The Air We Breathe 37 



water in a warm room. The water vapor will condense and settle 

 in drops of moisture on the outside of the pitcher. 



Moisture is absolutely necessary to the life of plants, animals 

 and man. If there were no moisture in the air there would be no 

 rain, and consequently plants would cease to grow and produce 

 food. If this should happen, all living things would starve, and 

 there would be no life on the earth. 



The Relation of Air to Health. Air is called good or bad 

 according to its effect on health and feelings. Air is considered 

 good when it contains the proper amounts of oxygen and water 

 vapor. We all recognize the bracing effect of a walk outdoors 

 where there is plenty of fresh air. Such air is good. Air becomes 

 bad when 1 !! is rebreathed several times in a close, over-heated 

 room where there is too much moisture and no circulation. Odors 

 from the body in such a room also aid in making the air bad. 

 Such air is more likely to contain disease germs. 



Air is used by all living things. All living things are adapted 

 for securing air. Air may be taken from the water, in which it 

 is dissolved, by water animals and plants. 



Proper Methods of Breathing. Proper methods of breath- 

 ing are essential to good health. A good way to show these 

 methods is to have each member of a class stand erect with hands 

 on the hips and thumbs toward the back. Keeping the mouth 

 closed, each one should inhale air through the nostrils, until he 

 feels the thumbs rise. This will cause the diaphragm, the muscle 

 between the chest and the abdomen, to contract and allow deep 

 breathing. Then exhale the air, that is, breathe it out gradually. 



Still standing erect, with hands at the side and palms turned 

 outward with thumbs back, inhale as before. This method will 

 force the shoulders back and cause expansion of the chest. Then 

 exhale the air as before and repeat the processes. Make a prac- 

 tice of deep breathing. 



Properties of Air. Among the important properties of air 

 are that it will flow, is elastic, and exerts pressure. Although 

 we seldom think of it, air is a fluid because it flows, and it has 

 weight, because it exerts pressure. These properties account for 

 many of the interesting things we note in connection with air. 



