14 CLASSIFICATION OF THE BONES. 



motion, as in the spinal column and the upper and lower ex- 

 tremities. They perform, however, but a passive or mechanical 

 part in the movements of the body, forming supporting organs, 

 round which the muscles, nerves and vessels are wreathed, and 

 at the same time serve as levers, by which the limbs are lifted. 

 They are necessarily very numerous in the human body, and 

 exist as separate and distinct pieces, which touch one another 

 at their extremities, where they are generally expanded in. size, 

 and their parts so nicely adjusted to each other, as to form 

 the basis of the structure of the joints. At these places of 

 junction, the bones are fastened together, by strong, fibrous, 

 inelastic, inextensible bands, called ligaments. 

 The number of the bones in the human body, varies accord- 

 ingly as we examine them, in infancy, middle life, or in old 

 age. Nearly all the individual bones of the adult, are developed 

 in separate pieces in the infant, the number of which is very 

 great, and their consolidation into single bones, is not general 

 and complete till about the period of puberty : many of these 

 separate bones of the adult, especially of the head and trunk, 

 are found fused together in extreme old age. 

 Anatomists have generally agreed to consider as distinct 

 bones, those of the adult, and to these they have given indi- 

 vidual names. The skeleton is divided into trunk, head, and 

 extremities : 



Thus there are for the trunk, fifty-three bones ; the twenty- , 

 four true vertebras, the sacrum, the coccyx, twelve ribs on each 

 side, one sternum in three pieces, and two ossa innominata. 

 For the head, fifty-nine bones ; the occipital, sphenoid, 

 ethmoid, frontal, the two parietal, two temporal with the four 

 small bones of the ear, the vomer, the two superior maxillary, 

 two palatine, two molar, two nasal, two lachrymal or unguiform, 

 iwo inferior turbinated, the inferior maxillary, the teeth, and the 

 hyoid bone. 



For the two upper extremities, seventy-four bones ; there are 

 on each side, the scapula, clavicle, humerus, radius, ulna, eight 

 wrist or carpal bones, five metacarpal, fourteen phalanges, and 



five sesamoid bones. 



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