COOLING OF ANIMALS EXPOSED TO GREAT HEAT. 363 



quire precise notions of the vital powers, and how they 

 differ from physical, it must be by observing what is pe- 

 culiar to them in the vital functions, not by vaguely as- 

 cribing to them all the phenomena of organic bodies. 



One of the phenomena, in which it seems to me most Animals ex- 

 easy to make the distinction, is that exhibited by animals ['"^^^^^^^^^.^'^ 

 exposed to a high degree of heat. It is well known that generate cold, 

 they then assume a temperature much below that of the 

 surrounding medium. It is near half a century since this 

 remarkable faculty in animals was noticed ; and it has sub- 

 sequently given rise to various experiments, particularly 

 those made conjointly by Sir J. Banks, Sir C. Blagden, 

 Dr. Fordyce, and some other philosophers : but we have 

 not yet any precise ideas of its cause, which some suppose 

 to be the refrigeration produced by the evaporation of the 

 plerspirable matter, others the same with that of animal 

 heat, whether they imagine themselves acquainted with this, 

 or believe it to be yet unknown. Some considerations on 

 this question will form the subject of the present paper: 

 but I think it necessary in the first place to repeat an ob- 

 servatron, which I made some years ago*; this is, that we but not in such 



form a greatly exaggerated notion of this phenomenon, ^^^S""^^.^^'^ 



1 r , J- -t . -"^ , . commonly sup- 



when we suppose the faculty oi producing cold in animals posed. 



is as striking, as that of producing heat. I believe I have 



proved, that this opinion, which has generally prevailed 



since the publication of the experiments abovementioned, 



is altogether erroneous. In fact, in a number of experi- Their heat In- 



ments made in common with my friend Dr. Berger, I con- "eased 



stantly found, that the temperature of animals exposed to 



a higher heat than 35° or 40° cent. [95° or 104'' F.] rose 



in a very striking degree, without however reaching that of 



the surrounding medium. I frequently observed, that this 



rise of temperature amounted to 6° or 7° [10 8*? or 



12*6° F.] ; and I even ascertained, that, when the external 



heat is very considerable, this increase of temperature has 



* In my inaugural dissertation, entitled Experiments on the 

 Effects that a high Degree of Heat produces in the Animal Eco- 

 nomy. See, Collection of Theses of the Medical School at Paris, 

 for 1806, No. 11. 



no 



