484 I>. crawford on the Power that 
Various opinions have been entertained with regard to the 
caufes of the facts which were eflablifhed by thefe experiments. 
Some have attributed the cold folely to evaporation, and have 
conceived that the fame degree of refrigeration would have 
been produced by an equal mafs of dead matter, containing an 
equal quantity of moifture. Others have affirmed, that 
tire cold did not arife folely from this caufe ; but have 
maintained., that it depended partly upon the energy of the 
vital principle, being greater than what would have been pro- v 
duced by an equal mafs of inanimate matter. 
The ingenious Dr. munro, of Edinburgh, afcrihes the cold 
in the above mentioned experiments to the circulation of the 
blood, in confequence of which the warmer fluids are conti- 
nually propelled from the furface towards the center, where 
they are mixed with blood at a lower temperature, and hence 
the animal is (lowly heated, in the fame manner as the water in 
a deep lake, during the winter, is (lowly cooled, and not with- 
out a long continuance of froft congealed, no part of it becom- 
ing folid till the whole is brought down to the freezing point. 
The following experiments were made with a view to deter- 
mine with greater certainty the caufes of the refrigeration in 
the above inftances. 
To di (cover whether the cold produced by a living animal, 
placed in air hotter than its body, be not greater than what 
would be produced by an equal mafs of inanimate matter, I 
took a living and a dead frog, equally mold, and of nearly the 
fame bulk, the former of which was at 67°, the latter at 68°, 
and laid them upon flannel in air which had been raifed to ic6°. 
In the courfe of twenty-live minutes the order of heating 
was as follows 
* In the two following experiments the thermometers were placed in contaft 
with the Ikin of the animals under the axillae, 
111 
