132 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



cipitating the proteids still present in the solution and also 

 the gelatine formed on boiling. Now filter, wash once with 

 water, add double the volume of 90 per cent, alcohol, and stir 

 thoroughly. After the precipitate has settled completely 

 filter and wash, first with a mixture of two volumes of alco- 

 hol and one volume of water, then with absolute alcohol, and 

 finally with ether; or, in case it is somewhat voluminous, it 

 is better to remove it from the filter, grind with absolute 

 alcohol, let stand some time with this, filter, press out the 

 alcohol, and treat in the same manner with ether. Finally 

 the glycogen is freed from the adhering ether by pressing and 

 by grinding in a mortar. 1 The method of preparation of 

 S. Frankel 2 is also very convenient: Grind the liver, without 

 heating it, with 2.5 times the quantity of a 2 to 4 per cent, 

 solution of trichloracetic acid, filter, wash with some of the 

 trichloracetic acid solution, and precipitate with alcohol, etc. 

 The trichloracetic acid has the property of coagulating the 

 proteids and completely precipitating them. 



Thus prepared glycogen, C 6 H 10 5 (according to Huppert 

 6(C 6 H 10 5 ) + H 2 0), is a chalky-white fine powder in which 

 hard transparent pieces resembling gum arabic may be pres- 

 ent in case of insufficient dehydration; it dissolves readily, 

 though somewhat slowly, in water, always forming an opales- 

 cent solution, which is extremely strongly dextrorotatory 

 (according to E. Kiilz j is +211, according to Huppert a D is 

 + 196.63). On boiling with acids it forms glycogen-dextrin 

 and then glucose; when treated with saliva or pancreas 

 extract it is converted into glycogen-dextrin and maltose. 

 It forms, like other carbohydrates, oxalic acid when boiled 

 with nitric acid. It is distinguished by its characteristic con- 

 duct towards iodine solution. 



1 For a better method for the preparation of glycogen see Salkowski, 

 Zeit. f. Physiol. Chem. 36 (257). See also page isi of this book. 0. 



2 Pfliiger's Archiv, 52, 125. 



