LUMBAR VERTEBRA. 41 



forward and a little inward and downward. 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 outAvard, 

 presenting a clubbed extremity, which is tipped on its anterior part by a small 

 concave surface, for articulation with the tubercle of a rib. Besides the articular 

 facet for the rib, three indistinct tubercles may be seen rising from the transverse 

 processes, one at the upper border, one at the lower border, and one externally. 

 In man they are comparatively of small size, and serve only for the attachment 

 of muscles. But in some animals they attain considerable magnitude, either for 

 the purpose of more closely connecting the segments of this portion of the spine 

 or for muscular and ligamentous attachment. 



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

 (Fig. 6). 



The First Dorsal Vertebra presents, on each side of the body, a single entire 

 articular facet for the head of the first rib and a half facet for the upper half of 

 the second. The body is like that of a cervical vertebra, being broad trans- 

 versely ; its upper surface is concave, and lipped on each side. The articular sur- 

 faces are oblique, and the spinous process thick, long, and almost horizontal. 



The Ninth Dorsal 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. 



The Tenth Dorsal has (except in the cases just mentioned) an entire articular 

 facet on each side, above, which is partly placed on the outer surface of the 

 pedicle. It has no demi-facet below. 



In the Eleventh Dorsal the body approaches in its form and size to the lumbar. 

 The articular facets for the heads of the ribs, one on each side, are of large size, 

 and placed chiefly on the pedicles, which are thicker and stronger in this and the 

 next vertebra than in any other part of the dorsal region. The spinous process 

 is short, and nearly horizontal in direction. The transverse processes are very 

 short, tubercular at their extremities, and have no articular facets for the tubercles 

 of the ribs. 



The Twelfth Dorsal has the same general characters as the eleventh, but may 

 be distinguished from it by the inferior articular processes being convex and 

 turned outward, like those of the lumbar vertebrae ; by the general form of the 

 body, laminae, and spinous process, approaching to that of the lumbar vertebrae ; 

 and by the transverse processes being shorter, and marked by three elevations, the 

 superior, inferior, and external tubercles, Avhich correspond to the mammillary, 

 accessory, and transverse processes of the lumbar vertebrae. Traces of similar 

 elevations are usually to be found upon the other dorsal vertebrae (vide ut supra). 



Characters of the Lumbar Vertebrae. 



The Lumbar Vertebrae (Fig. 7) are the largest segments of the vertebral 

 column, and can at once be distinguished by the absence of the foramen in the 

 transverse process, the characteristic point of the cervical vertebrae, and by the 

 absence of any articulating facet on the side of the body, the distinguishing mark 

 of the dorsal vertebrae. 



The body is large, and has a greater diameter from side to side than from before 

 backward, slightly thicker in front than behind, flattened or slightly concave above 

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

 presenting prominent margins, which aiford a broad basis for the support of the 

 superincumbent weight. The pedicles are very strong, directed backward from 

 the upper part of the bodies ; consequently, the inferior intervertebral notches are 

 of considerable depth. The laminae are broad, short, and strong, and the spinal 

 foramen triangular, larger than in the dorsal, smaller than in the cervical, region. 

 The spinous processes are thick arid broad, somewhat quadrilateral, horizontal in 

 direction, thicker below than above, and terminating by a rough, uneven border. 



