Infections of the Ovum, Embryo and Fehis 495 



mentary tract very voluminous infection. When metritis 

 exists, with or without retained afterbirth, the alimentary 

 canal of the apparently healthy calf swarms with bacteria 

 and the calf probably breaks down with spesis, dysentery, 

 or pneumonia. When the cow calves vigorously and expels 

 the membranes promptly, the infection in the alimentary 

 tract of the fetus is scant. All clinical and bacteriological 

 evidence indicates that the abortion is in each case referable 

 to infection, and to infection only. 



In sharp conflict with all recorded evidence, the term 

 "contagious abortion" constructively suggests a non-con- 

 tagious abortion. The fiction of a non-contagious abortion 

 continues to be supported by many who believe that some 

 abortions are due to various causes other than infection. 



(c) Many believe in traumatic abortion but fail to ex- 

 plain how mechanical injury can cause the death and ex- 

 pulsion of a fetus. The bovine fetus lies upon the abdominal 

 floor, surrounded by the abundant amniotic fluid and almost 

 completely surrounded by the still more abundant allantoic 

 fluid (See Colored Plate I). The head of the fetus gener- 

 ally lies within the pelvic cavity. If in the posterior pre- 

 sentation, the head usually lies above the sternum of the 

 cow. When the abdominal floor is struck at a point against 

 which some part of the fetus rests, it promptly floats away 

 in its fluids. Fetal life is not dependent upon the same 

 vital functions as extra-uterine life. Since respiration and 

 nutrition are provided by the placentae, the sole vital func- 

 tion of the fetus is the fetal circulation. Fatal injury to 

 the fetus is, therefore, virtually limited to a traumatism 

 which can directly stop the fetal heart-beat. It is not known 

 that such injury is possible. 



Placental separation due to mechanical injury is unknown. 

 I have studied carefully in the abattoir the uteri of more 

 than two thousand pregnant cows and heifers, and have not 

 observed an instance of any injury to uterus, fetal mem- 

 branes, or fetus which, had the animal been permitted to 

 live might apparently have led to abortion. I have already 

 described inter-placental hemorrhage with fetal desiccation, 



