_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. [Illustration: 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.] _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.