Among the agents adapted for expelling the excretions from the system, few surpass the _Sudoriferous Glands_. These are minute organs which wind in and out over the whole extent of the true skin, and secrete the perspiration. Though much of it passes off as insensible transpiration, yet it often accumulates in drops of sweat, during long-continued exercise or exposure to a high temperature. The office of the perspiration is two-fold. It removes noxious matter from the system, and diminishes animal heat, and thereby equalizes the temperature of the body. It also renders the skin soft and pliable, thus better adapting it to the movements of the muscles. The _Sebaceous Glands_, which are placed in the true skin, are less abundant where the sudoriferous glands are most numerous, and _vice versa_. Here, as elsewhere, nature acts with systematic and intelligent design. The perspiratory glands are distributed where they are most needed,--in the eyelids, serving as lubricators; in the ear passages, to produce the _cerumen_, or wax, which prevents the intrusion of small insects; and in the scalp, to supply the hair with its natural pomatum. [Illustration: Fig. 48. A perspiratory gland, highly magnified. 1, 1. The gland. 2, 2. Excretory ducts uniting to form a tube which tortuously perforates the cuticle at 3, and opens obliquely on its surface at 4.] [Illustration: Fig. 49. A representation of oil-tubes from the scalp and nose.] [Illustration: Fig. 50. Anatomy of the skin. 5, 5. Cutis vera (true skin). 4, 4. Nervous tissue. 3, 3. Sensitive layer in which are seen the nerves. 2, 2. The layer containing pigment cells. 1, 1. Epidermis (cuticle).]