186 DISEASES OF CATTLE. 



cow this may be after seven and one-half months of pregnancy. Earl 

 Spencer failed to raise any calf born before the two hundred and forty- 

 second day. Dairymen use the term abortion for the expulsion of the 

 product of conception at any time before the completion of the full 

 period of a normal pregnancy, and in this sense it will be employed in 

 this article. 



Abortion in cows is either contagious or noncontagious. It does not 

 follow that the contagiuin is the sole cause in every case in which it is 

 pi vsent. We know that the organized germs of contagion vary much 

 in potency at different times, and that the animal system also varies 

 in susceptibility to their attack. The germ may therefore be present 

 in a herd without any manifest injury, its disease-producing power 

 having for the time abated considerably, or the whole herd being in a 

 condition of comparative insusceptibility. At other times the same 

 germ may have become so virulent that almost all pregnant cows suc- 

 cumb to its force, or the herd may have been subjected to other causes 

 of abortion which, though of themselves powerless to actually cause 

 abortion, may yet so predispose the animals that even the weaker germ 

 will operate with destructive effect. In dealing with this disease, 

 therefore, it is the part of wisdom not to rest satisfied with the discov- 

 ery and removal of one specific cause, but rather to exert oneself to find 

 every existent cause and to secure a remedy by correcting all the harin- 

 ful conditions. 



CAUSES OF KOXCOXTAGIOUS ADORTIOX. 



As abortion most frequently occurs at those three weeks intervals at 

 which the cow would have been in heat if noupreguant, we may assume 

 a predisposition at such times due to a periodicity in the nervous sys- 

 tem and functions. Poor condition, weakness, and a too watery state 

 of the blood is often a predisposing cause. This in its turn may result 

 from poor or insufficient food, from the excessive drain upon the udder 

 while bearing the calf, from the use of food deficient in certain essen- 

 tial elements, like the nitrogenous constituents or albuminoids, from 

 chronic wasting diseases, from round or tape worms in the bowels, from 

 flat worms (flukes, trematodes) in the liver, from worms in the liver, 

 from worms in the lungs, from dark, damp, unhealthy buildings, etc. 

 In some such cases the nourishment is so deficient that the fetus dies 

 in the womb and is expelled in consequence. Excessive loss of blood, 

 attended as it usually is by shock, becomes a direct cause of abortion. 



Acute inflammations of important organs are notorious causes of abor- 

 tion, and in most contagious fevers (lung plague, rinderpest, foot and 

 mouth disease) it is a common result. Affections of the chest which 

 prevent due aeration of the blood induce contractions of the womb, as 

 shown experimentally by Brown-Sequard. Pregnant women suffocated 

 in smoke aborted in many cases.* 



* Retcml. 



