CHAPTER XXV 



BREATHING 



Why is it necessary to breathe? We know that food 

 must be burned all the time in the body and that with- 

 out air (oxygen) any burning soon stops. Plants get 

 air through openings in the leaves and stem, insects 

 get it through small openings along their sides, while 

 -the higher animals take air into the body through the 

 nose and mouth. We know that a man can live only 

 a few minutes without air. 



How is air taken into the body? It is much better 

 to breathe through the nose, because the hairs inside 

 the nose strain out a great many of the dust and dis- 

 ease germs in the air, and the air is better warmed when 

 taken in through the nose than through the mouth. 

 Passing through the nose into the throat, the air comes 

 to the "Adam's apple 77 (larynx), which is really the 

 enlarged end of the windpipe. The air passes into this 

 by an opening which is closed by a sort of trapdoor 

 whenever food is being swallowed. Put your finger 

 to your throat as you swallow, and you will feel your 

 Adam's apple rising up to close the trapdoor. In this 

 way food is kept out of the windpipe. We all know 

 what happens when "food goes down the wrong way." 



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