Etiology

Deficient perspiration is a symptom common to a number of cutaneous affections, that is to say, accompanies various lesions. It sometimes, though rarely, is a prominent morbid condition without any other coexisting lesion of the skin. It may be due to congenital defective development of the sudoriparous glands, or to functional derangement of normal glands, or to other causes. For instance, examination of the palmar surfaces of the fingers with a lens will enable the observer to readily detect the situation of the mouths of the sweat-ducts, in a normal condition of the skin. They appear as numerous little circular depressions on the summit of the papillary ridges. In ichthyosis, on the other hand, they appear to be less numerous and smaller in size, and many of them fail to exhibit any depression, and some of them appear even a little elevated, and apparently blocked up and impervious. Again, if the palm of a normal hand, after having been thoroughly dried, be exposed to the direct rays of a hot sun, in a few minutes little droplets of fluid will be seen (with a lens) issuing from the pores. If the palm of an ichthyotic patient be treated in the same manner, it will be found that only a comparatively small number of pores give exit to fluid. In other words, a certain proportion of them are inactive. It is probable that this condition prevails to a greater or less extent over the whole surface of the body, as ichthyotics are proverbially anidrotic. In this case, there is a congenital defect of development in the sudoriparous system. In the affection known to English writers by the name of xeroderma, it is probable that the same condition prevails to a less extent. On the other hand, patients suffering with eczema, psoriasis, and some other cutaneous affections, do not, as a rule, sweat as freely as persons in the full enjoyment of health. Here there is no evidence to show that the sweat-glands themselves are defective, and the deficient secretion may be simply due to functional inactivity.

Therapeutics

If for any reason it is desirable to increase the accretion of perspiration, it may be readily accomplished by the use of almost any of the commonly employed diaphoretics. The most powerful of these agents is jaborandi, the full diaphoretic dose of which for an adult is a drachm of the fluid extract, or half a grain of some salt of its alkaloid pilocarpia. This produces free diaphoresis, commencing in ton or fifteen minutes and lasting for two or three hours or longer. It possesses the inconvenience of producing at the same time free salivation, a circumstance of which the patient should be informed. When practicable the most agreeable mode of obtaining free diaphoresis is by the aid of the Turkish or hot-air bath.