ARTICLE FOURTH.
PHENOMENA OF THE ACTION OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.
These phenomena are, as in the preceding system, relative to the state of contraction or to that of relaxation.
I. Force of the Contractions.
It is never capable of being raised to the point which the force of the muscles of animal life sometimes attains. Between the strongest and the weakest pulse, between the feeble jet which precedes some retentions of urine, and the jet of the most vigorous man, there is much less difference than between the langour of the voluntary muscles of some women and the power of those of a maniac, or a man in anger. The heart and the deltoid muscle are nearly equal in respect to their fleshy mass; now what would become of the circulation, if the first sometimes sent the blood with the force which the second uses to raise the superior extremity? A fit of anger, mania, &c. is sufficient to produce aneurisms. On the other hand the organic muscles are not affected with those prostrations of forces so common in the others; paralysis is foreign to them, because they are not within the cerebral influence. There is something which answers to convulsions; it is the irregular agitations which produce so many varieties in the pulse of acute fevers, agitations which must be distinguished from those produced by an organic defect of the heart; but these agitations are wholly different from spasms of the voluntary muscles; there is even no analogy.
There is not in the force of the contraction of the muscles of which we are treating, the waste which is so remarkable in that of the other muscles; the effort is nearly proportionable to the acting cause, and the distinction of this force into absolute and effective, cannot be applied here; only there is required more or less contractile energy, according as the body to be expelled from a hollow muscle, is solid or fluid. Hence why the great intestines are provided with longitudinal fibres more characterized than those of the small intestines; why the rectum especially, in which the excrements have their greatest degree of solidity, exhibits these fibres in a more evident manner than the colon or the cæcum, though under a different form; why in diarrhœas the weakest contraction is sufficient to evacuate the intestines, whilst the sensible organic contractility of the rectum being insufficient to void very solid excrements, it is necessary that the abdominal muscle should aid the expulsion; why when a hard body is introduced into the stomach, and the gastric juices do not soften it, it remains there a long time before being expelled, and produces an inconvenient weight, &c. &c. We know with what rapidity the passage of liquids takes place from the stomach to the intestines, and how long on the contrary solid aliments remain in the first.
The force of the organic muscles is incomparably greater in the phenomena of life than in our experiments. Once laid bare, the heart communicates only feeble motions, and most often irregular ones. There is no proportion between the force necessary to produce the jet, sometimes from seven to eight feet, which the blood exhibits coming from the open carotid of a dog, and the force of the contractions which the strongest stimuli produce when applied to the heart extracted from the body. Nothing equals in our experiments the force of contraction necessary for vomiting, &c. &c.
Numerous calculations have been made upon the force of contraction, in the organic muscles as in the preceding, and there has been the same variety of results. Can we in fact calculate the degrees of a phenomenon which a thousand causes make vary every instant, not only in different individuals, but even in the same, which sleep, digestion, exercise, rest, tranquillity of mind, violence of the passions, day, night, every thing in a word, incessantly modifies? I do not know that we digest twice in exactly the same period, if the urine twice remains the same length of time in the bladder before being discharged, if its jet is twice exactly equal, &c.
The force of the organic muscles often remains in its ordinary degree, or is even increased; whilst a general weakness possesses the others. The force of the pulse, vomiting, diarrhœa, &c. coinciding with a general prostration of the muscles of animal life, are not rare phenomena in diseases.
II. Quickness of the Contractions.
It varies singularly; very rapid in experiments, when death is recent and the stimuli are very strong, the contractions are in general slower in the natural state; we might say that it is in the inverse ratio of the force; often at the instant we open the pericardium, the heart moves with a rapidity which the eye can hardly follow, especially if we inject an irritating fluid into this serous sac, a little before laying the organ bare. The contractions increase much in quickness in certain diseases; those of the heart, for example, then acquire in the adult a rapidity often much greater than they have in the first age; this rapidity is also in this case entirely distinct from the force of its contractions; it is rare even that these two things are found united at the highest point. In general when the force of the heart is increased, there is a little more quickness; but there is very often a diminution of force with an increase of quickness, or the force remains the same, the quickness being much increased.