AUTO-FERMENTATION. 269 



of fusel oil ; according to Rayman and Kruis, it is produced 

 in larger quantities at high temperatures and in the absence 

 of air. Amyl alcohol is freely produced in liquids containing 

 grains which have been treated with sulphuric acid. According 

 to Ehrlich, fusel oil is formed in the ordinary growth of yeast 

 from leucin and isoleucin, two cleavage products of albumin. 

 It appears to be produced also in the auto-digestion of yeasts. 

 We must also record the production of acetic ether and 

 other volatile and non-volatile ethers which help to impart 

 the particular character to the fermented liquids. 



Auto-fermentation. 



Pasteur's researches indicated that yeast is capable of 

 forming alcohol and carbon dioxide under certain conditions, 

 even in the absence of sugar from the surrounding liquid. By 

 boiling yeast with dilute sulphuric acid, he prepared a ferment- 

 able sugar which he believed to be derived from the cell- wall. 



Salkowski has proved that in reality glycogen plays a part 

 in auto-fermentation. As glycogen can be fermented by 

 Buchner's yeast- juice, it is concluded that the yeast cells 

 contain an enzyme which can hydrolyse glycogen before it is 

 fermented. Salkowski states that by treatment with chloro- 

 form-water glycogen is split up, but auto-fermentation does 

 not take place. C. J. Lintner found that sodium chloride has 

 a similar action, and in the presence of chlorides of sodium, 

 calcium, magnesium, or ammonium no such fermentation 

 takes place. On the other hand, sodium sulphate and mag- 

 nesium sulphate react favourably. It is necessary, therefore, 

 in fermentation experiments to include in the calculation the 

 amount of alcohol and carbon dioxide produced from the 

 yeast cells. 



It is not only the carbohydrates, but also the nitrogen 

 compounds that are gradually resolved in the yeast cell. 

 Hahn proved the presence of a proteolytic enzyme in 

 Buchner's yeast-juice, and it is known that yeast has the 

 power of liquefying gelatine. In auto-digestion Kutscher and 

 Lohmann detected a number of cleavage products of the 

 proteins, more especially guanin and adenin, and also leucin, 



