326 THE URINARY APPARATUS 



the shaft, the portion extending from the surface; and 

 the point. 



The root of the hair presents at its deep extremity a 

 bulb-like enlargement, the hair-bulb, which is lodged in 

 a follicular involution of the epidermis called the hair 

 follicle. The hair follicle commences in the surface 

 of the skin with a funnel-shaped opening, and passes 

 inward in an oblique direction, to become dilated at 

 its deep extremity or fundus, where it corresponds 

 with the bulbous shape of the hair which it contains. 

 Each hair follicle has at its base a small, conical, 

 vascular eminence or papilla, the hair papilla, similar 

 to the papilla? found upon the surface of the skin. 

 The latter are highly vascular and probably supplied 

 with nerve fibrils. Each hair follicle has an opening into 

 it near its free extremity, the openings or orifices of 

 the ducts of one or more sebaceous glands. Connected 

 with the hair follicles are minute bundles of involuntary 

 muscle fibers called arrectores pilonim. They originate, 

 from the superficial surface of the true skin, or corium, 

 and are inserted into the outer surface of the hair 

 follicle, below the orifice of the duct of the sebaceous 

 gland. They are located on the side toward which 

 the hair slopes, and when they contract elevate the 

 hair. 



The Sebaceous Glands. These are simple and com- 

 pound racemose glands which open into the hair 

 follicle, and sometimes the skin surface, by means of 

 a duct. These glands are lodged in the surface of the 

 true skin or corium. They are very plentiful, and 

 are found in all parts of the body, especially in the 

 skin of the face and scalp; also numerous around the 

 openings of the mouth, anus, nose, and external ear, 

 but are not found in the skin covering the palms of 

 the hands and the soles of the feet. Their structure 

 consists of a delicate transparent membrane, enclosing 

 epithelial cells. 



