728 Veterinary Obstetrics 



that the fetus was dead and emphysematous destroys all evi- 

 dence of prolonged gestation. The fetus may have perished at 

 280 days. In 1908, Frost, instructor in the N. Y. State Veteri- 

 nary College, delivered a Holstein-Fresian cow of a calf weigh- 

 ing 147 lbs. The duration of pregnancy was normal, the calf 

 was normal, and was alive, but died during delivery. Calves 

 weighing over 100 lbs. are not rare in this breed. It is con- 

 sequently unwarranted to conclude that, because a fetus is un- 

 usually large, the duration of pregnancy has been excessive ; or 

 that, because pregnancy is being prolonged, dystokia from ex- 

 cessive volume of the fetus must occur. While rare exceptions 

 may occur, according to our observations the largest fetuses are 

 usually encountered in those cases where the full duration of 

 what we regard as normal pregnancy has merely been reached. 



It appears, from all that we can learn of the subject from a 

 clinical standpoint, that the retention of the fetus in the uterus, 

 beyond the average duration of time, is not dangerous from the 

 standpoint of causing dystokia by excess of volume, but rather 

 that other complications may arise which may be more or less 

 dangerous for the well-being of the mother and fetus. 



In multiparous animals, like the bitch and sow, it is frequent- 

 ly noted that when the number of fetuses is below the average 

 they tend to grow larger because of the increased nutritive 

 supply, and in this way tfend to cause diflBcult labor. 



Excessive size of the male animal, as compared with that of the 

 female, has been alleged to cause an excessive size of the fetus, 

 but this we have not been able to verify clinically. We have 

 had occasion to observe the results of crossing small mares of 

 700 to 1000 pounds with large draft stallions weighing from 1800 

 to 2500 pounds, or approximately three times the weight of the 

 mare. Yet we did not observe a case of dystokia, in such mares, 

 attributable to excessive volume of the fetus. 



Fleming cites several authors to show that such crosses do re- 

 sult in difiBcult labor, especially in the ewe and bitch. On vthe 

 other hand. Saint- Cyr states, in harmony with our personal ex- 

 perience, that he has repeatedly seen large Percheron stallions 

 crossed with small mares, without any resulting difficulty .in 

 foaling, because of size. 



It appears from clinical observation that the size of the female, 

 not that of the male, chiefly fixes the size of the fetus, and 



