'HE 



ANIMAL HEAT. 



by which it is surrounded ; an inverse proportion existing in most cases 

 between a loss by radiation and conduction on the one hand, and by 

 evaporation on the other. Indeed, the small loss of heat by evaporation 

 in cold climates may go far to compensate for the greater loss by radia- 

 tion ; as, on the other hand, the great amount of fluid evaporated in 

 hot air may remove nearly as much heat as is commonly lost by both 

 radiation and evaporation together in ordinary temperatures; and thus, 

 it is possible that the quantities of heat required for the maintenance of 

 a uniform proper temperature in various climates and seasons are not 

 so different as they, at first sight, seem. 



Many examples may be given of t he power which the body possesses of resist- 

 ing the effects of a high temperature, in virtue of evaporation from the skin. 

 Blagden and others supported a temperature varying between 92-100 C. 

 (198-212 F.) in dry air for several minutes ; and in a subsequent experiment 

 he remained eight minutes in a temperature of 126.5 C. (260 F.). "The 

 workmen of Sir F. (Jhantrey were accustomed to enter a furnace, in which 

 his moulds were dried, while the floor was red-hot, and a thermometer in the 

 air stood at 177.8 C. (350 F.), and Chabert, the fire-king, was in the habit of 

 entering an oven, the temperature of which was from 205-315 C. (400-600 

 F.)." (Carpenter.) 



But such heats are not tolerable when the air is moist as well as hot, so 

 as to prevent evaporation from the body. C. James states, that in the vapor 

 baths of Nero he was almost suffocated in a temperature of 44.5 C. (112 F.), 

 while in the caves of Testaccio, in which the air is dry, he. was but little 

 incommoded by a temperature of 80 C. (176 F. ). In the former, evaporation 

 from the skin was impossible ; in the latter it was abundant, and the layer 

 of vapor which would rise from all the surface of the body would, by its very 

 slowly conducting power, defend it for a time from the full action of the ex- 

 ternal heat. 



We are able by suitable clothing to increase or to diminish the amount 

 of heat lost by the skin. 



The ways by which the skin may be rendered more efficient as a cool- 

 ing-apparatus too, by exposure, by baths, and by other means which 

 man instinctively adopts for lowering his temperature when necessary, 

 are too well known to need more than passing mention. 



Although under any ordinary circumstances the external application of 

 cold only temporarily depresses the temperature to a slight extent, it is other- 

 wise in cases of high temperature in fever. In these cases a tepid bath may 

 reduce the temperature several degrees, and the effect so produced last in 

 some cases for many hours. 



( b) From the Lungs. As a means for lowering the temperature, the 

 lungs and air-passages are very inferior to the skin; although, by giving 

 heat to the air we breathe, they stand next to the skin in importance. 

 As a regulating power, the inferiority is still more marked. The air 

 which is expelled from the lungs leaves the body at about the tempera- 



