436 ANIMAL HEAT 



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 92 to 100 C. (i98-2i2 F.) in dry air for sev- 

 eral minutes; and in a subsequent experiment he remained eight minutes in a temperature 

 of I26.5C. (260 F.). " The workmen of Sir F. Chantrey were accustomed to enter a furnace, 

 in which his molds 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 2O5-3i5 C. (4oo-6oo 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 al- 

 most 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 external heat. 



Man is able by suitable clothing to increase or to diminish the amount of 

 heat lost by the skin. There are baths and other means which man and 

 animals instinctively adopt for lowering the temperature when necessary. 



Although under any ordinary circumstances the external application of cold only 

 temporarily depresses the temperature to a slight extent, it is otherwise in cases of high 

 temperature in fever. In these cases a cool bath may reduce the temperature several 

 degrees, and the effect so produced lasts in some cases for many hours. 



Extreme heat and cold produces effects too powerful, either in raising or 

 lowering the heat of the body, to be controlled by the proper regulating ap- 

 paratus. Walther found that rabbits and dogs kept exposed to a hot sun, 

 reached a temperature of 46 C. (114.8 F.), and then died. Cases of sun- 

 stroke furnish us with several examples in the case of man; for it would seem 

 that here death ensues chiefly or solely from elevation of the temperature. 



The effect of mere loss of bodily temperature in man is less well known 

 than the effect of heat. From experiments by Walther it appears that rab- 

 bits can be cooled down to 8.9 C. (48 F.) before they die, if artificial respira- 

 tion be kept up. Cooled down to 17.8 C. (64 F.), they cannot recover 

 unless external warmth be applied together with the employment of artificial 

 respiration. Rabbits not cooled below 25 C. (77 F.) recover by external 

 warmth alone. 



Loss of Heat from the Lungs. The lungs and air-passages are 

 very inferior to the skin as a means for lowering the temperature. In giving 

 heat to the air breathed, the lungs stand next to the skin in importance. As 

 a regulating power, the inferiority is very marked. The air which is ex- 

 pelled from the lungs leaves the body at about the temperature of the blood, 

 and is 'always saturated with moisture. No inverse proportion, therefore, 

 exists, as in the case of the skin, between the loss of heat by radiation and 

 conduction, on the one hand, and by evaporation, on the other. The colder 

 the air and the drier, for example, the greater will be the loss in all ways. 

 Neither is the quantity of blood which is exposed to the cooling influence of 



