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RESPIRATION AND EXCRETION 



b. Mechanics of Respiration 

 1. MOVEMENTS 



Observations. 1. Note the movements of your body while 

 breathing, both when breathing quietly and when breathing 

 deeply. Is there an elastic rebound as the breath goes in or 

 out? 



2. Does the air leave the lungs without effort ? 



Conclusion. Which movement requires the greatest effort, 

 taking in the air (inspiration) or sending it out (expiration) ? 



2. THE DIAPHRAGM 



Materials. Small bell jar with opening at top for a 2-holed 

 rubber stopper, sheet rubber tied over base of jar, with piece of 

 chalk in the center of the rubber. Y-tube 

 with toy balloons fastened to each branch 

 of the Y and with the straight part passing 

 through the stopper. When arranged as in 

 Figure 71, the toy balloons will represent 

 the lungs, or even air cells, the glass tube 

 the trachea, the branches the bronchial 

 tubes, and the glass jar the chest. 



Method. Catch the knobbed place 

 formed by the piece of chalk in the rubber 

 sheet, and pull it downwards. Watch the 

 effect on the toy balloons (lungs). Permit 

 the membrane to return to place and ob- 

 serve again. Or set the apparatus on a 

 bowl, the outer diameter of which is slightly 

 smaller than the inner diameter of jar. This will cause the 

 rubber to be pushed to an arched position. Lift the apparatus 

 from the bowl, and the rubber flattens to a position taken on 

 inspiration. 



Observations. 1. What is the effect on the size of the bal- 



FIG. 71. Diagram to 

 represent action of 

 the diaphragm. 



