THE VERTEBRAL COLUMN 161 



Thoracic Region 



The thoracic vertebrae (vertebrae thoracales) are twelve in 

 number. They form the backbone of the chest region and provide 

 attachment for certain muscles of the shoulder and muscles and 

 ligaments of the neck, but are distinguished chiefly by the possession 

 of articular pits for the attachment of ribs (Fig. 82, D). A typical 

 rib is articulated at two points, namely, one on the body of the 

 vertebra, the other on the transverse process. The former is 

 marked by a small round depression, the costal pit (fovea costalis), 

 or costal facet. In the last two vertebrae, the facet is borne wholly 

 on the vertebral body to which the rib belongs, but in the remaining 

 vertebrae, a complete articulating surface is formed by two demi- 

 facets, one on the vertebra to which the rib belongs, the other on 

 the vertebra immediately in front. The point of articulation of a 

 rib with a transverse process is marked on the latter by an oval 

 facet, the costal pit of the transverse process (fovea costalis trans- 

 versalis). It is present only in the first ten of the thoracic vertebrae, 

 the other two having the costal articulations on their bodies only. 



In all vertebrae of the thoracic series, the spinous processes are 

 well developed, mainly for attachment of the dorsal ligament of 

 the neck, which supports much of the weight of the head. They 

 increase in length to the third, and then become gradually shorter 

 but wider, so that their surfaces are, on the whole, slightly increased 

 in extent. The anterior ten are directed backward, the eleventh is 

 almost vertical (anticlinal vertebra), while the twelfth is directed 

 forward, like those of the succeeding lumbar vertebrae. The anti- 

 clinal vertebra is a centre about which the body bends in such 

 movements as galloping. 



Dorsolaterally, the more posterior vertebrae of the region have 

 small mamillary processes corresponding with the more conspicuous 

 ones of the lumbar region. 



Lumbar Region 

 The lumbar vertebrae (vertebrae lumbales) are seven in 

 number. As they not only support the longer part of the trunk 

 but also provide the origins for some of the proximal muscles of the 

 hind limb, they are large vertebrae, conspicuous for their extensive 

 surfaces and processes for muscular attachment (Fig. 82, E, F). 

 The transverse processes continue the general line of the ribs of 



