LUMBAR VERTEBRAE. 4T 



CHARACTERS OF THE LUMBAR VERTEBRA. 



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

 The body is large, broader from side to side than from before backwards, and 

 about equal in depth in front and behind, flattened or slightly concave above and 

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

 prominent margins which afford a broad basis for the support of the superincum- 

 bent weight. The pedicles are very strong, directed backwards from the upper 



Fig. 7. A Lumbar Vertebra. 

 Super. Artie. Proc. 



part of the bodies; consequently the inferior intervertebral notches are of large 

 size. The laminae are short, but broad and strong ; and the foramen triangular, 

 larger than in the dorsal, smaller than in the cervical region. The superior articular 

 processes are concave, and look almost directly inwards; the inferior, convex, look 

 outwards and a little forwards ; the former are separated by a much wider interval 

 than the latter, embracing the lower articulating processes of the vertebra above. 

 The transverse processes are long, slender, directed transversely outwards in the 

 upper three lumbar vertebras, slanting a little upwards in the lower two. By 

 some anatomists they are considered homologous with the ribs. Of the two tuber- 

 cles noticed in connection with the transverse processes in the dorsal region, the 

 superior ones become connected in this region with the back part of the superior 

 articular processes, the inferior ones with the posterior part of the base of the 

 transverse processes. Although in man they are comparatively small, in some 

 animals they attain considerable size, and serve to lock the vertebra? more closely 

 together. The spinous processes are thick and broad, somewhat quadrilateral, 

 horizontal in direction, thicker below than above, and terminate by a rough 

 uneven border. 



The Fifth Lumbar vertebra is characterized by having the body much thicker 

 in front than behind, which accounts for the prominence of the sacro-vertebral 

 articulation, by the smaller size of its spinous process, by the wide interval 

 between the inferior articulating processes, and by the greater size and thickness 

 of its transverse processes. 



STRUCTURE AND DEVELOPMENT OF THE VERTEBRAE. 



The structure of a vertebra differs iii different parts. The body is composed 

 of light spongy cancellous tissue, having a thin coating of compact tissue on its 

 external surface perforated by numerous orifices, some of large size, for the passage 



