DEVICES USING AIR PRESSURE 



11 



How do we make use of air pressure in breathing? 



The human body is in many respects like an engine. 

 It must have fuel upon which to run, and the fuel 

 must be burned in order that its energy may be re- 

 leased. Burning requires oxygen, which must be sup- 



FJG. 23. VACUUM SWEEPER 



plied to the fuel in that portion of the body where 

 the energy is being released. Air contains oxygen 

 which is taken into the body through the lungs and 

 there is taken up by the blood and distributed to the 

 various parts of the body. 



The lungs are two great sacs filling most of the 

 upper chest cavity. They are connected with the out- 

 side air by the windpipe. In the lungs the air tubes 

 divide, always getting smaller like the branches of a 

 tree. The lungs are in the upper part of the body 

 cavity, which is divided into two parts by a muscular 

 tissue called the diaphragm. This was represented by 

 the tightly stretched rubber at the bottom of the 

 lantern globe in your experiment. When the breast 

 bone is lowered the diaphragm collapses as shown at 

 B in Figure 24. This tends to decrease the size of the 

 body cavity and force the air from the lungs. As the 

 breast bone is raised as shown at A the diaphragm 

 straightens, slightly enlarging the cavity. The en- 

 largment slightly decreases the pressure in the cavity, 

 and air rushes into the lungs to fill them. This action 

 goes on automatically about eighteen times a minute. 



Deep breathing is desirable, for when we exhale 

 naturally only about one seventh of the air contained 

 in the lungs is breathed out. This leaves much un- 

 changed air in the lungs unless deep breathing forces 

 it out and allows a fresh supply to enter. 



REFERENCES FOR FURTHER STUDY 



Caldwell and Curtis, Science for Today, pp. 40-47 

 Clement, Collister, and Thurston, Our Surroundings, p. 41 

 Hunter and Whitman, My Own Science Problems, pp. 59-66 ; 



Science in Our Social Life, pp. 49-75 

 Lake, Harley, and Welton, Exploring the World of Science, 



pp. 24-32 

 Pieper and Beauchamp, Everyday Problems in Science, pp. 



482-485 



Powers, Neuner, and Bruner, The World Around Us, Chap. 9 

 Van Buskirk and Smith, The Science of Everyday Life, pp. 



18-23 



Watkins and Bedell, General Science for Today, pp. 11-19 

 Wood and Carpenter, Our Environment: How We Use and 



Control It, pp. 108-118 



WHAT YOU SHOULD AIM TO AC- 

 QUIRE FROM THIS STUDY 



1. A knowledge of the construction, 

 operation, and importance of lift 

 pumps. 



2. Ability to replace the worn 

 valves of a lift pump. 



3. A knowledge of how air pressure 

 is related to the operation of 

 pumps and siphons. 



4. Ability to start and use a siphon 

 in real situations. 



5. Knowledge of the construction 

 and operation of an air pump. 



6. Ability to care for an air pump. 



7. A knowledge of the uses and im- 

 portance of the vacuum. 



8. A knowledge of the importance 

 of air pressure in breathing. 



FIG 24. HOW WE 

 HREATHE 



TEST OF MASTERY OF 

 THE TOPIC 



In your notebook complete the fol- 

 lowing statements, answer the ques- 

 tions, and comply with the instructions. 



1. On the up stroke of a lift pump 

 the . . vahe is closed. 



2. The pressure of the atmosphere 



will hold up a water column feet 



high. 



3. Water rises into the cylinder of a lift pump because 

 the pressure in the cylinder is than pressure. 



4. On the (up, down) stroke of the piston in a 



lift pump the foot valve is closed. 



5. The force pump differs in one way from the lift pump 

 by not having in the piston. 



6. Is the pressure in a vacuum greater or less than at- 

 mospheric pressure? 



7. To start a siphon the tube must be with liquid. 



8. The ordinary bicycle or automobile pump has a (leather, 

 brass) . piston. 



9. The force pump can raise water to a greater height 



