BONES, MUSCLES, EXERCISE, AND REST 



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594. The skeleton is divided into the head, the trunk, and 

 the upper and. lower extremities. The trunk includes the 

 spine, or the back-bone, the ribs, the breast-bone, and the 

 pelvis. The hec(d is composed of the eight bones of the skull, 

 the fourteen bones of the face, and the six little bones of the 

 ears. The eight bones of the skull are arranged to form a 



FIG. XXXIH. Bones of the Head. 



a, Frontal bone. 



b, Parietal or side bone. 



c, Occipital bone. 

 d t Temporal bone. 



e, Nasal bone in the nose. 



/, Malar, or cheek bone. 

 g, Upper jaw. 



h, Thin bone below the eye. 

 t, Lower jaw. 



hollow box, to contain the brain. They are united and held 

 together by a v sort of dove-tailed joint, (Fig. XXXIII.) This 

 arrangement and utiion of these bones give great strength to 

 the skull, and enable it to bear heavy blows without break- 

 ing. The brain has, therefore, a secure resting-place. 



595. The chest- is composed of twelve of the vertebrae, or 

 bones of the spine, the twenty-four ribs, and the breast-bone, 

 (Fig. XV.) The spine or back-bone is composed of twenty- 

 four distinct bones, callejd vertebras. Each vertebra consists 

 of a body-, a ring, and various processes or projections, 



