The French physician Roubaud has given us the most vivid description of sexual intercourse: “As soon as the penis enters the vaginal vestibule, it first of all pushes against the glans clitoridis, which is situated at the entrance of the genital canal, and owing to its length and to the way in which it is bent, can give way and bend further before the penis. After this preliminary stimulation of the two chief centres of sexual sensibility, the glans penis glides over the inner surfaces of the two vaginal bulbs; the collum and the body of the penis are then grasped between the projecting surfaces of the vaginal bulbs, but the glans penis itself, which has passed further onward, is in contact with the fine and delicate surface of the vaginal mucous membrane, which membrane itself, owing to the presence of erectile tissue between the layers, is now in an elastic, resilient condition. This elasticity, which enables the vagina to adapt itself to the size of the penis, increases at once the turgescence and the sensibility of the clitoris, inasmuch as the blood that is driven out of the vessels of the vaginal wall passes thence to those of the vaginal bulbs and the clitoris. On the other hand, the turgescence and the sensitiveness of the glans penis itself are heightened by compression of that organ, in consequence of the ever-increasing fulness of the vessels of the vaginal mucous membrane and the two vaginal bulbs. “At the same time, the clitoris is pressed downwards by the anterior portion of the compressor muscle, so that it is brought into contact with the dorsal surface of the glans and of the body of the penis. In this way a reciprocal friction between these two organs takes place, repeated at each copulatory movement made by the two parties to the act, until at length the voluptuous sensation rises to its highest intensity, and culminates in the sexual orgasm, marked in the male by the ejaculation of the seminal fluid, and in the female by the aspiration of that fluid into the gaping external orifice of the cervical canal. “When we take into consideration the influence which temperament, constitution, and a number of other special and general circumstances are capable of exercising on the intensity of sexual sensation, it may well be doubted if the problem regarding the differences in voluptuous sensation between the male and the female is anywhere near solution; indeed, we may go further, and feel convinced that this problem, in view of all the difficulties that surround it, is really insoluble. So true is this, that it is a difficult matter to give a picture at once accurate and complete of the phenomena attending the normal act of copulation. Whilst in one individual the sense of sexual pleasure amounts to no more than a barely perceptible titillation, in another that sense reaches the acme of both mental and physical exaltation.