On Respiration and Animal Heat. 17 
subject to a continual expenditure of heat 
from the action of the surrounding atmo- 
sphere; it must therefore have a continual 
supply; an adequate supply appears to be 
provided by the continual combustion of ihe 
charcoal of the blood in the lungs; but how 
is so large a quantity of heat applied to so 
delicate a viscus as the lung's, without injuring 
it, and even without raising its temperature ? ~ 
It is to Dr. Crawford we are indebted for 
the complete solution of this difficult ques- 
tion; his admirable work on animal heat and 
combustion will be a lasting monument of his 
‘superiority to all his cotemporaries in this 
walk of science. 
The essential characteristics of Dr. Craw- 
ford’s theory of animal heat are two; namely, 
Ist. That the specific heat of carbonic 
acid gas is less than that of oxygenous gas 
and of atmospheric air. 
2d. That the specific heat of blood drawn 
from an artery, is greater than the cote 
heat of that drawn from a vein. 
The former of these facts, indeed, might 
be inferred a priori from Lavoisier’s experi- 
ments on the combustion of charcoal; but it 
. was first proved experimentally by Dr. Craw- 
ford. The latter was, for aught that appears, 
c 
