vii FERMENTATION AND DRYING 205 



the rise of temperature is a consequence of this process. 

 This conversion of sugar into acetic acid is a fairly 

 simple process. The sugar is first converted into 

 alcohol and carbon dioxide, and the alcohol again is 

 oxidised (combined with the oxygen from the air) into 

 acetic acid. It can easily be demonstrated that the 

 presence of the sugar of the pulp is a conditio sine 

 qua non for obtaining fermentation. When the seeds 

 are washed, so as to remove the sugar from the pulp, 

 fermentation does not take place ; but if these washed 

 seeds are sprinkled with a solution of sugar they again 

 become suitable for fermentation. 



This conversion of the sugar of the pulp into 

 alcohol and carbon dioxide, and, secondly, the oxidation 

 of the alcohol into acetic acid, are both the work of 

 very small living organisms. Just as in brewing, it is 

 in this case also a kind of yeast (Saccliaromyces) which 

 splits the sugar into alcohol and carbon dioxide ; while 

 the oxidation of the alcohol into acetic acid is the work 

 of a bacterium, belonging to the group containing the 

 ordinary vinegar-making bacterium (Mycoderma aceti), 

 which causes the conversion of wine or beer or alcohol into 

 vinegar in the vinegar industry. Both these organisms 

 still need thorough investigation, but it has already 

 been proved that fermentation without living organisms 

 is not possible. The addition of a little chloroform or 

 ether to the heap of beans prevents fermentation, or 

 stops it if it has already begun ; this addition does not 

 prohibit pure chemical processes, but it prevents the 

 action of living organisms. Its influence on fermenta- 

 tion shows, therefore, that fermentation is the work of 

 living organisms. 



In the vinegar industry we know that the work 

 of the vinegar bacterium namely, the combination of 

 alcohol with oxygen from the air is always accompanied 

 by a rise of temperature. The extent of this rise is 

 dependent upon various conditions, e.g. the amount of 

 alcohol present, the extent to which the air has free 

 access, and last but not least, the hindrance opposed to 



