CHAPTER VIII 



Respiration (continued) 



You must not imagine that vital combus- 

 tion is carried on in the same way as in our 

 fires, or that there is some kind of stove in 

 our bodies. Although there is actual com- 

 bustion there is no fire. Remember the wood 

 turning to dust and slowly consumed in the 

 air, and the stack of damp hay becoming 

 heated till sometimes it catches fire. Vital 

 combustion is quicker than that of decaying 

 wood, and slower than that of wood that 

 burns. Therefore it produces heat, but not 

 enough to be dangerous, as a hot fire would 

 be. 



When passing through a fire and maintain- 

 ing its combustion, the air changes its nature. 

 It dissolves carbon and takes up carbonic 

 acid gas, which passes out through the 

 chimney, while pure air constantly comes in 

 to take its place. Exactly the same thing 

 happens in the combustion that supports life. 



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