n the seminal vesicles strongly excites the
sexual appetite of man, and he is momentarily satisfied by their
evacuation. But we shall soon see that this purely organic or
mechanical excitation, which seems at first to be only adapted for
natural wants, does not in man play the principal role. We can easily
understand that it cannot be the principal moving power of the sexual
act. In fact, for any of the animals in which copulation occurs, the
possibility of accomplishing this is not connected solely with the
accumulation of semen, for it depends on obtaining a female. It is
necessary, therefore, for the accumulated semen to wait, and for the
perception of the female by the aid of the senses to excite the male
to coitus.

=External Signs of the Sexual Appetite.=--Like every other desire the
sexual appetite betrays itself by the physionomy. This consists in the
play of cerebral activity, that is the thoughts, sentiments and
resolutions, on the muscles by means of motor nerves and nerve
centers. It is not limited to the face but extends to the whole body.
The abdomen, the hands and even the feet have their physionomy; that
of the muscles of the face and eyes is, however, the most active and
most expressive. Sexual desire betrays itself in looks, by the
expression of the face and by certain movements in the presence of the
female sex. Men differ greatly in the way in which they betray or hide
their sentiments and thoughts by the play of their muscles, so that
the inner self is not always reflected without. Moreover, the
expression of sexual desire by the play of the physionomy may be
confounded with that of other sentiments, so that one who appears
libidinous is not always so in reality, and inversely.

=Continence in Man.=--Abstinence or sexual continence is by no means
impracticable for a normal young man of average constitution,
assiduous in intellectual and physical work, abstaining from all
artificial excitations, especially from all narcotics and alcohol in
particular, for these substances paralyze the judgment and will. When
sexual maturity is complete, that is after about twenty years,
continence is usually facilitated by nocturnal emissions accompanied
by corresponding dreams. The health does not suffer from these in any
way. However, in the long run this state cannot be considered as
normal, especially when there is no hope of it coming to an end in a
reasonable time. What is much more abnormal are the numerous