The Mnellerian Ducts 27 



upon the degree of fusion which has occurred between the 

 two tubes. There are recognized in domestic animals a 

 uterine body and two cornua, each having essentially like 

 functions in varying degrees. This is in sharp contrast to 

 the uterus of woman, where the uterine body constitutes es- 

 sentially the entire functional organ and the cornua are un- 

 important appendages. In the rabbit there is no uterine 

 body, but two distinct tubular uteri opening separately into 

 the vagina. In the bitch, cat, and sow the uterine body is 

 limited in extent and physiologically unimportant, rarely 

 containing placental attachments and only a small portion 

 of one fetus except while in transit at the time of birth. 

 The two cornua are extensive, and in them develop the 

 fetuses, so that physiologically the horns represent the two 

 separate uteri of the rabbit. In ruminants the uterine body 

 is larger and assumes higher importance physiologically, 

 while the cornua remain relatively large. The one, two, or, 

 very rarely, more fetuses are habitually located almost 

 equally in the body and the cornua, so that they represent a 

 middle stage in the transition between the double uterus of 

 the rabbit and the single uterus of woman, physiologically 

 devoid of cornua. In the mare the uterine body becomes re- 

 latively more important than in the ruminant. 



The relative sizes of the cornua and of the uterine body 

 bear a close relation to the number of young brought forth 

 at a given birth. In muciparous animals, there are two 

 uteri, as in the rabbit, or the two extensive cornua with 

 functionally unimportant uterine body, as in the bitch, cat, 

 and sow. In ruminants, which are largely biparous, the 

 uterine body and cornua become approximately equal in ex- 

 tent and function. In the normally uniparous mare, the 

 cornua are smaller than the body. 



The uterus and its cornua, within the above limitations, 

 are uniform in their plan of structure and function. They 

 consist of three coats : mucous, muscular and peritoneal. 



The mucous coat constitutes the essential physiologic basis 

 of the organ. The mucous epithelium is very elaborate, con- 

 sisting superficially of columnar cells, embedded deeply with- 



