SOURCE OF GLYCOGEN 417 



Bernard subsequently found that a liver removed from the body, and 

 from which all sugar had been completely washed away by injecting a stream 

 of water through its blood-vessels, contained sugar in abundance after the 

 lapse of a few hours. This post-mortem production of sugar was a fact 

 which could be explained only on the supposition that the liver contained a 

 substance readily convertible into sugar. This theory was proved correct 

 by the discovery of a substance in the liver allied to starch, termed glycogen. 



Bernard's brilliant researches led him to announce the theory that the 

 carbohydrate which is periodically absorbed in large amount is stored in the 

 liver only to be reconverted to dextrose and discharged back into the blood 

 stream whenever the percentage falls below a certain level. He regarded the 

 liver as a storehouse which regulated the blood dextrose to a constant level. 

 This is the glycogenic function of the liver. 



Source of Glycogen. The greatest amount of glycogen is produced 

 by the liver upon a diet of starch or sugar, but a certain quantity is, or at 

 least may be, produced upon a proteid diet. The glycogen, when stored in 

 the liver cells, may readily be demonstrated in sections 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 proto- 

 plasm 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 glyco- 

 gen stored up in the liver cells is very considerable. 



AVERAGE AMOUNT OF GLYCOGEN IN THE LIVER OF DOGS UNDER VARIOUS DIETS. (PAVY.) 



Diet. Amount of Glycogen in the Liver. 



Flesh food 7 . 19 per cent 



Flesh food with sugar 14.5 



Vegetable diet, i.e., potatoes with bread or barley meal I 7- 2 3 " 



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

 is also 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. 



After three days' fasting Practically absent 



" diet of starch and grape-sugar 15.4 per cent 



cane-sugar 16.9 " 



Glycogen is also formed from fats in diabetes, but there is no clear proof 

 that fats increase the amount of glycogen in the cells. Glycerin injected into 

 the alimentary canal may also increase the glycogen of the liver. The diet 

 most favorable to the production of a large amount of glycogen is a mixed 

 diet containing a large amount of carbohydrate, but with some proteid. 



Glycogen is stored in other organs of the body. Of these the muscles 

 are deserving of special mention. The amount of glycogen in the muscles 

 27 



