THE HISTORY OF BACTERIOLOGY. 453 



germination of spores in the two species is very 

 different (Prazmowsky and Brefeld). Never- 

 theless Buchner intentionally and with a clear 

 understanding of his aim attempted to influ- 

 ence the disease-producing activity of the par- 

 asite, which was the factor considered by Koch 

 as causal and necessarily constant, and this 

 result he was the first within certain limits to 

 achieve. A similar result was accidentally 

 obtained in 1880 by Pasteur, who found that 

 virulent cultures of the bacteria of chicken 

 cholera become impotent after standing for 

 some time in the air. From this discovery by 

 Buchner and Pasteur we may date a new period, 

 the scientific epoch in bacteriology. If we are 

 able at will to diminish or altogether annul 

 the most important characteristic of bacteria 

 and the one formerly supposed to be necessarily 

 constant, that is the " specific " ability to pro- 

 duce " specific " diseases, fermentations, putre- 

 factions or pigments, and on the other hand to 

 heighten this power, then we must change our 

 whole conception of causal relationship. By 

 means of artificial protective inoculations such 

 as Pasteur in 1880 undertook for the first time 

 with the attenuated bacteria of chicken cholera, 

 the whole realm of experimentation became 

 accessible. 



These investigations caused stress to be 



