294 AGRICULTURAL BACTERIOLOGY 



siderable economic importance in cattle. It is a very slowly 

 progressing disease, and until recently no method of de- 

 tecting it was available other than by the symptoms, the 

 most marked of which are intermittent diarrhea and pro- 

 gressive emaciation. The symptoms become apparent only 

 after the disease has made such progress that the organisms 

 are being eliminated from the affected animal. 



The isolation and cultivation of the causal organism in 

 pure culture has made it possible to prepare a product com- 

 parable to tuberculin in its manner of preparation and use. 

 This diagnostic agent is injected into the blood stream, and 

 causes a thermal reaction in the case of infected animals. 

 Its use has been limited. It can not be said at this time 

 whether it will be possible to free a herd from the disease 

 through the detection of the infection in the individual ani- 

 mal before the organisms are eliminated. 



