2d. The antagonist of the divided muscle which has no effort to overcome, contracts and makes the moveable part incline from its side, if there are not other muscles, which acting in the direction of the first supply its functions. This last phenomenon takes place also to a certain extent in paralysis of the face. The mouth is then drawn from the sound side. I have observed however in this respect, that this deviation is never as evident as it would be by the division of the paralytic muscle, which has preserved its contractility of texture. This remaining contractility forms a partial equilibrium with that of the muscles of the sound side, during the absence of motions; thus the deviations do not become very evident until the patients wish to speak, until consequently the vital forces bring into action the sound muscles, which the others cannot oppose. The paralysis of the sterno-mastoideus exhibits for the whole head a phenomenon analogous to that which the preceding muscles produce for the mouth. Strabismus also oftentimes arises from this cause.
In general in all the phenomena, it is necessary to distinguish that which belongs to the vital forces, from that which arises from the contractility of texture. The muscles are antagonists as it respects these forces, as well as it respects this contractility; now as the contraction dependant on the nervous influence or irritability, is much more conspicuous than that arising from the organic texture, the phenomena of the antagonists are much more striking in paralysis, when the sound muscles are brought into action in the first manner. It appears that in many cases of paralysis, the contractility of texture of the affected side is also a little altered; but it is never so completely destroyed, that in the amputation of a paralyzed limb, there is no muscular retraction. I have made this experiment upon a dog; the nerves having been cut ten days before, and the limb having remained immoveable since that period, the division of the muscles produced a manifest separation between their edges; and even, in afterwards cutting for the sake of comparison the limb that remained sound, I did not find any difference.
It is especially when muscles have been first stretched, and this stretching has ceased, that the contractility of texture becomes evident. The puncture in ascites and an accouchement as it respects the abdominal muscles, the opening of deep abscesses as it respects those of the trunk, the extirpation of a tumour situated under any muscle, &c. show us this property in action in a very striking manner. There is however an observation to be made on this point, viz. that if the extension has been of long continuance, or if it has been frequently repeated, the subsequent contraction is much less, because the muscular texture has been weakened by the painful state in which it has been; hence, 1st, the flaccidity of the abdomen after repeated pregnancy; 2d, the laxity of the scrotum, after the puncture of an old hydrocele; 3d, I have seen at Desault's a man who was operated upon in Germany for a fungus in the mouth, and who had, on that side on which the disease had been, remarkable wrinkles, owing to the greater extent of the fleshy part of that side, which could no longer contract like the other; mastication, at this time could only be performed on the sound side; 4th, when women have had many children, the diaphragm is weakened by repeated pressure, and hence in part the greater mobility of the ribs, which compensate in some measure in females for the deficiency of action of this muscle. I think that in many chronic affections of the chest and abdomen, in which there is a long continued distension of this muscle, physicians ought more than they do, to have regard to this cause of difficulty of respiration, when the principle of distension no longer exists, as after the evacuation of dropsies, &c.
The extent of the contractility of texture is in the muscles in proportion to the length of the fibres; hence why in amputations, the superficial part retracts more than the deep-seated; why in sleep the phenomena of contractility of texture are very apparent in the extremities, the muscles of which are very long; why, in the antagonists, nature has in general opposed muscles of proportional length; why consequently, a muscle with long fibres has rarely for a counterpoise one with short ones, and vice versa. The flexors and extensors of the arm, the fore-arm, the thigh and the leg are nearly of the same extent; the rotators of the humerus within and without, the first inserted into the sub-spinal depression, the others into the sub-scapular, resemble each other also in this respect. The proportion between the antagonists is still more remarkable on the face, where the same muscles act most commonly in an opposite direction on each side of the median line.
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.