88 ANATOMY OF THE RAT 



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 mesoneph- 

 ros 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 ab- 

 dominal 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 ex- 

 erts a favorable influence. It is claimed that extirpation 

 of the glands reduces the animal's reproductive capacity. 



