HOW WE BREATHE 



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Experiment. To illustrate the process of breathing. 



Materials: A bell jar fitted with a rubber cork, and wide glass tubing 

 from the ends of which are tied two rubber balloons. Over the lower 

 end of the bell jar is tied a piece of sheet rubber such as dentists use, 

 with a piece of string attached at the middle outside the jar. 



Method: Pull on the string so that the cavity inside the jar is increased 

 in size. What effect does this have on the rubber balloons ? Allow the 

 rubber diaphragm to go back to its former position by releasing the 

 tension of the string. What happens to the balloons? Why? 



Conclusion: Explain the different actions you have seen and apply 

 them to the action of breathing. If your finger were placed on the 

 tube leading into the balloons and then the rubber diaphragm were 

 pulled, do you think the action would be the same ? Try it. 



It is very evident from 

 this experiment that the 

 air pressing in on the bal- 

 loons through the tube 

 causes them to expand. 

 If we now compare this 

 apparatus in its working 

 with our own lungs, ribs, 

 and diaphragm, we are 

 able to understand how 

 we breathe. If you will 

 stand upright and take 

 a full deep breath, you 

 will readily notice that 

 as your chest expands 

 the ribs rise. This makes 



Apparatus to show the mechanics of breathing. 



the chest cavity some- 

 what larger. As the ribs rise the muscular diaphragm 

 assumes a straighter line. The lungs lying in this cavity 

 are now filled by the air which rushes into the larger 

 space thus made. This enlargement of the chest cavity 



