OSTEOLOGY 



tachment to the various muscles, to act as levers to move 

 the spine in different directions, and 

 to articulate with neighboring bones. 

 The arches of the vertebrae form a 

 canal for the passage of the spinal 

 cord ; between each pair of vertebrae 

 apertures exist through which the 

 spinal nerves pass from the cord. 



The atlas supports the head; the 

 axis articulates with the atlas; each 

 of the 12 dorsal segments articu- 

 lates with the ribs of each side ; the 

 sacrum articulates with the two 

 hip-bones (ossa innominata) and 

 the last lumbar; the coccyx articu- 

 lates with the last sacral. The 

 average length of the spine is about 

 2 feet 4 inches. It presents several 

 curves that correspond to the dif- 



FIG. 4. The figures 

 indicate the relations of 

 the vertebral bodies and 

 spines to the correspond- 

 ing spinal segment? of 

 the cord (Church^. 



FIG. 5. A type-vertebra: i, body; 2, ped- 

 icle ; 3, lamina; 4, spinal foramen; 5, spinous 

 process; 6, transverse process; 7, articular 

 process (Leidy). 



ferent segments of the column, viz. : the cervical with 



