THE CERVICAL. VERTEBRM. IJ 



21. In individual cervical vertebrae, note the follow- 

 ing peculiarities : 



a. TYiQ first (atlas) is a ring- like mass, composed of 

 three pieces : a ventral and two dorso-lateral, 

 united by cartilages. Its anterior end presents, 

 where the three pieces meet, a deep pit, in 

 which the occipital condyle (25, a) plays ; pos- 

 teriorly is a similar pit for the odontoid pro- 

 cess of the axis (21, b). 



b. The second cervical vertebra (axis) has a large 

 odontoid process, attached by cartilage to the 

 anterior end of its centrum. 



c. The postzygapophyses of the seventh and eighth 

 cervical vertebrce are remarkably large and stout, 

 and those of the eighth arch backward to ar- 

 ticulate with the prezygapophyses of the first 

 dorsal vertebra (11, a). These two vertebrae 

 are also peculiar in their neural spines, which 

 consist of a pair of ridges which meet ante- 

 riorly, but diverge behind to run out over the 

 postzygapophyses. 



d. The variety in the surfaces by which the cen- 

 tra of the cervical vertebrae articulate with 

 one another. The second and third vertebrae 

 are opistho-cxlous ; the fourth has a convexity 

 on each end of its centrum ; the fifth is con- 

 cave anteriorly, and has a pair of convexities 

 behind. The sixth has two concavities in 

 front, and two convexities behind. The sev- 

 enth has two concavities in front, and two 

 behind. The eighth has two convexities in 

 front and two behind. 



