become largely a question of physiological chemistry. The chief parts in
the drama of sex, alike on its psychic as on its physical sides, are thus
supposed to be played by two mysterious protagonists, the hormones, or
internal secretions, of the testes and of the ovary. Even the part played
by the brain is now often regarded as chemical, the brain being considered
to be a great chemical laboratory. There is a tendency, moreover, to
extend the sexual sphere so as to admit the influence of internal
secretions from other glands. The thymus, the adrenals, the thyroid, the
pituitary, even the kidneys: it is possible that internal secretions from
all these glands may combine to fill in the complete picture of sexuality
as we know it in men and women.[16] The subject is, however, so complex
and at present so little known that it would be hazardous, and for the
present purpose it is needless, to attempt to set forth any conclusions.

It is sufficiently clear that there is on the surface a striking analogy
between sexual desire and the impulse to evacuate an excretion, and that
this analogy is not only seen in the frog, but extends also to the highest
vertebrates. It is quite another matter, however, to assert that the
sexual impulse can be adequately defined as an impulse to evacuate. To
show fully the inadequate nature of this conception would require a
detailed consideration of the facts of sexual life. That is, however,
unnecessary. It is enough to point out certain considerations which alone
suffice to invalidate this view. In the first place, it must be remarked
that the trifling amount of fluid emitted in sexual intercourse is
altogether out of proportion to the emotions aroused by the act and to its
after-effect on the organism; the ancient dictum _omne animal post coitum
triste_ may not be exact, but it is certain that the effect of coitus on
the organism is far more profound than that produced by the far more
extensive evacuation of the bladder or bowels. Again, this definition
leaves unexplained all those elaborate preliminaries which, both in man