Etiology. Susceptibility. 43 



of infected feed or drinking water. Artificially it is successful 

 in this way only in exceptional cases (Bollinger, Arloing), but 

 the fact that in blackleg regions the intestinal canal as a rule 

 contains blackleg bacilli (Leclainche & Vallee), while lesions 

 on the surface of the body are observed only in exceptional 

 cases, and furthermore, that crepitant areas are present in the 

 internal organs, speaks in favor of the frequency of infection 

 through the intestines. In the rare cases when such swellings 

 originate in the region of the throat or in the wall of the 

 esophagus, the infection is evidently brought about through the 

 mucous membrane of the throat or the mouth. 



Attacks of the disease in swine have so far only been ob- 

 served in fattening establishments, where tlie symptoms also 

 have indicated infection of the tonsils (Marek). 



Blackleg is a disease connected with infected soil, and trans- 

 mission from animal to animal, as in contagious diseases, or 

 through intermediary objects, evidently occurs very seldom. 

 The blackleg bacilli seem to be capable of multiplying in the 

 soil, and through their resisting 'spores, to preserve their 

 capacity of development and infectiveness even under unfavor- 

 able conditions. This, as well as the fact that bacteria from 

 carcasses of dead animals again infect the soil, explains tlie 

 stationary occurrence of blackleg in certain regions. In fact, it 

 appears most frequently in swampy, low pastures, and in 

 regions subjected to occasional inundations; also in pastures 

 where carcasses of cattle infected with blackleg had previously 

 been buried, and sometimes after feeding hay or other feed 

 in the neighborhood of which carcasses had been skinned, or 

 after drinking from creeks in which parts of blackleg carcasses 

 had been thrown. 



Saner suggests the possibility that flies which have been feeding on blackleg 

 carcasses, and in whose bodies the bacilli have increased in number, may be capable 

 of transmitting the infection. 



Susceptibility. In blackleg regions the cattle contract the 

 disease with few exceptions only at the age of from i/o to 4 

 years; sucking calves are only attacked in exceptional cases 

 (Strebel observed the disease in a 3 days old calf), and animals 

 over 4 years as a rule only when they are transferred at an 

 advanced age from disease-free places to ian infected place. 

 Whether or not the breed has any influence on the suscepti- 

 bility is not yet determined with certainty; it is a fact that 

 cattle of the native breed contract the disease, but not as 

 often as the improved breed; the same also is true of the 

 Algerian cattle (Bremond). As to the susceptibility of the 

 bntlalo, no satisfactory data are so far available (Cronevin ob- 

 served in 2 buffaloes inoculated with virulent material only 

 intermittent changes of temperature, while, according to 

 Makoldy. these animals contract blackleg) . In sheep Vogdt and 

 Monseur. and in swine Marek, Battistini and Born have found 



