98 GLYCOGEN. 



is the same in both cases. Thus when treated with dilute mineral 

 acids at 100 C., the opalescence disappears, some dextrin is formed 

 en passant, and finally the solution contains only dextrose 1 . On the 

 addition of saliva or pancreatic juice to a solution of glycogen at 40, 

 the first change observed is an immediate disappearance of the 

 opalescence, followed by a rapid conversion into some form of dextrin 

 and a considerable proportion of a sugar which is apparently identical 

 with maltose 2 . Some trace of dextrose may perhaps at the same time 

 be formed. 



The change which glycogen in the liver undergoes post-mortem and 

 presumably also during life is strikingly different from that which has 

 been described above. Whereas by ordinary enzymic hydrolysis, 

 maltose is the chief final product obtained, there is now no doubt 

 that in the liver little if any maltose is formed, the so-called liver-sugar 

 being apparently identical with true dextrose. This fact throws con- 

 siderable light on the mode of conversion of glycogen into sugar by the 

 liver. It has been most usually taught that this conversion is due 

 to some fermentative action ; if this were so then the enzyme which 

 is the active agent must be possessed of powers differing from those 

 of most other enzymes since it forms dextrose and not maltose. 

 But as a matter of fact it does not appear possible to extract any 

 appreciable quantity of enzyme from the liver, and if a trace is 

 obtained it is of one whose action on starch and glycogen yields chiefly 

 maltose and not dextrose. It is hence a legitimate conclusion that the 

 conversion of glycogen into sugar by the liver is the outcome of the 

 specific metabolic activity of the hepatic cells and not of any enzymic 

 action 3 . It is also significantly probable, from what has been already 

 said (see above, p. 58), that the liver receives its carbohydrates 

 supplied in the form of dextrose, and there is no doubt that 

 diabetic sugar is closely related to, if not identical with, true 

 dextrose. 



The dextrin which some observers have obtained from muscles is not to be 

 regarded as a specific constituent, but as formed from their glycogen by some 

 post-mortem change. Horse-flesh is peculiarly rich in glycogen, and it was chiefly 

 from this source that dextrin was obtained in large amount 4 . 



1 Maydl, Zt. f. physiol. Chem. Bd. m. (1879), S. 194. Ktilz u. Borntrager, 

 Pfliiger's Arch. Bd. xxiv. (1881), S. 28. Seegen, Ibid. Bd. xix. (1879), S. 106. 



2 Musculus u. v. Mering, Zt. f. physiol. Chem. Bd. n. (1878), S. 403. Seegen, 

 loc. cit. Kiilz, Pfliiger's Arch. Bd. xxiv. (1881), S. 81. 



3 Eves, Jl. of Physiol. Vol. v. (1884), p. 342 (contains lit. to date). See more 

 recently Langendorff, Arch. f. Physiol. 1886. Suppl.-Bd. S. 277. Panormow, 

 Klin. Wochenb. 1887, No. 27. Dastre, Arch, de Physiol. (4) T. i. (1888), p. 69. 



4 Limpricht, Liebig's Ann. Bd. cxxxni. (1865), S. 293. 



