230 THE HOUSE I LIVE IN* 



smaller than males, inspire a still smaller quan- 

 tity, and children a quantity smaller still. 



BREATHING. But how is the process of 

 breathing performed ? To understand this, it 

 is necessary to revert once more to the struc- 

 ture of the frame-work of the human system. 



The ribs, though fastened to the spine or 

 back bone, are not so firmly fixed but what 

 they admit of considerable motion. This mo- 

 tion is very curious, and somewhat difficult to 

 describe. I can only say that it is of such a 

 nature, if unconfined and unrestrained, as to 

 enlarge the cavity of the chest when we in- 

 spire, and to diminish it when we expire. 



This motion of the ribs is caused, in part, 

 by the shortening or contracting of the muscles 

 about the chest. Of these, there are two be- 

 tween every two ribs; and as there are, on 

 both sides, twenty-four ribs, there are forty- 

 four of these muscles concerned in moving the 

 "bellows," every time I wish to breathe. In 

 addition to these, there are nearly one hundred 

 others, that have more or less concern in this 

 matter. 



