THE LIBERATION OF ENERGY 163 



that occur in muscle and in secreting glands, 

 The amount of heat produced in other ways is 

 comparatively small. The body may also 

 receive heat by the ingestion of hot food or 

 drink and by conduction and radiation from 

 the surrounding medium. The amount of 

 heat thus produced in a living body is very 

 large, and if it were not lost from the body in 

 in some way, the mean temperature of the 

 body would soon rise to a degree incompatible 

 with life. But the arrangements for the 

 removal of heat are efficient. It is thrown 

 off from the body into the surrounding 

 medium by conduction and radiation if the 

 temperature of the medium is below that of the 

 mean temperature of the body. Heat is lost 

 by, in some circumstances, taking cold food 

 or drink, or by the evacuations. It is also 

 lost by becoming latent in the evaporation of 

 sweat from the surface of the skin, that is to 

 say heat is lost in converting the sweat into 

 vapour. Thus the body is maintained in 

 normal circumstances at a mean temperature 

 in the armpit of 98.40 Fahrenheit. 



89. If we estimated all the heat entering the 



