THE POL YSA CCHARIDES. 1 5 



liver and muscle, 1 in embryonic tissues generally, 2 and in the bodies of 

 molluscs. 3 It has been described in pathological growths, 4 and in 

 the vegetable kingdom in many fungi 5 (truffles, mucor, yeast, 

 niyxomycetes). 



It may be dissolved out with boiling water (Briicke), 6 2 per cent, 

 potash (Klilz), 7 or by trichloracetic acid, 8 from the tissues in which it 

 occurs. The extraction with this acid is, however, incomplete, and the 

 product is impure. 9 Huizinga 10 recommends that glycogen should be 

 extracted from the liver by a mixture of equal parts of saturated 

 solution of mercuric chloride, and Esbach's reagent (10 grms. of picric 

 and 20 of citric acid in a litre of water). From this solution, 

 which is proteid free, glycogen is precipitable by alcohol. 



The pure material is a white tasteless powder, soluble in water, forming 

 a strongly opalescent solution. It is insoluble in alcohol and in ether. 

 It is strongly dextrorotatory ; n (a) D = + 196'63. With Trommer's test 

 it gives a blue solution, but no reduction occurs on boiling. 



With iodine it gives a port-wine red colour, which easily distin- 

 guishes it from starch. Its precipitability by basic lead acetate dis- 

 tinguishes it from dextrin. 



Prolonged boiling with water or boiling with dilute mineral acids 

 converts it into sugar. The diastatic ferments act similarly. 



Max Cremer 12 investigated the action of dilute acids on glycogen ; he 

 found glucose and isomaltose (identified by their osazones), but no maltose. 

 Kiilz and Yogel 13 investigated the action of diastatic ferments ; parotid saliva 

 produced isomaltose and maltose in the proportion of 1 to 2 from liver-glycogeri, 

 and isomaltose with small amounts of maltose and dextrose from nmscle- 

 glycogen ; pancreatic juice and malt diastase produced practically the same 

 result. The ferment in the liver which acts on glycogen produces dextrose. 



The physiological relationships of glycogen will be treated elsewhere. 

 There is much controversy on the subject of the origin and fate of glycogen. 

 There is, however, little doubt that it is chiefly a storage product from the 

 carbohydrates of the food, 14 and that after death it is transformed into dextrose ; 

 the principal controversies of recent years have centred round the question 

 whether glycogen normally leaves the liver in the hepatic blood as sugar (as 



1 Claude Bernard, Compt. rend. Acad. d. sc., Paris, 1857, tome xliv. pp. 578 and 1325 ; 

 xlviii. pp. 77, 683, 763 and 784; Hensen, Virchow's Archiv, 1857, Bd. xi. S. 395; O. 

 Nasse, Arch. f. d. ges. PhysioL, Bonn, 1869, Bd. ii. S. 97. 



2 Claude Bernard, " Physiologie expei-.," 1855, tome i. p. 241; iv. p. 44; Salomon, 

 Centralbl. f. d. med. Wissensch., Berlin, 1874, S. 738 ; Moriggia, ibid., 1875, S. 186 ; v. 

 Wittich, Hermann's " Handbuch," 1883. 



3 Bizio, Ztschr. f. Chem., Leipzig, 1866, S. 222 ; Bernard, " Lecons sur les phe'nomenes 

 de la vie," 1879, tome ii. ; Krukenberg, " Vergl. physiol. Studien," 1880, Bd. ii. S. 52. 



4 Kiihne, Virckows Archiv, Bd. xxxii. S. 536 ; Sotnitschewski, Ztschr. f. physiol. 

 Chem., Strassburg, 1880, Bd. iv. S. 220. 



5 Kiihne, "Lehrbuch der physiol. Chem.," 1868, S. 334; Reinke and Rodewald, 

 "Studien ueber das Protoplasma, " Berlin, 1881, S. 34, 54, and 169; Errera, Bull. Acad. 

 roy. de med. de Bcly., Bruxelles, Bd. iv. S. 451. 



6 Sitznngsb. d. k. AJcad. d. Wissensch., Wien, 1871, Bd. Ixiii. S. 214. 



7 Ztschr. f. BioL, Miincheu, 1886, Bd. iv. S. 191. 



8 Friinkel, Arch. f. d. ges. Physiol., Bonn, Bde. lii. S. 125 ; Iv. S. 378. 



9 Weidenbaum, ibid., Bde. liv. S. 319 ; Iv. S. 380. 



10 Arch.f. d. ges. PhysioL, Bonn, Bd. Ixi. 



11 Huppert, Ztschr. f. physiol. Chem., Strassburg, Bd. xviii. S. 137. 



12 Ztschr. f. BioL, Miinchen, 1894, Bd. xxxi. S. 181. 13 Ibid., S. 108. 



14 According to Voit and his pupils (Ztschr. f. BioL, Miinchen, Bd. xxviii. S. 245), the 

 liver forms glycogen only from dextrose and levulose, or from those carbohydrates which 

 are converted into these sugars before they reach the liver. 



