THE PURIFICATION OF THE BLOOD, ETC. 43 



ten minutes, and then only by the robust, or by 

 those inured to it. The reason why heated air 

 is borne more easily than heated vapour or 

 Water, appears to be chiefly this — that from its 

 expansion when thus heated, fewer ultimate 

 particles come in contact with the body than 

 would be the case were it at a lower degree of 

 temperature. It must not be supposed, however, 

 that the temperature of the body subjected to a 

 heated atmosphere is not increased, for the con- 

 trary is the truth, but it is not increased beyond 

 a certain point. Dr. Fordyce, in his experi- 

 ments, ascertained that the heat of the human 

 body, under the influence of a high tempera- 

 ture, speedily reached 100°, but that exposure 

 to 211° did not raise it higher. Dr. Blagden, 

 who was conjoined with Dr. Fordyce in a series 

 of experiments upon animal heat, obscrv.s : 

 " Being now in a situation in which our bodies 

 bore a very different relation to the surround- 

 ing atmosphere from that to which we had been 

 accustomed, every moment presented a new 

 phenomenon — wherever we breathed on a ther- 

 mometer the quicksilver sank several degrees. 

 Every expiration, particularly if made with 

 any degree of violence, gave a very pleasant 

 impression of coolness to our nostrils, scorched 

 just before by the hot air rushing against them 

 when we inspired. In the same manner, our 

 now cold breath cooled our fingers whenever it 

 reached them ; upon touching my side it felt 

 cold like a corpse."* We know well how cold 



* Phil. Trans. 1775, p. 118. 



