to our mind, that is,
to the activity of our cerebral hemispheres, but it is produced there
by a secondary irradiation from the sexual appetite, which alone
concerns us at present. We may also remark that sexual ideas when once
awakened in the cerebral hemispheres by sexual appetite, are worked up
there by the attention, that is to say by concentrated cerebral
activity, then associated with other ideas, which on their side react
strongly on the sexual appetite, developing or paralyzing it,
attracting or repelling it, or finally transforming its attributes and
objects.

By sexual desire (libido sexualis) we mean the manner in which the
sexual appetite manifests itself in man. Each term may be employed for
the other.

=The Sexual Appetite in Man.=--Man represents the active element in
sexual union, and in him the sexual appetite, or desire for coitus, is
at first the stronger. This desire develops spontaneously, and the
role of fecundator represents the principal male activity. This
appetite powerfully affects the male mind, although sexual life plays
a less important part in him than in the female.

In boys, the sexual appetite is often prematurely awakened, excited in
unnatural ways by bad example. Moreover, it varies enormously in
different individuals, a point to which we shall return when dealing
with pathology. Leaving aside unnatural appetites and abnormal forms
of sexual instinct we shall describe here its most spontaneous and
normal form.

=Puberty. Awakening of the Sexual Instinct in Boys.=--Sooner or later
in different individuals, the boy pays attention to his erections,
which are at first produced in a reflex and involuntary manner.
Mental development and reflection, so precocious in man, are causes
which draw attention to the differences of the sexes before the sexual
appetite is developed. It is, however, the first signs of this
appetite which concentrate the attention on these differences, for in
their absence, the boy is more indifferent to them than to the
straight or crooked form of a nose. Man has the habit of passing by
without notice anything which does not interest him, and this is why
we find, in individuals whose sexual appetite is developed late or
feebly, an indifference and ignorance in these matters which appear
almost incredible to those whose sexual appetite is precocious and
violent; while, on the contrary, the lively interest which the latter
show in everything concerning the sexes