54 



SPECIAL ANATOMY OF THE SKELETON 



Processes. Spinous Processes. Each spinous process is long, triangular on 

 transverse section, directed obliquely downward, and terminates in a tubercular 

 extremity. They overlap one another from the fifth to the eighth vertebra, but 

 are less oblique in direction above and below. 



Articular Processes. The articular processes are flat, nearly vertical in direction, 

 and project from the upper and lower part of the pedicles; the superior being 

 directed backward and slightly outward and upward, the inferior forward and a 

 little inward and downward. 



Superior articular process. 



Demi-facet for head of rib. 



Facet for tubercle of rib. 



Demi-facet for head of rib. 

 Inferior articular process. 



FIG. 19. A thoracic vertebra. 



Transverse Processes. The transverse processes arise from the same parts 

 of the arch as the posterior roots of the transverse processes in the neck, and 

 are situated behind the articular processes and pedicles; they are thick, strong, 

 and of great length, directed obliquely backward and outward, presenting a 

 clubbed extremity, and having on its anterior part near its tip a small concave 

 surface, for articulation with the tubercle of a rib (fovea costalis transversalis}. 

 Besides the articular facet for the rib, three indistinct tubercles may be seen 

 arising from the transverse processes one at the upper border, one at the lower 

 border, and one externally. In man they are of comparatively small she, and 

 serve only for the attachment of muscles. But in some animals they attain con- 

 siderable magnitude, either for the purpose of more closely connecting the segments 

 of this portion of the vertebral column or for muscular and ligamentous attachment. 



The peculiar thoracic vertebrae are the first, ninth, tenth, eleventh, and twelfth 

 (Fig. 20). 



First Thoracic Vertebra. The first thoracic vertebra presents, on each side 

 of the body, a single entire articular facet for the head of the first rib and a demi- 

 facet for the upper half of the second. The body is like that of a cervical vertebra, 

 being broad transversely, its upper surface is concave, and lipped on each side. 

 The articular surfaces are oblique, and the spinous process thick, long, and almost 

 horizontal. 



Ninth Thoracic Vertebra. The ninth thoracic vertebra has no demi-facet 

 below. In some subjects, however, the ninth has two demi-facets on each side; 

 when this occurs the tenth has only a demi-facet at the upper part. 



