ACETIC FERMENTATION. 71 



conditions the wine becomes sour. But if we take 

 the precaution of putting the bottle into hot water, so 

 that the wine and the air in the bottle may be heated 

 for some instants to a temperature of 60 Centigrade, 

 and if, after cooling, we leave the bottle to itself, 

 the wine in these conditions will never become trans- 

 formed into vinegar. The heating, however, must 

 have left intact the albuminoid or nitrogenous sub- 

 stances contained in the wine. These, then, cannot 

 constitute the ferment of the vinegar. Can it be 

 maintained that by heating the wine to 60 we have 

 altered the albuminoid matter, which is, on this 

 account, no longer able to act as a ferment, or, in other 

 words, no longer able to determine the union of the 

 oxygen of the air with the alcohol ? This hypo- 

 thesis falls to pieces before the following experiment. 

 Open the bottle, blow into it with bellows, so that 

 the once heated wine shall come into contact with 

 ordinary air, and the acetification of the wine will take 

 place. 



But the master experiment is the following. We 

 have seen that pure alcoholised w r ater never turns sour 

 unless some albuminoid matter is introduced into it. 

 Pasteur saw that this albuminoid matter might be 

 completely suppressed and replaced by saline crystal- 

 lisable substances, alkaline and earthy phosphates, to 

 which has been added a little phosphate of ammonia. 

 In these conditions, especially if the alcoholised water 



