FORMATION OF GLYCOGEN. 373 



as it changes into a chrysalis. In general it is believed that fat does 

 not increase the amount of glycogen in the liver or in the animal 

 body, although a carbohydrate formation from glycerin, but not a gly- 

 cogen formation, is probable. PFLUGER explains this by the fact that the 

 extent of fat metabolism is not dependent upon the quantity of fat 

 supplied, but upon the amount of fat required by work. If more 

 fat is supplied, then it is not destroyed, but is stored up. Even 

 if sugar is continuously formed from the fat, in metabolism this is 

 immediately burned and does not yield any material for the formation 

 of the reserve substance glycogen. 



Opinions in regard to the influence of the proteins are somewhat 

 contradictory. From several investigations the conclusion has been 

 drawn that the proteins cause an increase in the glycogen of the liver. 

 Among these investigations must be included certain feeding experi- 

 ments with boiled beef (NAUNYN) or blood-fibrin (v. MERING), and espe- 

 cially the very careful experiments made by E. KULZ on hens, with 

 pure proteins, such as casein, seralbumin, and ovalbumin. The value 

 of these experiments is disputed by PFLUGER, and as a direct proof against 

 the formation of glycogen from protein he refers to SCHONDORFF'S inves- 

 tigations when feeding carbohydrate-free protein (casein) to frogs without 

 finding the least increase in the total glycogen. Later BLUMENTHAL 

 and WOHLGEMUTH arrived at similar results. They found no glycogen 

 accumulation in frogs after feeding with casein or gelatin, but did find 

 it after feeding with ovalbumin, which contains a carbohydrate group. 

 On the contrary, BENDIX was able to show an increase in the glycogen 

 in dogs by feeding casein and gelatin, as well as ovalbumin, and in fact 

 a greater increase by casein than by ovalbumin. STOOKEY 1 arrived at 

 similar results in hens, as he found a glycogen formation after feeding 

 casein, while he obtained no positive results after feeding glucoproteids. 

 It seems as if the conditions in cold-blooded animals were different from 

 those in warm-blooded ones. According to PFLUGER, the experiments 

 of BENDIX are not conclusive, and he doubts the formation of glycogen 

 from protein. 



Many investigators are still of the opinion that an increase in the 

 glycogen of the liver as well as of other organs can be brought about by 

 feeding animals with carbohydrate-free proteins. The circumstance 

 that, as shown by PFLUGER, 2 the glycogen by long-continued starvation 

 does not entirely disappear from the body but is being reformed, and that 



1 Schondorff, Pfluger's Arch., 82 and 88; Blumenthal and Wohlgemuth, Berl. klin. 

 Wochenschr., 1901; Bendix, Zeitschr. f. physiol. Chem., 32 and 34; Stookey, Amer. 

 Journ. of Physiol., 9. 



9 Pfluger's Arch., 119. 



