In the fifth chapter of his work on “The Nature of Man,” Metchnikoff has collected all the numerous disharmonies of the reproductive organs and the reproductive functions, in consequence of which the modern man, become self-conscious, suffers so severely. Among these disharmonious phenomena in social life, Metchnikoff enumerates, _inter alia_, the troublesome, painful, and unæsthetic menstrual hæmorrhage in women, which all primitive peoples regarded as something unclean and evil; the pains of childbirth; the asynchronism between puberty and the general maturity of the organism, the latter occurring much later than the former, and thus giving rise to temporal inequalities of development in different parts of the sexual functions, causing, for example, masturbation actually before the development of spermatozoa; the long interval that commonly elapses between the onset of sexual maturity and the conclusion of marriage; the numerous disharmonious phenomena occurring in connexion with the decline of reproductive activity at a later stage of life, when marked specific excitability and sexual sensibility often persist after the capacity for sexual intercourse has been lost; and finally the disharmonies in sexual intercourse between man and woman. According to Metchnikoff, this disharmony of the sexual life, from the earliest to the most advanced age, is the source of so many evils, that almost all religions have harshly judged and severely condemned the sexual functions, and have recommended abstinence from coitus as the best means for the harmonious and ideal regulation of life. In addition to this, we have to take into consideration the opposition between spirit and matter, deeply realized already by primitive man. The sexual, as the most intense and most sensuous expression of material existence, was opposed to the spiritual, and was regarded as an unclean element, which must be fought, overcome, and, when possible, utterly uprooted, in favour of the spiritual life. In one of the most ancient of mythologies the first recorded instance of the gratification of sexual desire resulted in excluding man for ever from “Paradise”--in excluding him, that is to say, from the highest kind of spiritual existence. The principal psychological characteristic of asceticism is therefore to be found, not only in the vow of poverty, but, in addition, and even more, is it found in =sexual abstinence=, in the battle against the “flesh” (“caro,” to the fathers of the early Church, always denoted the genital organs).