The hereditary or instinctive nervous actions produce after coitus a profound effect of contrast. When the sexual appetite commences, the odors, especially those of the sexual organs, the contacts, the movements, and the sight of the individual of the opposite sex, all increase desire, producing a voluptuous excitation stronger than all contrary feeling. Hardly is the sexual act consummated than all vanishes like a dream. What was a moment before the object of the most violent desire becomes indifferent, and sometimes even excites a slight feeling of disgust, at least as regards certain odors, sometimes even regarding touch and sight. The name sexual appetite (libido sexualis) is given to the passionate and purely sexual desire of the two sexes for each other. It varies greatly in different individuals.
According to Ferdy and other authors, the neck of the womb, during the venereal orgasm of the woman, executes movements of suction in the glans penis. I do not know if this is a fact, but it is certain that the female orgasm is useless for conception. Absolutely cold women, incapable of the least voluptuous sensation are as fruitful as those who have pronounced venereal orgasms. It proves that the spermatozoa arrive at their goal even when the womb is entirely passive. The great variation of sexual desire in different individuals renders mutual adaptation often very difficult. The venereal orgasm is sometimes more rapid in man, sometimes in woman (more rarely in the latter). This inequality is rather to the detriment of the woman, for the man can still satisfy himself when the orgasm of the woman has terminated, while the contrary is not possible without artificial manipulation. Moreover, the frequence and intensity of the sexual appetite are often much greater in one than in the other, which is detrimental to both. Here again it is the woman who suffers the most, for the man can always satisfy himself without the woman having voluptuous sensations. What is commonly called good manners generally prevents the conjoints from speaking of their sexual desires before marriage. This very often results in grave deceptions, dissensions, and often even divorce. I shall return to this subject in Chapter XIV.
Voluptuous sensations only represent the means employed by nature to bring together the sexes with the object of reproducing the species. A woman can be fecundated and give birth to a child by the aid of semen injected into the uterus by a syringe. Moreover, it is rather exceptional for the venereal orgasm to occur in the two sexes at the same moment. It is essential for fecundation that the semen should enter the womb. When the spermatozoa have reached the neighborhood of the neck of the womb they swim by their own movements, not only along the whole uterine cavity, but also along the Fallopian tubes and even in the abdominal cavity, so that the force of ejaculation is of little importance.
Pregnancy.—The womb enlarges considerably during pregnancy. It exceeds the size of an adult head, and the muscles of its walls are greatly increased, so as to be capable of expelling the child later on.
The phenomena of pregnancy, birth and suckling are known to all, so that I shall be brief. The almost sudden activity of the breasts after childbirth is a very interesting correlative phenomenon. It suffices to glance at one who has just become a mother and to observe the complications which profoundly influence all her organism with regard to the life of the infant, to comprehend to what extent the role of sexual life is more important, more profound, even more vital, in woman than in man. The latter no doubt requires a more violent appetite to urge him to copulation because he plays the active part, short though it be. But fecundating coitus having been effected, his contribution to the reproduction of the species is ended.
While the activity of man is terminated at conception, that of woman only begins at this moment. In the first chapter we have indicated in a few words the transformations of the human embryo up to its birth. During nine months it grows from the size of a pin's head (the ovule) to that of the new-born child. Although a woman seldom bears more than one embryo at the same time, twins being rare on the whole, she has nevertheless more pain and fatigue to bear than any female animal. This is due not only to the fact that our artificial and alcoholized civilization, with its specialized labor which disturbs vital equilibrium, has made women indolent and degenerate, but also to the enormous development of the human brain. The head of the human embryo is disproportionately large because the brain, as I showed with Schiller in 1889, already contains at birth all the nerve elements which it will possess during the rest of its life (Comptes rendus de l'Académie des Sciences). No doubt these elements are small and embryonic but the nerve fibers are ready to be covered with myelin and to enter upon their functions, and all this requires a cranium of considerable size. But it is not everything for the mother to nourish with her blood the brain and the cranium of the child; it is also necessary for this relatively large head to pass through the pelvis at the time of childbirth, and we know that this moment is the most dangerous for the life of the pregnant woman. As boys have on the average a larger brain and cranium than those of girls, their birth is usually more difficult.
Accouchement.—The sexual organs of woman undergo great changes in order to render childbirth possible. These organs become larger and more vascular, especially the womb, the growth of which is astonishing. Originally the size of a small egg (a guinea fowl's) it exceeds the size of a human head, and there is an enormous increase of muscular tissue in its walls. Large blood vessels develop in the uterine wall, especially in the placenta (Figs. 22 and 23), where they enter into endosmotic relations with the circulation of the embryo.
From the abdomen of the embryo arises an organ, the allantois, which is destined to carry the blood-vessels of the embryo to the placenta, and at the same time to give rise to the formation of the latter. In the placenta the blood-vessels of the embryo are separated from those of the mother by walls so thin that the nutritive juices of the maternal blood transude into the venous blood of the embryo, as well as combined oxygen in the blood necessary for its respiration. Up to this point the vitellus of the egg, nourished by endosmosis through its membranes, had sufficed for the nutrition of the still very small embryo. While these phenomena are taking place, and while the substance of the two conjugated germs divides into an ever increasing number of cells, which become differentiated in layers to form the future organs (Fig. 21), while certain groups of cells are prepared some to form the intestinal canal, others the muscles and blood vessels, others the skin and organs of sense, others arising from the last to form the brain, the spinal cord and the nerves, the mother can still live her ordinary life. She suffers, however, from different disorders connected with what is passing on in her body.
It is a curious fact that these disorders are more accentuated at the commencement of pregnancy, when the womb is hardly enlarged, than at the end. They consist chiefly of nervous troubles—slight derangement of the cerebral functions and sensations, etc. Obstinate vomiting, peculiar desires, and changes of temper are some of the most frequent troubles of pregnant women, and probably arise more from local nervous irritation than from general transformations of the nutrition of the body. The mother's body is becoming adapted to the development of the infant in the womb. However embarrassed a woman may be in the last months of pregnancy by the great swelling of the belly (Fig. 22) the disorders are less accentuated than at the beginning of pregnancy.
During pregnancy menstruation ceases. The sexual appetite is very variable; in many pregnant women it is diminished, in others there is no change, and it is seldom increased. There are other troubles which are more or less frequent, such as varicose veins in the legs caused by pressure of the uterus on the veins.