DISEASES OF WINE AND VINEGAR 117 



as is well known, is derived from the fermentation 

 of alcohol. Wine, cider, and other liquids contain- 

 ing not too high a percentage of alcohol, turn sour 

 under the proper conditions, owing to the trans- 

 formation of alcohol into acetic acid. The city of 

 Orleans in France was a great center for the manu- 

 facture of vinegar and those engaged in this occu- 

 pation frequently suffered great losses, because the 

 fermentations failed, for some unknown reason, to 

 proceed in the proper way. Ordinarily in the half- 

 filled casks of partly ripened vinegar and wine 

 which were used, a thin film developed on the sur- 

 face which the manufacturers knew, from experi- 

 ence, was important for the proper fermentation of 

 the underlying liquid. When the film sank, or 

 became dislodged, fermentation was checked. It 

 was known that the film required air for its devel- 

 opment, although it was not known why. Pasteur, 

 in making a microscopic examination of this film, 

 found it to consist of minute organisms, about 

 twice as long as wide and %oo of a millimeter in 

 length. He called this form Mycoderma aceti, and 

 he showed that it had the property of taking 

 oxygen from the air and oxydizing the material 

 below. One gram of these minute organisms was 

 proven to be capable of transforming ten thousand 



