4 HOG CHOLERA 



among some scientists relative to the true signifi- 

 cance of this organism in its relation to epizootic 

 hog cholera. This doubt was aroused because 

 hogs that sickened as a result of injections of B. 

 suipestifer cultures failed to transmit disease to 

 checks, because those that survived injection with 

 cultures of the organism were not immune when 

 exposed in field outbreaks, and because these cul- 

 tures did not always produce disease, while blood 

 from hogs sick as a result of natural infection 

 proved to be quite generally infectious. In 1903, 

 de Schweinitz and Dorset of the United States 

 Bureau of Animal Industry demonstrated that the 

 true cause of epizootic hog cholera is a filterable 

 virus, and this marked an epoch in th6 history of 

 the disease. 



Proceeding in the light of this new knowledge, 

 Dorset, Niles and McBryde succeeded, in 1908, in 

 adapting to hog cholera the principles employed 

 by Kolle and Turner, Nicolle and Adil-Bey in pro- 

 ducing a protective serum against rinderpest, a 

 disease of cattle caused by a filterable virus. 

 The work of Dorset and his associates was con- 

 firmed by numerous investigators, among whom 

 were Uhlenhuth, Hutyra and Xylander, and the 

 epochal field experiments conducted in this coun- 

 try by Dr. Niles and described by him in the re- 

 port of the United States Bureau of Animal In- 

 dustry, 1908, fully established the great practical 



