138 



THE VERTEBRA. 



Fig. 32* 



True VertehrcE. 



The true vertehrct are the twenty-four 

 upper bones of the spine, on which the seve- 

 ral motions of the trunk of our bodies are per- 

 formed. Their name is derived from the 

 Latin verb vertere. 



Each of these vertebrae is composed of its 

 body and processes. 



The body is the thick spongy forepart, 

 which is convex before, concave backwards, 

 horizontal and flat in most of them above and 

 below. Numerous small holes, especially 

 on the fore and back part of their surface, 

 giving passage to their vessels, and allow the 

 ligaments to enter their substance. The edges 

 of the body of each vertebrae are covered, 

 especially at the forepart, with a ring of bone 

 firmer and more solid than the substance of 

 the body any where else. These rings seem 

 to be joined to the vertebrae in the form of 

 epiphysis. They are of great use in pre- 

 venting the spongy bodies from being broken 

 in the motions of the trunk. 



Between the bodies of each two adjoining 

 vertebrffi, a substance between the nature of 

 ligament and cartilage is interposed ; which 

 seems to consist of concentrical curved fibres, 

 when it is cut horizontally ; but when it is 

 divided perpendicularly, the fibres appear 



f^d^ 



* The vertebral column — consisting of twenty-four 

 true vertebrae ; and two false, the sacrum and os coccygisj 

 each made up by the consolidation of four bones which 

 are separate in the young subject. — It extends the 

 whole length of the trunk. — It may be divided mto four 

 regions — ihe cervical comprising the seven vertebrae from a to b. — The dorsal, the 

 twelve vertebrae from b to c. — The lumbar, the five vertebrae from c to (/. — The 

 pelvic or sacrc-ccccys;eal portion comprising the false vertebrae, the sacrum and 

 coccyx from d to /. — From c to /. are the four small bones forming the os 

 coccygis. 



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