22 THE HUMAN BODY. 



and from standing on one foot habitually, or sitting much 

 of the time at a desk or table with one arm resting upon 

 it while the other hangs down. 



4, The ribs and breast-bone with the backbone form the 

 thorax. The ribs are twenty-four in number, twelve on 

 each side. They are joined to the backbone behind. The 

 first seven are called true ribs. They are connected with 

 the breast-bone by the costal cartilages. The last five are 

 called false ribs. They are not directly connected with the 

 breast-bone. The last two false ribs are called floating-ribs, 

 because their front ends are not joined to any bone. 



The costal cartilages are continuations of the ribs. 

 Cartilage is more elastic than bone, and the wall of the 

 thorax expands and contracts more freely for being partly 

 cartilage. It is by this expansion and contraction that we 

 breathe. Whoever has harnessed horses has 

 noticed that they generally swell their chests, 

 and manifest displeasure, when the girths are 

 buckled tight. It interferes with their breath- 

 ing, and so with their comfort. If we are wise 

 we shall resist, as they do, any compression of 

 our chests or waists by tight clothing. The 

 elastic walls readily yield to pressure, and after 

 a time become permanently misshapen. The 

 heart and lungs are then crowded; and the 

 liver is displaced, and encroaches on the other 

 organs. Thus, a figure is acquired which is 

 Fig. 6. neither beautiful nor healthful. 

 THE STEKNUM. R The sternuiri) or breast-bone, is a flat, nar- 

 row bone, about five inches long, which is in the middle 

 line of the chest in front. The collar-bones and the car- 

 tilages of the rib? are joined to it. 



