250 Cattle Problems. 



natural time, or in the natural way, however strong the in- 

 stinctive or natural tendency of such cows to breed may 

 be, because these arteries a^e incontractible, in conse- 

 quence of being relaxed in the muscular tunics. 



The failure of such deep and long-yielding milkers to 

 breed results, also, from the relaxation of their udder-sup- 

 ply arteries. A certain but variable proportion of all the 

 blood produced by digestion is required to nourish the 

 cow's individual system. Any surplus remaining is natu- 

 rally breeding blood, provided for the breeding function. 



Continuing a large yield, long, but at the same time not 

 breeding, nor coming into heat, is a certain indication of 

 most of the breeding blood being conveyed to the milk 

 glands ; and the reason of the continued flow in that di- 

 rection, is that the arteries that supply the udder with blood 

 do not contract ; not contracting because they are relaxed 

 to such a degree that their contractile power is either 

 much weakened or lost. 



Not having power to contract, or if any, not sufficient 

 to cause such a supply of blood and blood heat, in the 

 ovarian circulation, as is required to produce the accumu- 

 lation of heat that causes coupling fever. The blood and 

 heat supply in the ovarian vessels thus failing, the heat 

 that would naturally bring on coupling does not appear, 

 nor occur. So there is neither impregnation, nor the heat 

 that leads to it, because the uterine circulation is reduced 

 and delayed in such large degrees, by the continued large 

 supply of blood, and its heat together, to the udder, as to 

 render the providing of a sufficient quantity of blood and 

 heat to give rise to the oestrum, is impracticable; hence 

 the failure of deep milking cows to breed is directly due 

 to reduced blood-supply in the uterine and ovarian circu- 

 lation, and primarily to the relaxation of the udder-supply 

 arteries at the greatly increased size that convevs so much 



