10 The Feeding of A^iimals 



liberated energy becoming manifest as heat. With the 

 animal, a greatly varying proportion of the dry matter 

 of the plant is retained to form his body substance, 

 and the remaining part suffers decomposition, largely 

 into the same compounds that are carried away by the 

 draft from the fire on the hearth. As a result there is 

 built a living organism that is warmed to a tempera- 

 ture generally much above that of the surrounding air, 

 which is the seat of complex internal activities and is 

 capable of performing external work. 



