202 MINERAL FOODSTUFFS. 



saccharose and 0.5 per cent, of Gastine's nutrient salt mixture 

 ( 2 59) i n which the calcium sulphate had been replaced by 

 magnesium sulphate, was inoculated with pure wine yeasts from 

 Portugal and Champagne, Brussels beer yeast, Saccharomyces 

 apiculatus and Sacch. Pastorianus, all of which yeasts proved 

 capable of producing the gas in question. The question, arising 

 from this result, as to the dependence of the reduction phenomenon 

 on the environment of the culture, was more closely examined 

 by A. L. STERN (I.), who failed to discover any substance of 

 known constitution capable of supplying the yeast with sulphur- 

 without the concurrent liberation of sulphuretted hydrogen. 

 This agrees well with the fact, known to every chemist and 

 fermentation technologist and first pointed out by Reischauer, 

 that the distillates from beer very frequently contain sulphuretted 

 hydrogen, or a compound exhibiting all the characteristics of the 

 same. 



Moreover, the formation of sulphuretted hydrogen by the 

 reducing action of yeast is not confined to the sulphates ; even 

 sulphur itself may serve by combining with the hydrogen 

 liberated from other substances by the activity of a yeast enzyme 

 (philothion), which will be dealt with, in conjunction with other 

 allied matters, in a subsequent chapter. 



