5 



HUMAN PHYSIOLOGY 



Coughing, sighing, crying, laughing, sobbing, sneez- 

 ing, yawning, snoring, singing, and talking are all 

 respiratory movements of a modi- 

 fied nature. 



FIG. 23. Showing how the movement of the diaphragm changes the capacity 

 of the lungs (Zuppke) . 



Cut off the bottom from a bottle. Tie on a piece of dentist's 

 rubber for a bottom and attach a small elastic bag to a piece of glass 

 tubing that extends through a well-fitting cork, as shown in the figure. 

 The bag represents the lungs ; the glass tubing the windpipe ; the 

 bottle the chest; the dentist's rubber the diaphragm. When the 

 diaphragm is pushed up, the capacity diminishes and the rubber 

 bag collapses. Explain. Compare with the action of the lungs. 



51. Capacity of the Lungs. It is not possible to 

 determine accurately the capacity of the lungs. By 

 means of a spirometer it is easy to measure the amount 

 of air inhaled and exhaled in ordinary quiet breathing. 



