, as we rise in the animal scale, the form of the body itself is observed to indicate a certain number of very definite directions along which the energy travels. These directions are marked by so many chains of nervous elements. Now, the nervous element has gradually emerged from the barely differentiated mass of organized tissue. It may, therefore, be surmised that in the nervous element, as soon as it appears, and also in its appendages, the faculty of suddenly freeing the gradually stored-up energy is concentrated. No doubt, every living cell expends energy without ceasing, in order to maintain its equilibrium. The vegetable cell, torpid from the start, is entirely absorbed in this work of maintenance alone, as if it took for end what must at first have been only a means. But, in the animal, all points to action, that is, to the utilization of energy for movements from place to place. True, every animal cell expends a good deal—often the whole—of the energy at its disposal in keeping itself alive; but the organism as a whole tries to attract as much energy as possible to those points where the locomotive movements are effected. So that where a nervous system exists, with its complementary sense-organs and motor apparatus, everything should happen as if the rest of the body had, as its essential function, to prepare for these and pass on to them, at the moment required, that force which they are to liberate by a sort of explosion.

The part played by food amongst the higher animals is, indeed, extremely complex. In the first place it serves to repair tissues, then it provides the animal with the heat necessary to render it as independent as possible of changes in external temperature. Thus it preserves, supports, and maintains the organism in which the nervous system is set and on which the nervous elements have to live. But these nervous elements would have no reason for existence if the organism did not pass to them, and especially to the muscles they control, a certain energy to expend; and it may even be conjectured that there, in the main, is the essential and ultimate destination of food. This does not mean that the greater part of the food is used in this work. A state may have to make enormous expenditure to secure the return of taxes, and the sum which it will have to dispose of, after deducting the cost of collection, will perhaps be very small: that sum is, none the less, the reason for the tax and for all that has been spent to obtain its return. So it is with the energy which the animal demands of its food.

Many facts seem to indicate that the nervous and muscular elements stand in this relation towards the rest of the organism. Glance first at the distribution of alimentary substances among the different elements of the living body. These substances fall into two classes, one the quaternary or albuminoid, the other the ternary, including the carbohydrates and the fats. The albuminoids are properly plastic, destined to repair the tissues—although, owing to the carbon they contain, they are capable of providing energy on occasion. But the function of supplying energy has devolved more particularly on the second class of substances: these, being deposited in the cell rather than forming part of its substance, convey to it, in the form of chemical potential, an expansive energy that may be directly converted into either movement or heat. In short, the chief function of the albuminoids is to repair the machine, while the function of the other class of substances is to supply power. It is natural that the albuminoids should have no specially allotted destination, since every part of the machine has to be maintained. But not so with the other substances. The carbohydrates are distributed very unequally, and this inequality of distribution seems to us in the highest degree instructive.

Conveyed by the arterial blood in the form of glucose, these substances are deposited, in the form of glycogen, in the different cells forming the tissues. We know that one of the principal functions of the liver is to maintain at a constant level the quantity of glucose held by the blood, by means of the reserves of glycogen secreted by the hepatic cells. Now, in this circulation of glucose and accumulation of glycogen, it is easy to see that the effect is as if the whole effort of the organism were directed towards providing with potential energy the elements of both the muscular and the nervous tissues. The organism proceeds differently in the two cases, but it arrives at the same result. In the first case, it provides the muscle-cell with a large reserve deposited in advance: the quantity of glycogen contained in the muscles is, indeed, enormous in comparison with what is found in the other tissues. In the nervous tissue, on the contrary, the reserve is small (the nervous elements, whose function is merely to liberate the potential energy stored in the muscle, never have to furnish much work at one time); but the remarkable thing is that this reserve is restored by the blood at the very moment that it is expended, so that the nerve is instantly recharged with potential energy. Muscular tissue and nervous tissue are, therefore, both privileged, the one in that it is stocked with a large reserve of energy, the other in that it is always served at the instant it is in need and to the exact extent of its requirements.

More particularly, it is from the sensori-motor system that the call for glycogen, the potential energy, comes, as if the rest of the organism were simply there in order to transmit force to the nervous system and to the muscles which the nerves control. True, when we think of the part played by the nervous system (even the sensori-motor system) as regulator of the organic life, it may well be asked whether, in this exchange of good offices between it and the rest of the body, the nervous system is indeed a master that the body serves. But we shall already incline to this hypothesis when we consider, even in the static state only, the distribution of potential energy among the tissues; and we shall be entirely convinced of it when we reflect upon the conditions in which the energy is expended and restored. For suppose the sensori-motor system is a system like the others, of the same rank as the others. Borne by the whole of the organism, it will wait until an excess of chemical potential is supplied to it before it performs any work. In other words, it is the production of glycogen which will regulate the consumption by the nerves and muscles. On the contrary, if the sensori-motor system is the actual master, the duration and extent of its action will be independent, to a certain extent at least, of the reserve of glycogen that it holds, and even of that contained in the whole of the organism. It will perform work, and the other tissues will have to arrange as they can to supply it with potential energy. Now, this is precisely what does take place, as is shown in particular by the experiments of Morat and Dufourt.[56] While the glycogenic function of the liver depends on the action of the excitory nerves which control it, the action of these nerves is subordinated to the action of those which stimulate the locomotor muscles—in this sense, that the muscles begin by expending without calculation, thus consuming glycogen, impoverishing the blood of its glucose, and finally causing the liver, which has had to pour into the impoverished blood some of its reserve of glycogen, to manufacture a fresh supply. From the sensori-motor system, then, everything starts; on that system everything converges; and we may say, without metaphor, that the rest of the organism is at its service.

Consider again what happens in a prolonged fast. It is a remarkable fact that in animals that have died of hunger the brain is found to be almost unimpaired, while the other organs have lost more or less of their weight and their cells have undergone profound changes.[57] It seems as though the rest of the body had sustained the nervous system to the last extremity, treating itself simply as the means of which the nervous system is the end.

To sum up: if we agree, in short, to understand by "the sensori-motor system" the cerebro-spinal nervous system together with the sensorial apparatus in which it is prolonged and the locomotor muscles it controls, we may say that a higher organism is essentially a sensori-motor system installed on systems of digestion, respiration, circulation, secretion, etc., whose function it is to repair, cleanse and protect it, to create an unvarying internal environment for it, and above all to pass it potential energy to convert into locomotive movement.[58] It is true that the more the nervous function is perfected, the more must the functions required to maintain it develop, and the more exacting, consequently, they become for themselves. As the nervous activity has emerged from the protoplasmic mass in which it was almost drowned, it has had to summon around itself activities of all kinds for its support. These could only be developed on other activities, which again implied others, and so on indefinitely. Thus it is that the complexity of functioning of the higher organisms goes on to infinity. The study of one of these organisms therefore takes us round in a circle, as if everything was a means to everything else. But the circle has a centre, none the less, and that is the system of nervous elements stretching between the sensory organs and the motor apparatus.