GENITAL ORGANS. 309 



latter opens into the vas deferens. The urethra has erectile 

 walls, and begins at the bladder and ends at the tip of the 

 penis, the erectile tissue commencing towards its end portion. 

 The single jjvustate gland (/) lies across the neck of the bladder. 

 Cmoper's glamU (J) are two in number : tliej' secrete a fluid 

 which is poured into the urethral canal just before the ejection 

 of the semen. The corjnis eavernonum is the erectile body which 

 passes up the penis from its base to its tip and supports the 

 urethra. There is considerable variation in the sexual organs of 

 animals, into which we cannot enter. 



The female organs (fig. 161), as seen in the mare, consist of 

 two secretory organs, the ovaries (.3), oval bodies lying just 

 behind the kidneys in the abdomen. The ovaries lie free and 

 detached in the body cavity. Closely applied to them are the 

 oviducts, which expand near the ovaries into funnel-shaped 

 hodies. The oviducts are very small tubes lodged in broad 

 ligaments (4), about as thick as a straw. They open into a 

 large sac, the uterus (1 and 2), the space in which the embryo 

 develops. This membranous sac lies in the sub-lumbar cavity 

 of the abdomen, and consists of the body and two so-called 

 " comua " or horns of the uterus. The cornua pass amongst the 

 intestines, the uterus being supported by the broad ligaments, 

 the rectum (13), and posteriorly by the vagina (16). The inner 

 walls of this cavity are lined by mucous membrane ; outside there 

 is a serous layer, and between a thick muscular layer. From the 

 uterus proceeds the vagina, a thin tube which terminates in the 

 vulva or external orifice. Inside this orifice is found a solid 

 body from two to three inches long in the mare, the clitoris, 

 which protrudes into the vulvular cavity, and which is erectile. 

 The ova are dehisced at certain periods, the periods of menstru- 

 ation, "heat," or "rutting.'' 



