52 THE STORY OF LIFE'S MECHANISM. 



heat or some other vital function. Herein is 

 the really mysterious part of the life process ; 

 but for the present we will overlook the mystery 

 of this action, and consider the results from a 

 purely material standpoint. 



In a steam engine the fundamental process by 

 which the latent energy of the fuel is liberated 

 is that of oxidation. The oxygen of the air 

 unites with the chemical elements of the fuel, 

 and breaks up that fuel into simple compounds 

 which may be chiefly considered as three 

 carbonic dioxide (C0 2 ), water (H 2 0), and ash. 

 The energy contained in the original compound 

 cannot be held by these simpler bodies, and it 

 therefore escapes as heat. Just the same pro- 

 cess, with of course difference in details, is 

 found in the living machine. The food, after 

 reaching the living cell, is united with the 

 oxygen, and, so far as chemical results are 

 concerned, the process is much the same as if 

 it occurred outside the body. The food is 

 broken into simpler compounds and the con- 

 tained energy is liberated. The energy is, by 

 the mechanism of the machine, changed into 

 motion or nervous impulse, etc. The food is 

 broken into simple compounds, which are chiefly 

 carbonic dioxide, water, and ash ; the ash being, 

 however, quite different from the ash obtained 

 from burning coal. Now the engine must have 

 its chimney to remove the gases and vapours 

 (the C0 2 and H 2 0) and its ashpit for the ashes. 

 In the same way the living machine has its 

 excretory system for removing wastes. In the 

 removal of the carbonic acid and water we have 



