26 Diseases of the Genital Organs 



species. The investment is very close in ruminants and the 

 sow, so that the ducts are readily seen without dissection. 

 In the mare the duct is surrounded by much connective 

 tissue, which serves to conceal it from view until the peri- 

 toneal and fibrous coverings are dissected away. In the 

 bitch the concealment is further accentuated by large 

 amounts of adipose tissue. 



The oviduct opens anteriorly through the ostium abdomi- 

 nale into the pavilion of the tube and posteriorly into the 

 uterine cornu through the ostium uterinum, which usually 

 projects somewhat as a small eminence into the cavity of 

 the cornu. 



The muscular coat of the oviducts is characterized chiefly 

 by its density, which gives to it an almost cartilaginous con- 

 sistency, and its paleness, which amounts almost to trans- 

 lucency. The superficial layer of the mucosa of the oviducts 

 consists of ciliated columnar epithelium with the cilia vi- 

 brating toward the uterus. The oviduct is the most rigid 

 and undilatable portion of the genital tube. It provides 

 passage for the migration of the spermatozoa of the male, 

 which, in spite of the movements of the cilia in the contrary 

 direction, advance from the uterus toward the ovary, in 

 virtue of their inherent power of movement, meet the ovum 

 in the pavilion, and fecundate it. Later the oviduct conveys 

 the ovum, fecundated or not, from the ovary to the uterus. 

 In this function the cilia play an essential part. In rare 

 cases the fecundated ovum lodges in the duct and under- 

 goes partial development, to constitute tubal pregnancy, but 

 the undilatability of the duct serves, as a rule, to cause a 

 rupture of its walls and leads to the escape of the fetus from 

 the duct into the peritoneal cavity, either to cause sudden 

 death of the mother from hemorrhage or to constitute extra- 

 uterine, or abdominal, pregnancy. 



b. The uterus, see Figs. 12, 13, a bifurcated, musculo- 

 membranous sac, designed for the reception, nutrition, and 

 protection of the ovum, finally takes the initial part in the 

 expulsion of the fetus at the time of birth. The uterus 

 varies greatly in form and disposition, dependent partly 



