THE BONES AND JOINTS. 



33 



painful. They sometimes become enlarged and stiff and 

 misshapen. 



4, The joints of young chil- 

 dren bend very freely: as they 

 grow older, they become less 

 flexible. Some have "looser" 

 joints than others. Those pub- 

 lic performers who can twist 

 themselves into marvelous 

 shapes, are persons, who, by a 

 course of training begun early 

 in life, have gradually stretched 

 their ligaments. 



5, Ligaments are tough, and 

 not easily hurt; but when we 

 do "sprain" a joint, which 

 means that we have torn or 

 overstretched its ligaments, they recover slowly. 



GROWTH OF BONES. 



SECTION VIII. 1. Bone, though it is so firm and 

 hard, is all the time wasting and being repaired, like the 

 soft parts. If madder, which is of a bright red color, is 

 mixed with the food of animals, their bones will soon 

 become dyed with it. This shows that the madder has 

 passed into the bones. After the madder is stopped, the 

 bones lose the red color. This shows that the madder 

 has passed out. It is reasonable to conclude that nour- 

 ishing matter passes in with the madder, and that waste 

 matter passes out as in other tissues. 



It is therefore important for the growth of the bony 

 frame to keep the blood pure. 



Fig. 22. 

 THE SHOULDER-JOINT. 



