93 



rectal temperature reaches 16° and still recover, provided 

 they are then warmed artificially. 



Tait (1922) reported that, while the excised, perfused 

 heart of an ordinary mammal stops beating at about 17°, 

 that of a hiheruailng hedgehog or woodchuck will cease to 

 beat only when it freezes. 



The same author, in collaboration with Britton (1923), 

 found that, in the woodchuck, respiration ceases without 

 signs of asphyxia at 12° to 3° ; but, when warmed, the 

 animal may recommence breathing, and spontaneously 

 resume its former body temperature; with artificial res- 

 piration, it always recovers. 



Britton (1923) repeated the earlier work of Simpson 

 and Herring, using a cooling apparatus similar to that of 

 these investigators, and working almost exclusively with 

 deeply anaesthetized cats. He called attention to the fact 

 that the ''deep rectal" temperature (the thermometer 

 bulb placed 8 cm. deep in the rectum) may be 0.5° to 2° 

 higher than the "anal" temperature (thermometer bulb 

 4 cm. deep). Cats, whose deep rectal temperature had 

 been lowered to 19°, could still spontaneously recover 

 their previous body temperature, even though very slowly. 

 Below 18°, recovery could be effected only by artificial 

 warming. The lowest deep rectal temperature at which 

 a cat gave evidence of being alive was 16°, while a guinea- 

 pig could be cooled to 14°. 



According to Kalabuchov (1934), the hat Nyctalus 

 noctida can withstand a 5-15 minutes' subcooling to -2.9 

 to -5.9°. Of 10 bats of the same species, frozen after 

 subcooling, 7 were killed, though the minimal body tem- 

 perature reached only -0.5 to -1.5°. If, however, freez- 

 ing set in without a previous subcooling, the animals could 

 survive a 12-60 minutes' exposure, and a minimal body 

 temperature of -0.8 to -1.9°, but were killed after a 67- 

 145 minutes' exposure and minimal body temperature of 

 -1.2 to -5.5°. Myotis dauheutonii is not so resistant; 4 

 out of 5 bats of this species were killed when freezing with- 

 out subcooling occurred during a 17-90 minutes' exposure. 



