The Position of the Fetus in the Uterus. 383 



and less conspicuous than in the larger animals, are more fre- 

 quently extended and the neck, being very short, is not curved. 



When parturition approaches and the fetus of the uniparous 

 animal has well-nigh outgrown the available room in the abdomi- 

 nal cavity, the presenting end of the fetus pushes up to, or into, 

 the pelvic cavity and is readily felt by manual exploration per 

 vaginam or per rectum. In the cow, the fetus having a com- 

 paratively short neck, the head is frequently extended a few 

 days before parturition, pushes up into the pelvic cavity and, 

 extending over the top of the vagina by pushing the superior 

 wall of the uterus backward, it appears to the inexperienced 

 veterinarian to be outside the uterus, although in reality the 

 position is not rare and not abnormal. Along with the head, 

 there may present also, in these cases, two anterior feet, extended. 

 We have not observed this attitude of the fetus in the mare, 

 although it may occur. 



At the termination of pregnancy, the fetus changes its position 

 and, when it begins to move toward the pelvic inlet, as a result of 

 labor pains, it normally revolves slightly upon its long axis and, 

 changing from lateral recumbency, presents with its dorsum 

 toward the lumbar vertebrae of the mother and its ventral surface 

 toward her pelvic floor. This is essential in relation to the 

 resistance offered to the passage of the fetus through the pelvic 

 canal. Whenever it presents otherwise than with the dorsal sur- 

 face corresponding to the spinal column of the mother, it causes 

 great or insuperable difficulty in expulsion and call's for a version 

 of the fetus upon its long axis before delivery can readily occur. 

 This difficulty arises from the fact to which we have already al- 

 luded, that the fetus maintains the form of an arc, the ventral 

 surface being concave. The direction of the roof of the passage 

 through the pelvis is also somewhat arciform, with its concavity 

 downwards, so that the arciform fetus can readily pass only in the 

 one position and a very great obstacle is offered to its passage when 

 its dorsum is directed downward or to the right or left, its arci- 

 form body becoming impacted against some portion of the 

 maternal passage. 



