28 OBSTETRICAL ANA TOMY. 



The lips {labice vidvce) are usually in contact, and they, with the opening 

 which separates them {rimcE vulvce), vary in size according to age and con- 

 dition. They are slightly prominent and thick, being composed of firm, 

 flexible, and elastic tissue, which is covered with a fine, smooth, unctuous 

 skin destitute of hair, but rich in pigment in the majority of animals. In- 

 ternally, they are covered with mucous membrane, a continuation of that 

 lining the vagina, and which is constantly lubricated by a greasy mucus 

 possessing a special odor, according to the species of animal ; on the 

 free border of the vulva, this membrane and the skin meet.* 



At the junction of the labia above and below are the commissures, due 

 to this junction. The superior commissure is situated close to the anus, 

 from which it is only separated by a narrow space — the. per if leum. It is 

 very angular, and corresponds to the fourchette in woman. The ififerior 

 commissure IS obtuse, rounded and more voluminous ; it lodges the clitoris, 

 and is situated immediately above the raphe. The cainty of the vulva 

 sometimes contains the hymen, which separates it from the vagina at a 

 certain period of life ; it also contains the meatus urinarius and its valve, 

 as well as the clitoris. 



The structure of the vulva consists of tho. mucous membrane lining its in- 

 terior, which is covered by pavement epithelium ; an erecticle structure 

 connected with it, named the vaginal bulb; two constrictor muscles ; two 

 muscular ligaments, fascice, etc. The, mucous membrane is continuous with 

 that of the vagina and bladder ; it is usually of a pink or rosy tint, but at 

 the period of oestrum it has a bright-red hue. Near the margin of the 

 labia it frequently shows black pigmentary patches, which give it a 

 marbled appearance. It is provided with numerous mucous follicles and 

 sebaceous glands ; the latter are chiefly found near the free border, and 

 particularly around the clitoris and the space between it and the inferior 

 commissure, where they aggregate to form several small sinuses. This 

 membrane is also furnished with great numbers of papillae. The vaginal 

 bulb is wholly composed of erectile tissue with wide spaces, which con- 

 stitutes the plexus retiformis. This tissue passes from the base of the 

 clitoris to the sides of the vulva, where it terminates in a round salient or 

 ring-like lobe. Covered by the posterior constrictor of the vulva, this 

 bulb communicates inferiorly with the cavernous veins, and afflux of 

 blood into its meshes diminishes the capacity of the vulva ; thereby con- 

 curring to render the co-aptation of the copulatory organs more complete 

 during coition. 



The jnuscles of the vulva are constrictors — an anterior and posterior — 

 and are voluntary. The anterior constrictor is analogous to Wilson's 

 muscle in the male, and is formed of arciform fibres which surround the 

 sides and lower part of the vagina at its commencement, its extremities 

 being continued by means of aponeurotic fasciculi as far as the sides of 

 the rectum, where they disappear. Posteriorly, this muscle is confounded 

 with the next to be described. The posterior constrictor {constrictor cunni) 

 is analogous to the constrictor of the vagina, and forms a real sphincter ; 

 it is comprised within the substance of the lips of the vulva. Superiorly, 

 its fibres are mixed with those of the anal sphincter, and are attached 

 to the sacrum by means of the suspensory ligaments. Inferiorly, the 

 most forward are fixed to the base of the clitoris, and the middle are pro- 

 longed to both sides of the thighs, where they are inserted into the skin. 



* The two lips correspond to the labia m.%jora of woman ; there are no labia minora in animals. 



