THE FEMALE GENITAL OEGANS. 883 



fibres; some flat fasciculi attach it to the periosteum of the ischia. The 

 urethra is not surrounded by a spongy body as in the male.) 



THE HYMEN. This membrane, when it exists, distinctly separates the 

 vulvular from the vaginal cavity. It is rarely present, however ; though 

 we have observed it several times in the adult Mare. It forms a circular 

 partition, fixed by its margin to the vulvo- vaginal walls, as well as to the 

 valve of the meatus urinarius, and is perforated by one or more openings 

 which establish a communication between the vulva and vagina. On many 

 occasions we have found, in old brood-mares, pediculated appendages, the 

 remains of this septum. 



STRUCTURE OF THE VULVA. The vulva offers for study in its structure : 

 1, The mucous membrane lining its interior ; 2, An erectile body lying on 

 that membrane, and named the vaginal bulb; 3, Two constrictor muscles 

 anterior and posterior ; 4, Two muscular ligaments ; 5, The external skin. 



1. Mucous membrane. Continuous with that of the vagina and bladder, 

 this membrane has a rosy colour, which may become a bright-red at the 

 period of heat. It often shows, near the free border of the labia, black 

 pigment patches, which give it a speckled appearance. It has in its 

 substance a greater quantity of mucous follicles and sebaceous glands. 

 The latter exist near the free border, particularly about the clitoris, and es- 

 pecially in the space between that erectile body and the inferior commissure 

 of the vulva, where they meet in several small sinuses. (These glands 

 secrete an unctuous matter possessing a special odour ; they are most active 

 during oestrum.) 



2. Vaginal bulb. This is an organ entirely formed of erectile tissue 

 with wide areolse ; it is divided into two branches (bulbi vestibuli), which 

 arise from the vicinity of the crura of the clitoris and pass on the sides 

 of the vulva, where they terminate in a round lobe. Covered by the 

 posterior constrictor of the vulva, the vaginal bulb communicates, inferiorly, 

 with the veins of the corpus cavernosum. The influx of blood into the 

 cells of its tissue contracts the vulvular cavity, and concurs to render the 

 coaptation of the copulatory organs more perfect during coition. 



3. Muscles of the vulva. Imperfectly described and determined in books 

 on Veterinary Anatomy, these belong to the category of voluntary muscles. 

 We recognise two, which will be described as the posterior and anterior 

 constrictors. 



POSTERIOR CONSTRICTOR OF THE VULVA. Analogous to the constrictor 

 vagince of Woman, this muscle, included in the labia of the vulva, forms a 

 veritable sphincter. Above, its fibres are mixed with those of the sphincter 

 ani, and are attached to the sacrum through the medium of the suspensory 

 ligaments. Inferiorly, the most anterior are fixed to the base of the clitoris ; 

 the middle are prolonged to between the thighs, and are inserted into the 

 inner surface of the skin. 



Inwardly, it is in relation with the vaginal bulb and the mucous 

 membrane of the vulva. Its external face is separated from the skin of the 

 labia by a very vascular cellulo-fibrous tissue capable of contraction, and 

 in the midst of which are always found isolated red fasciculi dependencies 

 of the principal muscle. 



This muscle, in contracting during copulation, constricts the aperture of 

 the vagina and compresses the penis ; and as. in consequence of its attach- 

 ment to the clitoris, it cannot act without raising that erectile body, it 

 applies this to the male organ and causes a greater degree of excitement. 

 With animals in heat, the movements of the clitoris are frequently observed 



