, the
crystallizations of love elaborated, and, to a large extent, the
individual erotic symbols determined. But we can by no means altogether
pass over the final phase of detumescence. Its consideration, it is true,
brings us directly into the field of anatomy and physiology; while
tumescence is largely under control of the will, when the moment of
detumescence arrives the reins slip from the control of the will; the more
fundamental and uncontrollable impulses of the organism gallop on
unchecked; the chariot of Phaethon dashes blindly down into a sea of
emotion.

Yet detumescence is the end and climax of the whole drama; it is an
anatomico-physiological process, certainly, but one that inevitably
touches psychology at every point.[73] It is, indeed, the very key to the
process of tumescence, and unless we understand and realize very precisely
what it is that happens during detumescence, our psychological analysis of
the sexual impulse must remain vague and inadequate.

From the point of view we now occupy, a man and a woman are no longer two
highly sensitive organisms vibrating, voluptuously it may indeed be, but
vaguely and indefinitely, to all kinds of influences and with fluctuating
impulses capable of being directed into any channel, even in the highest
degree divergent from the proper ends of procreation. They are now two
genital organisms who exist to propagate the race, and whatever else they
may be, they must be adequately constituted to effect the act by which the
future of the race is ensured. We have to consider what are the material
conditions which ensure the most satisfactory and complete fulfillment of
this act, and how those conditions may be correlated with other
circumstances in the organism. In thus approaching the subject we shall
find that we have not really abandoned the study of the psychic aspects of
sex.

The two most primary sexual organs are the testis and the ovary; it is the
object of conjugation to bring into contact the sperm from the testis with
the germ from the ovary. There is no reason to suppose that the germ-cell
and the sperm-cell are essentially different from each other. Sexual
conjugation thus remains a process which is radically the same as the
non-sexual mode of propagation which preceded it. The fusion of the nuclei
of the two cells was regarded by Van Beneden, who in 1875 first accurately
described it, as a process of conjugation comparable to that of the
protozoa and th