8 



ELEMENTS OF PHYSIOLOGY 



the hair. A hair, therefore, grows from the top of a 

 papilla which stands in the bottom of a pit in the true 

 skin. The outside of the hair is formed of colorless, over- 

 lapping cells (Fig. 7). The hair 

 is pithy in the center and contains 



l^flHB pigment cells. In old people, the 

 : v^ pigment is replaced by air, and the 



mj * hair turns white. The only point 



I w, ^ at which the cells of the hair, and 



therefore the hair itself, are living 

 and growing is at the top of the 

 papilla, deep down in the follicle 

 (Fig. 7). From this it is easy to 

 see that the common notion that 

 cutting off the ends of the hair, 

 either by shaving or trimming with 

 scissors, causes it to grow faster 

 and stronger, is erroneous. It 

 may stop the splitting of hairs and 

 thus prevent the wearing away of 

 the hair. Of course when the hair 

 or beard is short, its growth is 

 more noticeable. Long hair seems 

 by its weight to give exercise to 

 minute muscles in the skin and 

 strengthen the flow of blood, thus 

 FIG. 7 . -A Hair in its Follicle, adding to the vigor of the hair. 

 ^^h.tS^^ The cut end of a hair is nearly 

 cst portion of ths hair growing roun d in the straight-haired races, 



on the papilla z ; a, cuticle of t ... 



hair; e, cavity of hair follicle; as Indians and ChinCSC J it is OVal 



f t epidermis of follicle corre- - . . j , . j 



to ,, the epidermis in the wavy-haired white race, and 



S'A-^SiS flattened stm more in the kink y- 



k, dermis of foiiicie correspond- haired negro race. Which races 



ing to dermis, /, near the surface ; . 1-1 



k, mouths of sebaceous or oil have black hair ? In which races 

 *' h rny CpidermiS at is the color of the hair variable ? 



