Retained Placenta in the Cow 793 



all rarely, in cases which are apparently normal, they remain from 

 4 to 12 hours or even more, before becoming detached and drop- 

 ping away. However, if they remain for a longer period than 10 

 to 1 2 hours after the expulsion of the fetus, especially if the latter 

 has been carried for the full term, most obstetrists would regard 

 the further retention as abnormal. 



In the smaller ruminants, the ewe and goat, the placenta is 

 usually eScpelled with more promptness and uniformity than in 

 the cow. 



In multiparous animals it is the rule, if not a necessity, that the 

 placenta of each fetus shall become expelled prior to the expul- 

 sion of the next fetus from the same cornu, and the last fetus is 

 almost immediately followed by the expulsion of its membranes. 



I. Retained Placenta in the Cow. 



Although, among all the domestic animals, the cow is by far the 

 most subject to retained fetal membranes, the causes of such re- 

 tention have not been made wholly clear by veterinary writers, 

 and in fact comparatively little investigation has been made, 

 with a view to a scientific explanation of the pathologic condi- 

 tion. 



By many it has been regarded as a disease of the membranes, 

 by which they adhere with abnormal tenacity to the maternal 

 placenta. While the tufts of the chorion are very long and nu- 

 merously branched, and sink into the recesses in the cotyledons 

 of the mother, they have no power within themselves of holding 

 fast to the maternal tissues. It has already been stated that, at 

 no time during fetal life, is there any direct communication be- 

 tween the maternal placenta and the placental tufts of the cho- 

 rion, but they are always normally separated by two layers of 

 epithelial cells, the one maternal, the other fetal. 



It has long been believed and taught that, under certain dis- 

 eased conditions, adhesions take place between the tufts of the 

 fetal chorion and the corresponding septa of the maternal pla- 

 centa, but no such adhesions have as yet been observed by his- 

 tologic examination. While we are not in a position to deny the 

 possibility of such adhesions, it is certain that, if they occur at 

 all, they are so rare as to constitute no important element in the 

 question as a whole. 



