136 PASTEUR: THE HISTORY OF A MIND 



ing oily, which are not the sole changes which wine can 

 undergo, but only those best known, are each dependent 

 upon a special micro-organism which lives at the expense 

 of one of the elements of the wine, and imprints on this 

 beverage a characteristic change of composition and of 

 taste. This is not the place to insist on the morphology 

 or the properties of these different organisms represented 

 in Fig. 8, page 70. We will take from the history of the 

 facts only what is necessary to explain the history of 

 the ideas. 



The solution of this first problem allowed two others to 

 be approached. What goes on in a wine which becomes 

 old normally, in the absence of organisms? What is it 

 necessary to do, in order that wine may always grow old 

 normally? It is on these last two questions that some 

 developments are necessary. I would like to show to 

 what degree the new manner of regarding them and of 

 treating them rendered them fertile. 



V 

 ACTION OF OXYGEN ON WINE 



In the way in which it was stated, the first question 

 was evidently one of pure chemistry, and Pasteur found 

 himself brought back to his first domain. The natural 

 aging of a wine, when microbes are absent, can only take 

 place by the play of forces within the liquid, and of 

 those which may result from its contact with oxygen. 

 What did science and practice have to say on this subject? 



The practical man seemed to be inspired with a terror 

 of the oxygen of the air. The wine was exposed to the 

 ah* only so long as absolutely necessary for the decanting. 

 It was the custom to sulphur, that is to say, to fill with 



