CHAPTER XIII 



BONES AND JOINTS 



123. Uses of Bones. The bones of the human body 

 are so put together as to form a complete human figure 

 in size, shape, and general outline ; they constitute the 

 framework of the body. The bones form protecting 

 walls for some of the most delicate organs, as the brain, 

 the eye, the ear, and the heart and lungs. Muscles are 

 attached to bones which serve as levers for moving any 

 part of the body and for locomotion. We could not 

 stand, walk, and run about if we had no bones to give 

 strength and firmness to the body. 



In all there are t^vo hundred and six bones of various 

 sizes and shapes, joined together by strong bands called 

 ligaments. This large number of bones makes possible 

 the great freedom of movement, as in the wrist, fingers, 

 ankles, toes, spine, neck, and other parts. 



124. The Skeleton. The two hundred and six bones 

 of the body that together constitute the skeleton may be 

 grouped into three classes : those of the head, the trunk, 

 and the extremities. 



The bones of the head may again be divided into 

 those of the cranium, the face, and the ears. In the 

 cranium, which is a firm, thick case for the brain, there 



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