50 



circumstances of the experiment from sudden transition in 

 the one case and not in the other. 



The last influence is that of climate. No direct experi- 

 ments, so accurate as those which have just heen recorded, 

 have heen made to illustrate this influence. There are yet 

 some well-known facts which show that, hy the warm climate, 

 the constitution is enervated, and the power of function 

 diminished, although its rapidity may, in some degree, be 

 increased. The temperature of man, within the tropics, has 

 been shown by Davy and D'Urville to be higher than in cold 

 climates, and the insensible transpiration is greater, which 

 might lead to the conclusion, that his heat-producing 

 power is greater in warm climates than in cold ; but he 

 loses less heat by conduction, which compensates the loss 

 by transpiration, and if he preserve nearly a similar tem- 

 perature in a hot climate as in a cold, it may be inferred, 

 that the power of generating heat is diminished. A man 

 passing from a temperate into a hot climate, carries with 

 him the constitution of his climate, more active habits, and 

 a greater power of generating heat, his active habits cause 

 greater transpiration, and he thus, if he be temperate, may 

 be preserved from the injurious consequence of this rapid 

 transition, and avoid the seasoning fever. He, at first, is able 

 to bear the heat of the climate under these circumstances 

 even better than the habitual resident : the enervating 

 influence of the climate gradually reduces him to the habits 

 and condition of functions of the latter. A person, after 

 long residence in a warm climate, returning to the colder, 

 is, from the increased power and activity of function con- 

 sequent upon the application of cold, for a period, able 

 to bear the cold climate even better than the habitual resi- 

 dent. If his constitution be not permanently impaired by 

 the habits too generally indulged in warm climates, and if 

 he return sufficiently young, he may, after the temporary 

 excitement from the change, yet preserve, or recover the 

 the heat-producing power of his age : but, in general, in 



