604 GENITAL ORGANS OF THE MARE 



The clitoris is the homologue of the penis and consists of similar parts (minus 

 the urethra and its muscle). The corpus clitoridis is about two inches (ca. 5 cm.) 

 long, and its diameter about that of one's little finger. It is attached to the ischial 

 arch by two crura (Crura clitoridis). The glans clitoridis is the rounded and en- 

 larged free end of the organ which was noted above as occupying the fossa clitoridis 

 in the ventral commissure of the vulva. It is covered by a thin pigmented integu- 

 ment, similar to and continuous with that which lines the fossa; these constitute 

 the prepuce of the clitoris (Praeputium clitoridis). The organ is composed of erectile 

 tissue similar to the corpus cavernosum penis. The ischio-cavemosus is the 

 homologue of the muscle of the same name of the male; it is a very feeble muscle. 

 The veins of the clitoris communicate by an intermediate plexus on either side with 

 the bulbus vestibuli. 



THE FEMALE URETHRA 



The female urethra (Urethra feminina) represents only that part of the canal 

 of the male which lies between the internal urethral orifice and the colliculus semi- 

 nalis. Its length is two to three inches (5-7.5 cm.), and its lumen is sufficient to 

 allow easily the introduction of the finger; it is, however, capable of remarkable 

 dilatation if sufficient care and patience are exercised in the process. It lies centrally 

 on the pelvic floor, and is related dorsally to the vagina, to which it is in part at- 

 tached. The external orifice is at the anterior end of the vulva, as described above. 



Structure. — The intrinsic muscular coat consists of external longitudinal and 

 internal circular fibers; it is absent where the urethra is attached to the vagina. 

 The mucous membrane is thro^vn into longitudinal folds when the canal is closed; 

 it is highly elastic, and is covered with stratified epithelium. There is a rich sub- 

 mucous network of veins, forming a sort of corpus cavernosum. 



The urethral muscle (M. compressor urethras) embraces the urethra and is 

 continuous with the constrictor vestibuli. It is covered by a fibro-elastic membrane. 



THE MAMMARY GLANDS 



The mammary glands (Glandulffi lactiferae) are modified cutaneous glands 

 which are so closely associated functionally with the genital organs as to be con- 

 sidered accessory to them. 



In the mare they are two in number, and are placed on either side of the median 

 plane in the inguinal region. Each gland has the form of a very short, flattened 

 cone, much compressed transversely, and having a flat medial surface. It consists 

 of the glandular mass or body of the gland (Corpus mammae) and the papiUa or 

 teat (Papilla mammae). The base is related to the abdominal wall, to which it is 

 attached by areolar tissue, which contains a venous plexus, the superficial inguinal 

 Ij'mph glands, and a variable amount of fat. The apex is constituted by the teat, 

 which is also flattened transversely and varies in length from one to two inches 

 (ca. 2.5 to 5 cm.). Between the bases of the teats is the intermammary groove. 

 On the apex of each teat there are usually two small orifices placed close together; 

 these are the openings of the lactiferous ducts. 



Structure. — The skin covering the glands is thin, pigmented, chiefly hairless, 

 and supplied with numerous large sebaceous and sweat glands. Under this are two 

 layers of fascia, except on the teats. The superficial fascia presents no special 

 features. The deep fascia consists of elastic tissue ; centrally two laminae detached 

 from the abdomihal tunic descend on either side of the median plane, forming a 

 septum between the two glands, and constituting their ligamentum suspensorium.^ 



The gland substance or parenchyma is pinkish gray in color, and of firmer 



' These laminae are separated almost completely by a layer of areolar tissue, so that it is pos- 

 sible to remove a diseased gland by careful dissection between the layers of the septum. 



