GLYCOGEN 127 



varying quantities of erythro-dextrin and glucose. It dissolves 

 in an equal volume of water to give a neutral sticky solution 

 with a faint sweet taste; the solution is strongly dextro- 

 rotatory. Dextrin is insoluble in alcohol and ether. 



GLYCOGEN. 



This substance, although one of the most important and 

 widely distributed reserve foods in the animal kingdom, has 

 a restricted distribution in plants. It occurs abundantly in 

 certain Fungi, especially in Saccharomjces cereviseae, where it 

 may sometimes form as much as 30 per cent of the dry weight. 

 It has also been described as forming part of the cell-contents 

 in Myxomycetes, Flagellates, and possibly in certain Algae 

 and Cyanophyceae. In the yeast plant the glycogen varies in 

 amount according to the physiological phase of the organism, 

 and, it appears, accumulates and disappears often with great 

 rapidity. 



The glycogen appears in the cells of Saccharomyces during 

 the early stages of fermentation as minute refractive granules 

 scattered through the protoplasm ; after a few hours these 

 granules give place to small vacuoles, which in turn are re- 

 placed by one large vacuole, which may occupy the greater 

 space in the cell. According to Harden and Rowland,* this 

 progressive increase in the size of the glycogen-vacuole may 

 result from the formation of some substance, besides carbon 

 dioxide, from the glycogen. 



Wager and Penistonf have shown that the amount of 

 glycogen present is correlated with the periodical fluctuations 

 in the fermentative activity. 



On adding yeast to the nutrient fluid, e.g., Pasteur's solu- 

 tion, fermentation may start at once, in which case it was 

 found that the cells float and contain very little glycogen. 

 On the other hand, the cells may contain much glycogen and 

 sink to the bottom ; in this case fermentation is slow to 

 commence, but gradually increases, and eventually becomes . 

 much more active ; also the budding is much more extensive 

 as compared with a yeast which contains but little or no 

 glycogen. 



* Harden and Rowland: " J. Chem. Soc., Lond.," 1901, 79, 1234. 

 t Wager and Peniston : "Ann. Bot.," 1910, 24, 45. 



