THE UROGENITAL SYSTEM. 267 
vesical pouch of the peritoneum, which lies between the rectum 
and the bladder. It holds the body of the uterus to the lateral 
wall of this pouch, and together with the opposite ligament 
and the body of the uterus forms thus a transverse partition, 
which divides the rectovesical pouch into dorsal and ventral 
portions. 
The round ligament (/) is a fibrous band which extends 
from a point of the body wall, which corresponds exactly to 
the internal inguinal ring of the male, to the cornu of the 
uterus about two centimeters from the cranial end. It is 
attached to the broad ligament by an intervening fold of 
peritoneum. 
The Vagina (m).-—The vagina extends from the os uteri , 
(at 7) dorsad of the symphysis of the pelvis to a point a short 
distance craniad of the caudal border of the ischiatic symphysis. 
At this point it joins the neck of the bladder (4) to form the 
vestibulum or urogenital sinus (7), which is homologous with 
the urethra of the male. 
Urogenital Sinus (x).—The urogenital sinus extends from 
the caudal end of the vagina (7) to the external opening, 
which is situated ventrad of the anal opening. It is about a 
centimeter long and nearly as wide, and is marked off from 
the vagina by a circular fold of mucosa, while its inner surface 
presents longitudinal folds. On its ventral wall at its cranial 
end is the opening of the neck of the bladder, which is 
enclosed by a ring-like elevation of the mucosa, most prominent 
at the sides. The external entrance to the urogenital sinus 
forms the vulva. ; 
The Clitoris.—The clitoris is a minute organ homologous 
with the penis and lying on the ventral floor of the urogenital 
sinus. Its distal end lies at the entrance of the urogenital 
sinus on its ventral border. In adult specimens the prepuce 
of the clitoris appears as a slight elevation of the integument 
surrounding a central vascular structure which appears red in 
the fresh organ. From the clitoris there are two small cor- 
pora cavernosa clitoridis (0) passing craniad and then diverging 
to be attached to the ischiatic rami. The ischiatic portion of 
