GLYCOGENIC THEORY. 257 



Formation of Glycogen from Carbohydrates. The 



liver weighs between 1500 and 1900 grams, and as the amount 

 of glycogen in this organ may reach 10 per cent, of its weight, 

 150 to 190 grams, it is manifest that the carbohydrates of a single 

 meal, which would ordinarily amount to about 100 or 150 grams, 

 could be stored as glycogen in the liver, provided that before the 

 next meal this was all reconverted into liver-sugar, and as such 

 passed out into the blood, leaving the liver free from glycogen ; 

 but this does not occur, so that we may conclude that all the 

 carbohydrates are not deposited in the liver. As has been 

 stated (p. 62), the muscles contain glycogen, sometimes to the 

 amount of 1 per cent., and this undoubtedly comes from the 

 carbohydrates of the food. If, however, all the glycogen in the 

 liver and the muscles is taken into account, together with the 

 dextrose in the blood, about 0.12 per cent., there still remains an 

 overplus unaccounted for, and this is believed to enter into the 

 formation of proteids and other substances ; indeed, it is not by 

 any means certain but that some of the absorbed dextrose may 

 exist in the blood as dextrose and never undergo conversion into 

 glycogen, but perform the same office as the dextrose which does 

 result from liver or muscle glycogen i. e., serve as a source of 

 energy. 



Formation of Glycogen from Proteids. It has been 

 abundantly demonstrated that feeding animals on proteids alone, 

 without any admixture with carbohydrates, results in the forma- 

 tion of glycogen in both liver and muscles. It follows from this 

 that there exists in the body the power of decomposing proteids, 

 and from the carbon, hydrogen, and oxygen which enter into their 

 composition to form glycogen. By this statement it is not in- 

 tended to convey the idea that the proteid is broken up into its 

 chemical elements, but rather that it is decomposed into a non- 

 nitrogenous and a nitrogenous portion ; the non-nitrogenous portion 

 becoming ultimately glycogen, possibly passing through a prelimi- 

 nary stage of dextrose, some of which may remain as dextrose, 

 and not undergo conversion into glycogen. 



Formation of Glycogen from Fats. It is generally 

 accepted that no glycogen is formed from fat. There are authori- 

 ties, however, who hold the contrary opinion, basing this upon cer- 

 tain experiments, and upon the fact that in germinating seeds such a 

 change does take place. It may be regarded as an unsettled question. 



It is an interesting fact that liver-glycogen is increased upon 

 the administration of glycerin. While glycerin is not convertible 

 into glycogen, it seems to prevent the change of the glycogen in 

 the liver into dextrose, and hence causes its retention, which has 

 the same effect upon the total amount in the liver as if more had 

 been formed. 



Glycogenic Theory. The carbohydrates serve as sources 

 of energy i. e., they are oxidized to CO 2 and HoO in the body, 



17 



