238 



out of digestion or fermentation in the living body ; 

 no imagined combustion of phosphorus in the blood ; 

 nor liberation of the phlogistic, or any other princi- 

 ple, through the system, can be received as suffi- 

 cient to account for the uniform height and steadi- 

 ness of this temperature. As, therefore, the animal 

 system, by virtue of its own powers, is unable with- 

 in itself to produce this high degree of heat, to what 

 external agent shall we have recourse, and to what 

 organs shall we refer the production of that elevated 

 temperature, which, in all animals, we have seen to 

 have place ? 



189. In our review df the temperature of the in- 

 ferior animals, it ha$ been observed, that insects, 

 worms, and fishes, which have no respiratory struc- 

 ture similar to that of the lungs ; and the amphibia, 

 the surface of whose lungs, in proportion to that of 

 the body, is comparatively small, and whose blood, 

 at each circulation, is but partially exposed to the 

 influence of the air, possess a degree of heat but 

 little above that of the medium in which they 

 live : while the mammalia class has a temperature 

 considerably higher, and birds, whose lungs bear 

 the largest proportion to their bodies, a're the warm- 

 est of all animals. The observation of these facts 

 led naturally to the opinion, that the temperature of 

 animals was immediately connected with the function 

 of the respiratory organs ; and we have endeavoured 

 to prove, that the small excess of temperature, which 

 not only the inferior animals, but which vegetables 

 also possess, is actually derived from the decompo- 

 sition of the air by these several classes of beings, 

 so long as living action continues. No explanation, 



