f
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'Academie 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.