102 



OSTEOLOGY 





transversarium may be as large as that in the other cervical vertebrae, but is 

 generally smaller on one or both sides; occasionally it is double, sometimes it is 

 absent. On the left side it occasionally gives passage to the vertebral artery; 

 more frequently the vertebral vein traverses it on both sides; but the usual 

 arrangement is for both artery and vein to pass in front of the transverse pro- 

 cess, and not through the foramen. Sometimes the anterior root of the trams- 

 verse process attains a large size and exists as a separate bone, which is known 

 as a cervical rib. 



The Thoracic Vertebrae (Vertebrae Thoracales). 



The thoracic vertebrae (Fig. 90) are intermediate in size between those of 

 the cervical and lumbar regions; they increase in size from above downward, the 

 upper vertebra? being much smaller than those in the lower part of the region. 

 They are distinguished by the presence of facets on the sides of the bodies for 

 articulation with the heads of the ribs, and facets on the transverse processes of 

 all, except the eleventh and twelfth, for articulation with the tubercles of the ribs. 



Superior articular process 



Demi-facet for head of rib 



Facet for articular part 

 of tubercle of rib 



Demi-facet for head of rib 

 Inferior articular process 



FIG. 90. A thoracic vertebra. 



The bodies in the middle of the thoracic region are heart-shaped, and as broad 

 in the antero-posterior as in the transverse direction. At the ends of the thoracic 

 region they resemble respectively those of the cervical and lumbar vertebrae. 

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

 side to side in front, deeply concave behind, and slightly constricted laterally 

 and in front. They present, on either side, two costal demi-facets, one above, 

 near the root of the pedicle, the other below, in front of the inferior vertebral 

 notch; these are covered with cartilage in the fresh state, and, when the vertebrae 

 are articulated with one another, form, with the intervening intervertebral fibro- 

 cartilages, oval surfaces for the reception of the heads of the ribs. The pedicles 

 are directed backward and slightly upward, and the inferior vertebral notches 

 are of large size, and deeper than in any other region of the vertebral column. 

 The laminae are broad, thick, and imbricated that is to say, they overlap those 

 of subjacent vertebrae like tiles on a roof. The vertebral foramen is small, and of 

 a circular form. The spinous process is long, triangular on coronal section, directed 

 obliquely downward, and ends in a tuberculated extremity. These processes 



