The trembling of which the voluntary muscles become the seat, the debility of the pulse which the weakness of the action of the heart produces, &c. are phenomena which the influence of the skin affected by cold alone causes. In fact, only this organ, the commencement of the mucous surfaces and all of that of the bronchia, are made cold by the external air; all the others remain at their usual temperature.
We know the innumerable phenomena which arise from the disappearance of herpes, the itch, &c. imprudently produced; in all these cases it does not appear that the morbific matter is carried to the other organs, though I do not pretend that this never happens. It is the vital forces of these which are raised and which then occasion different accidents; now as these forces vary in each system, these accidents will be essentially different; thus the same morbific cause disappearing from the skin, will produce vomiting if thrown upon the stomach, in which the sensible organic contractility predominates; pains, if it goes to the nerves which are especially characterized by animal sensibility; derangements of sight, hearing and smell, if it affects the respective viscera of these senses; hemorrhage, catarrhs, phthisis, tubercular inflammation, &c. if it attacks the mucous surfaces, the lungs, the serous membranes, &c. in which the organic sensibility is much raised. Now, if the same morbific matter carried upon these different organs, produced these accidents, they ought to be uniform. Do not their varieties, and especially the constant analogy which they have with the predominant vital forces of the organs in which they appear, prove, that they depend upon the cause which I have pointed out?
We know that the serous surfaces and the cellular texture on the one part, and the skin on the other, are often in opposition in diseases. There is no sweat when dropsies are formed; the dryness of the skin is often even more remarkable than the small quantity of urine, &c.
3d. When the cellular texture contained in the dermoid spaces is inflamed, as in phlegmonous inflammation, in biles, in some malignant pustules, &c. there comes on many sympathies which can be referred to those of the general cellular system, which have been already noticed.
4th. The affections of the chorion itself, all marked with a chronic character, on account of the kind of vitality and structure of this portion of the skin, occasion also sympathies which have the same chronic character, but of which we know but little.
The organic contractility cannot be put sympathetically in action in the skin, as it does not exist there.
Characters of the Vital Properties. First Character. The Cutaneous Life varies in each organ.
Though we have spoken in general of the vital properties of the skin, they are far from being uniform or at the same degree in all the regions.
1st. There is no doubt that the animal sensibility of the soles of the feet and the palms of the hands is greater than that of the other parts. Many persons are so sensible in the hypochondriac region, that the least tickling there produces convulsions. The anterior and lateral part of the trunk is always more sensible than the region of the back.
2d. The organic properties do not vary less. The extreme susceptibility of the face to receive the blood, is a proof of it, as I have said. It is generally known that some parts are more proper than others for the application of blisters. Observe on this subject that the places where the animal sensibility predominates, are not the same as those in which the organic is in the greatest proportion. The soles of the feet and the palms of the hands hold the first rank in relation to one, and the face in relation to the other.