84 NON-SPECIFIC OR GENERAL DISEASES 



and a layer of epithelial cells. This pennits a change of 

 material betrween the fetal and maternal circulation. The 

 arrangement of the placenta differs in the different species. In 

 the mare and sow, the villi are diffused. In ruminants, the 

 villi are grouped at certain points. These vascular masses are 

 termed cotyledons. The maternal cot^'ledons or " buttons " 

 form appendages or thickened points that become greatly en- 

 larged in the pregnant animal. 



Toward the end of the pregnant period, the attachments 

 between the fetal and maternal placentulir undergo a tatty 

 degeneration and finally separate. This results in contractions 

 of the muscular wall of the uterus, and the expulsion of the foetus 

 and its envelopes. In the mare, it is not uncommon for the colt 

 to be born with the covering intact. This is not common in the 

 cow. Usually the envelopes are not expelled until a short time 

 after birth in all animals, and it is not uncommon for them to 

 be retained. This complication is most commonly met with in 

 the cow. 



In the mare the retention of the fetal envelopes or " after- 

 birth " is commonly due to the muscles of the womb not con- 

 tracting properly following birth. Abortion, especially the 

 infectious form, is commonly complicated by a retention of the 

 fetal membranes. Any condition that may produce an in- 

 flammation of the lining membrane of the womb may result in 

 retention of the *' after-birth." Injuries to the uterus resulting 

 from the animal slipping, fighting and becoming crowded are, 

 no doubt, common causes of failure to " clean " in cows. 



The symptoms are so marked that a mistaken diagnosis is 

 seldom made. A portion of the membranes is usually seen 

 hanging from the vulva, and the tail and hind parts may be 

 more or less soiled. The latter symptom is especially promi- 

 nent if the membranes have been retained for several days, and 

 decomposition has begun. In such case, the discharge from the 

 vulva is dark in color, contains small pieces of the decomposed 



