THE PREPARATION OF FARM PRODUCTS. 28 I 



the whole class of phenomena as chemical processes and which 

 strongly opposed the physiological view of their nature. The 

 great weight of Liebig's name, and the brilliancy of his dis- 

 cussions, prevented further advance along the line of fermenta- 

 tive discoveries for many years. 



Eventually the subject was taken up by Pasteur, who soon 

 succeeded in putting beyond dispute the conclusion that the 

 phenomenon is due to the microorganisms present in the 

 mother of vinegar, although his explanation of the phe- 

 nomenon was incorrect. With this conclusion it becomes evi- 

 dent that the equation given above cannot longer be regarded 

 as expressing more than an approximation toward the actual 

 phenomenon which occurs. It is certain that, as the micro- 

 organisms produce this change in the alcohol, they do it for 

 their own benefit and probably make use of part of the prod- 

 uct. The equation above given leaves nothing for the bacteria 

 to appropriate to their own use, and is therefore, though easily 

 understood from the chemical standpoint, unintelligible from 

 the standpoint of bacteria. It is quite certain that the phe- 

 nomenon which occurs is far more complicated than indicated 

 by the equation, and this must therefore be looked upon only 

 as a useful expression of the essential nature of the process. 

 Various by-products are at the same time formed which do 

 not enter into the equation at all, as above represented. 



The relation of the organisms in this " mother" to the process 

 of acetic acid formation may readily be understood by a brief 

 description of a common method of vinegar-making. In the 

 Orleans process, oaken casks are used which are kept in a 

 room with a temperature of about 70 F. Each new cask is 

 first steamed and then impregnated with boiling hot vinegar to 

 "sour" the cask. After this it is filled partly full of good 

 clear vinegar and about half a gallon of wine is added. About 

 a week later a little more wine is added and in another week 

 still another lot. This is continued until the cask contains 

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