Argument on Abortion. 227 



5. The thin and relaxed condition of the artery-walls 

 becomes more or less chronic or permanent, in many cows, 

 the arteries losing their natural elasticity by prolonged in- 

 action, from loss of contractile power, their enlarged size 

 becoming fixed, from assimilation in their walls during the 

 continued engorgement, while they are too thin and weak 

 to contract. 



6. The size of the udder-supply arteries, when relaxa- 

 tion takes place, varies in different cows. But the enlarged 

 artery tubes convey much more than the previous quantity 

 of blood to the milk glands ; the necessary supply of blood 

 to the embryo being correspondingly reduced by the un- 

 natural increase in the udder-supply, thus reducing the 

 source of embryo nutrition, by increasing blood flow to 

 the udder. 



7. At some stage of embryo growth, or enlargement, 

 the reduced or fixed supply of blood to the embryo be- 

 comes insufficient, because, being fixed by artery relaxation, 

 in cannot be increased, as the size of the udder-supply ar- 

 teries, and the supply of blood they convey to the milk 

 glands, being fixed, cannot be reduced. 



8. There is no source from which embryo nutrition, or 

 growth, can be increased, except by diverting a sufficient, 

 and constantly increasing quantity of the large and fixed 

 blood supply flowing to the udder, into the ovarian and 

 uterine artery channels, to thereby increase the placental 

 circulation, and so increase the nutrition required by the 

 embryo. 



9. The deficient, non-increasing placental circulation 

 is also fixed by the over-strain and relaxation of the 

 udder-supply arteries, there being no increase in the total 

 of mammary blood, unless the cow starves her own tis- 

 sues. Hence there can be no increase of blood nutrition 

 to the embryo, except by, and in proportion to, some re- 

 duction in the udder-supply of blood. 



