Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/106

92 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.

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 opening 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, inserting 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 corresponding to functional reproductive organs in the opposite sex. The penis of the male mammal is represented in the female by the diminutive clitoris, which is terminated 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 orifice. 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-