HOW ABORTION BECOMES DISSEMINATED 



195 



other breeds of cattle with little less severity. Many heifers 

 will abort once and then carry their second calf for the full 

 period. A less number will abort their second calf and it is a 

 rare condition when a cow aborts the third time. Heifers from 

 aborting mothers may be less susceptible than those born to 

 healthy or noninfected dams. 



The Manner by Which Abortion Becomes Disseminated. — 

 The mucous lining of the uterus of infected heifers and cows 

 harbors the Bacillus abortus. The contents of the uterus, such 



Fig. 68. — Heifer, thin and in poor condition, though not affected with tuberculosis. 

 (Courtesy of M. H. Reynolds.) 



as the foetus, foetal membranes, and the fluids, are all virulent 

 and when expelled from the uterus become vehicles by which the 

 disease spreads. The discharge from the uterus following abor- 

 tion contains myriads of bacilli (germs) which may be carried 

 to various parts of the stable by aid of the surface drainage ; 

 attendants may carry the infection on their boots or on the milk- 

 ing utensils which are at times carelessly handled. The bull 

 is undoubtedly a frequent carrier of the infection, especially 

 where several breeders use the same animal. Infected pregnant 

 heifers or cows introduced into healthy herds are often responsi- 

 ble for establishing new centers of the disease when they abort. 



