ACETIC FERMENTATION. 87 



ordinarily clean. It might be said that they had just 

 been carefully washed. Pasteur has shown that this 

 is but a deceptive appearance, and that in reality 

 these shavings are partly or wholly covered with a 

 mucous film of mycoderma aceti of excessive tenuity. 

 It is necessary to scrape the surface of the wood with a 

 scalpel and examine the scrapings with the microscope 

 to be assured of the presence of this pellicle. 



Liebig, who somewhere speaks, not without a cer- 

 tain contempt, of the microscope, denied formally the 

 exactitude of these assertions. 



* With diluted alcohol, which is used for the rapid 

 manufacture of vinegar,' he wrote, ' the elements of 

 nutrition of the mycoderm are excluded, and the 

 vinegar is made without its intervention.' He asserted 

 also in his memoir of 1869 that he had consulted the 

 head of one of the principal manufactories of vinegar 

 in Germany, that in this manufactory the diluted al- 

 cohol did not receive during the whole course of its trans- 

 formation any foreign addition, and that beyond the air 

 and the surfaces of wood and charcoal for charcoal is 

 sometimes associated with the beech shavings nothing 

 can act upon the alcohol. Liebig added that the 

 director of the manufactory did not believe at all in 

 the presence of the mycoderm, and that finally he, 

 Liebig, in examining the shavings which had been 

 used for twenty-five years in the manufactory, saw no 

 trace of mycoderm on their surface. 



