EXTERNAL GENERATIVE ORGANS. 



Sheep. 



31 



In the Sheep which has not copulated, a filamentary band, stretching 

 across the constriction between the urogenital canal and the vagina, rep- 

 resents the hymen. The Malpighian canals open into that passage near 

 the constriction, and the crura of the clitoris are enfolded by erector 

 muscles ; while the clitoris itself protrudes immediately within the peak 

 of the vulva. 



Pig- 



In the Pig, the urethra opens between two longitudinal ridges ; but the 

 surface of these and other similar prominences in the urogenital passage is 

 interrupted by numerous fine, wavy, oblique furrows. There is no vaginal 

 valve, as in the other animals. The clitoris is comparatively small, and 

 the inferior commissure of the vulva is still more acute and pointed than 

 in the Cow and ruminants in general Towards the meatus are numerous 

 fine points — the openings of glands analogous to the prostates ; and on the 

 sides of that orifice are two small fossae surrounded by a raised border. 



Bitch and Cat. 



In the Bitch, the vulva is triangular, and the inferior commissure acute. 

 The clitoris is a small tubercle, and the urethra opens between a little 

 transverse fold and the triangular flattened clitoris ; beyond which is a 

 second transverse cresentic fold with its concavity opposite that of the 

 preceding. In the Cat, a small cartilage or bone exists in the clitoris; 

 this is not found in any other of the domesticated animals. 



The Perineum is the name given to the space between the superior 

 commissure of the vulva and the lower margin of the anus. Its length 

 varies in different species, and in different-sized animals of the same 

 species, but it is shorter in creatures which have produced young than 

 those which have not. It is composed of various tissues : externally is 

 the smooth, fine, and very elastic skin, with the vertical prominent line 

 passing down its middle — the " raphe ; " beneath this are connective and 

 adipose tissue, and fascia, with various muscles, blood-vessels, and nerves. 



The internal limits of the vulva are defined by the constriction or bulb, 

 which forms a marked prominence in early life, but tends to disappear in 

 relaxed folds after the animal has brought forth young several times. 

 The dimensions of this aperture are rathef adapted for the passage of 

 the foetus than the penis ; though its narrowness is sometimes an obstacle 

 to the delivery of a primipara. The limbs, body, or head of the foetus 

 are at times arrested at the superior or perineal commissure, which they so 

 distend as to threaten rupture of that part. In emaciated animals, and 

 particularly Mares, the vulva is deeply retracted above the ischia, and 

 consequently disposes them to be injured in this region during coitus, by 

 the accidental introduction of the male organ into the anus, the mechani- 

 cal action of which damages, and may even rupture, the rectum. Rainard 

 alludes to several occurrences of this kind, which terminated in the death 

 of the Mares. 



SECTION II. — THE MAMM^. 



The mammcB, or udders^ may be said to be appendices to the external 



