THE THORAX. 



The thorax is that part of the body-cavity separated by the diaphragm from 

 the abdomen below, but without complete separation from the neck above. Its 

 bony walls are formed behind by the thoracic vertebrae, at the sides by the ribs, and 

 in front by their continuations, the costal cartilages, and the sternum. 



» Fig. 173. 



The bony thorax, anterior view. 



THE RIBS. 



The ribs, arranged as twelve pairs, are flat bars of bone, curved and twisted, 

 which are attached behind to the spine and continued in front by the costal cartilages ; 

 they form the greater part of the bony walls of the thorax. The first seven pairs, 



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