FOOD-STUFFS AND GLYCOGEN FORMATION 333 



were obtained by Kiilz, there being, in none of the observations, any 

 undoubted glycogen formation. 



A repetition of the work of Kiilz is urgently required, and, in 

 doing so, the precaution will require to be taken, not only that a 

 more accurate method of glycogen estimation than that of Briicke- 

 Kiilz is employed, but also that the control animals are examined at 

 the same time of the year as the animals to which proteids are 

 administered : for, as we have seen, at different periods of the year 

 the amount of glycogen per kilo body weight varies considerably. 

 Kiilz did not take this precaution. Great care must also be taken 

 that the proteid administered is free of carbohydrates. 



Even from the more recently recorded observations on the 

 influence of proteid feeding on glycogen formation little that is 

 definite can be stated. We will content ourselves with only two of 

 the observations. SchondorfE ( n ) compared the amount of glycogen 

 (estimated by Pflliger's method) in frogs which had received 

 several subcutaneous injections of a ten per cent, solution of pure 

 casein (given in one c.c. doses) with the amount in frogs 

 which had been starved, and found that no increase of glycogen 

 was caused by the injections that is to say, that carbo- 

 hydrate-free proteid causes no deposition of glycogen. This con- 

 clusion for frogs fed on casein has been confirmed by Blumenthal 

 and Wohlgemuth ( 12 ), who also found that similar experiments 

 with egg albumin did cause glycogen to be deposited, since, as we 

 have seen (p. 317), this proteid contains a considerable amount of 

 carbohydrate in its molecule. 



Of course, as Bendix points out, it is scarcely allowable, as a 

 general principle, to assume that physiological processes are the 

 same in frogs as in warm-blooded animals ; but still it must be re- 

 membered that, in the case of glycogen formation, the translation of 

 results from the one group of animals to the other may not be so far- 

 fetched, for both groups of animals live on proteids, fats, and carbo- 

 hydrates, and cold-blooded animals are energetic glycogen formers. 



Bendix ( 8 ) made several observations on dogs which he states 

 that he tried to render glycogen-free by starvation for two days 

 followed by four hours' work on a tread-mill. He found that by 

 feeding such dogs with various proteids (egg albumin, casein, 

 gelatin) for from two to five days glycogen deposition occurred. 

 Pfltiger, in reviewing these results of Bendix, sees a positive 

 glycogen formation only after gluco-proteid had been administered ; 



