CHAPTER XXVI 



MUSCULAR MOVEMENT AND EXERCISE 



What is needed for motion? Two things are needed, 

 muscles and bones. When you raise your hand, a 

 large muscle contracts or shortens, and this pulls the 

 bones of the forearm upward. Figure 186 shows how 

 the muscles are attached so as to bring this about. 

 (You can easily 

 make a model of 

 this with two 

 sticks and a piece 

 of elastic band.) 

 Something similar 

 is found at each 

 joint of the arms, 

 hands, legs, and 



FIG. 186. Action of biceps muscle of the arm. 



feet. 



What is bone? 



The bone is not a dead thing, but very much alive. 

 If you break a bone, it soon grows together again. 

 The hard part contains little living matter, but the 

 marrow is full of it ; it is in this marrow that the blood 

 corpuscles are formed (page 364). 



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