354 THE MUSCLE-TISSUE. 



synthesis is now undoubted. It has thus been shown that in frogs 

 a deposition of glycogen occurs following the subcutaneous injection 

 of a solution of glucose, even after removal of the liver. The 

 amount of glycogen which is deposited in the muscle-tissue probably 

 represents about one-half of the total amount that i's found in the 

 entire body, and in man corresponds to 150 grammes. It repre- 

 sents the most important source of energy which is at the disposal 

 of the tissue, and is constantly consumed, even when the muscle is 

 at rest. This is apparent from the fact that after section of the 

 nerves more glycogen is found in a given muscle than in the cor- 

 responding muscle of the other side, while ordinarily this is the 

 same. While at work the consumption of glycogen increases, and 

 after a comparatively short time already the substance has entirely 

 disappeared. If now a period of rest follows, glycogen is again 

 stored in the muscle, and so on. It is to be noted, however, that 

 the working muscle is constantly taking up sugar from the blood, 

 which in turn is derived from the glycogen of the liver, and that 

 its function may continue even though a deposition of glycogen, as 

 such, does not occur. This shows that the muscle glycogen, like 

 that of the liver, is in reality a reserve food, and is here deposited 

 for immediate use. In starving animals it gradually disappears, 

 but, in contradistinction to the glycogen of the liver, its supply is 

 not exhausted until the liver itself is free from glycogen. 



The chemical changes which are involved in the transformation of 

 glycogen into glucose are probably the same as those which occur 

 during the process of digestion. Erythrodextrin thus first results, 

 and is then transformed into achroodextrin, and this into maltose, 

 which in turn is inverted to glucose. This is finally decomposed, 

 with the formation of carbon dioxide and water. The amount of 

 carbon dioxide that is eliminated during a period of exercise, as com- 

 pared with one of rest, may thus serve as an index of the amount of 

 muscular work done. I have already pointed out that the nitro- 

 genous constituents of the muscle-tissue cannot be regarded as a 

 source of muscular energy, and that this must be sought in its non- 

 nitrogenous components. This fact was well shown during the ascent 

 of the Faulhorn mountain by Fick and Wislicenus, in which it was 

 calculated that the total amount of work done by the latter amounted 

 to at least 368,000 kilogram meters. The amount of nitrogen which 

 he eliminated during the ascent and the six hours following corre- 

 sponded to 37 grammes of albumin. Translated into calories, this 

 would represent about 106,000 kilogrammeters of work. Deducting 

 this from 368,000, there would remain 262,000 kilogrammeters, 

 which could not be accounted for by a decomposition of nitrogenous 

 material, and which must hence be referable to the destruction in the 

 muscles of other bodies which are free from nitrogen. Of these, the 

 glycogen which is referable to ingested carbohydrates is no doubt the 

 most important. But while normally the muscle glycogen is prob- 

 ably derived from this source exclusively, there is evidence to show 



