66 



SWEAT GLANDS. 



Where the hairs are large, and especially where they serve as 

 tactile organs, there may be a papilla furnished with nerves and 

 vessels, in the bottom of the follicle, which projects into the bulb, as 

 in the whiskers of a cat, and the quills of a porcupine ; an approach 

 to this papillary projection may be seen in some of the hairs of 

 man, but their size is much overrated. 



The hairs maintain a vital, though not a vascular connexion with 

 the body ; the moisture is partly due to the sebaceous glands, whose 

 secretion passes through them by capillary attraction. Mental 

 emotion has occasioned the hair to become white in a single night ; 

 some account for this by a secretion of fluid acid which percolates 

 the tissue of the hair, and chemically destroys the colour. Ordinary 

 gray hairs resemble other hair in every respect, save that of colour. 



The disease called Plica Polonica^ is a malting together of the 

 hairs by a glutinous matter, probably from the cutaneous glands ; 

 the hairs so affected bleed if cut close to the skin, owing to a morbid 

 elongation of the vascular papillae at their roots. 



SWEAT GLANDS. 



These are found in great number upon the inferior surface of the 

 cutis vera generally. In the axilla they form a layer, an eighth of 

 an inch thick, which is mammillated, and of a reddish colour. They 

 are about the size of a pin's head, are soft, and often compressed 

 and surrounded by a network of capillary blood-vessels. They 

 are distinguishable from pellets of fat by their pink colour, and semi- 

 transparent texture. When highly magnified, it is seen to consist 

 of a solitary tube, intricately ravelled, one end of which is closed, 

 and buried within the gland, and the other opens upon the skin. 

 The duct at first meanders through the interstices of the cutis vera, 



becomes straight between 



Fig. 53. 



the papillse, then assumes 

 a spiral course in perfo- 

 rating the cuticle. (Fig. 

 51.) The secretion varies 

 in odour in different por- 

 tions of the body, and in 

 different races. 



SEBACEOUS GLANDS. 



The sebaceous glands are 

 found in most parts of the 

 skin, except in the palms 

 and soles ; they are most 

 abundant on the scalp and 

 face, especially about the 

 nose. The orifices open 

 into hair follicles, or upon 



