730 Veterinary Obstetrics 



fat, her young is not as a rule so large as the young of an animal 

 which is simply well nourished. 



Diagnosis. Excessive volume of the fetus is difficult of accu- 

 rate determination, prior to its entrance into the pelvic canal. 

 Various means have been suggested for determining this excess 

 in volume, but they are necessarily unreliable. Some have sug- 

 gested an unusual size of the abdomen, but this may depend upon 

 twin pregnancy, an excessive number of fetuses, or hydramnios 

 or other cystic disease. In many animals we note an enormous 

 abdomen as the result of the character of the food or of individual 

 peculiarity. 



Along similar lines, some veterinarians have suggested that 

 the excess in size may be anticipated owing to increased weight 

 of the animal. 



Its final determination must occur when, with a normally di- 

 lated cervix and normal genital canal, labor sets in and the ex- 

 pulsive efforts are vigorous, and, although the fetus is normal 

 in form and position, httle or no progress is made in its expul- 

 sion. If, under these conditions, the veterinarian examines the 

 patient, he is enabled to judge that comparatively the size of the 

 fetus is too great to pass readily through the birth canal. How- 

 ever, this opinion does not depend upon any definite measure- 

 ment which he is able to make of the dimensions of the pelvis. 



The principal obstacles to birth, in most of these cases, are the 

 head and chest. The obstruction caused by the head is especially 

 notable in the bitch and cow. In the bitch the difficulty most fre- 

 quently occurs in those breeds, like the bull-dog, which have 

 short muzzles and consequently present a blunt extremity to 

 pass through the undilated canal. 



In the mare, the head of the foal is small and elongated and 

 rarely offers any serious obstacle to birth. Generally it is only 

 when the chest or croup arrives at the pelvic inlet that serious 

 difficulty arises because of volume. 



We have already noted in the preceding pages that the dimen- 

 sions of the chest of the foal are greater than those of the pelvis 

 of the mother, and that it is only by some displacem^ent of the 

 parts, especially of the shoulders, that the chest of the foal is 

 capable of passing through the birth canal. When the dimen- 

 sions of the fetus are such that it is impracticable for the diminu- 

 tion by displacement to be sufficiently great to permit it to 



