CHAPTER XXXVII 

 BONES. 



642. Use of bone. Bones give shape and support to 

 the body and impart to it strength and stiffness. Like 

 beams of the strongest oak, they extend the length of 

 every limb, and form arches for the protection of the 

 organs in the head, chest, and abdomen. They are of va- 

 rious sizes and shapes, as are suited to the different parts. 

 In the whole body, about two hundred are jointed together 

 to form its framework, called the skeleton. 



643. The skeleton. Eight rounded plates of bone form 

 the top of the head, and fourteen of irregular shape form 

 the face. Together, they form the skull. 



Twenty-six irregular rings of bone piled one upon the 

 other form a support for the trunk of the body. It is 

 called the backbone or spinal column, or simply the spine. 

 The lowest bone is called the coccyx, and the one next 

 above it, the sacrum. Each ring of bone is called a verte- 

 bra. The spine is made of a series of small bones so that 

 it can bend without breaking. It is gently curved so as to 

 lessen the jarring in running and other violent movements 

 of the body. 



From the vertebrae, beginning at the eighth, twelve pairs 

 of bones called ribs curve around the body. In front they 

 join a flat bone called the sternum or breastbone. They 

 inclose and protect the heart and lungs. 



Each shoulder is formed in front by a slender bone 



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