122 SCIENCE OP COMMON THINGS. 



The windpipe. Larynx. What is coughing ? 



768/71 the human system, what are the parts concerned in the produc- 

 tion of speech and music ? 



They are the windpipe, the larynx, and the glottis. 



769 What is the windpipe f 



The windpipe is merely a cartilaginous canal through 

 which the air issues from the lungs. 



770 What is the larynx f 



The larynx is an enlarged continuation of the wind- 

 pipe, formed, like it, of cartilage or gristle, membrane, 

 and muscle y it is, however, more complicated, ter- 

 minating above in two lateral membranes which 

 approach near together, leaving an oblong, narrow 

 opening, called the glottis. 



771 How is sound produced by the organs of voice ? 



The air expired from the lungs, passes through tLe 

 windpipe and out at the larynx, through the opening- 

 of the membrane called the glottis. The vibration of 

 these membranes, caused by the passage of air, causes 

 sound. 



77S How can the tones of the voice be made grave or acute f 



By varying the tension of these membranes and the 

 size of the opening. 



773 What is the force exerted by the healthy chest in blowing f 



About one pound on the inch of its surface ; that 

 is to say, the chest can condense its contained air with 

 that force, and can therefore blow through a tube the 

 mouth of which is ten feet under the surface of water. 



774 What is the vocal action of coughing ? 



In coughing the top of the windpipe or the glottis is 

 closed for an instant, during which the chest is com- 

 pressing and condensing its contained air ; and on the 

 glottis being opened, a slight explosion, as it were, of 

 the compressed air takes place, and blows out any irri- 

 tating matter that may be in the air-passages. 



775 Why does a popgun make a loud report when the paper bullet is 

 discharged from it? 



Because the air confined between the paper bullet 

 and the discharging rod is suddenly liberated, and 



