THE SKIN, HAIR, AND NAILS.
The diseases of the skin are numerous, and many of them are troublesome. The structure of the skin, as indicated in Section XX, is comparatively complicated. The true skin itself is supplied with blood-vessels and nerves, and is therefore liable to various forms of inflamma tory change to which any other structure rich in vessels and nerves is exposed. But there are also to be taken into account the sweat glands and canals that are imbedded in and pass through it, and the appendages that belong to it, in the shape of hairs and nails with their at tendant glands, all of them liable in themselves to various departures from a healthy condition. Moreover, the skin ranks as a blood-purifying organ in as true a sense as the lungs or the kidneys, though in a less degree, and it may thus be not only the seat of a disease which affects it exclusively, but may likewise be a sharer in an unhealthy condition that disturbs more or less generally the rest of the body. A disease of the skin may be, that is to say, a mere local disturb ance, an affection limited to the part where it is manifested, or it may be the indication and result of a general condition of body. Thus the eruptions, or rashes, that attend many special fevers, such as scarlet fever, measles, typhus, and typhoid fever, &c., are evidently mere occur rences in the course of a disease affecting the whole body. No one would think of treating these eruptions by themselves, for they will gradually disappear as soon as the constitu tional disturbance, in whose train they come, has passed away. But there are other eruptions, as well as affections of the skin not attended by any rash, as truly produced by a general disorder, not to be got rid of till the general disorder has been set right, that are not so readily traced to their true cause. Here, however, an error must
be guarded against. It is a common belief that ninny skin diseases are peculiarly the expression of a "vice of blood," which is seeking an outlet in this way, and that, if this way of escape is denied to it, it will, in revenge, as it were, attack deeper and more vital parts. The common con clusion, accordingly, is that the disease ought to be permitted to run riot through the skin, if it pleases, lest attempts to cure it drive A inwards. Now we have seen (p. 414) that the skin is a blood-purifying organ, that by means of its glands it separates from the blood and casts out of the body certain impurities. It is also true that in fevers, accompanied by rash, such as measles, scarlet fever, &c., the treatment consists in the use of warm baths or hot packs, and in the administration of medicines which, besides relieving the bowels, "determine to the skin and kidneys," as the phrase is, that is, stimulate the activity of skin and kidneys to be more vigorous in their work of purifying the blood, to aid in "throwing off" the disease, or at least in abating its severity. As a sign that this is being done, so far as the skin is con cerned, one is accustomed to view with satisfac tion a rapid and full development of the rash characteristic of the disease. While this is all true, it 'is a totally wrong view of the facts that encourages the idea that a cure of any skin eruption runs the risk of creating disease else where. It never is so. Many skin diseases are entirely local, are due, that is to say, to disturb ances limited to the part affected, the cure of which implies that the disturbances have been got rid of.