I20 Veterinary Obstetrics 



through her increase iu age and, having been idle for a year, has, 

 probably, become very fat, the sexual system somewhat weak- 

 ened and the tendency to sterility intensified. 



Jn dairy cows, the results of sterility may be equally, or more, 

 disastrous. The production of milk is an essentially sexual func- 

 tion, enduring, as a rule, but for a year or two, when it may be 

 re-established or reinvigorated only by bringing forth young. 

 Hence, in a dairying establishment, a failure to breed causes not 

 only the loss of the value of the young, but, generally of far more 

 importance, a serious diminution in the amount, or total lo.ss of 

 the milk. The sterility of a large part of, or an entire herd, is a not 

 uncommon observation in the experience of breeders and veter- 

 inarians, and, while such instances are very impressive, they do 

 not equal in the aggregate, the widely disseminated and oft re- 

 peated individual cases. 



If a highly valuable dairy cow fails to produce a calf in a given 

 year, the fact is somewhat masked by the success with other 

 portions of the herd, but the loss occurs and, add these individ- 

 ual instances together, the total cost to breeders becomes enor- 

 mous. If a given cow fails to breed for several years in succes- 

 sion, she becomes far more than a total loss, because the owner 

 retains her, year after year, in the hope that she may yet breed 

 before he sends her to the butcher, where, at best, her value is 

 usually trivial. 



The function of reproduction being exceedingly complex, the 

 causes leading to sterility are correspondingly varied. 



In higher animals, reproduction can only occur as a result of 

 union under favorable conditions of a spermatozoon, or male cell, 

 with an ovum, or female pronucleus ; the first elaborated bj| the 

 testicles of the male, the second by the ovaries of the female. 

 Anything which may interrupt normal coition of the two sexes, 

 or the physiologic activity of either male or female, may end in 

 sterility. 



We consequently meet with sterility in both sexes but, in the 

 female, the genital apparatus is more complex and sterility more 

 common and widely diffused though intrinsically of no greater 

 importance than in the male. The function of the male parent 

 ends with the ejaculation of healthy semen into the uterus or 

 vagina of the female. In the female, there is still to occur the 

 migration of the male cells through the uterus and oviducts until 



