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LECTURE III. 



The head is placed on the top of a column 

 of bones, which, from their having in ge- 

 neral a kind of turning motion on one 

 another, are called vertebras, and the whole 

 pile is called the vertebral column. The 

 base of the column rests upon a wedge- 

 shaped bone, interposed between the 

 side-bones of the pelvis. Each vertebra 

 has belonging to it, a part called its body, 

 which is of an oval or circular form, and 

 presents two plain surfaces to the bone 

 above and below, which are cemented to- 

 gether by the intervertebral substance. The 

 bodies of the vertebrae appear in front of 

 the pillar, laid one upon another, like the 

 stones with which a column is erected. 

 They chiefly support the weight of the 

 head and trunk, and regularly and consi- 

 derably increase in size, as they descend, 

 because the weight is proportionately aug- 

 menting. 



