The psycho-physiological processes involved in the sexual impulse would appear to be, then, the mental concept of sexual pleasure, and the realization of that pleasure as derived from, or simulating, the sexual act. But many factors govern the intensity of the sexual feeling. The man who embraces a beautiful, passionate womanó himself in the prime of health and sexual vigorówill necessarily derive from the act a greater degree of pleasure than the sexually feeble man, having intercourse with an old or repulsive woman; and so closely is the aesthetic idea associated with sexual feeling that disgusting acts, or habits of uneleanliness, may inhibit it altogether.3
While female prostitution is perfectly well recognized as a social institution, and the man who picks a woman up in the streets knows perfectly well that he is about to travel a very well-beaten road, the psychological instinct of ownership, nevertheless, struggles to assert itself; and nothing so cheapens and lessens the pleasure of the act as the reflection that another has been there very recently. The power of excluding this idea, however, as well as inhibiting the sexual desire entirely, for prudential reasons, is fortunately inherent in man; and the moral freedom of the individual, in this, as in everything else, is manifested in the power of the inhibiting concept to overcome organic impulse.
The quite uniform experience of physicians, therefore, is that sexual diseases are contracted mainly, if not entirely, not through the strength of the sexual impulse, but through the loss of inherent aversion for filth and prostitution, and the weakening of the will-power, through alcohol, opium, or some other narcotic, many of which, while intensifying the libidinous passion, render it, at the same time, less capable of moral restriction within safe lines. In other words, a drunken man will go with a woman who, in his sober moments, would be perfectly loathsome to him.