S72 METABOLISM. 



constituents took place. The influence of digestion work in ZUNTZ'S 

 sense is especially apparent in herbivora, in which this work, according 

 to ZUNTZ and collaborators, may amount to the consumption of more 

 than 50 per cent of the total energy content of the raw fodder. 



On partaking of large amounts of food, especially proteins, by car- 

 nivora, the digestion work in the above sense is not sufficient to account 

 for the increase in metabolism, and in these cases, besides this, we must 

 accept an increase in the chemical transformation process in the animal 

 body brought on by the foodstuffs in an unknown manner (specific 

 dynamic action of foodstuffs, according to RUBNER). The only real 

 difference in opinion between the various experimenters consists, so far 

 as HAMMARSTEN can see, in that according to the ZUNTZ school, normally 

 on supplying sufficient food it is the digestion work in the above sense, 

 which chiefly causes the rise in metabolism after taking food, while 

 according to the views of VOIT-RUBNER, with which HEILNER agrees, 

 it is on the contrary the specific dynamic action. 



That the proteins or their cleavage products cause a specific dynamic 

 action seems to be generally accepted. It is difficult to decide how 

 far the fats have such an action while, from the investigations of 

 JOHANSSON, 1 there is no doubt that the carbohydrates have a specific 

 dynamic action. 



JOHANSSON, who has studied the rise in the CO 2 elimination after the intro- 

 duction of carbohydrates, found that this rise was proportional to the sugar 

 supply up to a maximal limit, but that this rise was considerably less, or indeed 

 absent when the store of glycogen was diminished. This behavior, as well as the 

 circumstance that levulose increased the C0 2 elimination nearly twice that of 

 glucose, cannot be explained by digestion work, which indicates a specific 

 dynamic action of carbohydrates. 



The investigations of JOHANSSON, HELLGREN and GIGON 2 have also 

 shown that the foodstuffs, at least in the first hours after the taking of food, 

 act for each other in the metabolism, but not according to their iso- 

 dynamic values, and that they probably first pass into the various depots 

 of the body and then are transformed by the various tissues. JOHANSSON 

 and KORAEN have in a similar manner found that the muscles in their 

 work do not probably take the carbohydrate directly from the intestine, 

 but first, after their transformation into glycogen, from the supply. 



1 Skand. Arch. f. Physiol., 21. 



2 Johansson with Hellgren, Hammarsten's Festschrift, 1906; Gigon, Skand. Arch. 

 f. Physiol., 21. 



