13* 



GOOD HEALTH 



elephant breathes only eight times, and I have heard that 

 a mouse breathes a hundred and twenty times each min- 

 ute. This breathing is so important that we should die 

 in a few minutes if the air could not get into our lungs. 

 Then, too, the more air they hold the better it is for us. 



Each lung is some- 

 what like a big sponge. 

 If you could take a 

 piece of one of them 

 in your hand and 

 squeeze it hard, you 

 would make a large 

 slice look very small. 

 The reason is plain. 

 The main part of each 

 lung is a bunch of 

 branching tubes. It 

 looks like a tree hang- 

 ing downwards; only 

 in the tree of the lungs every twig and branch is hollow, 

 and you know a bunch of hollow tubes can be squeezed 

 up small. 



Look at the picture carefully and you will see that 

 the largest tube is at the top. This is the windpipe. 

 Now press your finger up and down in front of your 

 neck and you will find several ridges. They are rings 

 of cartilage which hold the windpipe out round and 



THE AIR TUBES OF THE LUNGS 



