930 METABOLISM. 



like a cold-blooded animal, and the metabolism decreases parallel with 

 the body temperature. In normal animals, on the contrary, the body 

 temperature can be kept constant, on lowering the external temperature, 

 by an increased metabolism; but also in such animals because of a rise 

 in the external temperature a rise in the metabolism above a certain 

 limit can also take place. 



A very interesting and important question is the action of high altitude 

 upon the oxidation processes, the economy of temperature, the protein 

 exchange and the general metabolism. The results of the laborious 

 and important investigations on this subject may be found in the large 

 work of N. ZUNTZ, A. LOEWY, F. MULLER and W. CASPAR!. 1 



That the ingestion of food raises the metabolism has been known for 

 a rather long time, and this has been studied by ZUNTZ, v. MERING, MAG- 

 NUS-LEVY, VOIT, RUBNER, JOHANSSON and collaborators, also by HEILNER 

 and by GiGON. 2 It follows from these investigations that this rise in 

 metabolism, which in man, on sufficient supply of food, amounts to a rise 

 of 10-15 per cent of the basal requirement and with abundant supply of 

 food may be still larger (35 per cent in the researches of JOHANSSON, 

 TIGERSTEDT and collaborators), has a double cause, namely, partly a 

 digestion work (ZUNTZ) and partly a chemical decomposition (specific 

 dynamic action of RUBNER) which takes place at the same time. 



The sum of all the work which is necessary for the chemical trans- 

 formation of the foods, as well as for the mechanical division and trans- 

 portation of the food in the intestinal canal, is called the digestion work by 

 ZUNTZ. That such work exists has been shown by ZUNTZ and v. MERING 

 by comparative tests of the different action upon metabolism by 

 foods introduced per os and intravenously, and recently CoHNHEiM 3 

 has shown that in sham feeding an increased catabolism of non- 

 nitrogenous body 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 consump- 

 tion of more than 50 per cent of the total energy content of the raw 

 fodder. 



1 Hohenklima und Bergwanderungen in ihrer Wirkung auf den Menschen, Berlin, 

 1906. 



2 Zuntz and v. Mering, Pfluger's Arch., 15; Zuntz, Naturw. Rundschau, 21 (1906), 

 with Hagemann, 1. c., with Magnus-Levy, Pfluger's Arch., 49; Magnus-Levy, ibid., 

 55, and v. Noorden's Handbuch; Voit, Hermann's Handbuch, 6; Rubner, Zietschr. 

 f. Biol., 19 and 21; and Arch. f. Hyg., 66; Johansson, Skand. Arch. f. Physiol., 21, 

 with Koraen, ibid., 13; Heilner, Zeitschr. f. Biol., 48 and 50; Gigon, Pfluger's Arch., 

 140. 



3 Arch. f. Hyg., 57. 



