28 I 'eicn'uary Obstetrics 



The origin of this projection of the cervix into the vagina 

 seems somewhat analogous to intestinal intussusception, a partial 

 invagination of the anterior portion of the genital tube into the 

 vaginal cavity. At the time of parturition this projection and 

 the cervix as a whole becomes obliterated and the uterus and 

 vagina temporarily indistinguishable except in the character of 

 their mucosa. 



The dimensions and dilatability of the os uteri and cervical 

 canal vary widely in individuals and at different times. Nor- 

 mally, the mucosa of the circumference of the os 7cteri sho\\\6. be 

 in contact. In the mare it should permit of the ready intro- 

 duction of one or two fingers through it and along the canal of 

 the cervix into the uterine cavity. 



At the time of estrum the os becomes more dilated and, fre- 

 quently, readily admits three or four fingers or the entire hand. 

 It is not unusual to find cases where the os iiteri of the mare is 

 abnormally dilated and flaccid to such a degree as to interfere 

 with fecundation. More rarely in the mare the os iiteri may be 

 closed or the cervix very much constricted in a manner to render 

 the passage of spermatozoa into the uterine body uncertain and 

 thus tend to induce sterility. 



Anteriorly, the cavity of the uterine body of the mare is con- 

 tinuous with that of the two cornua, without a distinct line of 

 demarcation beyond an abrupt turn at right angles or a slight 

 recurvation to its long axis. This peculiar relation of the cornua 

 to the uterine body and to each other renders bi-cornual preg- 

 nancy (which see) possible in the mare (see Figs. 2, 120, 121). 

 Each cornu is much like the body and the combined length of 

 the two surpasses the latter in extent. They end obtusely, not 

 far from the ovary, and present, on their interior, conical pro- 

 jections in which there is an opening, the os uterinum, or uterine 

 orifice of the oviducts. 



In the cow, and other ruminants, the uterine body is less pro- 

 nounced in size when viewed exteriorly and yet more so upon 

 section, while the cornua are much longer, tapering and more 

 ample than in the mare. The two cornua separate at a very acute 

 angle and for a time extend forwards almost parallel to each 

 other and then, becoming .somewhat more divergent, curve down- 

 wards, outwards, backwards and then upwards to end above the 



