CH. xxxvnt.] THE SKIN-GLANDS. 575 



follicle (fig. 441). When it contracts, as under the influence of 

 cold, or of certain emotions such as fear, the hair is erected and the 

 whole skin is roughened ("goose skin"). The nerves supplying 

 these muscles are called pilo-motar nerves. The distribution of 

 these nerves closely follows those of the vaso-constrictor nerves 

 of the skin ; their cell stations are in the lateral sympathetic chain. 

 The sebaceous glands (tigs. 441 and 445) are small saccular 



Fig. 445. Sebaceous gland from human skin. (Klein and Noble Smith.) 



glands, with ducts opening into the upper portion of the hair 

 follicles. The secreting cells become charged with fatty matter, 

 which is discharged into the lumen of the saccules owing to 

 the disintegration of the cells. The secretion, sebum, contains 

 isocholesterin (see p. 505) in addition to fatty matter. It acts 

 as a lubricant to the hairs. 



The sweat-glands are abundant over the whole human skin, 

 but are most numerous where hairs are absent, on the palms and 

 soles. Each consists of a coiled tube in the deepest part of 

 the dermis ; the duct from which passes up through the dermis, 

 and by a corkscrew-like canal through the epidermis to the 

 surface. 



