Does there exist any difference of form between straight, waved, frizzy, or woolly hair? The microscopical examination of transverse sections of the hair allows us to reply affirmatively to this question. This examination, already applied to the hair in 1822 by Heusinger, then successively by Blower (of Philadelphia), Kölliker, Pruner-Bey, Latteux, and Waldeyer,[44] has yielded results which have been vigorously discussed, and are still debatable if we cling to the individual and absolute figures, comparing sections made according to defective methods, or carried out on different levels of the hair. But if we calculate the index—that is to say, the relation of the breadth to the length (= 100) of the section (and that in a great number of individual cases)—we obtain satisfactory results, as Topinard and Ranke[45] have shown in general, as also Baelz in the case of the Japanese, and Montano in the case of the races of the Malay Archipelago.[46]
FIG. 9.—Agni Negro of Krinjabo, Western Africa; woolly hair type.
(Photo. Thoman, lent by Collignon.)
If we consider a great number of microscopical sections, all obtained from the same level of the hair, we note that straight hair gives a circular section, whilst woolly hair gives one in the form of a lengthened ellipse. This ellipse is less extended, a little more filled out, in the sections of wavy hair. If the major axis of the ellipse be supposed to equal 100, the minor axis will be represented by figures varying from 40 to 50 for the woolly hair of the Bushmen and the Hottentots, from 50 to 60 for that of the Negroes, while the straight hair of the Eskimo will have this axis = 77, that of the Thibetans = 80, that of the Japanese = 85, etc. The hair of Europeans represents an elliptical section in which the major axis being = 100, the minor axis will be represented by figures varying from 62 to 72 (Topinard). It can be said to-day with certainty, after the work of Unna,[47] that the woolly hair of Negroes rolls up into a compact spiral precisely because of the flattened shape of this elliptical section, and of the special form of the follicle and papilla. In fact, in the Negro the follicle, instead of being straight, as in the European (Fig. [3], A), is curved inward in the form of a sabre, or even of the arc of a quarter of a circle (Fig. [3], B); further, the papilla is flattened instead of being round. One would say that the hair has encountered in its development so much resistance on the part of the dermis (which is so hard, in fact, among the Negroes), that it would be twisted, as it were, from the first. Emerging from an incurvated mould, it can only continue to roll up outside, given especially its flattened shape; it rolls up into a spiral, the plane of which, at the beginning, is perpendicular to the surface of the skin.[48] As to the thickness of the hair, it appears that in general it is greater in straight hair than in woolly; however, the hair of the western Finns is straight and fine at the same time.
A certain correlation appears to exist between the nature of the hair and its absolute and relative length. Thus straight hair is at the same time the longest—Chinese, Americans, Indians (Fig. [4]), while woolly hair is shortest, from 5 to 15 centimetres (Fig. [9]); wavy hair occupies an intermediate position. Moreover, the difference between the length of the hair of men and women is almost inappreciable in the two extreme divisions. In certain straight-haired races the hair of the head is as long with men as with women; one need but to call to mind the plaits of the Chinese, or the beautiful heads of hair of the Red Indians, which may attain in certain cases a length of even two metres (Catlin). In frizzy-haired races the hair of the head, on the contrary, is equally short in the two sexes; the hair of the head of women among the Bushmen, Hottentots, and even Negroes, is not appreciably longer than among the men. It is only in the categories of wavy and in part of frizzy hair, that the differences are appreciable. With European men the length of the hair rarely exceeds 30 or 40 centimetres, while with the women it averages 65 to 75 centimetres, and may attain in exceptional cases to 2 metres (as in the case of an Englishwoman, according to Dr. D. Watson).
Another fact to be noted is that the general development of the pilose system on the face, as on the rest of the body, seems also to be in relation to the nature of the hair of the head.
Straight-haired races are ordinarily very glabrous, the men have hardly a rudimentary tuft of beard—American Indians (Fig. [4]), Mongols (Fig. [20]), Malays; while in the wavy or frizzy-haired races, the development of the pilose system is considerable—Australians, Dravidians, Iranians (Fig. [22]), Ainus (Fig. [117]), etc. The woolly-haired races are not, however, included in this rule; glabrous types (Bushmen, western Negroes) are found side by side with rather hairy types (Melanesians, Akka, Ashanti). There appears to be a certain likeness between the abundance of hair on the head and on the body. Thus, according to Hilgendorf, the Japanese who are glabrous have from 252 to 286 hairs to each square centimetre on the head, whilst the hairy Ainus have only 214. Negroes and white men do not appear, however, to present the same differences (Gould). Even baldness results largely from the nature of the hair. According to Gould, baldness is ten times less frequent among Negroes than among Whites, between 33 years and 44 years, and thirty times less so between 21 and 32. Among Mulattos it is more frequent than among the Negroes, but less than among Whites. Lastly, among Red Indians it seems to be still more rare than among Negroes. White hair follows almost the same rule.[49]
In the mass, the human races may be divided according to the character of their hair as follows:—
Woolly Hair.—Bushmen, Negro, and Melanesian races.