GLYCOGEN. 355 



that it may be formed from the albumins as well. If animals are 

 allowed to starve until the entire reserve of glycogen has been con- 

 sumed, and they are then fed on albumins exclusively, it will be 

 observed that a gradual deposition of glycogen occurs nevertheless, 

 which can be referable only to the ingested albumins. In the severer 

 forms of diabetes, moreover, as will be shown later, sugar appears 

 in the urine although all carbohydrates are excluded from the 

 diet. Of the decomposition-products of the albumins, however, 

 from which glycogen is formed synthetically under such conditions, 

 we have no knowledge that is definite. But it is conceivable that the 

 p:iralactic acid, which is now generally regarded as an albuminous 

 derivative, and which, as we shall presently see, is constantly formed 

 during the activity of muscle-tissue, may here be of moment. This 

 is a mere supposition, however, and lacks definite proof. 



Whether or not the fats finally can also give rise to the formation 

 of glycogen has not been established beyond a doubt. It seems, 

 however, that this does not occur. At the same time we must 

 admit that there is evidence to show that to a certain extent they 

 can supply the energy which is necessary for the functioning of 

 muscle-tissue when a suffiaient supply of glycogen is not avail- 

 able. 



While I have stated above that as a result of muscular activity 

 the glucose which is derived from the muscle glycogen is decom- 

 posed into carbon dioxide and water, there is evidence to show that 

 this decomposition does not occur in the sense of a direct oxidation. 

 It is hence assumed that a primary splitting up of the glucose 

 imlecule occurs, but of the products which are formed nothing 

 definite is known. On the one hand, we may suppose that lactic 

 acid thus results, but we may also imagine that alcohol is produced, 

 and is then oxidized to carbon dioxide and water. As a matter of 

 fact, traces of alcohol are always found when perfectly fresh organs 

 are distilled with water immediately after their removal from the 

 body. 



Of the forces which are at work in effecting both the synthesis 

 of glycogen and its- inversion to maltose and glucose, and the sub- 

 sequent decomposition of the latter, nothing definite is known. But 

 in view of the constant presence of ptyalin and maltase in muscle- 

 tissue there is some ground for the assumption that, in part at least, 

 these changes may be referable to the action of enzymes. 



Isolation. If it is desired to isolate the glycogen from muscle- 

 tissue, it is necessary to place the material in boiling water imme- 

 diately after the death of the animal, so as to prevent its trans- 

 formation into glucose and the resulting products of decomposition. 

 Otherwise this will occur, as the death of the individual cells does 

 not coincide in point of time with the death of the animal as a 

 whole, and there is danger, moreover, that the inverting ferments 

 of the tissue remain active. That this actually occurs can be 

 readily demonstrated by treating one portion of the muscle-tissue as 



