GLYCOGEN 169 



Preparation. 



The following method of obtaining glycogen was devised 

 by Pflijger.* Fresh finely-cut liver is stirred up with water 

 and 60 per cent caustic potash, and heated for two hours ; the 

 filtered solution, containing 15 per cent of potash, is then 

 mixed with an equal volume of 96 per cent alcohol, and the 

 precipitated glycogen is collected and washed with a mixture 

 of I part of 15 per cent potash with 2 parts of 96 per cent 

 alcohol ; if necessary, the substance may be redissolved and 

 purified in the same way. 



Glycogen may also be prepared from yeast, but not in a 

 particularly pure state, in the following manner : A quantity 

 of baker's yeast, which has been previously well washed with 

 water, is mixed with fine well-cleaned sand and ground very 

 thoroughly in order to rupture the cells. The mixture is then 

 placed in a vessel with about thrice its volume of water and 

 heated for some time, being constantly stirred. The liquid is 

 then filtered off, cooled, and strong alcohol added to the filtrate 

 in order to precipitate the glycogen, which is filtered off. 

 The glycogen so obtained may be purified by redissolving it 

 in water, adding a little acetic acid, and boiling in order to 

 remove any proteins which may not have been removed by 

 the initial heating, filtering, and precipitating with alcohol. 



An elaborate method has been described by Harden and 

 Young,f which has been modified by Ling, Nanji, and Paton.| 

 Dried yeast, a commercial by-product of many breweries, is 

 boiled for two hours with 2 per cent caustic soda, and after 

 removal of the insoluble cell wall residue, the crude glycogen 

 is precipitated by alcohol and freed from protein and nucleo- 

 protein by heating with 60 per cent caustic potash. From 

 this solution the glycogen is once more precipitated by alcohol, 

 and is further purified from mannan (yeast gum) by precipi- 

 tating the latter from a warm alkaline solution by means of 

 Fehling's solution. The filtrate containing the glycogen is 



* Pfluger : " Pfliiger's Archiv f. Phys.," 1902, 91, 119. and 1903, 93, 



163. 



t Harden and Young : " J. Chem. Soc," 1912, loi, 1928. 

 I Ling, Nanji, and Paton : " J. Inst. Brewing." 1925, 31, 316. 



