18 VETERINARY OBSTETRICS, 
In the Bitch and Cat, the promontory of the 
sacrum is still more marked than in the Pig, which 
diminishes notably the inlet of the pelvis; the direction 
of the symphysis is rectilinear, and the general outline 
of the cavity is nearly cylindrical, although the inlet is 
larger below than above. The narrowest part of the 
canal is immediately above the obturator foramen, 
where the ischium is wide and shallow, and rises 
abruptly to almost a right angle. 
The Vulva. 
This is the most external portion of the female 
reproductory organs, and presents posteriorly an 
opening situated vertically under the rectum, from 
which organ it is separated by a narrow space—the 
perineum. : 
The labiz form the lateral boundaries, and, in the 
normal condition of the parts, are in contact with each 
other. They are lined on their internal surface with 
mucous membrane; externally with a very smooth skin 
devoid of hair. 
The cavity of the vulva varies in length in the cow 
and mare, from six to ten inches. At parturition, the 
walls become separated to allow of the escape of the 
foetus. 
The cavity contains several organs accessory to 
reproduction, which we will now notice separately. 
The Clitoris. 
This organ is situated on the inferior commissure 
of the vulva, and corresponds to the corpus cavernosum 
