In the sexual life, also, in correspondence with this preponderating development of the brain, purely psychical elements continually play a larger part, whilst parts and functions at one time intimately related to sexuality have undergone atrophy. Thus, as we have already pointed out, the human organ of smell had unquestionably in earlier times much greater significance in relation to the _vita sexualis_ than it has at the present day. Wiedersheim shows that in the ancestors of the human race this organ was much more extensively developed, and that it must now be regarded as in a state of atrophy. The mammary glands, the original function of which was perhaps the production of odoriferous substances, but which later became devoted solely to the secretion of milk, existed in our ancestors in a larger number than in the present human race. This is clearly shown by the fact that the human embryo normally exhibits a “hyperthelia,” an excess of breasts, of which, however, two only normally undergo development; moreover, the breasts of the male, which are now in a state of arrested development, were formerly better developed, and served, like those of the female, the purpose of nourishing the offspring. These facts are clearly explicable on the assumption that at one time the number of offspring at a single birth was considerable, and that in this way the preservation of the species was favoured (Wiedersheim). It is a very interesting fact that the principal “organ of voluptuousness” in women, the clitoris, is notably diminished in size absolutely and relatively as compared with the clitoris of apes. It certainly no longer represents an organ so susceptible to voluptuous stimulation and excitement as it was assumed to be by the older physicians and physiologists; so that, for example, Van Swieten, the celebrated body physician of the Empress Maria Theresa, recommended _titillatio clitoridis_ as the most certain means of curing the sexual insensibility of his royal patient. Moreover, the common variations in the external configuration of the female genital organs, which Rudolf Bergh has very fully and minutely described in his “Symbolæ ad Cognitionem Genitalium Externorum Femineorum,” are largely dependent on such arrests of development, which, indeed, occur also in the male.