54 THE STORY OF GERM LIFE. 



error. It is always found necessary in this method 

 to start the process by pouring upon the shavings 

 some warm vinegar. Unless in this way the shav- 

 ings become charged with the vinegar-holding 

 bacteria the alcohol will not undergo oxidation 

 during its passage over them, and after the bac- 

 teria thus introduced have grown enough to coat 

 the shavings thoroughly the acetic-acid produc- 

 tion is much more rapid than at first. If vinegar 

 is allowed to trickle slowly down a suspended 

 string, so that its bacteria may distribute them- 

 selves through the string, and then alcohol be al- 

 lowed to trickle over it in the same way, the oxida- 

 tion takes place and acetic acid is formed. From 

 the accumulation of such facts it has come to be 

 recognised that all processes for the commercial 

 manufacture of vinegar depend upon the action 

 of bacteria. While the oxidation of alcohol into 

 acetic acid may take place by purely chemical 

 means, these processes are not practical on a large 

 scale, and vinegar manufacturers everywhere de- 

 pend upon bacteria as their agents in producing 

 the oxidation. These bacteria, several species in 

 all, feed upon the nitrogenous matter in the fer- 

 menting mass and produce the desired change in 

 the alcohol. 



This vinegar fermentation is subject to cer- 

 tain irregularities, and the vinegar manufacturers 

 can not always depend upon its occurring in a 

 satisfactory manner. Just as in brewing, so here, 

 contaminating bacteria sometimes find their way 

 into the fermenting mass and interfere with its 

 normal course. In particular, the flavour of the 

 vinegar is liable to suffer from such causes. As 

 yet our vinegar manufacturers have not applied 

 to acetic fermentation the same principle which 



