In its descent the testis becomes invested with two coverings of peritoneum - one, the tunica vaginalis, derived from the roof of the abdomen, is closely adherent to its outer surface; the other, the tunica vaginalis reflexa, forms a loose pouch in which it is enclosed. This membrane is derived from the floor of the belly being pushed before the testicle as it enters the inguinal canal on its way to the scrotum. The two opposing surfaces of these coverings possess the power of secreting a watery fluid, so that, being constantly in a moist condition and perfectly smooth in themselves, the movements of the organ within its sac are permitted to take place with the least possible friction.

The Inguinal Canal, about 4 to 6 inches in length, is a passage through the abdominal wall. Before birth it is occupied, as we have already stated, by the gubernaculum testis (see Plate), which, on the descent of the testicle into the scrotum, gives place to the spermatic cord. It has two openings - one above: the internal abdominal ring, by which the testis enters; and another, much larger, below: the external abdominal ring, by which it emerges into the scrotum.