228 



ry part of an animal is not of the same degree of 

 heat : and that the more interior and vital parts pos- 

 sess the highest temperature. 



185. We have seen that animals which ordinarily 

 pbssess a degree of heat but little above that of their 

 surrounding medium, very readily adapt their tem- 

 perature (177.) to all the variations of that medium. 

 In man, however, and other warm-blooded animals, 

 the system is able to bear very great changes of tem- 

 perature without a corresponding change in the de- 

 gree of animal heat. Our sensations, indeed, often 

 apprize us of very slight alterations in the tempera- 

 ture of surrounding bodies, when no perceptible dif- 

 ference, ascertainable by the thermometer, exists. 

 These sensations again, are not only influenced by 

 the general healthy condition of the body, but by 

 the habits with regard to heat and cold which we 

 have been accustomed to indulge. Thus persons 

 who clothe themselves warmly, or live generally in 

 uniform temperatures, are affected by slight varia- 

 tions, which others of hardier habits totally disre- 

 gard : and those parts of the body which are com- 

 monly exposed to the irregularities of the season, arc 

 less susceptible of the sensations of heat and cold 

 than such as are more protected from them. The 

 sensation also of heat or of cold, when presenjt in 

 any part of the body, is not only in a great degree 

 independent of the actual temperature of that part, 

 but depends immediately on the previous state or 

 condition of the part itself with regard to sensation ; 

 for the same substance will feel hot or Cold when 

 applied to a part, according as that part previously 

 possessed the sensation of heat or cold relatively to 



