LOUIS PASTEUR. 245 



priority of actual demonstration cannot be claimed for him. 

 His subsequent work on anthrax was, however, perhaps even 

 more important than that which has been claimed for him. 



The history of the discovery of the anthrax bacillus and 

 its relation to anthrax may be told in a few words. It was 

 first seen, in 1849, in the blood of an animal that had suc- 

 cumbed to an attack of splenic fever. In the following year 

 Raver and Davaine described it as occurring under similar 

 conditions, whilst in 1857 Brauell noted its presence in the 

 blood of a human patient suffering from anthrax. For six 

 years nothing more was done, but in 1863 Davaine, stimu- 

 lated by the study of Pasteur's observations on fermentation, 

 returned to his investigations on anthrax, and continued 

 working at the subject for ten years, with the result that he 

 was able to give everything but actual proof that the bacillus 

 anthracis was the exciting cause of this malignant dis- 

 ease. At this point Koch took up the work. He applied 

 his plate cultivation method with solidifying media, and 

 after working for some time announced in 1876 that he had 

 been able to furnish most rigorous proof of Davaine's hypo- 

 thesis. He isolated pure cultures of the organism, described 

 its modes of development and reproduction, pointed out that 

 under certain conditions, like some of the organisms already 

 described by Pasteur, it formed spores, but that it also 

 multiplied by a process of direct division or fission. During 

 the following year Pasteur also succeeded in growing this 

 organism as a saprophyte. His methods are always as in- 

 genious as they are interesting. It had been found by 

 Davaine that the anthrax bacillus might be demonstrated in a 

 pure condition in the blood of living animals or immediately 

 after death, but that eighteen or twenty-four hours after 

 death the blood was invaded by a second organism, which, 

 inoculated, produced symptoms that could not be ascribed 

 to the bacillus anthracis. Pasteur was able to separate 

 these organisms by making both anaerobic and aerobic cul- 

 tures from the blood in which this mixture of organisms 

 occurred. In the presence of air the anthrax bacillus only 

 could grow, but in the culture from which air was excluded, 

 only the septic vibrio could develop. The one organism 



