sterility 197 



cases it mQ.y be necessary to make a small incision 

 ill order to dilate the opening. It is probable that 

 mechanical manipulation of the parts, aside from the 

 mere dilation of the passage, is conducive to fertili- 

 zation, hy increasing the blood supply to the part. 

 There are some mechanical contrivances, now on the 

 market, which are useful in dilating the mouth of the 

 womb, and increasing the probability of pregnancy, 

 especially in mares. 



Females that have aborted are not so likely to 

 breed, especially when the abortion has been due to 

 contagion. Tumors, malformations, or diseased con- 

 ditions of the genital organs in females, are frequent 

 causes of sterility. In mares that have been bred, 

 there is sometimes an opening from the vagina into 

 the rectum, through which pieces of dung often pass 

 and escape from the vulva. This opening usually 

 results from injury to the part while foaling. Such 

 mares do not breed readily and are liable to injury 

 in foaling afterward. In many cases this opening 

 between the rectum and the vagina can be closed hy a 

 good surgeon and the mare become as valuable as 

 ever for breeding purposes. Excessive sexual inter- 

 course in all animals tends to lessen the fertility of 

 the animal. 



Breeding very young animals is likely to stunt the 

 growth of females and to impair the vigor of the 

 reproductive s^'stem in males. Stallions should not 

 be used for breeding purposes until three years old, 

 and should be limited to fifteen or twenty mares the 

 first season, and not used very frequently even then. 



