85 



sLirc'd) being near zero. They could be revived after this 

 treatment, l)nt not if the temperature was 2 or 3 degrees 

 lower. 



According- to Harris (1910), pithed frogs, whose vis- 

 ceral temperature was maintained at 0.0° for 1 hour, sur- 

 vived; one frog died after having sustained for 100 min- 

 utes a visceral temperature of -2.1°. As to the external 

 temperatures supported, Harris summarizes his results 

 by saying that a frog weighing 10 to 12 grams could 

 probably withstand 1 hour but not 2, in water at -10°. 

 He states also that frogs which die after freezing experi- 

 ments, contain some subcutaneous or perivisceral ice, 

 those which survive do not. 



The most extensive investigation on the resistance of 

 frogs to low temperatures is probably that of Cameron 

 and Brownlee (1913). They inserted the bulb of a ther- 

 mometer and, in some experiments, a thermocouple into 

 the stomach of the animals, and exposed them to a con- 

 stant low temperature in the air. They found that frogs, 

 the stomach of which showed - 0.5° for 8 hours, or - 0.5° 

 to - 1.0° for 1 hour, recovered, while those cooled to - 1.5° 

 to - 1.8° for 2 hours or to - 2° to - 2.4° for U hours, died. 

 The authors conclude from these experiments that - 1.8° 

 is the lowest non-lethal internal temperature which can 

 be maintained for a short time. The authors then deter- 

 mined the freezing temperature of the body of the frog 

 as a whole and found it to be - 0.4-1:°. The freezing tem- 

 perature being - 0.44° and the lethal temperature - 1.8°, 

 it evidently follows that ice can be formed in the frog 

 without killing it. Concerning the external air tempera- 

 tures supported, the authors found that occasionally -25° 

 could be withstood for 1 hour ; which shows how slowly 

 heat is withdrawn from the animal tissues by the sur- 

 rounding air. 



According to Kalabuchov (1934), the toarl, Bufn hufo, 

 could not be subcooled below - 0.9° to - 1.0°. When frozen 

 without subcooling, it survived an exposure to sub-zero 

 temperatures for 20 to 145 minutes during which time its 



