OSTEOLOGY. 51 



and meet inferiorly in forming a median ridge (wliicli in 

 some of the vertebrae of tlie dorsal region is elongated to 

 form tlie inferior spinous process). Eacli of the sides at its 

 centre, though inclined to the anterior part, presents a 

 medullary foramen, through which a branch of the inter- 

 costal artery passes. The under surface of the bodies of the 

 anterior six dorsal vertebrae is covered by longus colli, of 

 the posterior three by psose parvi, of the central ones by the 

 vena azygos on the right side, thoracic duct centrally, 

 posterior aorta on the left. The anterior surface is convex 

 and circular, somewhat flattened superiorly. It gives 

 attachment to the intervertebral disc, and is adaj)ted to 

 the posterior surface of the body of the vertebra imme- 

 diately in front of it. The posterior surface is correspond- 

 ingly concave. The pedicles are internally smooth and 

 concave, externally rough, slightly encroached upon by the 

 facets for the heads of the ribs. Anteriorly and posteriorly 

 they have grooves for the intervertebral gaps scarcely per- 

 ceptible anteriorly, posteriorly, in some cases, converted 

 into a foramen. Centrally, at the point of junction with 

 the lamina, is a tuberous process, rough for muscular 

 attachment (of longissimus dorsi and levatores cos- 

 tarum). This is the transverse process, and has on its 

 external surface a small irregular convex synovial facet for 

 the tubercle of the rib, having between it and the posterior 

 facet on the body a smooth groove, extending from the 

 intervertebral gap. The laminae are concave inferiorly, 

 forming the roof of foramen magmini, supero-posteriorly, 

 wholly occupied by the superior spinous process, supero- 

 anteriorly presenting a small synovial facet od each side, 

 representing the anterior oblique processes ; the posterior 

 oblique processes are on the postero-inferior part. The 

 superior spinous process, remarkable for its length, runs 

 obhquely upwards and backwards. Superiorly it is tuberous, 

 affording attachment to the superior spinous ligament, and 

 so indirectly to muscles. Its anterior margin is sharp, 

 especially inferiorly, affording attachment to the inter- 

 spinous ligament. It is much longer than the posterior 

 margin, which is centrally sharp, having on either side 

 a groove, deepest inferiorly, bounded externally by a 

 roughened margin. They terminate just above the pos- 

 terior oblique processes. The central sharp ridge bifurcates 

 inferiorly, one division running to each oblique process. 



