The Urinogenital System 199 



rectum. The sphincter ani externus and sphincter ani internus are two 

 closely related muscles enclosing the rectum and urethra, the former arising from 

 the dorsum of the tail. 



The following parts of the urinogenital system may be made out: 



(a) The connection of the bladder with the outside of the body 

 through the urethra. It comprises a short prostatic 

 portion in relation to the genital ducts, a much longer 

 membranous portion traversing the pelvis, and a terminal 

 cavernous portion in the penis. 



(b) The seminal vesicle (vesicula seminalis) lies on the dorsal 

 surface of the base of the bladder. It is a flattened median 

 pouch, the anterior, slightly divided tip of which is directed 

 forward. 



(c) The deferent ducts lie between the seminal vesicle and the 

 dorsal wall of the bladder. They terminate in the ventral 

 wall of the seminal vesicle. 



(d) The prostate (prostata), a white or yellowish mass of 

 glandular tissue, lies in the posterior portion of the dorsal 

 wall of the seminal vesicle. Its ducts, three or four in 

 number on either side, open into the urethra. Accessory 

 paraprostatic glands (gl. paraprostaticae), minute finger- 

 like projections of the urethral wall, lie on either side of the 

 base of the seminal vesicle. 



(e) The bulbourethral gland (gl. bulbourethralis) ; situated on 

 the dorsal wall of the urethra behind the prostate. 



3. The internal surface of the dorsal wall of the urethra may be 

 exposed by a longitudinal incision extending into the bladder. The 

 crescentic aperture of the seminal vesicle lies immediately in front 

 of an oval elevation, the colliculus seminalis, on either side of 

 which some of the minute apertures of the prostate may sometimes 

 be made out. 



C. The Female Genital Organs. 



1. The organs may be traced from the abdominal cavity back- 

 ward, as follows: 



(a) The ovary (ovarium) is a small — in young animals minute- 

 elongated structure of greyish or yellowish coloration lying 



