THE THORACIC VERTEBRAE 



53 



nterior root. 



as in the other cervical vertebrae. The spinous process is of large size, very strong, 

 deeply channelled on its under surface, and presents a bifid, tubercular extremity 

 for the attachment of muscles which serve to rotate the head upon the spine. 



Seventh Cervical (Fig. 18). The most distinctive character of this vertebra 

 is the existence of a very long and prominent spinous process, hence the name, 

 vertebra prominens. This pro- 

 cess is thick, nearly horizontal Body. 

 in direction, not bifurcated, and 

 gives attachment to the lower 

 end of the ligamentum nuchae. 

 The transverse process is usually 

 of large size, its posterior tuber- 

 cles are large and prominent, 

 while the anterior are small and 

 faintly marked ; its upper surface 

 has usually a shallow groove, and 

 it seldom presents more than a 

 trace of bifurcation at its ex- 

 tremity. The foramen in the 

 transverse process is sometimes 

 as large as in the other cervical 

 vertebrae, but is usually smaller 

 on one or both sides, and is 

 sometimes absent. Usually the 

 vertebral artery and vein pass in 

 front of the transverse process, 



but occasionally it is traversed on both sides by these vessels, or the left one 

 alone may give passage to them. Occasionally the anterior root of the trans- 

 verse process exists as a separate bone, and attains a large size. It is then 

 called a cervical rib. 



Spinous process. 

 FIG. 18. Seventh cervical vertebra. 



The Thoracic Vertebrae (Vertebrae Thoracales). 



The thoracic vertebrae are intermediate in size between those in the cervical and 

 those in the lumbar region, and increase in size from above downward, the upper 

 vertebrae in this segment of the column being much smaller than those in the 

 lower part. A thoracic vertebra may be at once recognized by the presence on 

 each side of the body of one or more facets or half-facets for the heads of the ribs. 



Bodies. The bodies of the thoracic vertebras resemble those in the cervical 

 and lumbar regions at the respective ends of this portion of the vertebral column, 

 but in the middle of the thoracic region their form is very characteristic, being 

 heart-shaped, and as broad in the antero-posterior as in the lateral direction. 

 They are thicker behind than in front, flat above and below, convex and prominent 

 in front, deeply concave behind, slightly constricted in front and at the sides, 

 and marked on each side, near the root of the pedicle, by two demi-facets, one 

 above, the other below (fovea costalis superior et inferior). These are covered by 

 cartilage in the recent state, and, when articulated with the adjoining vertebra?, 

 form, with the intervening fibrocartilage, oval surfaces for the reception of the 

 heads of the corresponding ribs. 



Pedicles. The pedicles are directed backward, and the inferior intervertebral 

 notches are of large size, and deeper than in any other region of the spine. 



Laminae. The laminae are broad, thick, and imbricated that is to say, 

 overlapping one another like tiles on a roof. The vertebral foramen' is small, 

 and of a circular form. 



