RESPIRATION 8$ 



153. How rapidly oxygen is used. When the draft of 

 a stove is closed, the fire stops burning at once. Just so 

 the oxidation in the body stops when we stop breathing. 

 In a lung full of air there is enough oxygen to last from 

 one half to one minute. After that we feel very short of 

 breath and cannot keep ourselves from breathing. A frog 

 can take a big mouthful of air which will last him some 

 time while he is under water, but finally he must come to 

 the top for more air. A man cannot store air in his body, 

 and so must keep taking in air every moment. The oxy- 

 gen goes quickly to the cells, and starts the oxidation at 

 once. A few deep breaths will relieve almost any short- 

 ness of breath. 



154. Why we get short of breath. When we run or 

 work hard, our cells use a great deal of oxygen. Then 

 we breathe deeper and take in more oxygen. But after 

 a while the red blood cells have all they can carry. Then 

 we cannot get more, but feel very short of breath. So we 

 stop work until we have sufficient oxygen again. By train- 

 ing, we can educate the heart and lungs so that more 

 oxygen may be carried. Then we can run a long distance 

 without getting out of breath. 



155. Mouth breathing. You should always breathe 

 through the nose. This warms the air and strains out its 

 dust. When you breathe through the mouth, the cold air 

 and dust make you cough and are very likely to give you 

 a cold. 



Some children have masses of flesh growing either in 

 the throat, pharynx, or the nose. Such children always 

 keep their mouths open, for they cannot breathe through 

 the nose. The upper lip seems too short for their teeth. 

 The jaw is narrow and the teeth point forward. This 

 deforms the face for life. If these masses are removed 



