284 VERTEBRATE ZOOLOGY 



hinder end. Slit open the seminal vesicle and note the openings 

 of the two vasa deferentia in its ventral wall ; also its opening into 

 the urethra, which thus becomes the urogenital canal. 



The prostate gland is a lobed structure, the greater part of 

 which lies dorsal to the seminal vesicle ; its several ducts open into 

 the urogenital canal. Cowper's gland is a small body situated 

 posterior to the prostate, on the dorsal surface of the urogenital 

 canal; posterior to it lies the penis. This structure is formed 

 of three elongated cylindrical bodies,— the median corpus spongi- 

 osum, through which the urogenital canal runs, and the two lateral 

 corpora cavernosa. The two latter diverge to the right and left 

 at their proximal ends and form on each side the crus penis, which 

 is connected with the ischium. The distal end of the penis is 

 formed of the greatly enlarged end of the corpus spongiosum and 

 is called the glans penis; a fold of the skin called the prepuce 

 projects over it ; the projecting gland, covered by the prepuce, will 

 be seen just below the anus. 



Follow the vasa deferentia in the opposite direction into the 

 scrotum, which is a deep pocket formed by the protrusion of the 

 body wall containing a portion of the abdominal cavity with its 

 peritoneal lining. The scrotum will be seen to contain two com- 

 partments, in each of which is a testis. Open one of these com- 

 partments along its ventral wall and expose the testis. The wall 

 of the scrotum will be seen to be composed on the outside of skin 

 and, beneath this, of a muscle layer which is called the cremaster 

 muscle ; its inner cavity, or the vaginal sac, is lined by the tunica 

 vaginalis, which is a portion of the peritoneum. The testis is a 

 compact elliptical body containing the seminiferous tubules, which 

 produce the spermatozoa, and is closely invested on its ventral 

 surface by the tunica vaginalis ; its hinder end is attached to the 

 posterior wall of the scrotal sac by a ligament called the guber- 

 naculum. On the dorsal surface of the testis is a mass of con- 

 voluted tubes ; this is the epididymis, the beginning of the efferent 

 duct of the testis. It is composed of three parts : the head, which 

 caps the anterior end of the testis ; the body, which lies along the 

 surface of the testis ; and the tail, which is at its posterior end 

 and is continued in the vas deferens. The head of the epididymis 



