Artery Relaxation in Practice. 219 



sufficient to enlarge or continue its growth. Tire embryo 

 supply of blood nutrition is not increased, because the 

 blood supply to the udder is not reduced, the power of di- 

 verting the udder-supply to the embryo being lost, by the 

 loss of contractility in the udder-supply arteries, in the 

 cows that abort. 



The less the degree of engorgement and relaxation in 

 the udder-supply arteries, the larger the blood supply to 

 the embryo ; and the longer and later the growth of the 

 embryo continues. The earlier abortion occurs, the greater 

 the degree of engorgement and relaxation of the udder- 

 supply arteries, and the earlier the embryo dies, because 

 its blood supply is not, and cannot be, increased. 



As the very large majority of 86 per cent of aborted em- 

 bryos are dead when delivered, we here refer to a diagram 

 illustrating the arrest or stoppage of increase in blood 

 supply, and the arrested growth of the embryos. 



As engorgement affects small and large arteries similarly, 

 we assume, for the purpose of explanation, that all the 

 mammary blood flows in the large artery d, Fig. i, Plate 

 VII.,* as far as <?, same fig., where the branch,^, leads to 

 the embryo, h. The other branch, /, is the udder-supply 

 artery, leading to the udder, /. Assume that at about mid- 

 term half the blood flows to embryo, h, the other half sup- 

 plying the udder,/. At this time the embryo is about half 

 grown, as at kk, but its growth cannot be enlarged, nor 

 even continued, to the full-term size, nun, without an in- 

 creased supply of blood. There is no other source from 

 which an increased supply of blood to the embryo can come 

 than from the blood that supplies the udder through the 

 artery, / But the udder-supply artery, /, is relaxed at a 

 much enlarged size ; and being relaxed, cannot be contract- 



* It will be understood tliat all the plates are largely diagramatlc, and must 

 not be understood by the reader to be anatomical representations of the parts 

 referred to. 



