The Vulva 43 



and postero-superior border of the sacro-sciatic ligament, 

 thus affording the vulva a secure attachment to the posterior 

 opening of the pelvis and furnishing a fixed base upon which 

 the entire genital canal may act in parturition. This fixa- 

 tion enables the uterus, when contracting, to force the fetus 

 back toward and through the cervical canal, the vagina, and 

 the vulva. It is this fixed base of attachment which enables 

 the contracting uterus at the time of parturition to dilate 

 and virtually efface the cervical canal, obliterating all its 

 mucous folds and increasing its calibre sufficiently to afford 

 room for the passage of the fetus. 



The vulvar mucous membrane, continuous with that of 

 the urinary bladder and the vagina, is covered with squam- 

 ous epithelium and contains numerous mucous glands, 

 which are largely displaced near the labial margins and 

 about the clitoris by sebaceous follicles, the secretions from 

 which are odoriferous, especially during estrual periods, 

 when the odor becomes very marked in a manner charac- 

 teristic of the species. 



Within the vulvar cavity are to be noted the meatus urin- 

 arius, clitoris, Bartholin's glands, and vaginal bulb. In the 

 mare the meatus urinarius, or terminal opening of the 

 urethra, is located along the floor of the vulva at a distance 

 of three to four inches from the external opening. The 

 urethral canal passes obliquely downward and forward 

 through the vaginal floor to the urinary bladder. In most 

 animals the meatus urinarius is comparatively small and in- 

 extensible. In the mare it is large and freely dilatable. 

 With patience, one, two or more fingers may be pressed 

 gradually through it into the bladder, and it is not rare to 

 find the opening, in heavy, coarse animals, sufficiently large 

 to admit without great difficulty the entire hand. The am- 

 plitude of the meatus urinarius in the mare is of special 

 significance clinically, as it favors eversion and prolapse of 

 the bladder, an accident not particularly rare in this ani- 

 mal, though extremely so in others. In the cow the narrow 

 meatus urinarius has beneath its vulvar opening a small 

 sac, or infundibulum. The supero-anterior wall of the 



