548 Veterinary Obstetrics 



upon the fetus can be any greater after the expulsion of the fetal 

 liquids than before, although we admit that it does closely in- 

 vest the fetal body and may thus be prevented from expelling 

 the fetus from its cavity. The escape of the fetal fluids indi- 

 cates rather a delayed expulsion of the fetus than a premature 

 rupture of the membranes ; that is, the membranes normally 

 rupture, but after their rupture some mechanical obstacle or 

 some weakness of the uterus has served to prevent the expulsion 

 of the fetus, and consequently has led to its death. 



Indirectly the rupture of the fetal membranes and escape of 

 the fluids is probably the most common cause of the death of the 

 fetus during labor. The fact that a foal does not usually live more 

 than one to three hours after the first expulsive efforts, while 

 the calf may continue to live much longer, is explained by the 

 differences in the character of the placentae. The attachments in 

 the mare are less intimate and become detached very shortly after 

 labor sets in. The calf lives longer largely because the os uteri 

 of the cow dilates more slowly and hence the fetal waters do not 

 so completely escape, or they may be entirely retained and the 

 membranes remain unruptured for a considerable period of time. 

 In the cow also the allantoic sac may not rupture at first, but 

 only the amnion, whereas in the mare the allantoic sac must 

 necessarily rupture before the amniotic sac appears at the vulva 

 and, consequently, when this latter ruptures both .sacs are freely 

 open and all the fluids may escape. The escape of these fluids 

 permits a contraction of the uterus which certainly exerts an 

 important influence upon the dehi.scence of the placenta and 

 leads to the death of the fetus. 



The rupture of the water-bag in an approximately normal par- 

 turition may well be left wholly to nature, as it ordinarily requires 

 no interference, but, on the other hand, is usually better accom- 

 plished without it and will naturally occur at the most appropri- 

 ate time. The water-bag cannot protrude far beyond the vulva 

 in the cow or other ruminant, without rupturing, because the 

 amnion is adherent to the chorion over a large part of its area, so 

 that it cannot pass out with the fetus, but must rupture, and the 

 fetus be born naked. 



Some writers claim that it is at times necessary for an attendant 

 to rupture, or even to cut the chorion of the new-born. We 



