222 GLYCOGEN 



gen from solution by alcohol, converting it by hydrolysis into 

 sugar and determining the latter directly. 2 



Chemistry of Glycogen. The chemical study of glycogen 

 is almost stationary. It is true, Madame Gatin-Gruzewska 3 

 seems to have succeeded once in Pfliiger's laboratory in ob- 

 taining it in the form of minute prismatic crystals; the 

 method pursued consisting in adding alcohol to a weak 

 solution of glycogen until turbidity began to appear, dissolv- 

 ing the precipitate in water and allowing this solution to 

 stand in the refrigerator. Little further has been heard of 

 the procedure. The molecular weight of glycogen is un- 

 doubtedly very great. Zdenko Skraup, in collaboration 

 with E. v. Knaffl-Lenz, has attempted its determination, 

 treating the glycogen with acetic acid anhydride saturated 

 with hydrochloric acid. With polysaccharides it is possible 

 in this way to obtain chloracetyl products, the chlorine of 

 which may then be used in deduction of the molecular weight 

 of the original substances; in case of glycogen the figure 

 obtained was about 24000. Eeally, however, the molecule is 

 probably even larger. 4 The well-known opalescence of 

 glycogen solutions depends upon ultramicroscopic particles 

 suspended in it, as observed by Eahlmann and others, these 

 particles being capable of uniting to form granules of larger 

 size, and determining the physical-chemical characteristics 

 of the solutions. 5 It goes without saying that under these 

 circumstances it is difficult to expect much from cryoscopic 

 determinations. 6 



2 Literature upon the Quantitative Estimation of Glycogen : E. Salkowski, 

 Biochem. Zeitschr., 1, 337, 1903; K. Grube, H'andb. d. Biochem., 2, 159-106, 

 1910; cf. also W. Grebe, Pfliiger's Arch., 121, 602, 1908; B. Schondorff, 

 P. Junkersdorf and G. Franke, ibid., 126, 578, 582, 1909 ; 127, 277, 1909. 



* Z. Gatin-Gruzewska, Pfliiger's Arch., 102, 569, 1904. 



4 Zd. H. Skraup, Monatsh. f. Chem., 26, 1415, 1905; E. v. Knaffl-Lenz 

 (Chem. Instit., Gratz), Zeitschr. f. physiol. Chem., 46, 293, 1905. 



B Cf. Z. Gatin-Gruzewska and W. Biltz, Pfliiger's Arch., Wo, 115, 1904; 

 F. Bottazzi and G. d'Errico (Naples), ibid., 115, 359, 1906. 



Literature upon the Chemistry of Glycogen : C. Neuberg and B. Rewald, 

 Biochem. Handlexikon, 2, 255-264, 1911. 



