Physiological Researches on Life and Death

by Xavier Bichat

The necessity of similar movements when men are drawn up in line of battle, has induced almost all nations to handle their weapons with their right hands; the harmony too which prevails in the dances of even the most savage people exacts an accord in the limbs, which they constantly preserve by making all their principal movements with the right. We might add to these examples a great variety of others.

The general movements agreed on by society, which, if every one were not to execute them in the same direction, would be creative of much confusion; these movements, I say, by the influence of habit, oblige us for our own particular movements to use the limbs, which they have brought into action. Hence, the members of the right side of the body are perpetually in action either for our own particular wants, or for those which we feel in conjunction with others.

Now, as the habitude of acting, continually tends to the perfection of action, we may perceive the reason, why the right side acquires a greater facility in the performance of many motions than the left. This increased facility is not original, but acquired.

So remarkable a difference then, in the two symmetrical halves of the body, is not by nature meant as an exception to the general law of harmony of action in the external functions; for those movements, which are executed by the whole of the body, are the more precise in proportion to the smallness of the difference existing in the agility of the muscles of the two sides. How happens it that certain animals leap from rock to rock with such admirable precision, where the least deviation from the intended direction, would plunge them into an abyss? how happens it that they run with such astonishing address on planes, which are scarcely equal in breadth to the extremities of their limbs? how happens it that the walk of the very heaviest of animals is never attended with those false steps so frequent in the progression of man? The reason must be, that the difference in their locomotive organs in both sides of the body is scarcely any thing, and that in consequence there must be a constant harmony of action in these organs.

He, whose general movements, or those of the whole of the body are the most perfect, has the least command in particular over those of the right side; for, as I shall prove hereafter, the perfection of a part is never acquired but at the expense of that of the whole. The child, who should be taught to make an equal use of all his limbs, would possess a precision in his general movements, which he would find extremely difficult to acquire for those of the right hand, such as writing or fencing.

I can easily suppose, that some few natural circumstances may have exercised upon us an influence in our choice with respect to the direction of those general motions, which the habits of society have established. Such may be the slight excess of diameter in the right subclavian artery, and the sensation of lassitude during digestion, which is more perceived upon the left side on account of the situation of the stomach, and may therefore have determined us to act at such time upon the opposite side in preference. Such also may be the natural instinct, by which, to express our feelings we carry the right hand to the heart; but these circumstances are trifling in comparison with the very great difference of the movements which from the state of civilization exists between the symmetrical halves of the body; and from this view of the subject, we cannot but regard this difference as the effect of social convention, and by no means the intent of nature.

The voice, together with locomotion, is the last act of the animal life in the natural order of its functions. Now the greater number of physiologists, and Haller in particular, have indicated as the causes of want of harmony in the voice, the dissimilarity of the two portions of the larynx, the inequality of force in the muscles, which move the arytenoid cartilages, the same inequality of action in the nerves, which are distributed to each half of the organ, and the different reflection of sounds in the nostrils and frontal sinuses. Without doubt a defective voice must frequently depend upon a faulty ear; when we hear incorrectly, we sing incorrectly; but when a correct ear is united with a want of precision in the voice, the cause is then in the larynx.

The most harmonious voice is that, which the two portions of the larynx produce in an equal degree; where the vibrations on one side correspond exactly in number, strength and duration with those upon the opposite side.[12] In the same manner the most perfect singing will be produced by two voices exactly similar in tone, compass, and inflection.

From the numerous considerations which I have offered, the following general conclusion may be deduced—namely, that one of the most essential characteristics of the animal life, is a harmony of action in the two analogous parts, or in the two sides of the simple organ concurring to the same end. The relation which exists between this harmony of action, which is the character of the functions, and symmetry of form, which is the attribute of the organs of the animal life, will easily be seen.