Section IV., 1913. [107] Traxs. R.S.C. 



The Effect of Low Temperatures on the Frog. 

 By A. T. Cameron and T. I. Brownlee. 

 Presented by Professor Swale Vincent, F. R.S.C. 



(Read May 28, 1913.) 



In spite of the rapid changes of temperature met with in central 

 Canada, the sudden onset of winter, and the extremely low temperatures 

 which occur at fairly frequent intervals over a period of four or five 

 months, frogs appear, in full activity, within a few days of the frequently 

 sudden thaw. Further, in this locality (Winnipeg) , it is not uncommon 

 to hear statements that occasionally, during digging operations in winter, 

 frogs are found in a stiff, frozen condition, and that, removed to a 

 warmer atmosphere, they subsequently revive completely, the inference 

 being that they have survived a temperature at any rate comparable 

 with that of the external atmosphere, and well below the freezing point 

 of water. 



Examination of the literature dealing with the limits of extreme 

 cold which poikilothermic animals can survive at first sight shows 

 evidence apparently supporting such statements, and, since it suggests 

 an immunity to, and power of survival of prolonged low temperatures, 

 seems to yield an explanation for the survival and early appearance 

 of frogs after a Manitoban winter. Pembrey has summed up the 

 available evidence as follows: (Schafer's Text-book of Physiology, 

 volume 1, p. 817 et. seq., 1898). 



"The limits of extreme cold are generally reached when the water 

 in which the animals live, or the lymph of their tissues, is frozen. Fishes 

 live in salt water when the temperature is below zero, but usually die 

 when the water is frozen. 



"Boyle* exposed lampreys in a vessel of water to an exceedingly 

 sharp frost, and found next day that one lamprey was frozen to the 

 ice; when the ice was partly broken and partly thawed the animal 

 was at first motionless, but in a few minutes recovered, and dragged 

 after it a large mass of ice in which its tail was fixed. Similar experi- 

 ments were made with similar results upon gudgeons and frogs. 

 Hunter j found by experiment that the internal temperature of a frog 

 and an eel could be reduced to -0-6°, and that, although the animals 



*"Philosophical Works," Shaw's edition, Vol. 1, p. 688. 

 f'Works," Palmer's edition, London, 1837, vol. IV, p. 131 el seq. 



Sec. IV, 1913—7 /^ 



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