Buffon's Natural History. Volume 06 (of 10) / Containing a Theory of the Earth, a General History of Man, of the Brute Creation, and of Vegetables, Minerals, &c. &c

by comte de Georges Louis Leclerc Buffon

The motives, however, which incline us to doubt of this truth do honour to humanity. Animals, those at least which have senses, and are composed of flesh and blood, are, like us, capable of pleasure, and subject to pain; it is, therefore, a cruel insensibility to sacrifice, without necessity, those who approach or live with us, and whose feelings are reflected by the signs of pain; for by those, whose nature is very different to ours, we can be but little affected. Natural pity is grounded on the relations we have with the object that suffers, and it is more or less lively as the resemblance and conformity of the structure is more or less great. The word compassion indicates that we suffer, that we are acted upon. The mind partakes less of this pity than the body; and animals are susceptible of it as well as man; the voice of pain moves them, they run to the assistance of each other, and they shrink from the dead carcass of one of their own species. Thus horror and pity are less passions of the mind than natural affections, which depend on the sensibility of the body, and on the similitude of its conformation; therefore this sentiment must diminish in proportion as the nature of one animal differs from that of another. When we strike a dog, or kill a lamb, it excites some pity; but none do we feel in cutting down a tree, or swallowing an oyster. In fact, can it be doubted that those animals, whose organization is similar to ours, must experience similar sensations? And those sensations must be proportioned to the activity and perfection of their senses; those whose senses are obtuse can they have exquisite feelings? and those who are defective in any organ of sense, must they not also be defective in all the sensations which have any affinity thereto? Motion is a necessary effect of the exercise of sentiment. We have already evinced, (in treating of the nature of animals) that in whatever manner a being is organized, if it has sentiment, it cannot fail to express its feelings by outward motions. Thus plants, though rightly organized, are insensible beings, as well as all animals which have no apparent motion; those animals also which, like the sensitive plant, move only their bodies and are denied progressive motion, have a very small degree of sentiment; and, in fine, those which are capable of progressive motion, but whose actions are, like so many automatons, very few and always the same, have but a small portion of sentiment, and that limited to a few objects. There are numerous automatons in the human species: education and the respective communication of ideas augment the quantity as well as the vivacity of our sentiments. In this respect how great is the difference between the civilized man and the savage? In the like manner it is with animals; those that live in a domestic state, by their intercourse with man have their feelings improved; while those who remain wild possess only the sensibility they inherit from Nature, which is often more certain, but always less in quantity than that which is acquired.

Besides, if we consider sentiment as a natural faculty, independent of the movements which it necessarily produces, we may still be able to estimate and determine its different degrees by physical relations, to which sufficient attention does not seem to have been hitherto paid. Before the highest degree of sentiment can exist in an animated body it is necessary that this body should form a whole, not only sensible in all its parts, but so composed that all these parts should have an intimate correspondence with each other, insomuch that one cannot be agitated without communicating a portion of that agitation to all the rest. It is also necessary there should be one common centre in which the agitations may terminate, and on which the reaction of every movement may be performed. Thus man, and those animals which resemble him most in organization, will be the most sensible beings. Those, on the contrary, who do not form so complete a whole, whose parts have a less intimate correspondence, who have several centres of feeling, and under one cover seem less to comprise a perfect animal, than to contain several centres of existence separate from each other, will be beings far less sensible. The pieces of a polypus, which has been cut, live separately; the head of a wasp, which is divided from the body, lives, moves, and even eats as before; a lizard, when cut in two, is neither deprived of motion nor feeling; the amputated limbs of a lobster are renewed; the heart of a turtle vibrates for a long time after it is taken out of the body; all those insects, in which the principal viscera, as the heart and lungs, do not unite in the centre, extend throughout the body, and form, as it were, a series of hearts, and other viscera; all fishes, whose organs of circulation have but little action; in short, all animals, whose organization is more or less remote from ours, have more or less sentiment.

In man, and in the animals which resemble him, the diaphragm appears to be the centre of sentiment; it is on this nervous part that the impressions of pain and pleasure are directed; it is on this that all the movements of the sensitive system are exercised. The diaphragm, in a transverse form, divides the body into two equal parts, of which the superior contains the heart and lungs, and the inferior the stomach and the intestines. This membrane is possessed of the utmost sensibility; it is also so necessary for the propagation and communication of feeling, that the slightest injury of it is always accompanied with convulsions, and often with death. The brain, which is considered as the seat of sensation, is not, therefore, the centre of sentiment, since it may be wounded, and even parts of it removed without causing the death of the animal. Let us then distinguish sensation from sentiment. Sensation is nothing more than an agitation or impression on the sense, whereas sentiment is this very sensation rendered agreeable or disagreeable by the propagation of the agitation through the sensitive system, for the essence of sentiment, its sole characteristic is pleasure or pain, and all other movements, notwithstanding they pass within us, are totally indifferent, nor do they affect us. It is on sentiment that the whole exterior movements, and the exercise of animal force depend; it acts only in proportion as it feels, and the very part which we consider as the centre of sentiment is also the centre of force.

A slight examination will shew us that all lively emotions, whether of pain or pleasure, in a word, all sensations, whether agreeable or disagreeable, are felt internally in the region of the diaphragm. On the contrary, there is no token of sentiment in the brain; in the head there are none but pure sensations; we only recollect that this or that sensation has been agreeable or disagreeable; and if this operation in the head is followed by a lively and real sentiment, then we feel the impression of it within the region of the diaphragm. Thus the fœtus, where this membrane is without exercise, is without sentiment, and the little motions of the fœtus may therefore rather be considered as mechanical, than dependent either on sensation or on the will.

Whatever may be the substance which serves as the vehicle of sentiment, and produces muscular motion, it is certainly propagated by the nerves, and is communicated in an indivisible instant from one extremity to the other. In whatever manner this motion may be effected, (whether by vibrations, as in elastic fibres, or by a subtile fire, similar to that of electricity, which not only resides in animated, and in all other bodies, but is constantly regenerated in the former by the motion of the heart and lungs, by the action of the blood in the arteries, and also by that of exterior causes on the organs of sense) certain it is that the nerves and membranes are the only sensible part of the animal body. The blood, the lymph, the fat, the bones, the flesh, and all other solids and fluids, are of themselves insensible; the brain is a soft and unelastic substance, and on that account incapable of producing or propagating the vibrations of sentiment.

What may have given rise to the opinion that the brain was the seat of sensation, and the centre of sensibility, is the circumstance that the nerves, which are the organs of sensation, terminate in the brain; for which reason it was considered as the only part that could receive every agitation or impression. This supposition appeared so simple, and so natural, that no attention was paid to the physical impossibility that attends it, though abundantly evident; for how is it possible that a soft and insensible substance should not only receive impressions, but retain them for a length of time, and propagate all their agitations over the solid and sensible parts? Perhaps it will be answered after Descartes and Peyronie, that it is not in the brain, but in the pineal gland that this principle of sensation resides; but it is very easily distinguished that the pineal gland, the callous substance in which they would enclose the seat of the sensations, have no connection with the nerves, but are surrounded with the insensible substance of the brain, and so separated from the nerves that they cannot receive the motions of them, and therefore these suppositions, like the former, must fall to the ground. But what, in this case, is the use and functions of this very noble and principal part of the body? Is not the brain to be found in every animal? Do we not find it larger in man, quadrupeds, and birds, which have all much sentiment, than in fishes, insects, and other animals which have but little? When compressed, is not all motion suspended? Does not every action cease? If this part is not the principal of motion, why is it so essentially necessary to it? Why is it proportioned, in every species of animals, to the quantity of sentiment with which they are endowed?

However difficult these questions may appear, I think it is easy to answer them satisfactorily. By an attentive and deliberate examination, the brain, as well as the spinal marrow (which is nothing more than a prolongation of it) is a kind of mucilage, hardly organized. We distinguish in it only the extremities of the little arteries, which terminate there in great numbers, and carry no blood but a white and nutritive lymph; these small arteries, or lymphatic vessels, when disunited from the brain by maceration, appear in the form of very slender fibres. The nerves, on the contrary, never penetrate the substance of the brain, but only reach the surface of it, but previously to which they lose their solidity and elasticity, and their extremities next the brain are soft, and almost mucilaginous. Whence it appears that the brain, which is nourished by the lymphatic arteries, furnishes in its turn nourishment to the nerves, which we ought to consider as a kind of vegetable substance, that shoots forth from the brain, and is divided into an infinity of branches. The brain is to the nerves what the soil is to plants; the extremities of the nerves are the roots, which, as in every vegetable, are more soft, and tender than the trunk or branches; they contain a ductile matter proper for the growth and nourishment of the tree; and this ductile matter they derive from the substance of the brain, to which the arteries continually direct the lymph necessary for its supply. The brain, therefore, instead of being the seat of sensation, the principle of sentiment, is only an organ of secretion and nutrition, but it is an organ which is highly essential, and without which the nerves could neither grow nor be preserved.

The brain is also larger in man, quadrupeds, and birds, because in them the quantity of nerves is greater than in fishes and insects, which on this very account have very little sentiment; they have but a small brain, in proportion to the small number of nerves which it nourishes. And here I cannot help remarking, that man has not, as has been said, a proportionably larger brain than any other animal. There are species of apes, and of cetaceous animals, which, proportioned to the size of their bodies, have more brains than man; another fact which proves that the brain is neither the seat of sensation, nor the principle of sentiment, since were it so those animals would have more sensations, and more sentiment, than man. By observing the nutrition of plants we shall perceive that they do not absorb the gross parts of earth or water, and that these must first be reduced by heat into tenuous vapours. In like manner the nerves are nourished by the subtle moisture of the brain, which is received by their extremities or roots, and thence carried into all the branches of the sensitive system. This system, as we have already remarked, forms an individual whole, of which the parts have so close a connection that we cannot wound one without injuring all the rest. The slightest irritation of the smallest nerve is sufficient to throw the whole body into a convulsion, nor is it possible to cure the pain, or remove the convulsion, but by cutting away the nerve above the injured part, and then all the parts to which this nerve joined become at once motionless and insensible. The brain ought not to be considered as an organic part of the nervous system, because it differs both in properties and substance, and is neither solid, elastic, nor sensible. I own that, when compressed, a stop is put to sensation; but this proves it a body foreign to the system, which, from acting with a weight on the nerves, benumbs them in the same manner, as a heavy weight applied to the arm or leg, deadens the feeling; and this is evident, because the moment the compression is removed sentiment revives, and the motion is re-established. I own likewise that, by injuring the brain, convulsions, and even death, will ensue, but these effects are produced from the nerves being injured in their very source. To these reasons I might add particular facts, which would also prove that the brain is neither the centre of sentiment nor the seat of sensation. There have been animals, and even children, born without either head or brain, yet endowed with sentiment, motion, and life. In insects and worms the brain is not perceptible, having only a part which corresponds with the spinal marrow, and therefore the spinal marrow might more reasonably be supposed the seat of sensation, being common to all animals, which the brain is not.

The greatest obstacle to the advancement of human knowledge, lies not so much in the things themselves, as in our manner of considering them. However complicated the body of man may be, his ideas are more so. It is less difficult to understand Nature as she is, than comprehend her as she is represented. She has only a veil, but we give her a mask, and conceal her with prejudices; and we suppose she acts and operates as we act and think; but her actions however are clear, and our thoughts are obscure; her designs and operations are always uniform and certain, which we seem to confound with the variable illusions of our own imaginations. I speak not merely of arbitrary systems and imaginary hypotheses, but of the methods by which we generally study Nature. Even experiment, although the most certain method, has been productive of more error than truth; as the smallest deviation leads to barren wilds, or exhibits a glimpse of obscure objects; to which affinities and properties are ascribed, and those steps being followed by the whole world, the consequences derived from them are admitted as fixed principles. Of this I might give a proof by exposing what are called principles in all the sciences, both abstract and real. In the former the general basis of principle is abstraction, or one or more suppositions; in the latter, principles are nothing more than consequences, whether true or false, of the methods which we have adopted. Let us take anatomy for an example: must not the first man who surmounted natural repugnance, and ventured to open a human body, suppose that by dissecting and examining all its parts, he should obtain a knowledge of its structure, mechanism and functions? but finding the subject more complicated than he had imagined, he was obliged to renounce those pretensions, and to adopt a method, not by which he might know and judge, but by which he might view the parts in a certain order. This method, however, was not to be acquired by one man; it was to occupy the attention of ages, and even of our ablest anatomists to the present day, and even when acquired it is not science, but the road which leads to it; and which might have done so, if instead of keeping within the narrow and beaten track, anatomists had extended the path, by comparing the human body with that of other animals; for does not the foundation of all science consist in a comparison of similar and different objects, of their analogous and opposite properties, and of all their relative qualities? And hence it is, that although human bodies have been dissected for three thousand years, anatomy still remains nothing more than a nomenclature, and hardly any advances have been made towards the real object, the knowledge of the animal economy; in which Nature certainly appears very mysterious, not only because the subject is complicated, but because, having neglected those modes of comparison, which alone could have afforded us any light, we have been immersed in the obscurity of doubt, or bewildered in the labyrinth of vague hypotheses. We have millions of volumes descriptive of the human body, while the structure of animals has been almost entirely neglected. The most minute parts of man have been named and described, and yet we know not whether those parts are to be found in other animals. Certain functions have been ascribed to certain organs, without knowing whether those functions cannot be exercised by other beings though deprived of those organs; insomuch that in all the explications relative to the animal economy, we labour under the double disadvantage of first engaging in a complicated subject, and then reasoning on it without the assistance of analogy. Through the whole course of this work we have followed a different method; constantly comparing Nature with herself, we have considered her relatively and in her most distant extremes; and it will be easily perceived that, after all our labour to remove false ideas, destroy prejudices, and to separate realities from arbitrary opinions, the only art we have employed is comparison. If we have been enabled to throw any light upon these subjects, less is to be attributed to genius than method, and which we have endeavoured to render as general as our knowledge would permit.