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 appears foolish and absurd to the sexually indifferent.
The pairing of animals, even of insects, awakens a curious interest in those whose sexual dispositions are strong and precocious; they comprehend very quickly the reason and are led to draw analogies with their own sensations in the same domain. The aspect of the female sex has, however, a much stronger action still on the normal man. But here is produced a peculiar phenomenon. What especially excites the boy in the aspect of the female sex is anything unusual; the sight of certain parts of the skin which are normally covered, the clothes or ornaments, particular odors, women whom the boy is not accustomed to see, etc. It is for this reason that brothers and sisters do not excite, or excite very little, their reciprocal sexual appetite, at least if there are no anomalies or exceptional exhibitions. The sexual appetites of boys among savage peoples who live naked is hardly at all excited by naked girls; on the other hand, it is strongly excited by those who are clothed or ornamented in a peculiar manner. The sexual appetite of a Mahometan is strongly excited by the nudity of the feminine face, that of the European by that of a woman's legs, because women are accustomed to veil their faces in the first case and their legs in the second. These are naturally only relative differences. When the sexual appetite of man is violent and unsatisfied woman excites it in a general way, if she is not too old or repulsive.
A second important character of the normal sexual appetite is the special attraction that appearances of health and strength in woman produce in man. Healthy forms, normal odors, a normal voice, a skin healthy in appearance and to the touch, constitute attractions which charm and excite man, while all that is unhealthy or faded, every pathological odor, produce a repulsive effect and hinders or diminishes sexual desire.
Everything connected with the sexual organs, their appearance, touch and odor, tend to excite the sexual appetite, all the more when they are usually covered; it is the same with the breasts.
The first sexual sensations are of a quite indeterminate nature; something unconscious and obscure inclines the boy toward the female sex and makes it appear desirable. A boy may thus become enamored of the portrait of a woman with a swelling bosom and alluring eyes and be seized with desire, either at their sight or only on remembrance. This desire is not concentrated especially on the sexual act, as with an adult who is already experienced in these matters; it is more generalized and vague, although sensual.
For a long time, these repeated aspirations, impulses and desires, remain unsatisfied. In different individuals the imagination associates the most diverse images with such manifestations of the sexual appetite. The objects of the latter appear in dreams and provoke nocturnal erections. The boy soon remarks a sensory localization of his appetites in his sexual organs, especially in the glans penis, but also in the surrounding parts, and the known or only vaguely defined image of the female sexual organs, which is hardly present at the first appearance of his desires, begin to excite him more and more.
In natural or savage man, as well as in animals, the boy then makes attempts at coitus and soon attains his object, for, in the state of nature, man marries as soon as puberty is attained.