334 THE METABOLISM OF THE CARBOHYDRATES 



with casein and gelatin, on the other hand, he denies that the 

 results show any undoubted glycogen deposition. 



To sum up, then, we may state that, although glycogen formation 

 does probably occur by feeding with proteids which contain a carbo- 

 hydrate group, there is no unequivocal evidence, so far, that this is the 

 case for such proteids as casein, which contain no such group. The 

 whole question urgently requires reinvestigation, especially since, by 

 the indirect method, as we shall see later, the evidence undoubtedly 

 points to sugar formation from all proteids. 



Although, as we have seen, there is some doubt as to whether 

 ingested proteids can form glycogen, it has been recently shown 

 by Hirsch and Roily ( 13 ) that the proteids of the animal's own 

 tissues certainly can form it. Adopting all the precautions set 

 forth by Pntiger, and by the employment of his method for the 

 estimation of glycogen, these workers, after rendering animals 

 glycogen-free by the use of strychnine, inoculated them with an 

 attenuated culture of the bacillus Coli Communis. Fever followed. 

 After some time the animals were killed, and their tissues were 

 found to contain a considerable amount of glycogen. As is well 

 known, fever induces an active break-down of the proteid tissues, 

 and it was doubtless from the decomposition products of this that 

 the glycogen had been formed. 



As explained above (p. 325), evidence of this tissue-proteid 

 source for glycogen is also obtained when rabbits rendered glycogen- 

 free by strychnine are allowed to sleep under chloral for more 

 than twelve hours. 1 



WHAT BECOMES OF GLYCOGEN IN THE ORGANISM ? 



Concerning the fate in the organism of the glycogen stored in the 

 liver, there are two so-called theories, the one by Bernard ( x ), the 

 other by Pavy ( 10 ). Bernard's theory ascribes to glycogen a func- 

 tion in animal life analogous with that of starch in plant life, viz. 



1 In a series of investigations carried out on the same plan as that detailed 

 above for proteids, E. Kiilz has found urea to increase the glycogen contents 

 of the liver in hens and rabbits. Other workers (Rohmann, Nebelthau, &c.) 

 have recorded similar results with ammonium carbonate, glycin, asparagin, 

 &c. In most of these researches, the liver glycogen alone was estimated, 

 which renders the results of little value, and in those in which the glycogen 

 in the entire body was determined, the differences were so slight that nothing 

 definite can be stated from them. 



