Prevention of Abortion. 239 



mature ova, and a sufficient supply of breeding blood to 

 continuously sustain embryonic breeding, rarely concur 

 till two months after full-term delivery, heifers that abort 

 should not be allowed to couple till six or eight weeks 

 after the expiration of full-term. This interval allows 

 time for considerable recuperation, or recovery of strength 

 and contractility in the relaxed artery walls, by assimila- 

 tive repair. 



In nearly all cases, the less rapidly cows dry up their 

 yield, the more their arteries, and sometimes their milk- 

 glands and udder-sacks, are relaxed, whether this weakened 

 condition has been brought about slowly or rapidly. 



If heifers or cows abort early after pregnancy, their 

 udder-supply arteries are probably relaxed severely, and 

 the injury has most likely been rapidly inflicted. Hence, 

 when either heifers or young cows abort before the sixth 

 or seventh month of pregnancy, they should not be al- 

 lowed to couple till from three to nine motiihs after the 

 expiration of full term. If they abort before the middle 

 of their term, they should not be milked for about ten or 

 twelve months. 



The principle is the same as to over-strain in the udder- 

 supply artery walls, as in the human wrist, instep, or other 

 parts ; the greater the injury, the longer the time required 

 for repairing it, the more time required for rest. When 

 abortion, resulting from artery relaxation in cows, takes 

 place before mid-term, the relaxation of the artery walls 

 must certainly be severe, as the blood supply to the 

 embryo fails at an early period, showing great expansion 

 of the udder-supply arteries, and that these arteries do not 

 contract, as they should, when the embryo requires an in- 

 crease of blood nutrition, as indicated by the feeling of 

 hunger impressed on the nerves of the cow. 



The chances of young cows recovering full contractile 

 power, after extreme engorgement and relaxation of the 



