On Respiration and Animal Heat. 43 
«2, When the brain is injured or removed, the action of 
the heart ceases only because respiration is under its in- 
fluence, and if under these circumstances respiration is 
artificially produced, the circulation will still continue. 
«3, When the influence of the brain is cut off, the secre- 
tion of urine appears to cease, and nv heat is generated ; 
notwithstanding the functions of respiration and the circu- 
lation of the blood continue to be performed, and the usual 
changes in the appearance of the blood are produced in the 
lungs. 
“4, When the air respired is colder than the natural 
temperature of the animal, the effect of respiration is not 
to generate, but to diminish animal heat.” 
Mr. Brodie seems to doubt from the above conclusions, 
and from sundry observations in the paper, whether 
respiration is the source of animal heat. But it seems 
premature to draw conclusions respecting the source or 
acquisition of animal heat from experiments relating to 
its evolution; the two functions by which these processes 
are carried on may be variously affected in sueh extra- 
ordinary circumstances as those above alluded to, and there 
may not be that mutual and correspondent action which 
takes place when the animal is in full possession of all its 
vital energies. It should appear from the last experiment 
(though the results are not ascertained with the requisite 
accuracy) that the acquisition of heat goes on in some 
degree ; for carbonic acid is generated ; but the secretion 
of heat, like that of urine, is totally suspended. {t is 
somewhat remarkable, that in all the experiments previous 
to this, in which a comparison of the venous and arterial 
blood was made, (the Ist, 2d, 3d, 5th and 6th) the blood in 
the arteries was seen of a florid red, and that in the veins 
of a dark colour ; but in the 9th experiment, when oxygen 
gas was inspired, and the production of carboiric acid ob- 
served, “the blood in the arteries was very little more florid 
EF 2 
