THE SKELETON. 



59 



FIG. 22. PLAN OF A VER- 

 TEBRA. 



sp>, Spinous process; ar, 

 articular process; us, 

 transverse process; nc, 

 neural canal; pd, pedi- 

 cle ; lm, lamina ; en, cen- 

 trum or body. 



articulation with the occipital condyles (Fig. 17) of the 

 skull. The root of this articular process is pierced by a 

 foramen giving passage to the first 

 spinal nerve and the vertebral ar- 

 tery and vein (Fig. 23, }r). From 

 the lateral opening of this foramen 

 (fr) a groove is continued ventrad 

 to the middle of the transverse pro- 

 cess, where it leads into the longi- 

 tudinal vertebrarterial canal com- 

 mon to the first six cervical verte- 

 brae. The vertebral artery and vein 

 course through this canal (Fig. 23). 

 The axis, or second vertebra, is 

 characterized by its odontoid pro- 

 cess, which projects within the at- 

 las, and also by its elongated spi- 



nous process, which projects both cephalad and caudad. 



The transverse process projects 

 caudad from the body, which is 

 flattened dorsoventrally. This 

 . process is pierced at its base by 



>^ iH I the vertebrarterial canal. 



The remaining five cervicals 

 are very similar to one another. 

 The seventh has no vertebrar- 

 terial canal. The spinous pro- 

 cesses grow successively longer 

 from the third to the seventh 

 (Fig. 21). The transverse pro- 

 cesses of the fourth and fifth are 

 bifurcated, the dorsal branch be- 

 ing called the transverse element 

 and the ventral one the costal element, since it is really the 



FIG. 23. DORSOCAUDAL AS- 

 PECT OF ATLAS. 



fr, Transverse process; tic, 

 neural canal; sp>, spinous 

 process ; fr, aperture of the 

 transverse part of the ver- 

 tebrarterial canal which 

 enters the atlas at vf; azg, 

 anterior zygapophysis ; zg, 

 posterior zygapophysis. 



