s, in
which event the sexual excitement culminates in the orgasm of the
male, which empties the secreted semen into the organs of the female.

It will be easily understood that, in human subjects whose social
relations permit them to indulge in coitus, close physical proximity,
and various caresses lead, step by step in the normal course of nature
to sexual excitement and sexual desire which culminates as described
above for the lower animals.

To revert to the function of the testes, we may say that during these
various stages of sexual stimulation and excitement the testes are
actively secreting thousands upon thousands of nascent spermatozoa,
which being released, are hurried along, partly by their own
flagellate movements and partly by the action of the cilia in the
ducts of the epididymis and the peristaltic contractions of the vas
deferens--hurried along the vas to the ampulla. If the period of
sexual excitement extends over fifteen to thirty minutes, the whole
duct system from the epididymis to the ampulla becomes gorged with the
secreted testicular product. This secretion consists of active motile
spermatozoa, of spermatic granules and of mucus. The latter is
secreted by the ducts of the epididymis and the vas deferens, the
testicle itself furnishing only spermatozoa, spermatic granules and a
small amount of liquid, just sufficient in quantity to float the
spermatozoa out of the testes into the ducts.

At the moment of sexual orgasm occurs what is known as, the emission
of semen. In this act the whole contents of the ampulla, vas deferens
and ducts of the epididymis, the contents of the seminal vesicles, and
the contents of the ducts of the prostate gland are all poured out by
spasmotic muscular contractions into the urethra and by contraction of
the walls of the urethra, ejected from that tube through the mouth of
the urethra. Thus, in the act of emission, there is an intimate mixing
together of the three contributions to the semen, i.e., the
_testicular, vesicular and prostatic_.

_Sub-conscious Sexual Stimulation._--Sub-conscious sexual stimulation
is not accompanied by erection or any mental or physical manifestation
of sexual excitement.

When a sexually mature individual is brought into more or less
intimate relations with a sexually mature individual of the opposite
sex under conditions where the secondary sexual qualities may have
free and unrestricted play, there can be no reasonable doubt that
b