In the poorer classes of society, an increase of the sexual impulse occurs in women chiefly in consequence of bad example and of unfavorable domestic conditions, such as lead to persons of opposite sexes sleeping in the same bed, and also in consequence of the abuse of alcohol. In the well-to-do classes, it is the perusal of modern equivocal romances, visits to theatres, balls, and evening parties, and, speaking generally, idleness combined with luxurious living, that serve to stimulate the sexual impulse in woman. A certain dependence of the sexual impulse upon seasonal variations appears to exist also in the human species. At any rate in certain months of the year, a definite increase in the number of conceptions continues to recur, which indicates that during these months a larger number of sexually mature individuals is engaged in the discharge of sexual functions. _Rosenstadt_ regards this as the manifestation of a “physiological custom,” immanent in the physical constitution of civilized man, and inherited by him from his animal ancestors. He explains it in the following terms: “Primitive man inherited from his mammalian forefathers the peculiarity of reproducing his kind only during a certain definite period, the period of heat or rut. After humanity had entered upon this period, copulation was effected _en masse_, as was easy in view of the primitive community of sexual intercourse before the origin of marriage. In the course of his progress toward civilization, however, man began to reproduce his kind indifferently throughout the entire year; but the original “physiological custom,” in accordance with which reproduction occurred at definite seasons only, did not disappear, and persists, indeed, to a certain extent even to the present day as a survival of earlier mammalian life, and manifests itself in the annual recurrence in certain months of an increase in the number of conceptions. The analogy in structure and function between the genital organs of the human species and those of other mammals (the female anthropoid apes do not merely exhibit from time to time a period of heat, but are subject to a more or less regular menstruation), which for the most part reproduce their kind only at certain definite periods, leads to the conclusion that in the human species also the sexual impulse may originally have awakened only at a particular season of the year, and that the persistence of this physiological custom in man, in spite of the fact that sexual intercourse occurs all through the year, and notwithstanding that the conditions necessary to awaken the sexual impulse are actually perennial, must be ascribed to inheritance.”