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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.

We will not dwell here on a point we have treated at length in a former
work. Let us merely recall that the progress of the nervous system has
been effected both in the direction of a more precise adaptation of
movements and in that of a greater latitude left to the living being to
choose between them. These two tendencies may appear antagonistic, and
indeed they are so; but a nervous chain, even in its most rudimentary
form, successfully reconciles them. On the one hand, it marks a
well-defined track between one point of the periphery and another, the
one sensory, the other motor. It has therefore canalized an activity
which was originally diffused in the protoplasmic mass. But, on the
other hand, the elements that compose it are probably discontinuous; at
any rate, even supposing they anastomose, they exhibit a _functional_
discontinuity, for each of them ends in a kind of cross-road where
probably the nervous current may choose its course. From the humblest
Monera to the best endowed insects, and up to the most intelligent
vertebrates, the progress realized has been above all a progress of the
nervous system, coupled at every stage with all the new constructions
and complications of mechanism that this progress required. As we
foreshadowed in the beginning of this work, the r√іle of life is to
insert some _indetermination_ into matter. Indeterminate, _i.e._
unforeseeable, are the forms it creates in the course of its evolution.
More and more indeterminate also, more and more free, is the activity to
which these forms serve as the vehicle. A nervous system, with neurones
placed end to end in such wise that, at the extremity of each, manifold
ways open in which manifold questions present themselves, is a veritable
_reservoir of indetermination_. That the main energy of the vital
impulse has been spent in creating apparatus of this kind is, we
believe, what a glance over the organized world as a whole easily shows.
But concerning the vital impulse itself a few explanations are
necessary.

* * * * *

It must not be forgotten that the force which is evolving throughout the
organized world is a limited force, which is always seeking to transcend
itself and always remains inadequate to the work it would fain produce.
The errors and puerilities of radical finalism are due to the
misapprehension of this point. It has represented the whole of the
living world as a construction, and a construction analogous to a human
work. All the pieces have been arranged with a view to the best possible
functioning of the machine. Each species has its reason for existence,
its part to play, its allotted place; and all join together, as it were,
in a musical concert, wherein the seeming discords are really meant to
bring out a fundamental harmony. In short, all goes on in nature as in
the works of human genius, where, though the result may be trifling,
there is at least perfect adequacy between the object made and the work
of making it.

Nothing of the kind in the evolution of life. There, the disproportion
is striking between the work and the result. From the bottom to the top
of the organized world we do indeed find one great effort; but most
often this effort turns short, sometimes paralyzed by contrary forces,
sometimes diverted from what it should do by what it does, absorbed by
the form it is engaged in taking, hypnotized by it as by a mirror. Even
in its most perfect works, though it seems to have triumphed over
external resistances and also over its own, it is at the mercy of the
materiality which it has had to assume. It is what each of us may
experience in himself. Our freedom, in the very movements by which it is
affirmed, creates the growing habits that will stifle it if it fails to
renew itself by a constant effort: it is dogged by automatism. The most
living thought becomes frigid in the formula that expresses it. The word
turns against the idea.

The letter kills the spirit. And our most ardent enthusiasm, as soon as
it is externalized into action, is so naturally congealed into the cold
calculation of interest or vanity, the one takes so easily the shape of
the other, that we might confuse them together, doubt our own
sincerity, deny goodness and love, if we did not know that the dead
retain for a time the features of the living.

The profound cause of this discordance lies in an irremediable
difference of rhythm. Life in general is mobility itself; particular
manifestations of life accept this mobility reluctantly, and constantly
lag behind. It is always going ahead; they want to mark time. Evolution
in general would fain go on in a straight line; each special evolution
is a kind of circle. Like eddies of dust raised by the wind as it
passes, the living turn upon themselves, borne up by the great blast of
life. They are therefore relatively stable, and counterfeit immobility
so well that we treat each of them as a _thing_ rather than as a
_progress_, forgetting that the very permanence of their form is only
the outline of a movement. At times, however, in a fleeting vision, the
invisible breath that bears them is materialized before our eyes. We
have this sudden illumination before certain forms of maternal love, so
striking, and in most animals so touching, observable even in the
solicitude of the plant for its seed. This love, in which some have seen
the great mystery of life, may possibly deliver us life's secret. It
shows us each generation leaning over the generation that shall follow.
It allows us a glimpse of the fact that the living being is above all a
thoroughfare, and that the essence of life is in the movement by which
life is transmitted.

This contrast between life in general, and the forms in which it is
manifested, has everywhere the same character. It might be said that
life tends toward the utmost possible action, but that each species
prefers to contribute the slightest possible effort. Regarded in what
constitutes its true essence, namely, as a transition from species to
species, life is a continually growing action. But each of the species,
through which life passes, aims only at its own convenience. It goes
for that which demands the least labor. Absorbed in the form it is about
to take, it falls into a partial sleep, in which it ignores almost all
the rest of life; it fashions itself so as to take the greatest possible
advantage of its immediate environment with the least possible trouble.
Accordingly, the act by which life goes forward to the creation of a new
form, and the act by which this form is shaped, are two different and
often antagonistic movements. The first is continuous with the second,
but cannot continue in it without being drawn aside from its direction,
as would happen to a man leaping, if, in order to clear the obstacle, he
had to turn his eyes from it and look at himself all the while.

Living forms are, by their very definition, forms that are able to live.
In whatever way the adaptation of the organism to its circumstances is
explained, it has necessarily been sufficient, since the species has
subsisted. In this sense, each of the successive species that
paleontology and zoology describes was a _success_ carried off by life.
But we get a very different impression when we refer each species to the
movement that has left it behind on its way, instead of to the
conditions into which it has been set. Often this movement has turned
aside; very often, too, it has stopped short; what was to have been a
thoroughfare has become a terminus. From this new point of view, failure
seems the rule, success exceptional and always imperfect. We shall see
that, of the four main directions along which animal life bent its
course, two have led to blind alleys, and, in the other two, the effort
has generally been out of proportion to the result.

Documents are lacking to reconstruct this history in detail, but we can
make out its main lines. We have already said that animals and
vegetables must have separated soon from their common stock, the
vegetable falling asleep in immobility, the animal, on the contrary,
becoming more and more awake and marching on to the conquest of a
nervous system. Probably the effort of the animal kingdom resulted in
creating organisms still very simple, but endowed with a certain freedom
of action, and, above all, with a shape so undecided that it could lend
itself to any future determination. These animals may have resembled
some of our worms, but with this difference, however, that the worms
living to-day, to which they could be compared, are but the empty and
fixed examples of infinitely plastic forms, pregnant with an unlimited
future, the common stock of the echinoderms, molluscs, arthropods, and
vertebrates.

One danger lay in wait for them, one obstacle which might have stopped
the soaring course of animal life. There is one peculiarity with which
we cannot help being struck when glancing over the fauna of primitive
times, namely, the imprisonment of the animal in a more or less solid
sheath, which must have obstructed and often even paralyzed its
movements. The molluscs of that time had a shell more universally than
those of to-day. The arthropods in general were provided with a
carapace; most of them were crustaceans. The more ancient fishes had a
bony sheath of extreme hardness.[59] The explanation of this general
fact should be sought, we believe, in a tendency of soft organisms to
defend themselves against one another by making themselves, as far as
possible, undevourable. Each species, in the act by which it comes into
being, trends towards that which is most expedient. Just as among
primitive organisms there were some that turned towards animal life by
refusing to manufacture organic out of inorganic material and taking
organic substances ready made from organisms that had turned toward the
vegetative life, so, among the animal species themselves, many contrived
to live at the expense of other animals. For an organism that is animal,
that is to say mobile, can avail itself of its mobility to go in search
of defenseless animals, and feed on them quite as well as on vegetables.
So, the more species became mobile, the more they became voracious and
dangerous to one another. Hence a sudden arrest of the entire animal
world in its progress towards higher and higher mobility; for the hard
and calcareous skin of the echinoderm, the shell of the mollusc, the
carapace of the crustacean and the ganoid breast-plate of the ancient
fishes probably all originated in a common effort of the animal species
to protect themselves against hostile species. But this breast-plate,
behind which the animal took shelter, constrained it in its movements
and sometimes fixed it in one place. If the vegetable renounced
consciousness in wrapping itself in a cellulose membrane, the animal
that shut itself up in a citadel or in armor condemned itself to a
partial slumber. In this torpor the echinoderms and even the molluscs
live to-day. Probably arthropods and vertebrates were threatened with it
too. They escaped, however, and to this fortunate circumstance is due
the expansion of the highest forms of life.

In two directions, in fact, we see the impulse of life to movement
getting the upper hand again. The fishes exchanged their ganoid
breast-plate for scales. Long before that, the insects had appeared,
also disencumbered of the breast-plate that had protected their
ancestors. Both supplemented the insufficiency of their protective
covering by an agility that enabled them to escape their enemies, and
also to assume the offensive, to choose the place and the moment of
encounter. We see a progress of the same kind in the evolution of human
armaments. The first impulse is to seek shelter; the second, which is
the better, is to become as supple as possible for flight and above all
for attack - attack being the most effective means of defense. So the
heavy hoplite was supplanted by the legionary; the knight, clad in
armor, had to give place to the light free-moving infantryman; and in a
general way, in the evolution of life, just as in the evolution of human
societies and of individual destinies, the greatest successes have been
for those who have accepted the heaviest risks.

Evidently, then, it was to the animal's interest to make itself more
mobile. As we said when speaking of adaptation in general, any
transformation of a species can be explained by its own particular
interest. This will give the immediate cause of the variation, but often
only the most superficial cause. The profound cause is the impulse which
thrust life into the world, which made it divide into vegetables and
animals, which shunted the animal on to suppleness of form, and which,
at a certain moment, in the animal kingdom threatened with torpor,
secured that, on some points at least, it should rouse itself up and
move forward.

On the two paths along which the vertebrates and arthropods have
separately evolved, development (apart from retrogressions connected
with parasitism or any other cause) has consisted above all in the
progress of the sensori-motor nervous system. Mobility and suppleness
were sought for, and also - through many experimental attempts, and not
without a tendency to excess of substance and brute force at the
start - variety of movements. But this quest itself took place in
divergent directions. A glance at the nervous system of the arthropods
and that of the vertebrates shows us the difference. In the arthropods,
the body is formed of a series more or less long of rings set together;
motor activity is thus distributed amongst a varying - sometimes a
considerable - number of appendages, each of which has its special
function. In the vertebrates, activity is concentrated in two pairs of
members only, and these organs perform functions which depend much less
strictly on their form.[60] The independence becomes complete in man,
whose hand is capable of any kind of work.

That, at least, is what we see. But behind what is seen there is what
may be surmised - two powers, immanent in life and originally
intermingled, which were bound to part company in course of growth.

To define these powers, we must consider, in the evolution both of the
arthropods and the vertebrates, the species which mark the culminating
point of each. How is this point to be determined? Here again, to aim at
geometrical precision will lead us astray. There is no single simple
sign by which we can recognize that one species is more advanced than
another on the same line of evolution. There are manifold characters,
that must be compared and weighed in each particular case, in order to
ascertain to what extent they are essential or accidental and how far
they must be taken into account.

It is unquestionable, for example, that _success_ is the most general
criterion of superiority, the two terms being, up to a certain point,
synonymous. By success must be understood, so far as the living being is
concerned, an aptitude to develop in the most diverse environments,
through the greatest possible variety of obstacles, so as to cover the
widest possible extent of ground. A species which claims the entire
earth for its domain is truly a dominating and consequently superior
species. Such is the human species, which represents the culminating
point of the evolution of the vertebrates. But such also are, in the
series of the articulate, the insects and in particular certain
hymenoptera. It has been said of the ants that, as man is lord of the
soil, they are lords of the sub-soil.

On the other hand, a group of species that has appeared late may be a
group of degenerates; but, for that, some special cause of retrogression
must have intervened. By right, this group should be superior to the
group from which it is derived, since it would correspond to a more
advanced stage of evolution. Now man is probably the latest comer of the
vertebrates;[61] and in the insect series no species is later than the
hymenoptera, unless it be the lepidoptera, which are probably
degenerates, living parasitically on flowering plants.

So, by different ways, we are led to the same conclusion. The evolution
of the arthropods reaches its culminating point in the insect, and in
particular in the hymenoptera, as that of the vertebrates in man. Now,
since instinct is nowhere so developed as in the insect world, and in no
group of insects so marvelously as in the hymenoptera, it may be said
that the whole evolution of the animal kingdom, apart from
retrogressions towards vegetative life, has taken place on two divergent
paths, one of which led to instinct and the other to intelligence.

Vegetative torpor, instinct, and intelligence - these, then, are the
elements that coincided in the vital impulsion common to plants and
animals, and which, in the course of a development in which they were



Online LibraryHenri BergsonCreative evolution → online text (page 11 of 34)