436 HANDBOOK OF PHYSIOLOGY. 



tions of liver containing it by its reaction (red or port-wine color) with 

 iodine, and moreover, when the hardened sections are so treated that 

 the glycogen is dissolved out, the protoplasm of the cell is so vacuolated 

 as to appear little more than a framework. There is no doubt that in 

 the liver of a hibernating frog the amount of glycogen stored up in the 

 outer parts of the liver cells is very considerable. 



Average amount of Glycogen in the Liver of Dogs under Various Diets 



(Pavy). 



Diet. Amount of Glycogen in Liver. 



Animal food 7.19 per cent. 



Animal food with sugar (about Ib. of sugar daily) 14.5 

 Vegetable diet (potatoes, with bread or barley -meal) 17.23 



The dependence of the formation of glycogen on the kind of food 

 taken is also well shown by the following results, obtained by the same 

 experimenter : 



Average quantity of Glycogen found in the Liver of Rabbits after Fast- 

 ing, and after a diet of Starch and- Sugar respectively. 



Average Amount of Glycogen in Liver. 



After fasting for three days . . . Practically absent, 



diet of starch and grape-sugar . . 15.4 per cent, 

 cane-sugar . . . .16.9 



Glycogen is also formed on a gelatin diet, but fats taken in as food do 

 not increase its amount in the cells. The diet most favorable to the 

 production of a large amount of glycogen is a mixed diet containing a 

 large amount of carbo-hydrate, but with some proteid. Glycerin injected 

 into the alimentary canal may also increase the glycogen of the liver. 



Destination of Glycogen. There are two chief theories as to the desti- 

 nation of hepatic glycogen. (1.) That the glycogen is converted into 

 sugar during life by the agency of a ferment (liver diastase) also formed 

 in the liver; and that the sugar is conveyed away by the blood of the 

 hepatic veins, to undergo combustion in the tissues. (2.) That the 

 conversion into sugar only occurs after death, and that during life no 

 sugar exists in healthy livers; glycogen not undergoing this transforma- 

 tion. The chief arguments advanced in support of this view are, (a) 

 that scarcely a trace of sugar is found in blood drawn during life from 

 the right ventricle, or in blood collected from the right side of the heart 

 immediately after an animal has been killed ; while if the examination 

 be delayed for a very short time after death, sugar in abundance may 

 be found in such blood; (#), that the liver, like the venous blood in the 

 heart, is, at the moment of death, completely free from sugar, although 

 afterward its" tissue speedily becomes saccharine, unless the formation of 



