CH. XXXV.] GLYCOGBNIC FUNCTION 537 



Average Amount of Glycogen in the Liver of Dogs under various Diets (Pavy). 



Amount of 

 Diet. Glycogen in Liver. 



Animal food 7 '19 per cent. 



Animal food with sugar (about |-lb. 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 Fasting, 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 



The diet most favourable to the production of a large amount of 

 glycogen is a mixed diet containing a large amount of carbohydrate, 

 but with some protein. It is also possible that fats may form a 

 source of glycogen, in virtue of the glycerin they contain. 



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

 destination of the hepatic glycogen. (1) That the glycogen is con- 

 verted into sugar during life by the agency of an enzyme (liver 

 diastase or glycogenase) found in the liver; and that the sugar is 

 conveyed away by the blood of the hepatic veins, to undergo com- 

 bustion in the tissues. (2) That the conversion into sugar only occurs 

 after death, and that during life glycogen is transformed into fat. 



The first view is that of Claude Bernard, and has been adopted by 

 the majority of physiologists. The second view is that of Pavy: 

 he denies that the liver is a sugar-forming organ, he regards it as a 

 sugar-destroying organ; the sugar is stored as animal starch, but 

 never again leaves the liver as sugar during life. He has been unable 

 to find more sugar in the hepatic blood than in the portal blood. 

 Other observers have found an increase in the sugar of the blood 

 leaving the liver, but the accurate estimation of sugar in a fluid rich 

 in proteins is a matter of great difficulty. Even if the increase is so 

 small as hardly to be detected, it must be remembered that the 

 whole blood of the body passes through the liver about once a 

 minute, so that a very small increase each time would mount up to 

 a large total. 



Pavy further denies that the post-mortem formation of sugar from 

 glycogen that occurs in an excised liver is a true picture of what 

 occurs during life, but is due to an enzyme which is only formed after 

 death. During life, he regards the glycogen as a source of other sub- 

 stances, such as fat and protein. It is certainly a fact that increase 



