There is little to say about the differences in the nature and structure of the skin according to race. Its colouring, of which I shall speak later on (see Pigmentation), is more important. Attention has been drawn to the hardness of the corium and the velvety softness of the skin in the negro; the latter quality is probably due to the profusion and size of the sebaceous glands which accompany the hair. Bischoff has made an interesting observation on the relative rarity of the sweat glands (which are found in the thickness of the corium, Fig. [3], g.su.) among the Fuegians,[41] but comparative studies on this subject have not been pursued in regard to other races. The disposition of the papilla ridges on the tips of the fingers, so well studied by Galton,[42] is of great interest as regards the identification of the individual; but from this fact alone, that it is a good characteristic of the individual, it loses all its value as a characteristic of race.
FIG. 4.—Mohave Indians of Arizona; smooth hair type.
(Phot. Ten Kate.)
Hair of the Head and Body.—The most important horny product of the skin, as regards the differentiation of races, is undoubtedly the hair of the head and body. The general structure and number of the hairs (about 260 to each square centimetre) hardly show any difference between race and race; on the other hand, the length of the hair of the head, the relation of this length in one sex to that in the other, the nature of the hair, its consistence, its transverse section, its form, its colour, vary much according to race.
FIG. 5.—Pure Veddah of Dangala Mountains of Ceylon; wavy hair type.
(Phot. Brothers Sarasin.)
The body hair has its origin in a layer of the epidermis, deeply imbedded in the corium as though it were in a little sac or follicle (Fig. [3], fo.); from the bottom of this sac, and covering by its root a little papilla (Fig. [3], pa.) filled with vessels designed to nourish it, each hair rises and pushes its way to the outside; it is always accompanied by a little muscle which can move it (Fig. [3], m.r.), and by a sebaceous gland (Fig. [3], g.s.) designed to lubricate it.