70 HUMAN PHYSIOLOGY CHAP. 



SUMMARY OF THE MAIN POINTS 



1. The air always contains bacteria which get into the air 

 passages and lungs and may cause some of the most fatal dis- 

 eases known. 



2. Exposure to drafts and colds may cause congestion in 

 the capillaries of the mucous membrane. Such congestions 

 are favorable for the growth and development of harmful 

 bacteria. 



3. Among the diseases of the air passages are colds, influ- 

 enza, catarrh, bronchitis, adenoid growths, diphtheria, asthma, 

 pneumonia, and consumption. 



4. The atmosphere contains impurities that come from 

 various sources, as combustion, decay, respiration, sewage, 

 factories, old wells and close cellars, marshes, stagnant pools, 

 etc. 



5. There are many natural agencies at work to purify the 

 atmosphere, as diffusion, winds, rain and snow, growth of 

 plants, etc. 



6. The exhaled air contains impurities enough to pollute 

 several times its volume of pure air. Therefore, it is necessary 

 for each person in a room to have about thirty cubic feet of 

 fresh air to breathe every minute. " 



7. The air we breathe, the food we eat, the water we drink, 

 the clothes we wear, and the bed we sleep in, all need careful 

 ventilation. 



8. Buildings in which many persons work and live together, 

 as churches, factories, theaters, and schoolhouses, need to have 

 special provisions for the entrance of fresh air and for the exit 

 of foul air. 



9. The chest should be free to expand in all directions, thus 

 enabling us to use the entire lung at each inspiration. Proper 

 breathing makes use of all parts of the lungs constantly. 



