370 THE ANATOMY OF THE HORSE. 



externally by skin, which is thin, almost destitute of hairs, and generally 

 black-pigmented ; inwardly they are lined by mucous membrane ; and 

 at their sharp edges these cutaneous and mucous coverings meet. If 

 the cutaneous covering of the labia be removed, the posterior constrictor 

 of the vulva will be exposed. This is a red muscle corresponding to the 

 compressor bulbi of human anatomy. Its fibres are elliptically disposed 

 around the extremity of the vulva, being confounded with the sphincter 

 ani above, while inferiorly some of the fibres are attached to the base 

 of the clitoris, and others are attached to the inner surface of the skin 

 below the inferior commissure. When the muscle contracts it constricts 

 \ the orifice of the vulva. Its lower fibres may frequently be observed to 

 contract after micturition, depressing the inferior commissure and expos- 

 ing the clitoris, which is simultaneously erected. 



The Clitoris. This small erectile body is the homologue of the male 

 penis minus the urethra. It is lodged within the inferior commissure of 

 the vulva, and presents a base, or attached extremity, a body, and a free 

 extremity. The base is bifid, and attached to the ischial arch by the 

 branches, or crura, each crus being covered by a rudimentary erector 

 clitoridis muscle — the homologue of the erector penis. The body of the 

 clitoris, which is from two to three inches in length, projects backwards 

 and upwards, and is composed of right and left halves like the corpora 

 cavernosa of the penis. The free extremity is formed by a rudimentary 

 glans, with a small depression on its upper surface, and a mucous cap 

 analogous to the prepuce. The clitoris is composed of erectile tissue 

 resembling that of the penis. 



The Vestibular Bulb. This will be exposed by the removal of the 

 posterior constrictor muscle. It is an erectile body composed of right 

 and left halves, each of which is placed at the side of the vulvar cavity 

 (the vestibule), between the posterior constrictor and the mucous 

 membrane. Inferiorly the two halves of the organ are in communi- 

 cation with one another and with the erectile tissue of the clitoris, 

 and superiorly each terminates at the side of the vulva by a rounded 

 end. The bulb is the homologue of the corpus spongiosum of the 

 penis. 



Directions. — The pelvic viscera must now be removed to allow an 

 examination of the structure and interior of the organs just considered. 

 This is to be effected by cutting the meso-rectum and the peritoneal 

 ligaments of the bladder, carrying the knife above the anus and below 

 the inferior commissure of the vulva, and destroying the vascular 

 and connective-tissue attachments of the various organs to the pelvic 

 walls. The entire generative apparatus will thus be removed along 

 with the urinary bladder and the rectum. The latter organ should be 

 dissected from the vagina and vulva (for its structure see page 356), 

 and the other viscera examined seriatim. The canal of the vulva and 



