Section IV., 1914 [261] Trans. R.S.C. 



Further Experiments on the Effect of Low Temperatures on the Frog. 



By A. T. Cameron. 



(From the Department of Physiology and Physiological Chemistry, 



University of Manitoba, Winnipeg.) (Presented by Professor 



Swale Vincent, F.R.S.C.) 



(Read May 27, 1914.) 



In a previous communication Mr. Brovvnlee and I gave an ac- 

 count (Trans., 1913, Vol. 7, Sect. IV, p. 107) of some experiments 

 on R. pipiens, conducted with a view to determine the condition of 

 the frog during such cold winters as are experienced in central 

 Canada, and the States adjacent to the south. Our conclusions 

 were the following: 



(1) Frogs freeze at a temperature of — 0-44°+0-02°C. in a 

 manner very similar to that of solutions isotonic with their body- 

 fluid. 



(2) Specimens of R. pipiens obtained from the neighbourhood 

 of Chicago will survive a temperature of — 1°C. They will not sur- 

 vive a temperature of — 1 • 8°C. 



(3) The heart tissue, whether exsected or in vivo, of these frogs 

 survives a temperature of —2-5°, but is killed by a temperature of 

 -3-0°C. 



(4) Since this is the case, and since similar experiments by other 

 observers have shown that muscular tissue will survive a temperature 

 of —2-9°, w r hile the peripheral nerves are not killed by much lower 

 temperatures, it appears probable that the cause of death is con- 

 nected with a specific temperature effect on the brain or cord. 



(5) It is unlikely that frogs survive the low temperatures of the 

 air and superficial layers of the earth of a Manitoban winter. Their 

 winter quarters are probably situated in a layer of mud or soil which 

 retains a temperature in the neighbourhood of 0°C. 



During the past winter I have continued the experiments, with 

 a view to determining whether there is any permanent, climatic, 

 adaptation, or temporary, hibernatory, adaptation in the frog, which 

 would permit greater lowering of temperature without fatal result, 

 than that indicated in the above conclusions. My results negative 

 this suggestion, and at the same time specify somewhat more exactly 

 the actual death temperature of the frog R. pipiens. I have also 

 made a few observations on other species, and there appear indi 



