The secretion of sweat is of twofold importance: 1. The function of the sweat glands taken collectively may be considered as that of a single organ with an extensive influence on various processes in the human body. This "sweat organ" participates in the general water metabolism, acts as an excretory organ, aids in regulating the temperature of the body and has still other important functions which are not completely understood as yet, such as its influence on the carbon dioxide-combining power of the plasma (alkali reserve) and the oxygen-carbon dioxide metabolism of the skin. 2. The secretion of the sweat glands is important in the local processes of the skin itself under normal and pathologic conditions. Sweat moistens the upper layers of the epidermis and is an outstanding factor in the defense against parasites and the course of all chemical reactions at the surface of the skin and within the