CHEMISTRY AND CHIEF PRODUCTS. 489 



According to Grass, there is a still simpler explanation of 

 alcoholic fermentation expressed by the following formula : 



('ill, HjO 



(""OH Hp""; 



! C II i :j{jO ' > 2C 2 H 5 OH + 2C0 2 . 



== ^ ^ ^ 



I CH HiO 



T<5 [Hj 



This view is not open to discussion, since it coincides with the 

 old equation C 6 H 18 6 = 2C 2 H 5 OH + 2C0 2 , which does not afford the 

 slightest insight into the mechanism of fermentation. The other 

 explanation put forward by Grass presupposes the collaboration 

 of three molecules of sugar, and is therefore more complex than 

 the hypotheses previously mentioned. A valuable support would 

 naturally be afforded to these latter if one could isolate the inter- 

 mediate product between sugar and lactic acid, i.e., Nencki's 

 dioxypropionic aldehyde or Buchner's dioxy-y-ketonic acid. 



The remarkable property of yeast juice which brings about the 

 disappearance of lactic acid at one time and its production at 

 another, may be explained by the assumption of two different 

 enzymes, one capable of decomposing sugar into lactic acid and the 

 other transforming this acid into alcohol and carbon dioxide. With 

 both enzymes in excess or continually replenished, only the final 

 products of the reaction will be recoverable. This is the case in 

 fermentation with living yeast, with which there is also the pos- 

 sibility of the intermediate products disappearing in consequence 

 of the phenomena of nutrition. The first enzyme, namely, that 

 decomposing the sugar into lactic acid, has been named zymase, or 

 more precisely yeast zymase, by BUCHNER and MEISENHEIMER (II.), 

 whilst they apply the name lactacidase to the second enzyme, by 

 which the lactic acid is transformed into alcohol and carbon dioxide. 

 These workers have abandoned the idea that a dioxy-y-ketonic acid 

 is formed as an intermediate product between sugar and lactic 

 acid ; though as stated by A. Wohl and Nef, methylglyoxal may 

 possibly be formed as a product of this kind. This is in harmony 

 with the circumstance that inactive acid alone is invariably formed 

 in the fermentation of saccharose and glucose, as might be expected 

 with methylglyoxal (CH 3 -CO-CHO) as the regular transition 

 product. 



The question now arises whether similar transpositions can be 

 effected by purely chemical means, without the intervention of 

 enzymes; and a positive result would render Buchner's hypothesis 

 more feasible. DUCLAUX'S (II.) observation that alcohol and 

 carbon dioxide are formed in a solution of glucose treated with 

 caustic potash (see p. 459, vol. ii.), has been confirmed by BUCHNER 

 and MEISETSTFIETMER (I.), who obtained 2 per cent, of alcohol from 

 sugar treated in this way. When caustic potash is replaced by 



