300 AGRICULTURAL BACTERIOLOGY 



sential difference, as far as the cause is concerned, between 

 abortion early in the gestation period and that which occurs 

 later. 



Causes of abortion. The expulsion of the fetus may be 

 due to slipping, injury by another animal, or other me- 

 chanical causes, and to feeds that have a specific action on 

 the pregnant animal, such as grains and fodders that con- 

 tain large amounts of smut or ergot. It is quite certain, 

 however, that abortion as it is observed in cattle is almost 

 wholly due to the invasion of the animal by a specific or- 

 ganism which may pass from animal to animal, producing 

 what is commonly known as contagious abortion. The dis- 

 ease is of the greatest economic importance in cattle. A 

 similar trouble, caused, however, by a different organism, 

 is noted in mares, and a third organism is responsible for 

 abortion in sheep. 



The disease as it appears in cattle has spread rapidly in 

 recent years, owing to the great increase in the sale of 

 breeding animals. It is now rare to find a herd of any 

 considerable size that has an entirely clean record. The 

 losses it occasions are felt especially by the breeder who 

 relies on the progeny of his herd for a large share of his 

 returns, much more than by the farmer who is primarily in- 

 terested in the production of milk. In the beef districts 

 the disease, of course, becomes of major importance to the 

 farmer. 



The loss is not wholly confined to that incurred from the 

 death of the calf, for if the abortion occurs early in the 

 gestation period, the animal will rarely prove a profitable 

 producer of milk during that lactation period. If the abor- 

 tion occurs late in the period, the flow of milk will be nor- 

 mal. In economic importance the disease ranks with tu- 

 berculosis, Texas fever, and hog 1 cholera. Against these 

 the farmer has much hope of making a successful fight with 



