218 PASTEUR: THE HISTORY OF A MIND 



which I have affirmed above. Here is a fact: fermen- 

 tation takes place. All the world accepts it, but how 

 interpret it? The proof that this is not easy, is the fact 

 that it has received four different interpretations, namely, 

 one by Gay-Lussac, one by Liebig and two by Pasteur. 



Gay-Lussac was content to say: "It is the oxygen 

 which sets the fermentation going." Liebig, after him, 

 had searched more profoundly and said: "It is the albu- 

 minoid matter of the must which needs oxygen in order 

 to enter into decomposition and to acquire the proper- 

 ties of a ferment." For 30 years this interpretation 

 had enjoyed the honors and credit of a demonstrated 

 truth. Pasteur arrives on the scene and says: "The 

 albuminoid matter has nothing to do with the phenom- 

 enon. The ferment is a living organism which comes 

 from a germ, and if the air has conveyed into our test- 

 tube a cause of fermentation, it is because it has 

 brought a germ there." 



It was surely not without some regret that he came 

 to this conclusion, because this view furnished a weapon 

 to the partisans of spontaneous generation, and per- 

 mitted them to say: "How is this? Do you admit the 

 germ of a ferment in each bubble of air? Then what 

 becomes of your conclusions relative to the rarity of 

 germs in the atmosphere?" This objection embarrassed 

 him only a little; but if he had had a discussion to support 

 on this subject he would only have been able to multiply 

 words upon it. He must have uttered a cry of joy when 

 he was led by experiment to a fourth interpretation: 

 The germs of the yeast are carried by the grape-berry; 

 they are inert as long as they are deprived of oxygen 

 and it is the introduction of the bubble of gas which 

 gives the whipstroke of departure for existence in a state 

 of fermentation. 



It is a singular thing that all these results, so curious 



