260 PASTEUR: THE HISTORY OF A MIND 



which had been so successful with the anthrax bac- 

 teridium. He saw at once that he could cultivate 

 it only in the absence of air, as it was an obligate an- 

 aerobe. 



Therefore, he concluded, with the assurance that long 

 practice had given to him, it is a ferment, and, in fact, 

 in culture media it liberates gas, forms carbonic acid, 

 hydrogen and a small amount of hydrogen sulphide 

 which imparts an odor to the mixture. How is it that 

 this fact was not deduced at once from that other fact, 

 namely that when a post-mortem is made on an animal 

 which has died of septicemia, we find tympanites, gas 

 pockets in the cellular tissue of the groin or of the axilla, 

 and frothy bubbles in the serosity which flows from all 

 points in the body when an opening is made. The 

 animal exhales a characteristic odor toward the end 

 of its life. Its parasites, driven out it may be by this 

 production of hydrogen sulphide, leave the skin to take 

 refuge at the extremity of its hairs. In short, septicemia 

 may be termed a putrefaction of the living organism. 



When the anaerobic character of the septic vibrio 

 was once discovered, a series of logical deductions at 

 once presented themselves. 



"When a liquid containing the septic vibrio is ex- 

 posed to pure air, the bacteria ought to be killed and 

 all virulence destroyed. That is what happens. When 

 some drops of septic serosity are spread out in a very 

 thin layer in a tube placed horizontally, in less than half 

 a day the liquid becomes absolutely harmless, even 

 though in the first place it was so virulent that inocu- 

 lation with the very smallest fraction of a drop would 

 produce death. 



"Furthermore, all the vibrios which occur in profusion 

 in the liquid in the form of motile filaments, are de- 

 stroyed and disappear. We find after this exposure 



