36 Influence of Atmospheric Temperature 



The action of cold, regarded in the same general light of 

 locality or season, is perhaps less remarkable than that of heat, 

 as not equally involving those physical agents which become 

 the direct causes of disease. But, besides its effects on the 

 balance of circulation already noticed (and which, though more 

 strikingly shewn by sudden changes of temperature, are also 

 a result of continued cold), we have to notice its indirect in- 

 fluence in producing certain habits and necessities of life which 

 variously affect the health ; and more especially the alteration 

 it makes in all that relates to food in those countries, where it 

 gives the predominant character to the climate. 



The same manner of reasoning on the morbid effects of heat 

 and cold, whether immediate, or such as depend on long ex- 

 posure, must lead us to make large allowance for the momen- 

 tary condition of the body, and the general habits of life. A 

 man under strong exercise, or with habits of such, is very dif- 

 ferently affected from one in repose. Protection from, or ex- 

 posure to, the causes which augment the direct influence of 

 temperature, as the open sun, wind, and rains, — comfort or 

 privation in the manner of life, — habits of temperance or sen- 

 sual excess, — even the different occupations and temper of 

 mind ; — all these conditions modify more or less the effects of 

 heat and cold on the body ; and some of them, in particular 

 cases, so powerfully, as almost to invert the accustomed results 

 of such exposure. 



In practice also, and for a rule in the habits of life, regard 

 is not sufficiently paid to the different power which different in- 

 dividuals possess, of generating animal heat. This function, 

 whether depending on changes in the blood and manner of cir- 

 culation, or more directly on the nervous system, is as various 

 in its power and exercise as any other of the body, and requires 



one or two degrees. , The experiments of Berger and Delaroche, on the 

 effects of exposure to higher and more sudden heat, prove that a temperature 

 of 80° Fahr. above that of the body may raise the animal heat eight or ten 

 degrees ; a grade still below that evolved in some fevers, and under particu- 

 lar lesions of the nervous system. It is important to notice, that the same 

 conditions produced different results in the two experimentalists ; an effect 

 that might have been anticipated, seeing its probable dependence in part on 

 the excitement to circulation, which is so various in different individuals 

 from the same causes. 



