In the human species both the negative standard of castration and the positive standard of puberty alike indicate a correlation of this kind. Those individuals in whom puberty never fully develops and who are consequently said to be affected by infantilism, reveal a relative absence of pigment in the sexual centers which are normally pigmented to a high degree.[[160]] Among those Asiatic races who extirpate the ovaries in young girls the skin remains white in the perineum, round the anus, and in the armpits.[[161]] Even in mature women who undergo ovariotomy, as Kepler found, the pigmentation of the nipples and areola disappears, as well as of the perineum and anus, the skin taking on a remarkable whiteness.
Normally the sexual centers, and in a high degree the genital orifice, represent the maximum of pigmentation, and under some circumstances this is clearly visible even in infancy. Thus babies of mixed black and white blood may show no traces of negro ancestry at birth, but there will always be increased pigmentation about the external genitalia.[[162]] The linea fusca, which reaches from the pubes to the navel and occasionally to the ensiform cartilage, is a line of sexual pigmentation sometimes regarded as characteristic of pregnancy, but as Andersen, of Copenhagen, has found by the examination of several hundred children of both sexes, it exists in a slight form in about 75 per cent. of young girls, and in almost as large a proportion of boys. But there is no doubt that it tends to increase with age as well as to become marked at pregnancy. At puberty there is a general tendency to changes in pigmentation; thus Godin found that in 28 per cent, adolescent changes occurred in the eyes and hair at this period, the hair becoming darker, though the eyes sometimes become lighter. Ammon, in his investigation of conscripts at the age of 20 (post, p. 196), discovered the significant fact that the eyes and hair darken pari passu with sexual development. In women, during menstruation, there is a general tendency to pigmentation; this is especially obvious around the eyes, and in some cases black rings of true pigment form in this position. Even the skin of the negro women of Loango sometimes becomes a few shades darker during menstruation.[[163]] During pregnancy this tendency to pigmentation reaches its climax. Pregnancy constantly gives rise to pigmentation of the face, the neck, the nipples, the abdomen, and this is especially marked in brunettes.
This association of pigmentation and sexual aptitudes has been recognized in the popular lore of some peoples. Thus the Sicilians, who admire brown skin and have no liking either for a fair skin or light hair, believe that a white woman is incapable of responding to love. It is the brown woman who feels love; as it is said in Sicilian dialect: "Fimmina scura, fimmina amurusa."[[164]]
The dependence of pigmentation upon the sexual system is shown by the fact that irritation of the genital organs by disease will frequently suffice to produce a high degree of pigmentation. This may the neck, the trunk, the hands. Simpson long since noted that uterine irritation apart from pregnancy may produce pigmentation of the areolæ of the nipples (Obstetric Works, vol. i, p. 345). Engelmann discussed the subject and gave cases, "The Hystero-Neuroses," pp. 124-139, in Gynæcological Transactions, vol. xii, 1887; and a summary of a memoir by Fouquet on this subject in La Gynécologie, February, 1903, will be found in British Medical Journal, March 28, 1903,
Of all physical traits vigor of the hairy system has most frequently perhaps been regarded as the index of vigorous sexuality. In this matter modern medical observations are at one with popular belief and ancient physiognomical assertions.[[165]] The negative test of castration and the positive test of puberty point in the same direction.
It is at puberty that all the hair on the body, except that on the head, begins to develop; indeed, the very word "puberty" has reference to this growth as the most obvious sign of the whole process. When castration takes place at an early age all this development of pubescent hair is arrested. When the primary sexual organs are undeveloped the sexual hair is also undeveloped, as in a case, recorded by Plant,[[166]] of a girl with rudimentary uterus and ovaries who had little or no axillary and pubic hair, although the hair of the head was long and strong.[[167]]
The pseudo-Michael Scot among the Signa mulieris calidæ naturæ et quæ coit libenter stated that her hair, both on the head and body, is thick and coarse and crisp, and Della Porta, the greatest of the physiognomists, said that thickness of hair in women meant wantonness. Venette, in his Generation de l'Homme, remarked that men who have much hair on the body are most amorous. At a more recent period Roubaud has said that pubic hair in its quantity, color and curliness is an index of genital energy. A poor pilous system, on the other hand, Roubaud regarded as a probable though not an irrefragable proof of sexual frigidity in women. "In the cold woman the pilous system is remarkable for the languor of its vitality; the hairs are fair, delicate, scarce and smooth, while in ardent natures there are little curly tufts about the temples." (Traité de l'Impuissance, pp. 124, 523.) Martineau declared (Leçons sur les Déformations Vulvaires, p. 40) that "the more developed the genital organs the more abundant the hair covering them; abundance of hair appears to be in relation to the perfect development of the organs." Tardieu described the typically erotic woman as very hairy.
Bergh found that among 2200 young Danish prostitutes those who showed an unusual extension and amount of pubic hair included several women who were believed to be libidinous in a very high degree. (Bergh, "Symbolæ," etc., Hospitalstidende, August, 1894.) Moraglia, again, in Italy, in describing various women, mostly prostitutes, of unusually strong sexual proclivities, repeatedly notes very thick hair, with down on the face. (Archivio di Psichiatria, vol. xvi, fasc. iv-v.)
Marro, also, in Italy found that abundance of hair and down is especially marked in women who are guilty of infanticide (as also Pasini has found), though criminal women generally, in his experience, tend to have abnormally abundant hair. (Caratteri del Delinquenti, cap. XXII.) Lombroso finds that prostitutes generally tend to be hairy (Donna Delinquente, p. 320.)