792 Veterinary Obstetrics 



expulsion of the fetal membranes from the uterus. If they remain, 

 they inevitably undergo decomposition and cause more or less 

 serious disease. When the fetus has been removed or has ceased 

 to live, and the passage of blood through the umbilic cord has 

 ceased, these membranes become essentially foreign bodies, highly 

 subject to infection, which more or less seriously involves the 

 uterus and the animal system as a whole. 



A study of the placentae of the domestic animals shows that 

 the intimacy of contact between fetal and maternal placentae 

 varies greatly in the different species. The placental tufts are 

 very much longer and more complex in ruminants than in other 

 domestic animals. In ruminants the placental attachments are 

 not uniform over a large area, as in the mare and sow, but they 

 are concentrated upon certain well-defined areas, where their 

 attachment is all the more complex. It would at once be sus- 

 pected, after a study of the anatomy of the placentae of various 

 domestic animals, that ruminants, with their highly complex 

 cotyledonous placentae and very complex placental villi, would 

 be far more subject to retention of the fetal membranes than is any 

 other animal. This suggestion, however, holds true for but one 

 member of the group, the cow. Retained placenta may almost 

 be said to be a disease of the cow, so far as the domestic animals 

 are concerned. While the condition is met with in all domestic 

 animals, and acquires importance in mares, there is no such 

 number of instances in any other domestic animator in all others 

 combined, as in the cow. See Fig. 97, p. 361 and Fig. 139, p. 802. 



It is diflficult to define in exact terms what constitutes retained 

 placenta. The line between the normal and abnormal duration 

 of retention of the placenta, after the expulsion of the fetus, 

 constantly vacillates according to species and individual, so that 

 the term is largely a comparative one. In the mare the chorion 

 usually separates from the uterus within 10 to 15 minutes after 

 the expulsion of the fetus, and if it remains over 30 minutes it 

 might be very properly considered abnormal, although in all 

 probability it may yet separate and come away spontaneously 

 after a further trifling delay, and the case pursue an apparently 

 normal course. 



In cows the fetal membranes usually do not become detached 

 so quickly. In a large proportion of cases they still remain at- 

 tached to the cotyledons after one-half to one hour, and, not at 



