is
testes is due to two reasons. First, the male sex hormones have not
the instability nor cyclic rhythmicity of the female. Secondly, and
perhaps consequently, his sex instincts have become overlayered with
other more labile instincts, with habits and customs and necessities
that appear to oust the sex instinct into an altogether decentralized
position. Moreover, it is the function of the female to be the excitor
in the sex process: her subconscious, thoroughly aware of the fact,
sees to it that the sex instinct stands starkly central and dominating
in her life.

The moods of love, like the more stereotyped manifestations of sex,
are dependent upon a proper supply to the blood of the internal
secretions of the reproductive organs, the gonadal endocrines. If the
testes are removed from frogs, it is found that the clasp-reflex,
symptom of sex desire, is abolished. If, after an interval of several
days, the testes' extract is injected into the frog, the reflex
reappears for a few days. The hormone provoking this sex reflex is
present in the testes only during the breeding season. In birds,
the seasonal nesting and migrating instincts may be eliminated by
interfering with their ovaries. At the same tine there is a change in
their plumage toward the male type. Similarly, the males, when their
sex endocrines are cut off, will change their psychic nature as well
as physically. Besides owning his flag-waving comb, his spurs and
brighter feathers, the rooster struts to attract the female, and
fights aggressively with his sex competitors. When he is made a capon,
he loses his spurs and comb and distinctive plumage, and in addition
becomes retiring and submissive, in short, a pseudo-hen in his
instincts as well as in appearance. If the genital glands are
extirpated from a male before puberty, the wattles remain small, pale
and bloodless, no active, amorous or combative instinct emerges. The
creature maintains a demure silence, and may even be sought by a
virile male. So we may see homosexuality of a kind in the lowest
animals. On the other hand, hens deprived of ovaries tend to
metamorphose in the male direction, even to acquire the male spurs,
and to display the male attitudes.

All through the animal world, in the springtime, when the pituitary
awakens or increases its secretion, and so stimulates the sex glands
to augmented activity, emotions of sex and their expression are
provoked by the inner stirring. When the nightinga