THE EFFECT OF LOW TEMPERATURES ON COLD‐BLOODED ANIMALS

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 survive 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° C., while the peripheral nerves are not killed by much lower temperatures, it appears probable that the cause of death is connected 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.