INFLUENCE OF TEMPERATURE ON RANA A.REOLATA. 25! 



with some distilled water; care was taken to keep this quantity 

 as constant as possible for reasons given in a previous paper. 7 

 By taking 10 animals at the same time the individual differences 

 were eliminated as much as possible. The aquarium was placed 

 in a larger water container in w r hich the temperature of the water 

 could be automatically regulated, whereas a stirrer moved by a 

 motor kept the water constantly in motion. After 24 hours 

 the urine was centrifuged to remove the skin particles and the 

 faeces and then measured. In this urine I ran total nitrogen, 

 urea, ammonia and uric acid determinations. 8 A difference of 

 ten degrees was chosen because the classical formula of van't 

 Kofi's rule speaks of 10. Higher temperatures than 31 could 

 not be used because a temperature of about 33 is fatal for the 

 frog as appeared in some experiments in which I found all animals 

 dead after having them kept for some time at higher tempera- 

 tures. Even in the 31 experiments some of the frogs were very 

 faint and near death after 24 hours. 9 This is probably the 

 reason why my figures for this temperature were much more 

 irregular than the rest in one of the experiments I got for 

 instance 70 mgm. total nitrogen. The results are given in 



Table I. 



TABLE I. 



7 H. C. van der Heyde, "Studies in Organic Regulation, I., The Excretion and' 

 the Blood-Ficture of the Hibernating Frog," Joui-n. Biol. Chem., XL VI., 1921,. 

 p- 421- 



8 The total nitrogen, urea and ammonia figures are the average of three series of 

 determinations on each of which the determinations were made in duplo. It 

 should be noted that the figures of one series were not identical with those of the 

 others; but that though the way of increase of each series was identical the absolute 

 values showed some variation. The uric acid figures have only been determined in 

 one series. As previously I wish to state that my trust in the uric acid figures 

 is not very great for reasons given in my previous paper (7). 



9 It seems that the highest temperature which Rana pipiens tolerates according 

 to the experiments of Cameron and Brownlee (Transact, of the Royal Soc. of Canada 

 Ser. III., Vol. IX., p. 67) is even lower. 



