HIDDEN PROCESSES U7 



be transformed into a carbo-hydrate, and it 

 may be one of the sources of the distinguishing 

 carbo-hydrate in the liver known as glycogen. 

 78. The chief source of glycogen, however, 

 is undoubtedly grape sugar that has arrived 

 in the portal blood from the alimentary 

 canal. Glycogen is a non-nitrogenous body 

 much resembling starch, indeed it may be 

 regarded as an animal starch. After a period 

 of digestion and absorption, it is found in 

 the form of minute granules in the interior 

 of many hepatic cells. For a time it is stored 

 in these cells, so that the liver is a storehouse 

 of carbo-hydrate. It is interesting to note 

 that in digestion, as we have seen, all 

 carbo-hydrate is transformed into grape sugar, 

 while in the liver we find the process reversed 

 and a kind of starch, glycogen, is again formed 

 from grape sugar. The first transformation 

 is accomplished by various enzymes, while the 

 second is effected by the living hepatic cells, 

 or possibly by an enzyme in the cells While 

 absorption is going on, a certain amount of 

 grape sugar passes through the liver un- 

 changed, and is carried to the muscles, where 



