Love: A Treatise on the Science of Sex-attraction / for the use of Physicians and Students of Medical Jurisprudence

PART III.
ANATOMY

CHAPTER III
THE MALE GENITALS

The knowledge of the anatomy of the genitals, of the mechanism of erection and ejaculation, and the nervous centres which preside over these functions, is essential for a clear comprehension of sex-attraction in men and in women. It will, therefore, be of some profit even to medical men briefly to recall to memory those parts of the human anatomy which have a particular bearing upon the subject of this treatise.

Scrotum.—The main generative glands in the male, the testicles, are situated within a bag, the so-called scrotum, outside of the abdominal cavity. This bag or pouch, hanging between the thighs, below the symphysis, consists of two compartments which are separated by the septum scroti. The scrotum may be considered as a diverticle of the anterior abdominal wall. Before the descent of the testicles from the abdominal cavity, two diverticles of the abdominal wall are formed, at two points anteriorly to the genital swelling, where later on the inguinal canals are found. The diverticles extend to the swelling and coalesce to form the bag. The raphe, or last, at the point of their union, can be observed through the entire life of the individual. This median raphe runs from the perineum to the penis, indicating the inner division of the scrotum.

The scrotum being a derivative of the abdominal wall, it follows that its wall will consist of the same elements as the abdominal wall. The first layer of the abdominal wall, the epidermis or cutis, forms also the epidermis of the scrotum. The fascia superficialis abdominis constitutes the second layer of the scrotum, or the tunica dartos. The musculus obliquus abdominis externus goes to make up the third layer, the so-called Cooper’s fascia. The musculus obliquus abdominis internus forms the fourth layer, or the musculus cremaster externus. The musculus transversalis abdominis furnishes the cremaster internus muscle, and the tunica vaginalis communis, or the fifth layer. Finally, the double layer of the abdominal peritoneum forms the tunica vaginalis propria of the scrotum. Between the two lamina of this tunica is found some fluid which, when pathologically increased, constitutes the anomaly called hydrocele.

Testicle.—The testicle is an ovoid organ with two surfaces, a median and lateral, with two poles, an upper and lower pole, and two margins, an anterior convex and a posterior straight margin. In the natural position, the upper pole is somewhat anteriorly inclined. The average weight of the testicle is 15 to 25 grammes, average length 5 centimeters, breadth 2 to 5 centimeters and thickness 3 centimeters. The superior pole and the posterior margin of the testicle are covered by the epididymis. The left testicle, as a rule, hangs deeper than the right.

Descent of testicles.—In embryonic life already, the testicle is connected, at its lower pole, with the bottom of the scrotal diverticle, the latter ventricle of the scrotum, by a cord containing unstriped muscular fibres, the so-called gubernaculum testis. This cord does not grow in length, hence, with the growth of the embryo, the testicle has to descend from its position, on either side of the mesentary along the spinal column. Thus, in the seventh month of embryonic life, each testicle descends through its respective inguinal canal into its compartment in the scrotum. In this descent the testicle takes along its peritoneal covering. When the bottom of the scrotum has been reached this peritoneal covering, together with the lining of the scrotum coalesce, and the two lamina form the above-mentioned tunica vaginalis propria.

Structure of testicles.—The testicle is covered with a thick, white, fibrous coat, the tunica albuginea. This tunica sends off about 200 to 400 septa or trabeculae testis. These trabeculae divide the parenchymatous tissue of the testicle into numerous conical lobules, and, converging towards the posterior margin of the testicle, form a solid fibrous mass, the so-called corpus Highmori.

The parenchymatous tissue of the testicles consists of numerous fine tubules, the canaliculi seminiferi. Each lobule contains a number of these fine tubules. In the beginning and through their entire course the seminal tubules or canaliculi are tortuous; towards their ends, however, they become straight. When they reach the corpus Highmori, the thickened, enlarged part of the tunica albuginea, they collect and unite, to form a network, the rete vasculosum. This rete sends off 12 to 14 large tubules, the vasa efferentia, which, running in a straight line, pass the corpus Highmori and enter the epididymis. The corpus Highmori serves as a point of entrance for the arteries and nerves and as an exit for the veins of the testicles.

Epididymis.—The epididymis is the excretory duct of the testicle. It is situated at the posterior margin of the same, covering this margin and the upper pole of the testicle. The upper end of the epididymis tapers off to pass into the vas deferens. The epididymis is divided into the head, middle piece and tail. At the lower point, the tail turns directly upwards and backwards, and is now called vas deferens. The vasa efferentia enter the epididymis at the head. The unfolded vas epididymis is about six meters long. Its diameter is about 0.5 millimeter. It gradually dilates as it approaches the vas deferens.

Vas deferens.—The vas deferens runs down the posterior wall of the epididymis and turns upwards to enter the abdominal cavity through the inguinal canal. It then runs between bladder and rectum to end as the ductus ejaculatorius. Before the vas deferens receives the duct of the seminal vesicle it forms a spindle-like enlargement, the so-called ampulla. The vas deferens opens under the name of ductus ejaculatorius into the prostatic urethra.

The length of the vas deferens is about 60 centimeters, its diameter is about 3 millimeters. The wall of the vas deferens is very thick, giving on palpation the feeling of a piece of rope. It is lined inside with a light cylindrical epithelium which rests upon a layer of fibrous connective tissue. This fibrous substratum is surrounded by a thick, muscular coat of non-striated fibres. The muscular coat is composed of two longitudinal layers, which include between them a circular layer. The muscular coat is surrounded by a layer of connective tissue, the so-called adventitia.

Spermatic cord.—In its course from the testicle to the internal ring of the inguinal canal the vas deferens is accompanied by the arteria and vena spermaticae internae. The three organs form the spermatic cord. But although the three organs are intimately connected, still the vas deferens is recognizable without difficulty by its rope-like consistency and is easily severed, as in the operation for the sterilization of the male. The vein forms a tendril-like tress-work, which is called the plexus pampiniformis. In pathological conditions the plexus forms the varicocele.

Seminal vesicles.—The seminal vesicles may be considered as diverticles of the vasa deferentia. The vesicles are lying in the sulcus, between the prostate and the bladder, and extend obliquely outward and backward. The length of the seminal vesicles is about 8 centimeters, their diameter is about 7 millimeters. The vesicles form a bulbous mass of convoluted tubes. Being a derivative from the vas deferens, the wall of the tubes consists of the same strata as the vas deferens, i. e., of an adventitia followed by the muscular coat, then by the fibrous substratum, and finally by a layer of cylindrical epithelia. The mucous membrane possesses numerous tubulous glands. In this way the vesicles serve not only as reservoirs for the sperma, but may be considered as veritable glands. By the junction of the pointed ends of the seminal vesicles with the vasa deferentia, the ejaculatory ducts are formed.

Ductus ejaculatorii.—The ejaculatory ducts traverse the prostate and open, by slit-like orifices, into the sinus pocularis. The wall of the ducts is much thinner than that of the vas deferens. The muscular fibres of the latter are gradually substituted in the ducts by cavernous tissue. The mucous membrane differs little from that of the vas deferens and of the seminal vesicles.

Urethra.—The urethra is divided into three parts, the prostatic, the membranous and the cavernous parts. The prostatic part is the widest portion of the entire urethra. It is surrounded by an unstriped muscular layer and the muscles of the prostate. The membranous part is the narrowest, shortest, and most thin-walled portion of the three parts of the urethra. It is entirely surrounded by the muscular fibres of the diaphragma urogenitale, which takes here a circulatory course. It is in this way situated on the border-line of the abdominal cavity and the exterior, within the abdominal wall. The cavernous portion of the urethra is surrounded by the corpus cavernosum urethrae. This portion shows two dilatations, one in the bulbous part, just anterior to the termination of the membranous part, where the ducts of the two Cowper’s glands open; the other dilatation is near the end, behind the meatus, forming the so-called fossa navicularis. The meatus itself is the narrowest part of the entire urethra. Numerous mucous crypts, the glands of Littré and certain lacunae, the largest among them near the fossa, open into the lumen of this part of the urethra. The entire urethra is lined with a cylindrical epithelium, except at the fossa navicularis. The latter is covered by a layer of pavement epithelia. The length of the urethra is about 18 centimeters. In the usual state the urethra possesses only a virtual lumen, i. e., the walls touch each other.

Prostate.—The prostate is a gland, chestnut-like in shape. Its greatest diameter is in average about 4 centimeters. The diameter from the base to the apex is about 3 centimeters. The thickness of the prostate is about 2 centimeters, and its weight is about 18 grammes. The upper broad margin, the basis, is adjacent to the bladder, the lower, narrower end, or the apex, rests on the diaphragma urogenitale. It thus lies completely within the abdominal cavity. The anterior surface is connected with the lower end of the symphysis pubis by the ligamenta puboprostatica, the posterior surface is connected with the rectum by loose connective tissue. The prostate is lobulated and generally divided into three lobes, a median and two lateral lobes. The prostate embraces the neck of the bladder and the first portion of the urethra.

The structure of the prostate is a framework of muscular fibres, in which are embedded numerous racemous glands. The latter collect and open into the prostatic ducts. The main substance of the prostate is glandular. The mucous lining of the prostate, which forms at the same time the mucous membrane of the prostatic urethra, shows upon the posterior wall a linear elevation of the mucous membrane which covers a fold of erectile tissue, the so-called colliculus seminalis.

Colliculus.—The colliculus is a massive button, 3 millimeters in height and in breadth, and lies anteriorly to the fossa prostatica. On the summit of the colliculus there is an opening which leads to a pear-shaped pouch, the so-called sinus pocularis, a remnant of the Müllerian ducts. The two orifices of the ejaculatory ducts are found within the pouch, near its opening into the urethra. The orifices of the prostatic ducts are situated in the furrows, on either side of the colliculus. In the state of erection the colliculus fills out the urethra completely and closes it up tightly and absolutely, so that not a drop of urine can pass out of the bladder or escape during ejaculation.

Cowper’s glands.—Cowper’s glands are two acinose glands of the size of a pea. They are embedded between the muscular fibres of the musculus transversus perinei profundus. The ducts run between the two leaflets of the diaphragma urogenitale to the posterior end of the bulbus, hence within the cavernous tissue near the septum and open on either side of the bulbus on the floor of the bulbous urethra.

Penis.—The penis is chiefly made up of three erectile bodies, the corpus cavernosum urethrae and the two porpora cavernosa penis. The latter arise each from the ramus descendens ossis pubis, by strong fibrous processes, the crura. The crura converse and coalesce at the inferior margin of the symphysis to which they are fastened by the ligamentum suspensorium penis mediale. The anterior ends of the corpora cavernosa are rounded. They are situated in the furrow of the glans of the penis. After their coalescence the two corpora are divided only by a fibrous septum. The lower surface of the corpora shows a deep furrow which serves as a receptacle for the corpus cavernosum urethrae. The latter thus occupies the same relation to the corpora cavernosa penis as does the ramrod to a double-barreled gun.

The corpus cavernosum urethrae forms two expansions. The anterior expansion is represented by the glans penis, the posterior expansion by the bulb, a tuberous enlargement, situated between the diverging crura of the corpora cavernosa penis. The bulb is covered by the musculus bulbo-cavernosus.

Structure of the corpora cavernosa.—The walls of the corpora cavernosa are made up of a dense fibrous elastic membrane, the tunica albuginea. From this tunica arise numerous trabeculae, composed of fibrous tissue and non-striped muscular fibres. In this way a sponge-like tissue is formed in which the spongy superstructure consists of elastic fibres. The mesh-spaces are filled with circulating blood. The spaces of these cavernous bodies are covered with an endothelial lining like blood-vessels. The caverns communicate with each other by the arteriae helicinae, short arterial branches, anastomosing in the cavernous spaces. The arteries, capillaries, and veins pass along the trabeculae of the spongy tissue and open into the caverns. The caverns may thus be considered as enlarged capillaries. The arteria and vena profundae penis run through the middle of the corpus.

The arteries within the trabeculae possess not only circular muscular fibres, as all other arteries, but also longitudinal fibres. These muscular fibres are normally contracted and thus prevent the blood from flowing into the cavernous spaces. If by some inhibitory influence the muscles are relaxed, the caverns are immediately filled with blood. This blood has to return by the vena profunda communis which passes through the unstriped muscular fibres of the musculus transversus perinei profundus. Hence by the contraction of this muscle the veins are compressed, and the blood is prevented from flowing off. As a result, the spongy and cavernous bodies become turgid and the corpora cavernosa penis become stone hard. The blood of the corpus cavernosum urethra, on the other hand, returns through the vena dorsalis penis which enters the abdomen through connective tissue parts, beneath the symphysis. For this reason the corpus cavernosum urethrae remains compressible even during erection.

The main muscles of the penis are the erector penis and the bulbo-cavernosus. The latter arises from the central perineal tendon and inserts by embracing the bulb. The erector penis muscle arises at the inner surface of the tuberositas ossis ischii and inserts into the sides of the crura.

The penis is covered with an integument which forms the continuation of the skin of the abdominal wall, but it is somewhat darker than the latter. At the anterior end a fold of skin forms the prepuce which covers the glans penis.

Genital nerves.—The genital nerves are of three different kinds. There are first the efferent nerves, or centripetal nerves. They are the sensitive terminal branches of the nervus pudendus and end, or rather arise, in the genital nerve bulbs. They are richly distributed throughout the prostatic part of the urethra. These centripetal nerves are connected with the Pacinian corpuscles, within the prostate, and with the extensive nerve-plexus, interspersed with ganglia, which are found in the superficial layers of the urethral mucosa as well as in the cortical layers of the prostate. These nerves return to the centres in the spinal cord and in the brain through the rami of the nervus pudendus.

The second kind of nerves are the centrifugal nerves, which arise by two roots at the sacral plexus, from the first to the third pair of sacral nerves. This sacral plexus sends off anastomosing branches to the vesical plexus. The latter is made up of branches from the hypogastric plexus of the sympathetic nerve and of filaments from the sacral ganglia, the pudendal plexus and the sacral nerves. The latter innervates the bladder, seminal vesicles, the urethra, and the prostate. The nervi erigentes are vasodilator-nerves. Their centre, in the lumbar part of the spinal cord, is connected with the centre of the vasodilators of the medulla oblongata by filaments, running within the spinal cord. When these nerves or their centre are irritated, as in diseases of the cord, or excited by electricity, erections will ensue.

The third kind of nerves are those of ejaculation. They are centripetal and centrifugal nerves and run through the nervi perinei, the latter being branches of the nervus pudendus communis. They innervate the ejaculatory ducts, the seminal vesicles, vasa deferentia and testicles. The centre of these nerves has also its seat in the lumbar portion of the spinal cord.

Genital centres.—The centres for the genital nerves are six in number, three cerebral, one in the medulla oblongata and two spinal centres. There is first the cerebral centre of voluptas or cupido. It is the seat of the sexual instinct or of sex desire. The second centre is the centre of libido. It is the centre for experiencing pleasure. The third centre is that of inhibition. It is the centre where, under certain circumstances, sexual activity is prevented. The vasodilator centre in the medulla oblongata and the two spinal centres regulate erection and ejaculation. Connecting fibres are passing between the cerebral centres and the spinal centres. Hence psychic stimulation may cause erection and ejaculation.