Abortion in Cows. VM^ 



formed are enlarged by distensive engorgement, to tlie 

 same extent that the milk glands and bag are enlarged. 



2. The engorgement of the udder-supply arteries, when 

 the increase of blood is too rapidly made, thins down the 

 artery walls much faster than their circulation thickens or 

 repairs them ; so that many cows abort because the 

 artery-walls are so much thinned and weakened that the 

 cows can no longer contract their udder-supply arteries. 

 This is the effect when a large, or very large increase of 

 blood and yield is very rapidly made, taking less than half 

 the safe length of time, compared with the time taken in 

 Holland, for instance, to make as large an increase in blood 

 and milk-yield. 



Two things should here be considered : — 



1. Elastic muscles lose their contractile power, simply 

 by inaction or disuse when this inaction is too long contin- 

 ued ; and the loss of elasticity becomes permanent when 

 the uncontracting state continues several months. 



2. It cannot be disputed that the mammary artery walls 

 are very much thinned down by great degrees of rapid en- 

 gorgement ; nor that extreme engorgement continues or is 

 increased, as long as a large addition to yield continues, 

 or is increased ! The long continuance of the artery walls 

 in this thinned-down, inactive, and uncontracting con- 

 dition is therefore clearly evident. 



Inaction for a long time would alone lead to the loss of 

 artery elasticity. But when this relaxed condition is coup- 

 led with a reduction of half the natural thickness and 

 strength of their walls, and this stationary and weak con- 

 dition is certainly long maintained ; the same bulk of 

 blood and its expansive pressure, that first engaged the 

 udder-supply tubes, being continued, as the condition of 

 continuing the large yield, — in such cases the relaxed con- 

 dition of the udder-supply arteries is therefore made chron- 

 ic, from their tubes being thus kept as much expanded by 



