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ence a sensation of burning heat, in a part in which the thermometer 

 indicates no increase of temperature, in which it cannot be perceived 

 even by the touch. I have just^elt a young man's hand, that is swollen 

 from chilblains; though the pain which he feels in it, seems to him to be 

 occasioned by an accumulation of caloric; his hand is colder than mine, 

 which is of the same degree of warmth as the rest of my body, and in 

 which I have no peculiar sensation. It may, therefore, be laid down as 

 an axiom, that the real or thermometrical increase of heat is inconside- 

 rable in inflammation, but that it is intensely felt, in consequence of the 

 increase of sensibility. 



What is the reason, that during the cold fit of a febrile paroxysm, a 

 sensation of excessive cold is felt in a part in which no diminution of 

 heat can be discovered by the touch ? Whence comes the burning heat 

 which attends inflammatory fever (Kotvtroo-ty What is the cause of the 

 difference of the sensations attending the heat of erysipelas, bilious fe- 

 vers, and phlegmon, &c. These various sensations are owing to the dif- 

 ferent modifications of sensibility in these different diseases. Should 

 this explanation appear unsatisfactory, let it be recollected, that however 

 accurate the calculations may be, that have been made on the subject of 

 caloric, or of the matter of heat, the existence of caloric itself is hypo- 

 thetical, and that it is not known, whether caloric is a body, or whether 

 heat is merely a property of matter. 



LXXX. If we now inquire into the causes which enable the body to 

 resist the admission of a degree of heat superior to that which habitu- 

 ally belongs to it, we shall be compelled to admit, in all living bodies, a 

 power by means of which they repel an excess of heat, and retain the 

 same temperature. Cutaneous perspiration, it is true, acts very power- 

 fully in lowering the temperature, and as this evaporation increases with 

 the temperature, it would seem as if this function sufficed to moderate 

 the heat of the body, and to restore the equilibrium. 



It is a fact known since the time of Cullen*, that the evaporation of 

 fluids, or their solution in the air, is the most powerful means of cooling 

 bodies, and that the mercury in the bulb of a thermometer may be frozen 

 merely by moistening it with ether, spirits of wine, or any other volatile 

 substance, and then exposing it to a dry and warm air. This method is 

 equally successful in its application to the human body, and the hands 

 may be cooled to such a degree, as to feel benumbed, by being frequently 

 wetted with a spirituous fluid, and by being moved in a dry and renewed 

 air. But though cutaneous perspiration operates in a somewhat similar 

 manner, and though it may be ranked among the means which nature 

 employs to preserve the animal temperature in a nearly uniform state, it 

 must however be confessed, that it is not the only way in which this ob- 

 ject is accomplished, and that it does not satisfactorily account for this 

 phenomenon, for the evaporation of the fluids contained in dead animal 

 substances, doesnot prevent their being roasted on the application of heatf, 



* This celebrated physician made this discovery about forty years ago, which has 

 thrown much light on several physico chemical phenomena, and he published it in a 

 dissertation entitled, " Of the cold produced by evaporating fluids, and of some other 

 mean sot' producing cold," by Dr. W. Cullen. 'Author's Note. 



f These fluids are not renewed as fast as evaporated, in the roasting meat, which al- 

 ways takes place in the healthy living body. When the body is exposed to a high 

 t emperature, we find profuse perspiration without change of temperature in the system. 



