COMPARATIVE ANATOMY OF THE UROGENITAL SYSTEM 



291 



Now cut through the pubic and ischial symphyses and spread the legs apart. 

 Trace the vasa deferentia and the urethra caudad, separating them from the 

 rectum. The ureters may be cut through and the urinary bladder held poste- 

 riorly. The vasa deferentia pass along the dorsal surface of the urethra. In the 

 rabbit they enlarge and enter an expanded sac, the seminal vesicle, which pouches 

 forward between the rectum and the bladder. Cut into the seminal vesicle and 

 note the openings into its ventral wall of the two vasa deferentia, and in its 

 posterior dorsal wall the thickening caused by the prostate gland. Find the union 

 of the seminal vesicle and urethra to form a common tube, the urogenital sinus. 

 In the cat the two vasa deferentia join the urethra without the formation of a 

 seminal vesicle, the point of junction being surrounded by a slight enlargement, 



vas deferens 



peritoneal 

 cavity 

 / vas deferens 



\ 



epididymis 



gubernaculum 



FIG. 65. Diagrams to illustrate the descent of the testis in the male mammal. The testis descends 

 into the scrotum which is a sac of the body wall containing a portion of the peritoneal cavity called the 

 vaginal sac; in the descent the gubernaculum or ligament of the testis shortens; the passage x along 

 which the descent occurs and which at first forms a connection between the vaginal sac and the peri- 

 toneal cavity is later completely obliterated in the higher mammals; it does not correspond to the 

 inguinal canal. (From Prentiss and Arey's Textbook of Embryology, courtesy of the W. B. Saunder 

 Company.) 



the prostate gland. The common tube thus formed is the urogenital canal or 

 sinus. The bulbourethral glands or Cowper's glands are small swellings situated 

 on the urogenital canal shortly posterior to the prostate gland in the rabbit, 

 about an inch posterior in the cat. The terminal inch of the urogenital canal is 

 inclosed in the penis. Cut into the prepuce and note the pointed projection 

 within it, called the glans of the penis. Note that the prepuce is simply a fold 

 of skin around the glans. At the tip of the glans is the urogenital opening. The 

 glans in the cat bears a number of minute spines. Dissect anteriorly from the 

 glans exposing the remainder of the penis as a hardened cylindrical structure. 

 Find where the urogenital canal enters its anterior end. Note also the strong 

 attachments of the penis to the pelvic region. Cut across the middle of the 

 penis and note that it is composed of two cylindrical bodies, the corpora cavern- 

 osa or cavernous bodies closely placed. The urogenital canal, here called the 

 cavernous urethra, lies on the dorsal side of the penis resting in a depression 



