120 



LABOEATOEY MANUAL 



movements of the diaphragm. This action is demon- 

 strated by the following experiment : 



Fasten a toy balloon to one 

 end of a glass tube. Insert the 

 tube into a rubber stopper and 

 fit this into the bell jar with the 

 balloon suspended inside. Over 

 the other end of the belljar, 

 securely fasten the rubber sheet 

 to the center of which a handle 

 has been attached. The belljar 

 represents the chest walls, the 

 tube the trachea, and the bal- 

 loon a lung. The rubber sheet represents the 

 diaphragm. 



Pull the rubber sheet downward. What happens to 

 the balloon? Then let the rubber sheet return to its 

 normal position. What is the effect on the balloon? 

 The action of the balloon represents the action of the 

 lungs in response to the movements of the diaphragm. 



Exercise 80. Comparison of Expired and Inspired 

 Air. 



Object: To determine the changes which take place 

 in the air while in the lungs. 



Apparatus 



Thermometer 



Glass plate 



Wide mouth bottles 



Two-holed rubber stopper 



Glass tubing 

 Lime water 

 Pine splinter 

 Pneumatic trough 



