ON THE ROAD TO FAME 55 



forms which made an exception to a law that 

 was supposed to be general, were there some 

 that led an anaerobic life (i. e., without oxy- 

 gen), while it had previously been regarded as 

 settled that all animals led an aerobic life, in 

 which oxygen was a necessity? Pasteur solved 

 this question by passing a current of air into a 

 flask containing a butyric fermentation, and 

 immediately the life of the vibrions diminished 

 in intensity and finally ceased. The proof had 

 been obtained that there were animal forms to 

 which oxygen was fatal. 



But how did it happen that these anaerobic 

 vibrions had not met with oxygen in the me- 

 dium in which they were bred? It was because 

 the aerobic vibrions which preceded their evolu- 

 tion had exhausted all the oxygen in the liquid, 

 and thus gave them a chance to live and multi- 

 ply. Furthermore, these two forms of life were 

 found coexisting in the same liquid, a part of 

 the aerobic forms having died and fallen to 

 the bottom of the vessel after exhausting the 

 oxygen, while the more vigorous rose to the 



