DISEASES OF FARM ANIMALS 



183 



where characteristic " a " or even " i^ might be 

 present and yet the disease be not true hog cholera. 

 Until within recent years American authorities, 

 bacteriologists and veterinarians alike, have very 

 generally accepted a certain germ, the bacillus of 

 Salmon and Smith, as the specific cause of hog 

 cholera and another somewhat similar germ as the 

 cause of what was supposed to be a distinct but 



AN ATTACK OF CHOLERA 



One of the familiar attitudes assumed when the kog is 

 affected with cholera. When this far along, not many cases 

 of recovery are observed. 



curiously related disease — swine plague. But 

 within a few years workers in the Federal bureau 

 of animal industry have apparently demonstrated 

 that hog cholera is caused by a living germ so small 

 that it passes easily through germ filters which re- 

 move all known forms of the bacillus of Salmon 

 and Smith. 



It may be interesting to note further that this 

 new germ is so small as to be invisible to the 

 highest available powers of the best microscope. 

 That it is a living organism and not a chemical 



