92 ANATOMY OF THE RAT 



the bulb. Remove the plug of secretion and locate the 

 ventral orifice through which urine enters from the bladder, 

 also near this the openings of the ductus deferentia and 

 ureters. Urethral glands occur in the mucous membrane 

 of the urethra. 



Exercise XXIII. Make a full page drawing of the entire 

 urogenital system of the male. 



THE FEMALE UROGENITAL ORGANS 



Examine the anal region of a female rat and note the 

 three openings. At the base of the tail is the anus, ventral 

 to it the vaginal orifice, and below this the urinary open- 

 ing at the summit of a prominent elevation. As a rule 

 there is but one external opening for the female urogenital 

 systems in mammals. 



Cautiously cut the urinary elevation lengthwise, insert- 

 ing but one blade of the scissors into the urinary aperture. 

 This elevation is homologous to the prepuce in the male. 

 Note that it surrounds a body resembling the glans of the 

 penis, to which it is probably homologous. One sex among 

 animals frequently possesses rudimentary structures corre- 

 sponding to functional reproductive organs in the oppo- 

 site sex. The penis of the male mammal is represented 

 in the female by the diminutive clitoris, which is termi- 

 nated by the glans clitoridis, the homologue of the glans 

 penis. A pair of prominent glands just beneath the skin 

 correspond in position to the preputial glands of the male. 

 Locate the opening of the duct on the inner surface of 

 the prepuce a short distance in front of the urinary ori- 

 fice. Insert a bristle into the duct, slit it open, and ex- 

 amine the secretion, which has a waxy feeling when rubbed 

 between the fingers. 



Clear away the muscles ventral to the pelvic girdle, slit 

 the symphysis pubis lengthwise, and expose the female ure- 



