THE HISTOBY OF BACTERIOLOGY. 449 



eases, when Koch in 1878 published his 

 investigations upon wound infections. Ac- 

 cording to his conclusions every special dis- 

 ease had corresponding to it a special 

 disease germ just as there appeared to be a 

 special germ for each fermentation. Pasteur's 

 comprehensive work laid the foundation for the 

 conception that each special fermentation and 

 disease was causally dependent upon a special 

 micro-organism, and Koch's work capped this 

 view just as comprehensively. 



This idea corresponded so admirably with 

 the general expectations of a physician brought 

 up on ontological conceptions that in the imme- 

 diate future the wish became father to the 

 thought. Koch advanced this line of work in 

 a remarkable degree by the methods he de- 

 vised about 1880. The isolation of pure cul- 

 tures of a large number of micro-parasites was 

 achieved and in many cases it was demon- 

 strated by successful transfer to animals, that 

 the microbes had great significance in the 

 origination of those diseases in which they 

 were observed (cf. Chapter III., p. 87). In 

 this series of investigations, Koch's discovery 

 in 1882 of the germ of tuberculosis stands out 

 conspicuously as especially epochal. This is 

 indeed the greatest discovery due to the carry- 

 ing out of a method which has as yet been 

 29 



