CHAPTER X 



GLYCOGEN. FORMATION OF SUGAR FROM PROTEIN 



AND FAT 



GLYCOGEN 



IN the present lecture we have first to take up the subject 

 of glycogen. This is a reserve form of carbohydrate which 

 plays very much the same role in animal metabolism as 

 starch does in plant life, and its lot stands in very close con- 

 nection with the general questions of carbohydrate metab- 

 olism. One need not wonder, therefore, that the literature 

 upon the subject is a very extensive one, so bulky in fact 

 that there would be occasion for doubt whether it would be 

 possible to properly systematize even its principal features, 

 were it not for the fact that two scientists, Edward Pfliiger 

 and Max Cremer, had devoted themselves to the laudable 

 task of sifting and arranging it. Thanks to their work it is 

 no longer a matter of great difficulty to review with a reason- 

 able degree of clarity the problems which glycogen research 

 faces for the immediate future. 1 



Quantitative Determination of Glycogen. Our ability to 

 estimate with precision the glycogen supply accumulated in 

 the tissues has been of the greatest importance for research 

 in carbohydrate metabolism. In some of the later years of his 

 activity Edward Pfliiger performed a service of lasting value 

 by devoting his attention to the problem of quantitative es- 

 timation of glycogen, applying to it his phenomenal ability 

 and thorough critical acumen. It will not be easy for pos- 

 terity to replace Pfliiger 's method with a better. This 

 process consists in dissolving the tissues in a highly con- 

 centrated solution of caustic potash, precipitating the glyco- 



1 Literature upon the Physiology of Glycogen: E. Pfluger, Das Glycogen, 

 2d ed., Bonn, 1905, and Pfliiger's Arch., 96, 1-398, 1903 ; M. Cremer, Ergebn. d. 

 Physiol., 1', 803-909, 1902 ; E. Pfliiger, Pfliiger's Arch., 96, 55-127, 1903. 



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