METABOLISM OF CARBO-HYDRATES GLYCOSURI AS 553 



It is possible that in some cases the sugar coming from the ali- 

 mentary canal passes entirely or in too large amount through the 

 liver, owing to a deficiency in its power of forming glycogen. But 

 although in certain cases of diabetes specimens of the hepatic cells, 

 obtained by plunging a trocar into the liver, have been found free, 

 from glycogen, in others glycogen has been present. The muscles 

 also are usually stated to be much poorer in glycogen than normal 

 muscles, but this might just as well be the case because glycogen 

 was being transformed into sugar with abnormal ease as because 

 there was interference with glycogen formation. Indeed, it is said 

 that in the heart muscle of depancreatized dogs there is more glycc- 

 gen than in normal heart muscle. It must be carefully remembered 

 that the amount of glycogen present in a tissue gives no information 

 as to the rate at which it is being formed or decomposed. And if 

 the cause of the supposed defect in glycogen-forming power be the 

 absence of a glycogen-forming ferment, or its production in too small 

 an amount, the same circumstance may occasion a too tardy 

 transformation into sugar of whatever glycogen happens to be 

 present. In this case the sugar-regulating function of the glyco- 

 gen store would be equally lost, whether the storehouses were 

 permanently filled with long-formed glycogen or only half-filled or 

 empty. 



In addition to an interference with the due and regulated storage 

 of the surplus sugar as glycogen, it has usually been thought neces- 

 sary for a rational explanation of the facts of diabetes, to assume 

 that from some change in the tissues sugar has ceased to be a food 

 for them, or is used up in smaller amount than in the healthy body. 

 More and more the evidence points to this as the fundamental 

 change both in the human disease and in experimental pancreatic 

 diabetes. 



Why the tissues cannot decompose and utilize dextrose as they 

 normally do, if it be really the case that they fail in this regard, is a 

 question of great interest, but as yet no satisfactory answer can 

 be given. It appears probable that the failure occurs at one or more 

 of the earliest stages in the intermediate metabolism of carbo- 

 hydrates (p. 542) or in the preliminary processes, whatever they 

 may be, which, without profoundly altering the dextrose molecule, 

 prepare it for the series of decompositions, in the course of which it 

 eventually parts with all iis chemical energy. For it has been 

 shown that many of the products of the cleavage or oxidation of 

 sugar, even those in which the decomposition has proceeded but a 

 little way e.g., glyconic and glycuronic acids (p. 543) are com- 

 pletely utilized by the tissues of diabetics and of depancreatized 

 dogs. And the derangement in the normal sequence of events, of 

 whatever nature it may be, is not so deep-reaching as to prevent 



