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.
CUT VI.
Schema of the seminiferi tubules. After Brösike.
1, tubuli contorti; 2, tubuli recti; 3, rete vasculosum; 4, vasa efferentia; 5, coni vasculosi; 6, epididymis; 7, vas deferens.