epididymis. The convolutions of this tube form the body and tail of the epididymis. The tube emerges from the cauda epididymidis, and as the ductus deferens conducts the sperm cells to the urethra. This arrangement doubtless obtains, in all essential details, in the rat also.
The epididymis of Amniotes is homologous to a part of the mesonephros of the adult Ichthyopsida. The mesonephros is a kidney and a sperm carrier in the latter group. The excretory function is retained by the mesonephros in the mammalian embryo, but in the development of the male the organ undergoes partial degeneration, so that in the adult only the sperm-carrying function is retained.
The ductus deferens of the rat, after entering the abdominal cavity through the inguinal canal, turns medianly, curves around the ventral surface of the ureter, and joins the urethra.
There are several accessory glandular structures in this region. The vesicular glands are a pair of conspicuous, warty structures at the posterior end of the abdominal cavity. The anterior end of each gland bends abruptly caudad, so that each gland, as a whole, somewhat resembles an interrogation point. The gland is hard and brittle in a preserved animal. Open it and remove some of the coagulated secretion. It breaks into fine particles when rubbed between the fingers. This secretion is produced by the wall of the gland, which is said to contain a strong mantle of smooth muscle. Find the duct and trace it caudad to its entrance into the anterior end of the urethra. These organs were formerly called seminal vesicles, but they contain no spermatozoa. It is said that the glands produce an alkaline secretion which is mixed with the sperms, upon whose movements the secretion probably exerts a favorable influence. It is claimed that extirpation of the glands reduces the animal's reproductive capacity.
