ANIMAL HEAT. 321 



tion ; and the subject of animal heat has been considered almost solely 

 with regard to the ordinary case of man living in a medium colder than 

 his body, and therefore losing heat in all the ways mentioned. The im- 

 portance of the means however, adopted, so to speak, by the skin for reg- 

 ulating the temperature of the body, will depend on the conditions by 

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

 tween the 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 in ordinary temperatures; and thus, it is pos- 

 sible that the quantities of heat required for the maintenance of an uni- 

 form proper temperature in various climates and seasons are not so 

 different as they, at first thought, seem. 



Many examples may be given of the power which the body possesses 

 of resisting the effects of a high temperature, in virtue of evaporation 

 from the skin. Blagden and others supported a temperature varying 

 between 198-211 F. (92-100 0.) in dry air for several minutes, 

 and in a subsequent experiment he remained eight minutes in a temper- 

 ature of 260 K. (126.5 C.) "The workmen of Sir F. Chantrey were 

 accustomed to enter a furnace, in which his moulds were dried, whilst 

 the floor was red-hot, and a thermometer in the air stood at 350 F. 

 (177.8 0.), and Chabert, the fire-king, was in the habit of entering an 

 oven, the temperature of which was from 400 to 600 F. (205-315 

 C.)." (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 

 112 F. (44.5 C.), while in the caves of Testaccio, in which the air is 

 dry, he was but little incommoded by a temperature of 176 F. (80 0.). 

 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 external heat. 



(The glandular apparatus, by which secretion of fluid from the skin 

 is effected, will be considered in the Section on the Skin.) 



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

 ing*apparatus by exposure, by baths, and by other means which man in- 

 stinctively adopts for lowering his temperature when necessary, are too 

 well known to need more than to be mentioned. 



Although under any ordinary circumstances, the external applica- 

 tion of cold only temporarily depresses the temperature to a slight ex- 

 tent, it is otherwise in cases of high temperature in fever. In these 

 cases a tepid bath may reduce the temperature several degrees, and the 

 effect so produced lasts in some cases for many hours. 

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