v INTERNAL EESTITUTIVE SECRETIONS 311 



are surcharged with glycogen, is brought into an atmosphere of 

 20 C. or more, the glycogen entirely disappears after a certain 

 time (Foster). 



From all these facts we see that (a) glycogen arises principally 

 from the carbohydrates of the food; (6) it is formed (by a 

 synthetic regeneration and dehydration) from the sugar absorbed 

 by the intestine, not merely from the liver, but also from the 

 muscles and other tissues ; (c) it functions as a reserve material, 

 in analogy with vegetable starch, which plant tissues use as a 

 source of energy. 



XL Although the larger part of the glycogen stored in the 

 tissues of the body comes from the carbohydrates of the food 

 (owing to a synthetic chemical process due to the anabolic activity 

 of living cells in general, but particularly those of the liver and 

 of striated and plain muscle), it is certain that part at least of 

 the glycogen and glucose normally found in the body are formed 

 by an analytic chemical process from the proteins, and also by 

 decomposition of the fats a process effected by the katabolic 

 activity of the tissues. 



01. Bernard always insisted that part of the hepatic glycogen 

 came from the alimentary proteins, in view of the constant 

 presence of glycogen in the liver of dogs fed for a long time on an 

 exclusively flesh diet. This argument does not, however, settle 

 the question, since the muscles (as we have seen) always contain 

 a certain amount of glycogen or the sugar formed from it. But 

 protracted experiments with a diet of pure proteins, albumin, 

 fibrin, caseinogen, according to v. Mering, Klilz and others, do 

 cause the reappearance of glycogen, although in small quantities, 

 in animals deprived of it by fasting. 



The experimental evidence which Seegen and Weiss brought 

 forward in support of this theory (p. 303) was contradicted by 

 other workers (Montuori, E. Cavazzani, Hesse, Abderhalden). 



Pfliiger is among those who deny that glycogen is partly 

 formed from alimentary protein. In his classical monograph 

 Glycogen (1905) he reviews all his experiments on various animals 

 kept fasting for a longer or shorter time, and then fed up again 

 either with meat, or with special proteins destitute of glycogen 

 and glucoprotein. 



He demonstrates that the percentage of glycogen found in 

 the animals experimented on, came within the limits of that 

 in the fasting control-animals, plus that amount of glycogen due 

 to the carbohydrate present in the flesh diet. So that if, after 

 feeding-up again, glycogen appears in excess of that in the fasting 

 control, this does not, according to Pfliiger, prove it to be formed 

 from the alimentary protein. The latter may stimulate the 

 production of glycogen by utilising the fat, without actually 

 participating in such production. According to Pfliiger, this 



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