THE STRUCTURE AND FUNCTIONS OF THE SKIN. 345 



sudoriferous glands, except in being larger, and having very short 

 ducts. 



The peculiar bitter yellow substance secreted by the skin of the ex- 

 ternal auditory passage is named cerumen, and the glands themselves 

 ceruminous glands; but they do not much differ in structure from the 

 ordinary sudoriferous glands. 



(b) Sebaceous Glands. The sebaceous glands (Fig. 236), like the 

 sudoriferous glands, are abundantly distributed over most parts of the 

 body. They are most numerous in parts largely supplied with hair, as. 

 the scalp and face, and are thickly distributed about the entrances of 



FIG. 236. Sebaceous gland from human skin. (Klein and Noble Smith.) 



the various passages into the body, as the anus, nose, lips, and external 

 ear. They are entirely absent from the palmar surface of the hand and 

 the plantar surfaces of the feet. They are minutely lobulated glands 

 composed of an aggregate of small tubes or sacculi filled with opaque 

 white substances, like soft ointment. Minute capillary vessels overspread 

 them; and their ducts open either on the surface of the skin, close to a 

 hair, or, which is more usual, directly into the follicle of the hair. In 

 the latter case, there are generally two or more glands to each hair (Fig. 

 234). 



Hair. A hair is produced by a peculiar growth and modification of 

 the epidermis. Externally it is covered by a layer of fine scales closely 

 imbricated, or overlapping like the tiles of a house, but with the free 

 edges turned upwards (Fig. 237, A). It is called the cuticle of the hair. 



