THE SKIN. 359 



blood supply, a fact that may also be demonstrated 

 by physiological experiments. 



Sebaceous glands are associated with hair follicles, 

 into which they pour their contents. They are also 

 found on the red borders of lips, the labia minora, 

 the glans and prepuce, where hairs are absent. 

 They are simple branched alveolar glands that se- 

 crete an oily substance called sebum. This is a 



jollicle. 



Hair follicle. 



Fig. 251. Model of a sebaceous gland with a portion of the hair 

 follicle, reconstructed by Born's wax-plate method (Huber). 



fluid at the temperature of the body, keeps the skin 

 soft and flexible, and also supplies a natural dressing 

 for the hair. In the scalp there may be an exces- 

 sive secretion of sebum which dries and exfoliates 

 with the horny epidermis as dandruff. 



Each hair follicle has two or more sebaceous 



