154 



HUMAN PHYSIOLOGY 



CHAP. 



with a nail brush. A knife should never be used, except 

 for trimming the nails. It is best to cut the ringer nails 

 in a curved direction and the toe nails straight across. 



The entire body, except the palms and soles, is cov- 

 ered with a growth of hair, fine and scanty in some 



places and coarse 

 and abundant in 

 others. A hair 

 consists of two 

 parts: a ska ft 

 above the surface 

 of the skin, and 

 a root beneath, 

 placed in a little 

 sac or pocket of 

 epidermis called 

 \.\\Q follicle. Some- 

 times the follicle 

 extends down 

 through the true 



B/ootf vessel 

 Nerve 



FlG. 79. Showing a hair follicle. (Modified from 

 Heitzmann by Zinns.) 



skin into the layer 

 of fatty tissue 

 below. Blood ves- 

 sels enter the fol- 

 licle at the lower 



end, carrying nourishment to the root, where the hair 



grows by the constant formation of new cells which 



slowly push the hair upward. 



77?^ color of the hair is due to small air bubbles and 



pigment cells in the hair substance. In old age no color- 



