THE SKIN 19 



Immigrants from a Cloudy to a Sunny Climate. Adaptation. — The 

 cells of the deeper tissues can readily be exhausted by the stimulation 

 of too much light. The sunnier the climate, the greater the need of 

 pigment ; hence the dark skin of the negro and the blonde skin and 

 hair of the Norwegian. European immigrants to sunny America will 

 o-row darker. The Indian's skin is better suited to our climate than is 

 a fair skin. Brunettes have a better chance for adaptation than blondes. 

 The American type when developed will doubtless be brunette. 



The hair grows from a pit or follicle (Fig. 22). Blood 

 vessels and a nerve fiber go to the root or bulb from which 

 a hair grows. The hair will grow un- 

 til this papilla, or bulb, is destroyed 

 (Exp. 2). 



Adaptation of the scalp to a tight warm cov- 

 ering is accomplished through the shedding of 

 the hair rendered useless by the covering. It is 

 impossible to stop the growth of superfluous hair 

 unless the hair papillae are destroyed with an 

 electric needle, such is the vitality of hair ; yet 



manv men, by overheating the head and cutting 



~ , ... . , . , , , , , 1 Fig. 22. — Develop- 



off the circulation with tight hats, destroy much 



, ^^ . MhNl Ur A n A l K 



of the hair before reaching middle age. 1 he AND Two QlL 



health of the hair can be restored and its loss Glands. 



be stopped by going bareheaded except in the 



hot sun or in extremely cold weather. This frees the circulation; cold 

 air and light stimulate the cells of the scalp. Some men wear hats, 

 even at night in summer. The brain needs the protection of the hair. 

 Beard protects the larynx or voice box, which is large and exposed in man. 

 It was also a protection in hunting wild beasts and in war. Compare 

 mane of lion, not possessed by lioness. " Goose-flesh " after a cold bath 

 is caused by the contraction of small muscles (colored Fig. 1), raising 

 the now tiny hairs in an absurdly useless effort to keep the body warm. 



The nails are dense, thick plates of epidermis growing 

 from a number of papilla? situated in a groove, or fold, of 

 the skin ; there are many fine papillae along the bed from 

 which the nail grows. Since it grows from its under side 

 as well as from the little fold of skin at its root, the nail is 

 thicker at the end than near the root. 



