THE SKELETON 



57 



back. The neural arches are notched (Fig. 17, 7s and Fi), adjoin- 

 ing notches forming rounded openings through which the spinal 

 nerves pass on their way out from the spinal cord. 



is 



FIG. 16. 



FIG. 17. 



FIG. 16. A thoracic vertebra seen from behind, i. e., the end turned from the 

 head. 



FIG. 17. Two thoracic vertebrae viewed from the left side, and in their natural 

 relative positions. C, the body; A, neural arch; Ps, spinous process; Pas, anterior 

 articular process; Pai, posterior articular process; Pt, transverse process; Ft, facet 

 for articulation with the tubercle of a rib; Fes, Fci, articular surfaces on the centrum 

 for articulation with a rib. 



FIG. 19. 



FIG. 18. Diagrammatic representation of a segment of the axial skeleton 

 V, a vertebra; C, Cv, ribs articulating above with the body and transverse process 

 of the vertebra; S, the breast-bone. The lighter-shaded part between S and C is 

 the costal cartilage. 



FIG. 19. A cervical vertebra. Frt, vertebral foramen; Pai, anterior articular 

 process; R, rudimentary rib. 



The Cervical Vertebrae (Fig. 19), have rather small bodies and 

 large neural arches; in some of them the spinous process is bifid. 

 They move more freely upon each other than do the vertebra 

 lower down. A rudimentary rib (R, Fig. 19) becomes united 



