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

by Xavier Bichat

Nerves.

Their distribution is nearly the same as that of the blood vessels. Many very considerable branches, as different divisions of the musculo-cutaneous, the internal cutaneous, the lumbar, the saphena, the anterior tibial, the intercostals, the cervicals, &c. form a kind of sub-cutaneous nervous system, from which go all the branches that enter the dermis. These branches, in passing through the dermoid spaces with the arteries and the veins, appear to anastomose often together, go through the pores which terminate the spaces on the interior, and no doubt form the papillæ. Observe even that on the hand where the papillæ are very evident, there are, in proportion to the surface, many more sub-cutaneous nerves than any where else.

Absorbents.

Many absorbents creep under the skin; it is here that they can be the most easily studied. All the veins are surrounded with them; various fasciculi are observed in their interstices; so that a layer of absorbents, arranged in the form of a continuous layer, seems to separate, in the extremities, the aponeurosis and the skin. There is no doubt that the origin of the most of these vessels exists in the chorion, that they carry to the blood the fat and the cellular lymph of its spaces, and the nutritive matter of its fibres. But is there a particular order of branches opening upon the surface of the epidermis to absorb in certain cases foreign substances? This question cannot be answered by anatomical inspection. But the following considerations appear to me to throw great light upon it.

1st. The sub-cutaneous absorbents, visible by injections, are too numerous in proportion for the mere purpose of carrying back the fat and serum of the neighbouring parts.

2d. There are many medicines which appear to be evidently absorbed; such are mercury in the venereal disease, various purgative and emetic substances, febrifuges even, as cinchona, which, when applied by friction, have produced their effects as well as if taken by the stomach; cantharides often act upon the kidneys, when the tincture is used as a liniment, narcotic substances sometimes occasion a weight in the head and drowsiness when they have been externally applied, &c. These different effects are well known and many authors have given examples of them.

3d. There is we know absorption of different kinds of virus, of that of hydrophobia, of the small-pox, of the venom of the viper, &c. an absorption, it is true, which rarely takes place when the epidermis is whole, but which uniformly does, when this being removed, the matter is found in contact with the external capillary net-work of which we have spoken. I would remark even that the different kinds of inoculation of the small-pox, of the vaccine disease, &c. evidently prove both the existence and importance of this net-work, to which heretofore sufficient attention has not been paid. There are many contagious principles which are absorbed through the epidermis; such are those of the plague which the clothes communicate and those of different pestilential fevers which penetrate by the skin more than by respiration. I believe cutaneous absorptions from which diseases arise may be divided in the following way:

1st. Absorptions which take place through the epidermis, and which produce an effect	{	1st, local, as the itch, herpes, tinea capitis, &c. &c.
		2d, general, as pestilential diseases, putrid fevers taken in an unhealthy place, &c. &c.
2d. Absorptions which take place only when the epidermis is removed, and from which arises an effect	{	1st, local, as the vaccine disease, the small-pox, &c. &c.
		2d, general, as hydrophobia, the venom of the viper, a wound with an instrument impregnated with putrid matter, &c. &c.

We see by this table that the absorbents when charged with injurious substances, sometimes do not transmit them beyond the part and sometimes carry them to the blood, which conveys them to the different organs of the economy. Some authors have thought that in those cases in which the effects of the absorption become general, there is rather nervous action and sympathetic phenomena, than the transmission of an injurious matter into the circulation, and that consequently the solids take almost an exclusive part in these diseases. But to remove all doubt upon this point it is sufficient to observe, 1st, that, in the absorption of many contagious substances, for example, when from the puncture of the finger with a scalpel impregnated with putrid substances, a pain is produced, there is even a redness along the whole course of the absorbents of the arm, and the axillary glands afterwards swell; 2d, that by transfusing into the veins most of the substances that are applied in frictions, effects analogous to those which take place in these frictions are produced. Thus purgatives and emetics, transfused or absorbed, act upon the intestines and stomach the same as if introduced in any other way. It seems to me that sufficient use has not been made of the experiments of the last age upon transfusions. By comparing their effect with that which takes place upon the cutaneous organ, I think that it is impossible not to admit a morbific principle in the blood, at the time of contagious diseases.

3d. After the use of mercury taken in frictions, the emanations of this metal from the animal fluids, act evidently upon silver when placed in the mouth, the rectum, &c. I am persuaded even that the blood which in the natural state exerts but very little action upon this metal, would alter it then. Accoucheurs know that the waters of the amnios of those women who have made use of mercurial frictions exhibit the same phenomenon.