GLYCOGEN FORMERS. 393 



tion, as suggested by BRUCKE, it is better, for quantitative determinations 

 of glycogen, to precipitate it directly from the alkaline solution by alcohol 

 (PFLUGER ! ). 



The quantitative estimation is best performed according to PFLUGER' s 

 method, which is as follows: The finely divided organ is heated on 

 the water-bath for 2-3 hours in the presence of 30 per centKOH; after 

 diluting with water and filtering, the glycogen is precipitated with 

 alcohol, and the redissolved glycogen estimated in part by the polar- 

 iscope and in part as sugar after inversion. One part by weight of sugar 

 equals 0.927 part glycogen. As in the estimation the prescribed direc- 

 tions must be exactly followed, we must refer to the original work of 

 PFLUGER for the details of the method. Other methods of estimating 

 glycogen, such as those of BRUCKE-KULZ, PAVY, and AUSTIN, are described 

 in PFLUGER'S Archiv. 96. Also compare the recent works of PFLUGER. 2 



Numerous investigators have endeavored to determine the origin 

 of glycogen in the animal body. It is positively established by the 

 unanimous observations of many investigators 3 that the varieties of 

 sugars and their anhydrides, dextrins and starches, have the property of 

 increasing the quantity of glycogen in the body. The action of inulin 

 seems to be somewhat uncertain. 4 The statements are questioned in 

 regard to the action of the pentoses. CREMER found that in rabbits and 

 hens various pentoses, such as rhamnose, xylose, and arabinose, have a 

 positive influence on the glycogen formation, and SALKOWSKI obtained 

 the same result on feeding Z-arabinose. FRENTZEL, on the contrary, 

 found no glycogen formation on feeding xylose to a rabbit which had 

 previously been made glycogen-free by strychnine poisoning, and NEU- 

 BERG and WOHLGEMUTH 5 obtained similar negative results on feed- 

 ing rabbits with d- and r-arabinose. In general we can for the present 

 accept the view that the pentoses are not direct glycogen formers. 



The hexoses, and the carbohydrates derived therefrom, do not all 

 possess the ability of forming or accumulating glycogen to the same 

 extent. Thus C. VOIT 6 and his pupils have shown that glucose has a 

 more powerful action than cane-sugar, while milk-sugar is less active 

 (in rabbits and hens) than glucose, fructose, cane-sugar, or maltose. 



The following substances when introduced into the body also increase the 

 quantity of glycogen in the liver: Glycerin, gelatin, arbutin, and likewise, accord- 



1 See also the method suggested by Gautier, Compt. Rend., 129. 



2 Pfliiger's Arch., 103, 104, 121 and especially 129. 



3 In reference to the literature on this subject, see E. Kiilz. Pfliiger's Arch., 24, 

 and Ludwig, Festschrift, 1891; also the cited works of Pfliiger and Cremer, foot-note 

 2, p. 390. 



4 See Miura, Zeitschr. f. Biologic, 32, and Nakaseko, Amer. Journ. of Physiol., 4. 



5 Salkowski, Zeitschr. f. physiol. Chem., 32; Neuberg and Wohlgemuth, ibid., 35. 

 See also Pfliiger, 1. c., and Cremer, 1. c. 



6 Zeitschr. f. Biologic, 28. 



