172 CHEMISTRY OF THE YEAST CELL. 



the ordinary temperature. Possibly therefore we must assume 

 the presence of a synthetic enzyme in the cell contents. 



In view of the amorphous nature of this carbohydrate, some 

 surprise will be manifested at Laurent's report that the yeast 

 cells are capable of absorbing and accumulating the glycogen 

 present in a nutrient solution. And in fact this assumption 

 was contradicted both by M. Cremer (I.) and by A. Koch and 

 H. Hos^us (I.). The last-named observers found in the case of a 

 pressed yeast, a bottom-fermentation beer yeast, and the so- 

 called Frohberg yeast, that the glycogen added to the nutrient 

 solution (wort or meat extract solution, with or without an 

 addition of grape sugar), whether obtained from calves' liver, 

 rabbits' liver, or pressed yeast, not only remained unutilised, so 

 far as could be ascertained, but also retarded the cell reproduc- 

 tion and fermentative power, so that the yeast crop and the 

 percentage of alcohol in the treated samples were smaller than 

 in those left without addition of glycogen. They failed to detect 

 alcohol in the sugar-free cultures ; and concluded that yeast is 

 incapable of secreting a hydrolytic enzyme by means of which 

 the glycogen in the nutrient solution could be converted into 

 fermentable sugai'. General application cannot be accorded to 

 this deduction, since M. Cremer (TV.) noted hydrolysis of 

 glycogen on keeping yeast in chloroform water, and found that 

 dextrose was thereby formed. The contrary assumption, by 

 E. Salkowski (II.), of the formation of Isevo-rotatory sugar, is not 

 altogether free from objection, as the latter himself (VII.) 

 admitted. Since the conversion of the accumulated arlycoeen 

 withm the cell is probably connected with such an enzyme, a 

 strong presumption exists in favour of the occurrence of a similar 

 enzyme, produced by the plasma. This probability has been 

 brought to almost a certainty by the discovery of Buchner and 

 Rapp (II.) that glycogen can be fermented by expressed yeast 

 juice. The presence of a similar enzyme may also be assumed in 

 other fungi that store up glycogen, and consequently will have to 

 be reckoned with in the separation of this carbohydrate, especially 

 when a quantitative determination of the same is in question. It 

 may be remarked in passing, that, as was first shown by A. KoCH 

 and H. Hos^us (I.), the faculty of hydrolysing glycogen is also 

 possessed by various species of bacteina. This at the same time 

 explains Salkowski's (II.) discovery, previously reported by 

 ScHUETZENBERGER and Destrem (L), as also the results obtained 

 by N. VON Chudiakow (I.), and urged by him against the assump- 

 tion that autofermentatioii occurs in yeast. 



Glycogen has been rightly termed a reserve material. In 

 times of superfluity of nutrient materials the glycogen is stored 

 up in the cell for the purpose of consumption in case of need, 

 either for maintaining the vitality of the individual in an 

 environment destitute of the necessary foodstuff, or for the 



