4 1 



transpiration, wlndi would give, in Vierordt, a cutaneous 

 transpiration of twenty-seven ounces. These amounts are 

 increased by great elevation of temperature, and they must 

 have a proportionately cooling influence. The cooling effect 

 produced by insensible transpiration is well illustrated by 

 the experiments of Dobson, Blagden, and of Delaroche 

 and Berard, who were able to exist for a considerable 

 period of time, in atmospheres whose temperature varied 

 from 212° to 300° Farenheit, without inconvenience, the 

 temperature of their own bodies being not thereby raised 

 more than 5°. A third cooling influence which has not 

 been sufficiently appreciated, is the conversion of the solid 

 components of the body into fixed gases. A very large pro- 

 portion of the excrement of the body is thrown off from 

 the lungs in the form of carbonic acid and azote. The 

 heat rendered latent in the conversion is all at the expense 

 of that of the body. 



The amount of heat generated by an animal is that 

 required to keep its temperature at or near a fixed point, 

 while it is, at the same time, subjected to the cooling influ- 

 ences above enumerated. The amounts of these influences 

 vary under different circumstances. The most important is 

 the difference between the mean temperature of the body 

 and that of the medium. As these approach each other, 

 the loss from conduction of heat diminishes, and when the 

 two temperatures are equal is nil. In the warm blooded 

 animals, however, as the temperature of the air rises to that 

 of the animal, the loss of heat from insensible transpiration 

 increases, as the vaporization of fluid increases in an accele- 

 rating proportion with the increase of temperature. The 

 effect of this difference upon the formation of fixed gases 

 will be shewn afterwards, and causes comparatively little 

 change in this cooling influence. From what has been said, 

 it is clear that the temperature of the animal is not the ex- 

 pression of its heat-producing power, but is the result of 



