162 LOUIS PASTEUR 



by a number of investigators who claimed that in 

 many cases of anthrax the bacteria could not be 

 found. Davaine replied by showing evidence that 

 the bacteria had been overlooked or that the disease 

 had been wrongly diagnosed as anthrax. Davaine 

 found that rabbits inoculated with the blood of ani- 

 mals suffering from anthrax would take the disease 

 and die. But if the blood had been passed through 

 a filter so as to remove its corpuscles and bacteria 

 it could be inoculated into rabbits with no ill- 

 effects. 



But the disease presented many puzzling prob- 

 lems. Davaine adduced evidence that the bacteria 

 of anthrax disappeared from the blood of dead 

 animals after it began to putrefy, but he also ob- 

 served that dried blood retained its virulence for a 

 long time. It had long been known that fields over 

 which diseased animals had grazed might infect 

 healthy animals after a lapse of several years. 

 Much confusion and difference of opinion prevailed, 

 therefore, as to the mode of transmission of this 

 disease. 



Much light was thrown upon the problem by the 

 labors of Robert Koch, a German investigator who 

 was then at the beginning of his famous career, 

 Koch had studied the germ of anthrax in its various 



