HYDROCARBON COMPOUNDS 77 



Gum arable 



Erythrodextrine and dextrine 



Mucic acid 



Asparagin and glutanine 



Salicine, amygdalin, and other glucosides 



Egg albumin 



Peptones from fibrine and casein. 



It is stated, according to Laurent, that glycogen is able to serve 

 in the hydrocarbon nutrition of yeasts and the production of glyco- 

 gen in the cell. This statement is without doubt in error. From the 

 investigations of Koch and Hosaeus, 1 it has been established that 

 glycogen is not absorbed by yeasts, for it is not diffusible through the 

 cell membrane any more than the glycogenase enclosed in the cell. 



The conclusions of Laurent have been confirmed, in most part by 

 Cremer. This author has also stated that yeasts deprived of their 

 glycogen by autofermentation phenomena, which we shall study 

 further, produce it after a few hours if they are placed in a solution 

 with sugar (saccharose, levulose, glucose, d-galactoce, d-mannose) 

 but not if furnished with arabinose, rhamnose, sorbose, lactose, glyc- 

 erol or glycogen. 



According to Laurent, Boullinger, and Kayser and Meissner, 

 glycogen is rare or completely absent at the beginning of fermentation; 

 it increases progressively and soon reaches a maximum. It disappears 

 at the end of fermentation. These results are absolutely confirmed 

 by those of Wagner, Kohl and Guilliermond. It seems that toward 

 the middle of the fermentation, glycogen accumulates in the cell 

 much more quickly than it is consumed. 



The investigations of Lindner and Will indicate that glycogen is 

 unevenly distributed in the yeast cell and is able to exist under very 

 variable conditions. Thus it is that Lindner has observed glycogen 

 in yeasts which had been cultivated on gelatin for 4 months. The 

 same is true of most reserve products. It is difficult to state accu- 

 rately the conditions under which the formation of glycogen is greater 

 than the expenditure. 



These authors have come to regard glycogen as a transitory sub- 

 stance in the cell and intermediary between the sugars and alcohols. 

 According to Griiss, it constitutes, as we shall show later on, an ex- 

 clusive substance destined for respiration (in presence of air) and for 

 fermentation (in the absence of air). Glycogen is formed from the 

 sugars which are dissolved by the cell and is transformed either into 



1 Koch, A. and Hosaeus. Ueber einen neuen Froschlauch der Zuckerfabriken. 

 Cent. Bakt. 16, 1894. 



