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

by Xavier Bichat

Every body knows that these muscles are essentially involuntary. If some men have had the faculty of arresting the motions of the heart, it is not upon this organ that the brain has acted; the action of the diaphragm and the intercostals has first been suspended; respiration has ceased for a time; then consequently the circulation.

If we irritate the brain with a scalpel or any other stimulant, the muscles of animal life become convulsed; they are paralyzed if we compress this organ. Those of organic life, on the contrary preserve in both cases their natural degree of motion. The heart still continues to beat, the intestines and stomach move some time after the cerebral mass and spinal marrow have been taken away. Who does not know that the circulation goes on very well in acephalous fœtuses; that after the blow that has knocked down an animal, and rendered his whole voluntary muscular system immoveable, the heart is still for a long time agitated, the bladder rejects the urine, the rectum expels the excrements, &c. the stomach even sometimes vomits up aliments? Opium, which benumbs the whole animal life, because it acts especially upon the brain which is the centre of it, which paralyzes all the voluntary muscles, leaves the others unaffected in their contractions. Intoxication produced by wine exhibits the same phenomenon. A man staggers after drinking; his limbs refuse to carry him, and yet his heart beats with force; his stomach often heaves and rejects the surplus fluids it contains. All narcotic substances also produce this effect.

If from experiments we pass to observations on the sick, we see that all cerebral affections are foreign to the organic muscular system. Wounds of the head with depression, fungi of the brain, effusions of blood, pus and serum, apoplexy, &c. affect exclusively the voluntary muscles, the action of which they increase, weaken or destroy. In the midst of this general derangement of animal life, the organic remains unaffected. The paroxysm of mania and malignant fever likewise proves this fact. Who does not know that in this last the pulse is oftentimes scarcely altered, that sometimes even it is slower?

Frequently in diseases of the head, there are spasmodic vomitings; the action of the heart is accelerated in cerebral inflammations, &c. But these are sympathetic phenomena which happen in the organic muscles, as they do in all the other systems; they may not appear nor be developed; a thousand irregularities are observed in their progress. Whereas the contraction of the muscles of animal life by affections of the brain is a constant, invariable phenomenon, which nothing disturbs, and the development of which nothing prevents, because the means of communication are always the same between the affected organ and the one that moves.

If in the examination of the phenomena relative to the cerebral influence upon the organic muscles, we follow an inverse order, that is to say, that in the affections of these muscles we examine the state of the brain, we observe the same independence; consider most vomitings, the irregular motions of the intestines which take place in diarrhœas, those especially which form the iliac passion, &c.; observe the heart in the agitations of fevers, in the irregular palpitations of which it becomes frequently the seat, &c.; in these derangements of the organic muscles, you will very seldom find signs of lesions of the cerebral organ; it is calm, while every thing is disordered in organic life. Cullen thought that in syncope the action of the brain ceased first, and that that of the heart was afterwards consequently suspended. It is precisely the reverse in the greatest number of cases. The heart, at first affected, ceases to act; now its action being essential to that of the brain, whether from the motion it communicates to it, or from the red blood it sends, the functions of this last are suddenly suspended and the whole animal life ceases. This is remarkable especially in the syncopes that arise from the passions, in those from hemorrhages, polypi, great evacuations, &c. I refer upon this subject to my Treatise upon Life and Death.

If from the influence of the brain we pass to that of the nerves, we find new proofs of the absence of animal contractility in the organic muscles. The most of these muscles receive, as we have seen, two species of nerves, the one cerebral, the other from the ganglions.

The heart, the stomach, the rectum and the bladder are evidently entered by the first species of nerves; now by cutting, or irritating in any way the cardiac filaments of the par vagum, the heart experiences no alteration from it; its motion is neither retarded, nor accelerated. The division of both branches of the par vagum is fatal, it is true, but not until after some days; and I doubt whether it is by the heart that death commences in this case. The principal phenomena consequent upon this division show a great embarrassment in the lungs, a great difficulty of breathing; the circulation appears to be troubled only in consequence.

The same nerves going to the stomach, the same experiment serves to prove the cerebral influence upon this viscus. Now the division of that of one side is usually nothing upon it; that of both soon produces a remarkable derangement in it. But this derangement is wholly different from that which follows the section of the nerve of a muscle of animal life, which becomes suddenly immoveable, whilst that on the contrary the stomach not communicating with the brain except by the par vagum, seems to acquire in an instant an increase of power; it contracts and hence the spasmodic vomitings that are almost always observed during the two or three days that the animal survives the experiment, vomitings that I have constantly noticed in dogs, and which Haller and Cruikshank had before observed. It appears then from this, that though the brain has a real influence upon the stomach, this influence is of a nature wholly different from that which it exerts upon the voluntary muscles. I would observe however that the irritation of one branch of the par vagum, or of both, makes the stomach immediately contract, as happens in a voluntary muscle when we irritate its nerve. It is necessary, in order to make this experiment, to open the abdomen of a living animal, and afterwards to irritate the eighth pair in the region of the neck, so as to have in sight the organ that we make contract.

The bladder and the rectum appear to approximate the voluntary muscles, in their relation with the brain, more than the stomach and the heart. We know that falls on the sacrum, from which arises a shock of the inferior part of the spinal marrow, produce retention of urine; that they strike, as it were, this organ with the same paralysis as the inferior extremities, which then also cease to move. Yet as the bladder is very powerfully assisted in its functions by the abdominal muscles, by the levator ani and other voluntary muscles which surround it, the immobility of these muscles contributes much to the inability to evacuate the urine. That which makes me think so, is that, 1st, the irritation of the spinal marrow towards its inferior part which puts in motion all the voluntary muscles of the inferior extremities and of the pelvis, does not produce any effect upon this part. I have convinced myself of this fact many times upon dogs and guinea-pigs. 2d. By irritating the nerves coming from the sacral foramina and going to the bladder, nerves that it is often very difficult to find, on account of the blood in an animal recently killed, I have seen this muscle remain immoveable. On the contrary all these nerves having been cut, the injection of a fluid slightly stimulant makes it contract with force. 3d. In experiments upon living animals, as in surgical operations, the violence of the pain which sometimes produces spasmodic contractions of all the muscles of animal life, frequently occasions an involuntary discharge of urine. Now in these cases it is not the bladder that is convulsed; for if in an experiment this phenomenon takes place, open the abdominal parietes, in an instant the flow of urine ceases, because on the one hand the muscles of these parietes cannot act upon the intestines and press them against the bladder, and because on the other the levator ani which contracts and raises this organ, has no resisting point against which it can compress it above. Observe in fact that in strong jets of urine, the bladder is placed between two opposite efforts, one superior, which is the gastric viscera pressed by the diaphragm and the abdominal muscles, the other inferior, which is especially the levator ani which acts by contracting from below above, whilst the opposite effort acts from above below; now these two efforts are evidently under the cerebral influence. I have very frequently had occasion to observe the bladder full of urine in a living animal whose abdomen was opened; I have never seen it contract with sufficient violence to expel the fluid.

I do not deny but that the bladder, by the nerves it receives from the sacral plexuses, is to a certain extent a voluntary muscle; but I say that it is principally by forces accessory to its own and necessary to its functions, that it is subjected to the will; that the animal contractility is much greater in its functions than the sensible organic contractility. How then is the urine retained in this organ, or expelled from its cavity at will? In this way; when the urine falls into the bladder, and is there on the one hand but a short time, and on the other only in small quantity, it is not then an irritant sufficiently powerful to produce the exercise of the sensible organic contractility. The effort which the bladder makes is so small, that it cannot overcome the resistance of the urethra, which being shut by the contractility of texture, must be dilated by the impulse communicated to the urine. In order to void this fluid, there must then be added to the contraction of the bladder that of the surrounding voluntary muscles; now the least effort of these muscles is sufficient to overcome the resistance of the urethra. But if the urine is in great quantity in the bladder, and it has acquired by remaining in it a long time that deep colour which indicates the concentration of its principles, then the irritation that it produces on the organ brings powerfully into action the sensible organic contractility; the bladder contracts, and in spite of the animal, there is an evacuation of urine.