The nature of sexual tension is still entirely unknown. Freud assumes, in view of the recently recognized significance of the thyroid glands in relation to sexuality, that possibly some substance generally diffused throughout the organism is produced by stimulation of the erogenic zones, that the products of decomposition of this substance exercise a specific stimulus on the reproductive organs, or on the associated sexual centre in the spinal cord. For example, such a transformation of a toxic, chemical stimulus into a special organ-stimulus is known to occur in the case of certain foreign poisonous materials introduced into the body. Freud considers that the probability of this chemical theory of sexual excitement is increased by the fact that the neuroses referable to disturbances of the sexual life possess a great clinical similarity to the phenomena of intoxication induced by the habitual employment of aphrodisiac poisons (certain alkaloids).
The relief of sexual tension occurs in the natural way in the sexual act, in the completion of normal intercourse between man and woman. Notwithstanding the numerous observations of leading natural philosophers and physicians concerning the act of sexual congress, among which I need only refer to those of Magendie, Johannes Müller, Marshall Hall, Kobelt, Busch, Deslandes, Roubaud, Landois, Theopold, Burdach, and many others, we possess, for reasons it is easy to understand, no really exact investigations regarding the different phenomena occurring during the sexual act. More particularly, the demeanour of the woman during this act is a matter which remains extremely obscure.
The French physician Roubaud has given us the most vivid description of sexual intercourse:
“As soon as the penis enters the vaginal vestibule, it first of all pushes against the glans clitoridis, which is situated at the entrance of the genital canal, and owing to its length and to the way in which it is bent, can give way and bend further before the penis. After this preliminary stimulation of the two chief centres of sexual sensibility, the glans penis glides over the inner surfaces of the two vaginal bulbs; the collum and the body of the penis are then grasped between the projecting surfaces of the vaginal bulbs, but the glans penis itself, which has passed further onward, is in contact with the fine and delicate surface of the vaginal mucous membrane, which membrane itself, owing to the presence of erectile tissue between the layers, is now in an elastic, resilient condition. This elasticity, which enables the vagina to adapt itself to the size of the penis, increases at once the turgescence and the sensibility of the clitoris, inasmuch as the blood that is driven out of the vessels of the vaginal wall passes thence to those of the vaginal bulbs and the clitoris. On the other hand, the turgescence and the sensitiveness of the glans penis itself are heightened by compression of that organ, in consequence of the ever-increasing fulness of the vessels of the vaginal mucous membrane and the two vaginal bulbs.
“At the same time, the clitoris is pressed downwards by the anterior portion of the compressor muscle, so that it is brought into contact with the dorsal surface of the glans and of the body of the penis. In this way a reciprocal friction between these two organs takes place, repeated at each copulatory movement made by the two parties to the act, until at length the voluptuous sensation rises to its highest intensity, and culminates in the sexual orgasm, marked in the male by the ejaculation of the seminal fluid, and in the female by the aspiration of that fluid into the gaping external orifice of the cervical canal.
“When we take into consideration the influence which temperament, constitution, and a number of other special and general circumstances are capable of exercising on the intensity of sexual sensation, it may well be doubted if the problem regarding the differences in voluptuous sensation between the male and the female is anywhere near solution; indeed, we may go further, and feel convinced that this problem, in view of all the difficulties that surround it, is really insoluble. So true is this, that it is a difficult matter to give a picture at once accurate and complete of the phenomena attending the normal act of copulation. Whilst in one individual the sense of sexual pleasure amounts to no more than a barely perceptible titillation, in another that sense reaches the acme of both mental and physical exaltation.
“Between these two extremes we meet with innumerable states of transition. In cases of intense exaltation various pathological symptoms make themselves manifest, such as quickening of the general circulation and violent pulsation of the arteries; the venous blood, being retained in the larger vessels by general muscular contractions, leads to an increased warmth of the body; and, further, this venous stagnation, which is still more marked in the brain in consequence of the contraction of the cervical muscles and the backward flexion of the neck, may cause cerebral congestion, during which consciousness and all mental manifestations are momentarily in abeyance. The eyes, reddened by injection of the conjunctiva, become fixed, and the expression becomes vacant; the lids close convulsively, to exclude the light. In some the breathing becomes panting and labouring; but in others it is temporarily suspended, in consequence of laryngeal spasm, and the air, after being pent up for a time in the lungs, is finally forcibly expelled, accompanied by the utterance of incoherent and incomprehensible words.
“The impulses proceeding from the congested nerve centres are confused. There is an indescribable disorder both of motion and of sensation; the extremities are affected with convulsive twitchings, and may be either moved in various directions or extended straight and stiff; the jaws are pressed together so that the teeth grind against each other; and certain individuals are affected by erotic delirium to such an extent that they will seize the unguarded shoulder, for instance, of their partner in the sexual act, and bite it till the blood flows.
“This delirious frenzy is usually of short duration, but sufficiently long to exhaust the forces of the organism, especially in the male, in whom the condition of hyperexcitability is terminated by a more or less abundant loss of semen.
“A period of exhaustion follows, which is the more intense in proportion to the intensity of the preceding excitement. The sudden fatigue, the general sense of weakness, and the inclination to sleep, which habitually affect the male after the act of intercourse, are in part to be ascribed to the loss of semen; for in the female, however energetic the part she may have played in the sexual act, a mere transient fatigue is observed, much less in degree than that which affects the male, and permitting far sooner of a repetition of the act. ‘Triste est omne animal post coitum, præter mulierem gallumque,’ wrote Galen, and the axiom is essentially true—at any rate, so far as the human species is concerned.”