The sexual question

by Auguste Forel

In man, sexual differentiation has led to the formation of two kinds of individuals, differing little in their correlative attributes, but each bearing one kind of germinal cells. In sexual union man plays the active part, woman, the passive. When sexual activity, in the animal kingdom, is no longer limited to the movement of one of the cells but requires the displacement of the whole individual, we can quite understand that the organization of these individuals must become much more complex, and that it requires a central nervous system as a directing apparatus. Sexual individuality thus involves collaboration of the other organs of the body, and especially that of the central organs for reflex movements, the instincts and the higher mental faculties of man, in the accomplishment of the fecundating act those which are the consequences of it.

From this simple animal origin is evolved the complex sexual love of man. The duty of the active or male individual is to bring the spermatozoa to a point where they can easily reach the female cells or ovules. When this is done the duty of the male is accomplished. In the passive or female individual of the higher animals, pairing and conjugation are only the commencement of reproductive activity. However, this is not the case in the whole animal kingdom. For instance, fish have distinct sexes, but in them the female deposits her non-fecundated eggs in the water and is not concerned with them any further. The male then arrives and discharges his sperm on the eggs. In this case fecundation takes place without copulation. With such a system sexual love and maternal love lose their raison d'être, for the young fish are capable of providing for themselves as soon as they are born. There are, however, a few exceptions, one of the most curious being that of certain fish of the Dead Sea, in which the male incubates the eggs by taking them into his buccal cavity.

Reproduction in Vertebrates.—We should never finish if we were to describe even the chief varieties of sexual union among the vertebrates. As a rule, the male possesses a copulating organ which projects externally, while the female presents an invaginated cavity, more or less cylindrical, into which the male organ can penetrate. A certain amount of sperm is deposited by the male in the neighborhood of the mature ovules (Fig. 18) discharged from the female germinal gland or ovary, which renders conjugation possible. By means of their mobile tails, the spermatozoa (Fig. 11) are able to reach the ovules and fecundate them. The manner in which the egg when fecundated, either in the mother's body or after being laid, continues its development, varies enormously in different species. The eggs are often deposited by the female and the embryo develops outside the mother's body. This occurs in insects, mollusks, fish, amphibia, reptiles, birds and the lowest mammals or monotremes (ornithorhynchus and echidna).

In the lower mammals is developed an organ called the womb which allows the embryo to remain longer in the maternal body. This organ is very incomplete in them, and a pocket or fold in the skin of the belly allows the mother to carry her young, which are extremely embryonic at birth, till they have developed sufficiently to live alone. This occurs in marsupials (kangaroos and opossums), in which the vagina and uterus are double.

In the higher mammals the womb becomes more and more developed, opening into a single vagina in the middle line of the abdomen, between the two ovaries, and constituting a highly specialized organ which allows the mother to preserve the young for a long time in her belly. In most mammals the uterus has two elongated diverticula, each of which may contain a successive series of embryos. In man it forms a single cavity and normally contains a single embryo, occasionally two or more. These facts show that the role of the female mammal in reproduction is more important than that of the male. But this is not all. Whether it still lays eggs, or whether it gives birth to young which are more or less developed its sexual role is far from ended. The higher oviparous vertebrates, especially the birds, take care of their progeniture for some time after laying. The young are still fed by the mother, either by milk from the teats, as in mammals, or by nourishment obtained from outside, as in birds, or by both methods combined or succeeding each other, as in cats.

In many animals the male contributes to the raising of the young; a point to which we shall return. Here, we indicate these complicated details simply to show that sexual union only contributes one link in the long chain of reproduction. Let us study its mechanism in man.

The Copulatory Organ of Man. The Testicles. The Seminal Vesicles.—Nature is often very sparing even in the highest organizations. It has thus combined in the male the urethra with the copulatory organ, and the sexual germinal glands, or testicles, with an accessory gland, the epididymis. Hundreds of thousands of spermatozoa are contained in the glandular tubes of these organs, which, when they are mature can always produce new ones by cell division. The spermatozoa accumulate at the extremity of the duct of the gland in a reservoir called the seminal vesicle, where they float in the mucus, thus constituting the seminal fluid or sperm. This liquid has a special odor. The two seminal vesicles are situated in the abdominal cavity underneath the urinary bladder, each having a duct which meets that of the other side and opens by the side of it in the deep part of the urethra. Here the secretion of several other glands, especially of the prostate, is added to the sperm and mixes with it. The point where the two seminal ducts open into the urethra forms a small elevation, the verumontanum. From this point the male urethra emerges from the abdominal cavity and is continued along the special prolongation which forms the penis, or virile member of copulation. In the ordinary way the penis only serves for the emission of urine. It hangs flaccid and terminates in a rounded swelling called the glans, at the end of which opens the urethra (Fig. 18). This opening serves also for the emission of the sperm.

Erection. The Corpus Cavernosum.—The most curious part of this apparatus is the mechanism of erection, or the power possessed by the penis of swelling under the influence of certain nervous irritations, increasing in length and diameter as well as becoming rigid. This phenomenon is produced by three organs called the cavernous bodies which form the principal bulk of the penis. One of them, situated in the middle and underneath and formed by two bodies united into one, surrounds the urethra and terminates in front in a dilatation which constitutes the glans already mentioned. The two others are situated symmetrically on the dorsal part of the penis. All three consist of caverns or diverticula formed by blood-vessels, which are empty when the penis is flaccid. By a complex nervous mechanism based on vascular paralysis due to nervous phenomena called inhibition and dynamogeny, the nervous irritations cause an accumulation of blood in the spaces of the cavernous bodies which become so gorged with blood as to form stiff and hard rods. The size of the penis is thereby increased considerably and its stiffness allows it to penetrate the vagina of the female. At the same time and by the same mechanism the verumontanum swells so as to close the ureter from the bladder, while the seminal ducts open toward the urethral orifice. In this way the copulatory organ is ready for its function.

Repeated irritations are however necessary to provoke the ejaculation of semen. This is finally produced by excitation of a special muscle which compresses the seminal vesicles in a spasmodic manner and ejaculates the semen by the urethra. After ejaculation, the accumulation of blood in the cavernous bodies gradually diminishes and the penis again becomes flaccid.

This apparatus is thus very complicated and is put in action by several nervous irritations which may be disturbed in many ways in affections of the nervous system. We may observe here that the nervous centers of erection and ejaculation may be put in action directly by the brain, or indirectly by peripheral irritation of the glans.