238 THE POPULAR SCIENCE MONTHLY. 



of destruction are at last accompHslied through the work of latent 

 fermentation and slow combustion. Whatever animal or vegetable 

 matter is in the oj^en air or under the ground, which is always more 

 or less impregnated with air, finally disappears. The processes can be 

 stopped only under an extremely low temperature, ... in which the 

 microscopic organisms can not flourish. These facts come in to for- 

 tify the still new ideas of the part which the infinitely little play as 

 masters of the world. If their work, always latent, were suppressed, 

 the surface of the globe, overloaded with organic matters, would be- 

 come uninhabitable." 



Pasteur extended his observations to the acetic fermentation, or 

 conversion of alcohol into vinegar, in which he found an oi-ganism, the 

 Mycoderma aceti, actively jjromoting a process of oxidation. Liebig 

 had attributed this fermentation, also, to the presence of an albumi- 

 noid body in process of alteration, and caj^able of fixing oxygen. He 

 knew of the plant called " mother," but regarded it as an outgrowth 

 of the fermentation, and in no sense the cause. Pasteur proved, by 

 experiments that left no room for doubt — the prominent characteristic 

 feature in all his investigations — that the plant is the real agent in 

 producing the fermentation. He eliminated from his compositions the 

 albuminoid matter, which Liebig had declared to be the active agent, 

 and replaced it with crystallizable salts, alkaline phosphates, and 

 earths ; then, having added alcoholized water, slightly acidulated with 

 acetic acid, he saw the mycoderm develop, and the alcohol change into 

 vinegar. Having tried his experiments in the vinegar-factories at Or- 

 leans, he became so sure of his position that he ofl^ered to the Acad- 

 emy, in one of its discussions, to cover with the mycoderm, M^ithin 

 twenty-four hours, from a few hardly-visible sowings, a surface of 

 vinous liquid as extensive as the hall in which they were meeting. 



Liebig allowed ten years to pass after Pasteur's investigations, and 

 then published a long memoir traversing his conclusions. Pasteur 

 visited Liebig at Munich, in 1870, to discuss the matter with him. 

 The German chemist received him courteously, but excused himself 

 from the discussion, on the ground of a recent illness. The Franco- 

 German War came on ; but, as soon as it was over, Pasteur invited 

 Liebig to choose a committee of the Academy, and furnish a sugared 

 mineral liquid. He would produce in it, before them all, an alcoholic 

 fermentation in such a way as to establish his own theory and contra- 

 dict Liebig's. Liebig had referred to the process of preparing vinegar 

 by passing diluted alcohol through wooden chips, as one in which no 

 trace of a mycoderm could be found, but in which the chips appeared 

 perfectly clean after each operation. It was, in fact, impossible that 

 there should be any mycoderm, because there was nothing on which it 

 could be fed. Pasteur replied to this : " You do not take account of 

 the character of the water with which the alcohol is diluted. Like 

 all common waters, even the purest, it contains ammoniacal salts and 



