90 LOUIS PASTEUR 



confident and impressive manner, tended to make 

 opinion more favorable to the theory of the spon- 

 taneous origin of life. 



Naturally, these researches were closely followed 

 by Pasteur. Although their results were contrary 

 to his own experience and the conclusions to which 

 he was led, he refrained from any discussion of 

 the subject until he had carried out many investi- 

 gations of his own. No one was better prepared 

 than he to realize the difficulties that beset the 

 investigator in this field. Even with the most 

 scrupulous care, one may, quite unsuspectingly, 

 make little slips that entirely vitiate his results. 

 Pasteur strongly suspected the adequacy of the 

 technique employed by Pouchet, and he set himself 

 to repeat the experiments of his opponent and to 

 devise others which would afford a conclusive an- 

 swer to the much controverted question with which 

 he was grappling. Pouchet affirmed that suitable 

 infusions supplied with oxygen would develop living 

 organisms when every care was taken to exclude 

 outside germs. Pasteur, on the contrary, found, in 

 agreement with Schulze, that if air were drawn 

 through a heated tube before supplying the infu- 

 sions, no life would develop. 



One type of experiment which is particularly 



