362 



AGRICULTURE ON THE PACIFIC SLOPE 



The sound we make in speaking or singing is caused 

 by the air in passing over the membranes of the larynx, 

 and thus setting them in motion. 

 The air passes down through the windpipe into the 



lungs (figure 184). 

 Get from the butcher 

 the windpipe and 

 lungs of a sheep, 

 calf, or hen, and see 

 how they are made. 

 The lungs are very 

 soft and spongy. 

 Blow them up by 

 means of a tube 

 fitted into the wind- 

 pipe (or opening of 

 the larynx) : how 

 much air do they 

 hold when blown 

 up? 



Why does the air enter? We can best understand 

 this by making the apparatus shown in figure 185. A 

 cork or piece of wood is fitted into the end of a lamp 

 chimney, and through this passes a tube of glass or 

 metal, to the end of which a toy balloon or cat's lung is 

 tightly tied (the tube must be fitted into the windpipe 

 or larynx). At the other end of the chimney is tied a 

 sheet of thin rubber (such as dentists use), to folds of 



FIG. 184. Windpipe and lungs. 



