It may be added that this interpretation of the biological function of the hymen is supported by the facts of its evolution. It is unknown among the lower mammals, with whom fertilization is easy, gestation short and offspring numerous. It only begins to appear among the higher mammals in whom reproduction is already beginning to take on the characters which become fully developed in man. Various authors have found traces of a rudimentary hymen, not only in apes, but in elephants, horses, donkeys, bitches, bears, pigs, hyenas, and giraffes. (Hyrtl, _Op. cit._, vol. ii, p. 189; G. Gellhoen, "Anatomy and Development of the Hymen," _American Journal Obstetrics_, August, 1904.) It is in the human species that the tendency to limitation of offspring is most marked, combined at the same time with a greater aptitude for impregnation than exists among any lower mammals. It is here, therefore, that a physical check is of most value, and accordingly we find that in woman alone, of all animals, is the hymen fully developed. FOOTNOTES: [72] "Analysis of the Sexual Impulse," in vol. iii of these _Studies_. [73] "The accomplishment of no other function," Hyrtl remarks, "is so intimately connected with the mind and yet so independent of it." [74] The process is still, however, but imperfectly understood; see Art. "Fécondation," by Ed. Retterer, in Richet's _Dictionnaire de Physiologie_, vol. vi, 1905. [75] Thus a male foetus showing reptilian characters in sexual ducts was exhibited by Shattock at the Pathological Society of London, February 19, 1895. [76] J. Kohlbrugge, "Die Umgestaltung des Uterus der Affen nach den Geburt," _Zeitschrift für Morphologie_, bd. iv, p. 1, 1901. [77] There are, however, no special nerve endings (Krause corpuscles), as was formerly supposed. The nerve endings in the genital region are the same as elsewhere. The difference lies in the abundance of superposed arboreal ramifications. See, e.g., Ed. Retterer, Art. "Ejaculation," Richet's _Dictionnaire de Physiologie_, vol. v. [78] Hyrtl, _Op. cit._, vol. ii, p. 39. [79] Sensations of pleasure without those of touch appear to be normal at the tip of the penis, as pointed out by Scripture, quoted in _Alienist and Neurologist_, January, 1898. [80] See the previous volume of these _Studies_, "Sexual Selection in Man," p. 161. [81] See, e.g., Ploss and Bartels, _Das Weib_, vol. i, beginning of chapter VI. [82] Hyrtl states that the name _labia_ was first used by Haller in the middle of the eighteenth century in his _Elements of Physiology_, being adopted by him from the Greek poet Erotion, who gave these structures the very obvious name cheilea, lips. But this seems to be a mistake, for the seventeenth century anatomists certainly used the name "labia" for these parts.