452 BACTERIOLOGY. 



species, the specificity of the parasitic mi- 

 crobes is the cause of disease. As Henle de- 

 duced the etiology of disease from the con- 

 stancy of the specific disease germs, so, in 

 association with Perty, Billroth and Nageli 

 have just as logically developed the view 

 that the bacteria vary and adapt them- 

 selves both in form and action to the condi- 

 tions of existence. Both investigators over- 

 shot the mark, for Billroth assumed the 

 existence of only one pathogenic species which 

 he called Cocco bacteria septica, and Nageli 

 recognized no constant species outside of 

 Sarcina. 



Hans Buchner as far back as 1878 treated 

 the virulent anthrax germ culturally in such 

 a way that it became impotent ; unfortunately 

 in 1880 he went still further, supposing, in 

 accord with Nageli's idea, that by cultivation 

 he transformed the pathogenic anthrax bacil- 

 lus into the saprophytic hay-bacillus and vice 

 versa. Koch also went too far in his criticism 

 when he assumed that Buchner simply con- 

 founded these very different species of bacteria. 

 Prazmowsky and De Bary have found that at- 

 tenuated anthrax bacteria at times really form 

 pellicles on the surface of fluids like the hay 

 bacillus. It is impossible, however, by cultiva- 

 tion to change one kind into the other, and the 



