36 Diseases of the Genital Orga?is 



cular folds, with their summits, or free surfaces, directed 

 vaginalward. In the cow these circular folds measure one- 

 half to three-fourths of an inch from the base to the free 

 summit, and in disease may become elongated to several 

 inches and protrude into the vagina to constitute large 

 polypoid masses. The cervical mucosa is rich in special 

 mucous glands, which during pregnancy elaborate the 

 uterine seal — a very tough, firm, adhesive structure com- 

 pletely sealing the cervical canal from the uterus to the 

 vagina and constituting a highly elaborate and efficient bar- 

 rier against invasion of the pregnant uterus by infection 

 from the vagina. The cervical canal, elaborately barri- 

 caded by mucous folds and by the firm contraction of the 

 circular muscles, is extremely narrow, and in the ruminant 

 is besides exceedingly crooked (See Figs. 40, 41). This 

 disposition of the cervical mucosa has given rise in the past 

 to the fiction of "closure of the womb" and led to the belief 

 in "opening the womb" as a panacea in sterility. Anterior- 

 ly, the cervical canal opens into the uterine cavity by the os 

 uteri internum; posteriorly, at the summit of the conical 

 projection into the vagina by the os uteri externum. 



During estrum the muscular walls of the cervix relax and 

 the cervical canal dilates somewhat. When parturition en- 

 sues, the cervix, as such, becomes temporarily obliterated, 

 and the canal dilates sufficiently for the passage of the fetus 

 —-that is, until its cavity is co-extensive with the pelvic cav- 

 ity and with the cavities of the uterus and vagina. At this 

 time it becomes virtually non-recognizable ; all the posterior 

 segments of the genital tract — uterus, cervix, and vagina 

 — become one continuous tube of virtually uniform calibre. 

 In that type of cystic disease of the ovaries causing nymph- 

 omania, the cervical canal undergoes pathologic dilation. 

 In the sow the cervix is not so well defined and no elaborate 

 uterine seal forms. Instead, the vagina and cervix extend 

 as an irregular tube up to the bifurcation of the essentially 

 double uterus. 



d. The vagina is a musculo-membranous canal, formed 

 from the fusion of the posterior ends of Mueller's ducts and 



