General Anatomy, Applied to Physiology and Medicine, Vol. 3 (of 3)

by Xavier Bichat

It should be remarked, however, that life, without having contractility immediately dependant upon it, since the intestines, the stomach, and the bladder contract after death when their distension is removed, modifies it in a very evident manner. The causes even which alter or diminish the vital forces have an influence upon it; hence the following observation that all those accustomed to open dead bodies can make. When the subject has died suddenly, and the stomach is empty, it is much contracted; when, on the contrary, death has been preceded by a long disease which has weakened its forces, the stomach, though empty, remains flaccid, and is found but very little contracted.

We should consider the substances contained in the hollow muscles of organic life, as true antagonists of these muscles; for they have not muscles that act in a direction opposite to theirs. As long as these antagonists distend them, they do not obey their contractility of texture; when they are empty, this is brought into action. It is not, however, upon this property that the mechanism of the expulsion of matters from these organs turns, as aliments from the stomach and intestines, urine from the bladder, blood from the heart, &c. It is the organic contractility that presides over this mechanism. It is difficult to distinguish these properties in exercise. One occasions a slow and gradual contraction, which is without the alternation of relaxation; the other, quick and sudden, consisting in a series of relaxations and contractions, produces the peristaltic motion, those of systole, diastole, &c. It is after the organic contractility has procured the evacuation of the hollow muscles, that the contractility of texture closes them. In death from hemorrhage from a great artery, the left and even the right side of the heart send out all the blood they contain; afterwards empty, they contract powerfully, and the organ is very small. On the contrary, it is very large when much blood remaining in its cavities, distends it, as in asphyxia. These are the two extremes. There are, as I have said, many intermediate states.

The contractility of texture is, in the system of which we are treating, in proportion to the number of fleshy fibres. Thus, all things being equal, the rectum, when empty, contracts upon itself with much more force than the other large intestines; the contraction of the ventricles is much greater than that of the auricles, and that of the œsophagus is much greater than that of the duodenum, &c. &c.

II. Vital Properties.

They are almost in an inverse order of those of the preceding system.

Properties of Animal Life. Sensibility.

The animal sensibility is slight in the organic muscles. We know the observation related by Harvey upon a caries of the sternum that laid bare the heart; they irritated, without its being felt by the patient, this organ, which only contracted under the stimulant. Remove the peritoneum behind the bladder of a living dog, and irritate the subjacent muscular layer, the animal gives but few marks of pain. It is difficult to make these experiments upon the intestines and the stomach; their muscular coat is so delicate that we cannot act upon it without at the same time stimulating the subjacent nerves.

It appears that the organic muscles are much less susceptible of the feeling of lassitude, of which the preceding become the seat after great exercise. I do not know however if in those to which many cerebral nerves go, it does not take place; for example, when the stomach has been for a long time contracted, it is probable that the lassitude of its fibres, produces in part the painful sensation that we then have, and which we call hunger, a sensation that should be distinguished from the general affection that succeeds it, and which becomes truly a disease, when abstinence has been too much prolonged. We know that substances not nutritive then appease this sensation without remedying the disease, when the stomach is filled with them. I refer to the same kind of sensibility the anxiety and distress which patients experience, in whom we keep the bladder in permanent contraction by an open sound in the urethra, which transmits the urine as fast as it falls from the ureters. This sensation does not resemble that of hunger, because the sensibility of the bladder and that of the stomach being different, their modifications cannot be the same. Thus each of these two sensations is different from that of which the muscles of animal life, for a long time contracted, become the seat. I do not believe that the sensation of hunger belongs solely to the cause I have pointed out, and which others have not spoken of; but it cannot be denied that it has much part in it. Who knows if, after a fever in which the action of the heart has been for a long time accelerated, the weakness of the pulse which accompanies convalescence, is not a sign of the lassitude in which its fleshy fibres are, on account of the antecedent motion? We know the painful sensation of fatigue which the stomach experiences after the contractions of vomiting.

Contractility.

The animal contractility is foreign to the muscles of organic life. To be convinced of this, we must recollect that on the one hand this contractility always supposes the influence of the brain and the nerves, to bring in play the action of the muscle, and that on the other, the brain, in order to exert this influence, must be excited by the will, by stimulants or by sympathies. Now none of these causes acting upon the brain, the organic muscles cannot contract.