PECULIAR VERTEBRA. 



119 



The chief points of difference between typical vertebrae of the three presacral 

 groups may be tabulated as follows : 



Body. 



Spinal Foramen. 



Pedicles. 



Laminae. 



Transverse Pro- 

 cesses. 



Superior Articu- 

 lar Surfaces. 



Cervical. 



1. Broad. 



2. Upper surface with 

 raised sides and 

 rounded anterior bor- 

 der. 



3. No facets. 



Triangular, with great- 

 est diameter trans- 

 verse. 



Notches above and be- 

 low nearly equal. 



Nan-ow, with spaces be- 

 tween. 



Double foramen at root ; 

 two tubercles. 



Nearly p^ane ; face up- 

 ward and backward. 



Thoracic. Lumbar. 



Diameters nearly equal; Broad. 



concave behind. 

 Plane. 



Costal semifacets. 

 Nearly circular. 



Plane. 



No facets. 



Triangular, with diam- 

 eters nearly equal. 



Rising from top of body; Small notch above, 



great one below. 



Extending downward; 

 large spaces be- 

 tween. 



Slender. 



great notch below. 



Broad ; no spaces be- 

 tween. 



Strong, with articular 

 facet. 



Plane, vertical ; face Concave, vertical ; 

 nearly backward. face chiefly inward. 



PECULIAR VERTEBRA. 



Certain vertebrae differ more or less markedly from the type of their respective 

 groups ; in some cases, as the upper two cervical vertebrae, these variations result in 

 conspicuous modifications ; in others, as the lower thoracic, the peculiarities are less 

 pronounced. Although the most noteworthy differences are here given, the reader 



Fig. 148. 



Posterior tubercle 



Posterior arch 



Lateral mass 



Groove for vertebral artery 



Superior articular facet 



Transverse pro- 

 cess 



Transverse foramen 



Facet for odontoid process of axis 



Anterior arch 



Anterior tubercle 

 The atlas from above. 



is referred to the discussion of the gradual changes which occur in passing from one 

 region to the other (page 122) for a more complete account of the modifications to 

 be observed. 



The first and second cervical vertebrae, known as the atlas and axis, consti- 

 tute a special apparatus for the security and movements of the head. The key to 



