CHAPTER XVI. 

 HYGIENE OF RESPIRATION. 



1. Introductory. We all know, of course, that air which 

 is not fresh is unpleasant to breathe, but many persons 

 appear not to know that it is also poisonous. 



Suppose you put an air-tight bag, containing two or 

 three pints of air, close to your mouth, and kept your 

 nostrils closed, so that no air could enter the lungs but 

 that in the bag. For the first few breaths you would 

 have no trouble. But after you had breathed in and out 

 of the bag several times the air within it would not have 

 enough oxygen left to supply the needs of the body, and 

 would be so full of excretions as to be poisonous. 



If you want to keep a pet puppy or kitten in a box, 

 you make an air-hole. When asked why, you reply that 

 the animal would die without air, yet there is already in 

 the box as great a quantity of air as could get in if there 

 were dozens of holes. What you want is to give your 

 pet fresh air from the outside so that it will not have to 

 breathe over and over again that which becomes more 

 poisoned every time the animal draws it into his lungs. 

 When we shut ourselves up in rooms with tight win- 



i. What is said of air that is not fresh ? How is air altered every 

 time it is breathed ? What would happen if you tried to go on breath- 

 ing the air shut up in a small bag ? What is the real reason that an 

 animal shut up in a box needs an air-hole? Apply to closed rooms, 



