250 H. C. VAN DER HEYDE. 



The advocates of the confirming answer (as for instance Snyder 

 and Kanitz) explain the little differences between the theoretical 

 values and the experimental results as due to errors in our 

 methods, while those who deny the parallelism between the 

 reactions of organic material and those of ordinary chemistry 

 emphasize these differences and sometimes claim a regular 

 decrease in the value of the temperature coefficient, as Krogh 

 and Ege did in a controversy with Snyder. 



Several authors studied the influence of temperature on 

 metabolic processes. The CO 2 assimilation of plants was shown 

 by Matthaei and numerous other authors to follow the rule of 

 van't Hoff. The frog's metabolism was first studied by Hugo 

 Schulz. 3 The principal importance of his work was that he 

 showed that temperature has a tremendous influence on the 

 frog's metabolism. The frog's output of CO 2 is according to 

 him more than 16 times as much at 25 as at o. Aubert 4 gave 

 more accurate figures, but they can still not yet be used for 

 checking them up with the formula of van't Hoff. Vernon's 

 publications, 5 in which he tried to show that between 2 and 17 

 the CO 2 output was constant, provoked some other papers; the 

 results seem to be due to the sudden changes in temperature to 

 which he subjected the animals. The same fact, a very slow 

 increase in metabolism between 10 and 20, has also been found 

 in Cyclodus gigas, a lizard, by C. J. Martin 6 and in the work of 

 some other investigators. 



EXPERIMENTS. 



In my own experiments I tried to determine the influence of 

 temperature on the excretion of winter frogs. Ten animals were 

 kept for 24 hours in a small aquarium. The bottom was covered 



3 Hugo Schulz, "Ueber das Abhangigkeitsverhaltnis zwischen Stoffwechsel uad 

 Korpertemperatur bei den Amphibien," Pfliiger's Arch., 14, 78-91. 1877. 



4 Hermann Aubert, "Ueber den Einflusz der Temperatur auf die Kohlensaure 

 Ausscheidung und Lebensfahigkeit der Frosche in sauerstoffloser Luft," Pfluger's 

 Arch., 26, 293-323, 1881. 



6 H. M. Vernon, "The Relation of the Respiratory Exchange of Cold-blooded 

 Animals to Temperature," Journ of Physiol., 17, 277-292, 1895. H. M. Vernon, 

 "The Relation, etc., Part II," Journ. of Physiol., 21, 442-496, 1897. 



6 C. J. Martin, "Thermal Adjustment and Respiratory Exchange on Mono- 

 tremes and Marsupials," Transact. Roy. Soc. London, (Bj, 195, 1-37, 1902. 



