Dr. crawford on the Power that 
air : it is therefore highly probable, that this power does not 
depend folely upon evaporation. 
It may not be improper here to obferve, that healthy frogs, 
in an atmofphere above 70% keep themfelves at a lower tempe- 
rature than the external air, but are warmer internally than 
at the furface of their bodies : for when the air was 77 0 , a frog 
was found to be 68°, the thermometer being placed in contadt 
with the fkin ; but when the thermometer was introduced into 
the ftomach, it rofe to yo 0 |. 
It may like wife be proper to mention, that an animal of the 
fame fpecies placed in water at 6i°, was found to be nearly 
6i°| at the furface, and internally it was 66°|. Thefe ob- 
fervations are meant to extend only to frogs living in air or 
water at the common temperature of the atmofphere in fum- 
mer. They do not hold with refpeft to thofe animals, when 
plunged fuddenly into a warm medium, as in the preceding 
experiments. 
To determine whether other animals alfo have the power of 
producing cold, when furrounded with water above the ftan- 
dard of their natural heat, a dog at 102° was immerfed in 
water at 1 1 4 0 , the thermometer being clofely applied to the 
fkin under the axilla, and fo much of his head being uncovered 
as to allow him a free refpiration. 
In 5 minutes the dog was 108°, water 112 0 
6 - - 109 1 1 2 
11 - - 108 - 1 1 2 the refpiration 
having become very rapid. 
In thirteen minutes the dog was 108 0 , water 112 0 , the re- 
spiration being hill more rapid. 
In about half an hour the dog was 109°, water 112 0 , the 
animal was then in a very languid hate. 
Small 
