CHICKEN CHOLERA 



277 



and working as he had done with anthrax blood, Pasteur 

 saw develop everywhere small non-motile segments of an 

 extreme tenuity, slightly constricted in the middle (Fig. 

 22), and clearly approaching, much more than the anthrax 

 bacteridium and the other bacilli, those microscopic 

 granules to which Chauveau had attributed the active 

 role in the virulent humors of cowpox, smallpox, and 

 sheeppox. 



FIG. 22. Microbe of chicken cholera. 

 Young. Old. 



This organism is so tenuous that the precipitate which 

 it forms at the bottom of the flask is sometimes 

 almost invisible; it appears scarcely to touch the nutri- 

 tive substances placed at its disposal, and one might 

 ask himself the question whether it changes in any 

 respect the culture fluid. "Let us try," said Pasteur 

 to himself; and he tried, and saw with surprise that if 

 this bouillon culture was filtered by passing through 

 a porous wall in order to remove from it all the parasites, 

 and then re-inoculated, no growth took place. The 



