THE ABDOMEN. 251 



uterus, and sends off longitudinal folds; superiorly the 

 vagino -rectal, inferiorly the vagino-vesical, folds to tlie 

 rectum and bladder respectively. It presents also a mus- 

 cular coat with longitudinal and circular fibres ; in contact 

 with this lies a quantity of erectile tissue, analogous to that 

 forming the corpus spongiosum of the penis. It is lined 

 by' mucous membrane, with stratified squamous epithe- 

 lium, and which anteriorly becomes puckered up to join 

 that of the nect of the uterus ; posteriorly forms a re- 

 markable double fold, hymen, almost, but seldom com- 

 pletely, separating the vaginal cavity from that of the 

 vulva. Generally lunate in the virgin, it is lacerated in 

 the first act of coition by the penis of the stallion, and 

 subsequently appears as an irregular fringe extending 

 round the vagino-vulval opening, carunculsB myrtiformes. 



The vulva leads from the vagina to the external genera- 

 tive opening, and presents coats similar to those of the 

 vagina, with a much greater quantity of erectile tissue 

 (bulb of vulva). Posteriorly the muscular coat becomes 

 redder in colour, with its fibres striated and arranged in 

 a circular manner around the external opening, forming 

 the sphincter vaginsB (more correctly sphincter vulvse). 

 The floor of the vulva, just behind the hymen, about four 

 inches from the lower j)art of the external opening, pre- 

 sents the meatus urinarius externus, much larger than 

 that of the male, being the opening from a larger canal ; 

 between this and the hymen anteriorly is a valvular flap 

 of mucous membrane. 



The external generative opening is an elliptical fissure 

 extending from above downwards. It terminates above in 

 an acute angle, superior commissure, situated about two 

 inches below the anus, the intermediate space being peri- 

 neum. Below, it is more rounded, forming the inferior 

 commissure. The opening is bounded laterally by the 

 labia, elongated prominences consisting of the sphincter 

 vulvae, fat, and vascular structure covered externally by 

 thin, hairless skin, which externally is continuous with the 

 mucous membrane of the vulva, the latter becoming folded 

 longitudinally to form the labia minora or nymphse. At 

 the inferior commissure is a triangular space, which may 

 be exposed by sej^aration of the labia, fossa navicularis, 

 on which projects the clitoris, a small organ analogous to 

 the penis of the male, and the seat of the pleasure expe- 



