FEVERS. 547 



it to be, that of 98 degrees of Fahrenheit's thermometer ;* every 

 degree of temperature less than that, may be considered as cold 

 with respect to the human body ; and in proportion to its de- 

 gree, will have a tendency to diminish the temperature of the 

 body. But as the living human body has in itself a power of 

 generating heat, so it can sustain its own proper heat to the 

 degree above mentioned, though surrounded by air or other 

 bodies of a lower temperature than itself ; and it appears from 

 observation, that, in this climate, air, or other bodies applied to 

 the living man, do not diminish the temperature of his body, 

 unless the temperature of the bodies applied be below 62 de- 

 grees. From hence it appears, that the absolute power of cold 

 in this climate, does not act upon the living human body, un- 

 less the cold applied be below the degree just now mentioned. 



It appears also, that the human body's being surrounded by 

 air of a lower temperature than itself, is necessary to its being 

 retained in its proper temperature of 98 degrees : for, in this 

 climate, every temperature of the air above 62 degrees, applied 

 to the human body, though still of a lower temperature than 

 itself, is found to increase the heat of it. And from all this it 

 appears, that the absolute power of cold with respect to the hu- 

 man body, is very different from what it is with respect to inani- 

 mate bodies. 



LXXXIX. The relative power of cold with respect to the 

 living human body, is that power by which it produces a sen- 

 sation of cold in it ; and with respect to this, it is agreeable to 

 the general principle of sensation, that the sensation produced is 

 not in proportion to the absolute force of impression, but ac- 

 cording as the new impression is stronger or weaker than that 

 which had been applied immediately before. Accordingly, with 

 respect to temperature, the sensation produced by any degree 

 of this, depends ^upon the temperature to which the body had 

 been immediately before exposed ; so that whatever is higher 

 than this feels warm, and whatever is lower than it feels cold ; 

 and it will therefore happen, that the opposite sensations of heat 



* In every instance of our mentioning degrees of heat or cold, we shall mention them 

 by the degrees in Fahrenheit's scale ; and the expression of higher or lower shall always 

 be according to that scale. 



