The Sebaceous Glands nearly always open into hair follicles. They are small compound racemose glands (p. 149). Each presents a duct, opening near the mouth of the hair follicle ; when followed back this duct is found to divide into several branches which end in globular expansions.

Describe the perspiration. How much is secreted daily ? Point out conditions influencing its amount. What is meant by " insensible perspiration"? Under what conditions do we find "sensible perspiration "? What percentage of solids exists in the sweat ? What do they contain ? When is the proportion of urea in the perspiration apt to be increased ?

Where do the sebaceous glands open ? To what type of gland do they belong?

* In fever the sweat glands are paralyzed, and we find a high temperature of he body with a dry skin.

The latter are lined by secreting cells. The month of the duct of a sebaceous gland is seen on one side of the hair follicle in Fig. 77.

The Sebaceous Secretion

The Sebaceous Secretion is oily and semi-fluid. In healthy persons it lubricates the hairs and renders them glossy even when no " hair-oil" is used. It is also spread more or less over all the surface of the skin, and makes the cuticle less permeable by water, which in consequence does not readily wet the healthy skin, but runs off it, as " off a duck's back," though to a less marked extent.

The Skin As A Sense Organ

Besides its functions as a protective covering and an excretory organ, the skin is of extreme importance, as being the seat of one of our most important senses—the sense of touch. (Chap. XXIII).