Failure to Breed. 251 



of the mammary blood to the milk-glands, that the supply 

 to the ovarian vessels is too small to induce coupling. 



It is quite likely that these non-breeding deep milkers 

 are, many of them, the same cows that previously bred 

 only once or twice in alternate seasons. But this is not 

 important, as they are permanently disabled as breeders 

 when their udder arteries remain greatly relaxed. When 

 deep milkers fail in breeding power from a single instance of 

 engorgement of their udder-supply artery-tubes, the ex- 

 pansion is extreme, and most likely takes place at or be- 

 fore midsummer, when they are not pregnant ; and also 

 when the great abundance and juiciness of tempting grass 

 feed leads to excessive consumption ; the effect being a 

 great increase in the bulk of blood produced, as is clearly 

 evident by the doubling of the udder and artery-size in 

 some of such cases, in the short period of 6 to 12 weeks 

 in different cows. The extreme distention of the arteries 

 that supply it at the time of maximum yield, is as great as 

 that of the udder, and the painful effects of extreme dis- 

 tention of the udder, when long continued, are frequently 

 too evident to be disputed. And it is certain that great 

 pain in such cases results from actual injury to the udder 

 structure ; the nature of the injury in the milk-glands 

 probably being that of discohesion, from extreme tension, 

 or overstrain, in the fibrous substance of the milk-glands. 

 And this overstrain or extreme distention being increased 

 or frequently repeated, probably leads, in some instances, 

 to permanent relaxation in the milk-glands, also in the 

 udder sack ; and, at the same time, in the arteries that 

 supply the udder with blood ; the relaxation in each case 

 being, of course, due to an over-supply of blood in the 

 udder-supply arteries ; the over-supply of blood in such 

 cases being the result of rapid increase in feed, or over- 

 feeding. 



The breeding arteries of cows are limited in their con- 



