THE FORM OF THE PREGNANT UTERUS. 



The gravid uterus undergoes important changes in its form, 

 since it must adapt itself to the form, volume and position of the 

 fetus or fetuses and especially to the membranes which surround 

 them. In the muciparous animals, we have already stated that 

 the fetuses are distributed somewhat equidistant from each other 

 throughout the length of the cornua and that, at the points 

 where they develop, the organ becomes enlarged, while between 

 'them it is constricted so that it gives the organ a nodular 

 appearance. In animals, like the mare and cow, which usually 

 produce but one young at a time the uterus assumes a somewhat 

 oblong or globular form. In uniparous animals the fetus is usu- 

 ally contained in the uterine body and one horn, so that the princi- 

 pal changes take place in those parts and leave the non-gravid cornu 

 but slightly increased in size or changed in form, so that it appears 

 as a mere appendage upon the side of the enlarged cavity which 

 contains the fetus. In the raultiparous animal, whether there 

 be several fetuses or only one, the development of the young oc- 

 curs in the cornu or cornua and the so-called uterine body regularly 

 remains empty and serves merely as a passage for the fetus from 

 the point of its development, when the time for parturition 

 arrives. In rare cases in multiparous animals, not infrequently 

 in the mare, a fetus may develop more or less equally in the two 

 cornua, bicornual pregnancy, and, at the time of parturition, offer 

 serious or fatal obstacles to birth. (See Transverse or Bicornual 

 Pregnancy.) Usually, in multiparous animals, the number of 

 fetuses is approximately equal in the two horns. 



The cervix of the uterus undergoes well-marked changes dur- 

 ing the latter part of pregnancy. During pregnancy the os 

 uteri is firmly closed by the constriction of the circular muscle fibers 

 of the cervix and the occlusion is further secured by means of an 

 albuminous clot, which is quite thick and firm. The cervix is at 

 first quite firmly contracted, so that it is exceedingly difiicult to 

 force a passage through it into the uterus of the cow, while, in 

 the mare, as in the non- pregnant state, it is very easily dilated 

 and one or more fingers or the entire hand may be inserted. 



As parturition approaches, the os .uteri normally becomes 

 somewhat dilated. The walls of the cervix become :softer and 



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