Part 44

The quickness of the contractions, arising from the contractility of texture, is not like that produced by the animal or sensible organic contractility, which is uniformly more or less marked, according as the nervous influence of the stimulant acts more or less strongly. Every motion originating from the contractility of texture is slow, uniform and regular; it is only when the muscular texture is weakened that it diminishes; it does not increase except when this texture is more developed; hence it follows that the varieties of quickness can only be observed in different individuals, or in the same individual at different periods, and not, as in the exercise of the vital forces, from one instant to another. This is a great and remarkable difference between the two species of properties.

Death weakens the contractility of texture but does not annihilate it; a muscle being cut retracts a long time after life has left it. Putrefaction alone puts a limit to the existence of this property. It is the same with regard to extensibility. I would observe however that while the muscles retain the vital heat, they have more power of retraction, than when the chill of death has seized them.

Haller places on the same line and derives from the same principles, the phenomena resulting from the contractility of texture, which, with some slight differences, answers to his dead power, and those produced by the action of the concentrated acids, alkohol, fire, &c. on animal substances, which crisp, contract and acquire the horny hardness from the effect of these different agents. But there are many differences which essentially separate these phenomena from each other. 1st. The contractility of texture is very slight in the organs in which the faculty of having the horny hardness is very evident, for example, in all the organs of the fibrous, fibro-cartilaginous, serous systems, &c. &c. 2d. The contractility of texture is distributed in very various degrees, to the different parts; from the muscles and the skin, which possess the greatest degree of it, to the cartilages which seem destitute of it, there are many variations; on the contrary, the faculty of acquiring the horny hardness from the agents pointed out is almost uniformly distributed, or at least its differences are much less evident. 3d. One becomes nothing in dried organs, the other is evidently preserved for many years, as parchment is a proof. 4th. The first clearly receives an increase of power from life, especially in the muscles; the second appears to be hardly modified by it. 5th. This always exhibits sudden effects, rapid contractions. To feel the contact of the fire, of the concentrated acids or alkohol, and to assume the horny hardness, are two phenomena which the second brings together in the animal parts; the contractility of texture, on the contrary, exerts itself but slowly, as we have said. 6th. This last can never give to the parts, the muscles especially, that remarkable density which they exhibit in their horny hardening. 7th. The absence of extension of the fibres is the only thing necessary for the contractility of texture which has an unceasing tendency to activity; it requires on the contrary in order to crisp the fibres, that they should be in contact with a foreign body. I could add to these many proofs, in order to establish an essential difference between the phenomena confounded by the illustrious physiologist of Switzerland.

II. Vital Properties.

The most of these properties perform a very important part in the muscles. We shall first examine those of animal life, and afterwards treat of those of organic.

Properties of Animal Life. Sensibility.

Animal sensibility is that of all the vital properties which is the most obscure in these organs, at least if we consider them in the ordinary state. Cut transversely in amputations, in experiments upon living animals, they do not experience any very painful sensation; it is only when a nervous filament is touched, that pain is manifested. The peculiar texture of the muscle is but slightly sensible; irritation by chemical stimulants does not show much sensibility in it.

There is however a peculiar sensation, which in the muscles very evidently belongs to this property; it is that which is experienced after repeated contractions, and is called lassitude. After long standing, it is in the thick bundle of lumbar muscles that this sensation is especially felt. After walking, running, &c. if on a horizontal plain, it is all the muscles of the lower extremities which are more particularly fatigued; if on an ascending plain, it is especially the flexors of the ilio-femoral articulation; if on a descending one, it is the posterior muscles of the trunk. In the employments which exercise particularly the superior extremities, this sensation is often experienced in a remarkable manner, which is certainly not owing to the compression made by the muscles in contraction, upon the small nerves which run through them. In fact it can take place without this antecedent contraction, as is observed in the commencement of many diseases, in which it extends in general over the whole muscular system, and in which the patients are, as they say, fatigued and wearied, as after a long march. This sensation appears to depend on the peculiar kind of animal sensibility of the muscles, a sensibility which the other agents do not develop, and which the permanency of contraction renders here very apparent. Thus the fibrous system, sensible only to the means of distension which act upon it, does not receive a painful influence from the other agents of irritation. Observe that this painful sensation, which a too prolonged motion produces in the muscles, is intended by nature to warn the animal to place limits to it, without which the consequences would be serious. Thus the peculiar sensation which arises from distended ligaments, is designed to make the animal limit their extension. Observe how each organ has its peculiar kind of sensibility; how false an idea we should have of the existence of this property, if we judged of it only from mechanical and chemical agents, and observe particularly how nature accommodates to the uses of each organ its kind of animal sensibility.

In phlegmasia of the peculiar muscular texture, the animal sensibility is very often raised to a very great height; the least touch on the skin becomes painful; the patient can hardly bear the weight of the clothes, and frequently the least jar produces in the limbs the most acute pains. But in general these pains are wholly different from the painful sensation which we call lassitude; thus the pain of a ligament stretched in a sound state, is not the same as that which arises from the inflammation of a ligament or any other fibrous organ.

I would add to what I have said above upon this sensation, that some organs are fatigued like the muscles, from too long continuance of their functions; for example, the eyes by the contact of light, the ears by that of sounds, the brain by thinking, &c. and in general all the organs of animal life; it is even this general lassitude which brings on sleep, as I have proved in my Researches upon Life. But observe that the sensation which the eye, the ear, the brain and all the external organs produce when thus fatigued is not the same as that which arises from the over-exertion of the muscles; another proof of the peculiar kind of their sensibility, and in general of that of every living part.

Animal Contractility.

This animal property, upon which all the phenomena of locomotion and voice depend, which assists those of the internal and external functions, has its seat exclusively in the animal muscular system; it is this which distinguishes it from the organic, and from all the others. It consists in the faculty of moving under the cerebral influence, whether the will or other causes produce this influence. The animal contractility has then, like the sensibility of the same species, a peculiar character, differing from the two organic contractilities, a character which consists in this, that its exercise is not concentrated in the organ which is moved, but that it requires also the action of the brain and the nerves. The brain is the principle from which, if we may so say, this property goes, as it is that to which all the sensations come; the cerebral nerves are the agents which transmit it, as they are, though in an opposite direction, the conductors of the sensitive phenomena. Whence it follows, that in order to understand this property well, it is necessary to examine it in the brain, in the nerves and in the muscle itself.

Animal Contractility considered in the Brain.

Every thing in the phenomena of animal contractility proclaims the influence of the brain.

In the ordinary state if more blood is carried to this organ, as in anger; if opium, taken in a moderate dose, excites it slightly; if wine produces the same effect, the muscular action increases in energy in proportion as that of the brain is thus increased. If terror by retarding the pulse, by diminishing the force of the heart, and even the quantity of blood sent to the brain, strikes it with atony; if the different narcotics, carried to excess, produce the same effect; if wine prevents its action by its too great quantity, then observe these muscles languish in their motion and experience even a remarkable intermission. If the brain is wholly engrossed in its relations with the senses, or in its intellectual functions, it, if we may so say, forgets the muscles; these remain inactive; the man who looks or hears with attention, does not move; neither does he who contemplates, meditates and reflects. The phenomena of ecstasy, the history of the studies of philosophers, often present us with this important fact, this muscular inertia, the principle of which is in the distraction of the cerebral influence, which does not increase in other functions, only by diminishing in locomotion.

In diseases, all the causes which act strongly on the brain, re-act suddenly on the animal muscular system; now this reaction is manifested by two opposite states, by paralysis and by convulsions. The first is the indication of diminished energy, the second that of increased; one takes place in compressions from pus, effused blood, bones driven below their natural level, and from the consequences of apoplexy; it is seen in the attack of most hemiplegias, a sudden attack in which the patient falls down, loses all consciousness and has all the signs of a cerebral lesion. This lesion disappears, but its effect remains, and this effect is the immobility of a part of the muscular system. The other state or the convulsive, arises from the various irritations of the cerebral organ from osseous fragments driven into its substance, from its own inflammation or that of its membranes, from different tumours of which it may be the seat, from organic lesions that it may have, lesions which I have rarely observed in the adult, but which infancy sometimes exhibits, and from the causes even of compressions; for oftentimes we see this convulsive state existing at the same time with different effusions, with hydrocephalus, &c.

The state of the animal muscular system is truly the thermometer of the state of the brain; the degree of its movements indicates the degree of energy of this organ. Those who attend in a lunatic hospital have often occasion to consult this thermometer. At the side of a furious patient, whose muscular power is doubled, or even trebled, you see a man all whose motions languish in a remarkable inertia. A thousand different degrees are observed in these motions; now these degrees do not depend upon the muscles; the most furious madman is often he whose very delicate external forms indicate the weakest muscular constitution; as the most perfect automaton is sometimes he whose muscles are the most powerfully developed. The muscles are to the brain what the arteries are to the heart. The physician learns by these vessels the state of the central organ of circulation which communicates impulse to them; by the muscles of animal life, he learns the state of the central organ of this life. Observe patients in many important fevers; in the morning there is prostration, in the evening you find an extreme agitation in the muscles. Now what is the seat of this revolution? It is not the muscles, but it is the brain. There has been a translation to the head, as it is commonly called.

If from the bed of the sick we go to the laboratory of the physiologist, we shall see experiments in perfect accordance with the preceding observations. The ligature of all the arteries that go to the brain, interrupts immediately the movements of this organ, movements necessary to its action, and produces a sudden cessation of voluntary motion, and afterwards death. By injecting through the carotid and towards the head, ink, solutions of neutral salts, acids, substances whose contact is fatal to cerebral action, I have always seen the animal perish with previous convulsive motions. The injection of water does not produce this effect; it can with impunity to the life of the brain be introduced into the arterial blood, if it is injected moderately; but pushed with force, you will irritate extremely this organ, and in an instant the animal is seized with violent agitations; moderate the force, rest succeeds. I have already related this experiment elsewhere. If we lay bare the cephalic mass, and irritate it with a mechanical or chemical agent, &c. in an instant the animal muscular system is brought into action. It is however to be observed that in these experiments the convexity of the organ appears to be much less connected with the motions, than its base. The irritation confined to the cortical substance, to the superficial layers of the medullary, is almost nothing; it is not till we arrive at the inferior layers, that the convulsions come on. I have wished to try many times to ascertain with precision the place where the irritation becomes a cause of convulsion; but this has always appeared to me very difficult, and the results have been infinitely various. I believe that we can hardly establish any thing more than a general result, viz. that the nearer we approach in the experiments the annular protuberance, and in general the cerebral base, the more apparent are the convulsive phenomena; they are so much the less as we remove from them, they are nothing on the convex surface. Observe that it is on the side of its base, that is to say, on the side of its essential part, that the brain receives the numerous vessels which carry to it excitement and life, whether by the motion which they communicate to it, or by the nature of the red blood which they carry to it, as my experiments published the year passed have, I think, demonstrated.

Add to these experiments those of the artificial commotions. The muscles of the ox vacillate, and are unable to support themselves, the instant the blow is struck. At other times animals expire, their limbs convulsively agitated from a blow given on the occiput; rabbits often exhibit this phenomenon. Pigeons die with convulsive motions of the wings. Irregular agitations arising from an irregular influx of the power of the brain always precede the instant of death, which the commotion has produced.

Let us conclude from all these experiments and the observations that precede them, that the action of the animal muscular system is always essentially connected with the state of the brain, and that when this action is increased or diminished there is almost always an increase or diminution of the cerebral action.

Let us not however exaggerate the relation which connects the muscular to the cerebral phenomena; observation would prove us incorrect. There are various examples of aqueous, sanguineous and even purulent congestions in the brain, without having produced any alteration in muscular motion. Different tumours and defects of conformation have occasioned disturbance of the intellectual functions, without affecting those of the muscles; how many times is the brain disordered in various species of alienations; how many times do the understanding, memory, attention and imagination indicate these derangements by their irregular aberrations, without their being felt by the muscular system. Is there not often an alteration of the external sensation, without an alteration of motion? In general the brain has three great functions. 1st. It receives the impressions from the external senses; it is in this relation the seat of perception. 2d. It is the principle and the centre of the voluntary motions, which are not exerted but by its influence. 3d. The intellectual phenomena are essentially connected with the regularity of its life; it is as it were the seat of them. Now it can be deranged as to one of these functions, and remain sound as to the others; it can be a regular principle of the motions, and an irregular centre of the phenomena of the understanding; not communicating with external objects by the senses, and determining motions, or presiding over intellectual functions, as happens in sleep which is disturbed by dreams, &c.

From what has been said we can understand why acephalous fœtuses cannot live out of the womb of the mother. As animal life is nothing in the fœtus, as respiration does not take place, as the functions are limited to the great circulation, to the secretions, exhalations and nutrition, the acephalous fœtuses can live in the womb of the mother, and acquire a very considerable size; but at birth they cannot breathe, the intercostals and diaphragm being unable to act. The gastric viscera receives no influence from their muscular parietes; all the limbs are immoveable. Animal life, which commences in others at birth, cannot commence in them, because they have not the centre of this life; they have senses, but nothing to receive their impressions; muscles, but nothing to make them move; they can continue to live but a little while in themselves, without beginning to live from without. But as in general it appears that when the infant quits the womb, the red blood becomes necessary to it, that to have this, it must respire, and as this function cannot commence, it loses the internal life which it had in the womb of the mother. There are acephalous fœtuses which have at the origin of the nerves a small medullary swelling; in others the spinal marrow is larger. If these medullary swellings, if the spinal marrow by its peculiar texture, supply the place of the brain, life can continue, and it is in this way that we can explain some examples of acephalous subjects that have lived a certain time. But certainly an acephalous subject organized like ourselves, which has nothing to supply the place of the brain, cannot live. Thus in almost all the examples of these monsters, related by authors, and especially by Haller, the death of the individual took place at its birth.

Animal Contractility considered in the Nerves.

The brain, at a distance from almost all the muscles, communicates with them by the nervous system, and by it transmits to them its influence; now this communication is made in two ways. 1st. There are nerves which go directly from the brain to the muscles of animal life. 2d. The greatest number does not go from this organ itself, but from the spinal marrow. Almost all the muscles of the neck, all those of the chest, the abdomen and the extremities receive theirs from this last source. The spinal marrow is, as it were, a general nerve, of which the others are only divisions and principal branches.

All the lesions of this principal nerve are felt by the muscles that it has under its influence; the compressions that it experiences from a fracture of the vertebræ, from any displacement, from an effusion of blood, serum, pus, &c. in the vertebral canal, the derangements which take place from a violent blow received upon the whole region of the spine, from a fall upon the loins, or on the superior part of the sacrum, are followed by numbness and paralysis of the subjacent muscles. Divide the spinal marrow, by introducing a scalpel into the canal, immediately all motion ceases below the division. If you wish on the contrary to produce convulsions, introduce a stilet into the canal; irritate the marrow with it or by chemical agents placed on it, there will be immediately agitation and convulsion in all the animal and muscular system that is below.

The higher the lesion of the marrow is, the more dangerous is it. In the lumbar region its influence extends only to the inferior extremities, and the muscles of the pelvis; in the back it paralyzes these muscles and those of the abdomen; now as these last contribute indirectly to respiration, this function begins to be embarrassed; if the lesion is above the dorsal region, it becomes still more painful, because the intercostals lose their action; the diaphragm alone then supports the respiratory phenomena, because the phrenic nerve still receives and transmits the cerebral influence. But when the lesion happens above the origin of this nerve, there is no more action of the diaphragm, and no more contraction of the intercostal and abdominal muscles; respiration ceases; from the same cause the circulation is interrupted; the blood being no longer carried to the brain, the action of this organ is annihilated. Hence why the luxations of the first vertebra on the second are suddenly fatal, when the displacement is very great; why judicious surgeons dare not sometimes run the hazard of reduction, when these luxations are partial, for fear of rendering them complete, and of thus seeing the patient, whom they attempted to relieve, perish in their hands; why, when we wish to knock down an animal, the blow should be given on the superior and posterior part of the spine; and why a stilet plunged between the first and second vertebræ immediately destroys life.

We see very distinctly the successive influence of the different parts of the marrow on the muscles and on the general life, by introducing a long piece of iron into the inferior part of the vertebral canal of an animal, of a guinea pig for example, and carrying it up through this canal to the cranium, through the spinal marrow which it tears. We observe evidently as it ascends, at first convulsions of the inferior extremities, then those of the abdominal muscles, then derangement of respiration, then its cessation, then death which is the consequence of it.

From all these facts, we cannot, I think, call in question the influence of the spinal marrow upon motion, the principle of which it receives from the brain and afterwards transmits it to the nerves. These last carry this principle, which they have received, to the muscles, either by means of the spinal marrow, as in almost all those of the trunk and the extremities, or directly from the brain, as in those of the face, the tongue, the eyes, &c. There are the same proofs for this nervous influence, as for that of the preceding sensitive organs. The tying, division or compression of a nerve paralyzes the corresponding muscle. Irritate with any agent a nerve laid bare in an animal, convulsive contractions are immediately seen in the muscle. These experiments have been so often and so accurately repeated by many authors, that I think it useless to go into details, which the reader may find everywhere. Irritation continued some time upon one point of the nerve destroys its influence upon the muscle, which remains immoveable; but it is put in motion again, if the irritation is carried to a lower part of the nerve. If we tie it, the motion ceases, if irritation is made above the ligature, it returns when it is made below, or when the ligature is removed.