180 LOUIS PASTEUR. 



the antiseptic system which for the last nine years I 

 have been trying to bring to perfection. Allow me to 

 take this opportunity of sending you my most cordial 

 thanks, for having, by your brilliant researches, de- 

 monstrated to me the truth of the germ theory of 

 putrefaction, thus giving me the only principle which 

 could lead to a happy end the antiseptic system. 



Pasteur followed with lively interest the movement 

 of thought and the successful applications to which 

 his labours had given rise. It was a realisation of 

 the hopes he had ventured to entertain. Already, 

 in 1860, he expressed the wish that he might be able 

 to carry his researches far enough to prepare the 

 way for a profound study of the origin of diseases. 

 And, as he gradually advanced in the discovery 

 of living ferments, he hoped more and more to 

 arrive at the knowledge of the causes of contagious 

 diseases. 



Nevertheless, he hesitated long before definitely 

 engaging himself in this direction. ' I am neither 

 doctor nor surgeon,' he used to repeat with modest self- 

 distrust. But the moment came when, notwithstand- 

 ing all his scruples, he could no longer be content 

 himself to play the part of a simple spectator of the 

 labours started by his studies on fermentation, on 

 spontaneous generation, and on the diseases of wines 

 and beer. The hopes to which his methods gave rise, 

 the eulogies of which they were the object, obliged 



