FOOD-STUFFS AND GLYCOGEN FORMATION 331 



experiment, however, the evidence is not convincing enough to 

 allow of a positive assertion that such a transformation takes place 

 in the animal body ; although there is some evidence to show that 

 it possibly may. Seegen has also shown that if glycerine be added 

 to a mush of liver there occurs a formation of glycogen. It has, how- 

 ever, not been shown whether the glycogen in this case is derived 

 from the glycerine or from some of the liver constituents. 



We come now to the most interesting question of all, viz. 

 can proteid form glycogen in the animal body? As this question 

 has recently been the theme of much research, it will be necessary 

 for us to discuss it in considerable detail. It has already been 

 pointed out that, besides the direct method (i.e. the power of 

 glycogen formation), there are indirect methods (i.e. the behaviour 

 of proteids when fed to diabetic animals) by which the question 

 may be answered, and, since by the direct method only doubtful 

 results have, so far, been obtained, we will pass over it quickly, 

 and thus leave more space for the discussion of the results ob- 

 tained by the indirect method. 



Claude Bernard stated that abundant glycogen was stored in 

 the liver when a diet of flesh was taken, and he argued from this 

 that proteid could be transformed in the animal body into glycogen. 

 The fact that flesh may contain as much as 1 per cent, of glycogen 

 a fact not sufficiently considered by Bernard renders this 

 observation valueless. Numerous workers have repeated Bernard's 

 experiments, with the precaution to render the flesh as far as 

 possible glycogen -free. A full review of these researches is given 

 by Pfltiger ( 6 ), who points out that none of them on account 

 of errors similar to those indicated above is of much value 

 in deciding this important question. Most of the earlier workers 

 started out on the assumption that after a few days' starvation 

 the liver was glycogen-free, and they argued that any glycogen 

 which might be found in it, after this period, must have come 

 from whatever food had meanwhile been given. 



The inaccuracy of this premise we have already discussed. 



Few of these earlier workers, moreover, worked with a proteid 

 which was carbohydrate-free. 



It is true that in several of the researches, removal of the 

 glycogen in flesh was attempted by extraction with water, but, as 

 Nerkirig has shown, such treatment only removes a small proportion 



