The question of sexual relations during pregnancy is more difficult, on account of its long duration. In this case caution is necessary, but total abstinence from sexual connection is, in my opinion, superfluous.
=The Desire of Change in Man.=--A peculiarity of the sexual appetite in man, which is fatal for society, is his desire for change. This desire is not only one of the principal causes of polygamy, but also of prostitution and other analogous organizations. It arises from the want of sexual attraction in what one is accustomed to and from the stronger excitation produced by all that is new; a phenomenon of which we have spoken above. On the average, woman has a hereditary disposition which is much more monogamous than man. The sexual appetite thus loses its intensity from the prolonged habit of connection with the same woman, but, becomes much more intense with other women, if not in all men at any rate in most. Such desires may generally be overcome by the aid of a true and noble love, and by sentiments of duty and fidelity toward the family and toward a respected wife. We cannot, however, deny that they exist, nor that they are the cause of the worst excesses, and the most violent scenes, often with a tragic result. We shall return to this subject later.
=Excitation and Cooling of the Sexual Appetite.=--Without touching the domain of pathology, I must again dwell on the great individual diversity of the objects of the male sexual appetite. It is usually young but mature female forms of healthy appearance, and especially the sight of the nudity of certain parts of the body which are usually covered, particularly the breasts and sexual organs, which most strongly excite the sexual appetite in man. It is the same with the corresponding odors. The voice, the physionomy, the clothing and many other details may also provoke his desires. There are, however, men who are more excited by thin and pale women.
Certain attributes excite one and not another; for instance, the hair, certain odors, certain forms of face, a certain fashion of clothing, the form of the breasts, etc. The peculiarities, which are absent in women with whom a man has been on familiar terms in his youth are generally those which attract the most. In sexual matters contrasts tend to mutual attraction. Thin people often become enamored of fat, short ones of long ones, and inversely. One cannot, however, fix any rules. One often sees young men excited at the sight of women of older age, and old men enamored of very young women, even of children. All these discrepancies constitute the more important points of origin of sexual pathology. In spite of all, there still exist a great number of tranquil men with monogamous instincts and not fond of change. Lastly, we must not forget that super-abundant feeding and idleness exalt the sexual appetite and tend to polygamy, while hard work, especially physical, and frugal diet diminish it.