90 



Mr. E. C. Grey. Decomposition of 



It was suggested in the earlier communication that mannitol was thus in a 

 position to give rise to a greater proportion of alcohol than glucose, not simply 

 because it was a compound already more reduced than glucose, but because 

 the hydrogen atoms existing in excess in the case of mannitol rendered less 

 necessary the action of the reductase. If acetaldehyde were the intermediate 

 substance immediately preceding alcohol, it was suggested that an interference 

 with the reducing mechanism or reductase might lead to an accumulation of 

 the aldehyde, which in its turn would react upon the intermediate substance A, 

 If intermediate substance A had no alternative but ultimately to become 

 acetaldehyde and formic acid, the accumulation of the aldehyde resulting 

 from a weakening of the reductase would only lead to a slowing down of the 

 fermentation as a whole, but since the intermediate substance can, according 

 to the hypothesis, become changed by a mere molecular rearrangement into 

 its isomer lactic acid, the result of a weakening of the reductase is a 

 proportional increase in the production of lactic acid. 



This hypothesis concords entirely with the results of experiment. Further, 

 it would be expected to follow from this liypothesis that the more completely 

 the phenomenon of bacterial growth and consequent change in the enzymes 

 was excluded from the fermentation, and the less possibility there was for the 

 products of fermentation to accumulate and hinder the reaction, both of which 

 possibilities are minimised by the new technique, the more completely should 

 the fermentation products from mannitol resemble quantitatively those from 

 glucose, so that finally the only difference should be that part of the acetic 

 acid in the case of the glucose should be represented by alcohol in the case of 

 mannitol. How true this is may be seen by the following comparison 

 between one of the analyses of the products from glucose already described 

 and an analysis of the products of a mannitol fermentation carried out under 

 tlie same conditions. 





Glucose. 



Mannitol. 



Carbon dioxide and formic acid ... 



0-21 

 27 -53 

 25 -46 

 11 -23 



22 -02 1 „ 

 13-36r'' 



-54 

 27 -61 

 23-11 

 12 -03 

 10 -511 „_ 

 27-22p' 



99 -81 



101 -02 



These results speak very strongly, if not conclusively, in I'avour of the 

 writer's hypothesis that the two substances are fermented by the same set of 

 enzymes. 



