_Hegar_ maintains that under the term _sexual impulse_ two distinct conceptions are confounded: First, the impulse toward copulation, the desire of carnal union with a member of the opposite sex; secondly, the impulse toward reproduction, the desire for children. At the same time, this author admits that it is questionable if we can properly speak of an impulse toward reproduction, when reproduction is merely a consequence of copulation; in the case of civilized man, at any rate, so much reflection is connected with the idea of reproduction that it can hardly be proper to speak of anything of the nature of an impulse. In the case of woman, the expression is less unsuitable, since in woman special organs exist for the maintenance of the ovum after fertilization, and these organs may perhaps lead to the production of this peculiar form of mental activity.
According to _Darwin_, a comparatively less intensity of sexual desire is common to the females of all species of the animal kingdom. The female demands a prolonged courtship, and often endeavors for a considerable time to elude the male. In the lowest classes of the animal kingdom the female leads a separate existence as soon as she has been fertilized by the male, the sexual functions being thus subordinated to the maternal. Among birds at the pairing season the male is always the more passionate and active of the two, whilst the female commonly remains passive and occupies herself in building the nest. Among mammals, it is difficult to determine whether sexual feeling is stronger in the female or in the male; but it is certain that sexual relations are seldom long lasting, they continue in most cases only during the period of heat or rut, and at most only till the birth of the young.
From these phenomena witnessed in the animal kingdom, many naturalists have concluded that in females of the human species also, sexual sensibility and the intensity of the sexual impulse are less than in the males, and even that the sexual sense in general is but little developed in the female sex, or sometimes entirely wanting. The complicated apparatus which the primary and secondary sexual characters of the female combine to make up, exists, according to this view, not for the gratification of the sexual impulse, but for the fulfilment of the function of motherhood. “Love in women,” says _Lombroso_, “is in its fundamental nature no more than a secondary character of motherhood, and all the feelings of affection that bind woman to man arise, not from sexual impulses, but from the instincts, acquired by adaptation, of subordination and self-surrender.”