96 



PASTEUR : THE HISTORY OF A MIND 



contains (Fig. 10). We remove the air which it contains 

 by the current of vapor which the boiling produces: 

 we shall sterilize at the same time all the interior walls. 

 On leaving the neck of the flask, the vapor traverses 

 a platinum tube heated to redness in a gas furnace 

 (F, Fig. 10), and then escapes into the air. "When the 

 boiling has lasted some minutes, we extinguish the flame 

 under the flask; the liquid cools; the vapor condenses: 

 it is replaced by air w^hich will have traversed the red- 

 hot tube of platinum, where everything organic contained 

 in it will have been burned. When the flask is cold, 

 we separate it from the rest of the apparatus by fusing 



Fig. 10. Method of heating the air (to free it from germs) before intro- 

 ducing it into flasks. 



its tapering neck in a blowpipe. We shall have there 

 a flask of Spallanzani, that is to say an organic infusion 

 in contact with air containing all its oxygen, but robbed 

 of everything living, and even organic, which it contained. 

 Very well, nothing will be produced there; the infusion 

 remains clear because we have allowed nothing living to 

 enter it. 



"Now, for this is not the end, we take one of these flasks 

 which has remained sterile, and by a simple process, 

 which I shall not stop to describe, we pass into its neck, 

 always in the presence of air sterilized by heat, one of 

 these little pieces of cotton soiled by the dust of the air, 

 the living character of which you deny. As long as 



