ii8 



HUMAN ANATOMY. 



region there is a large opening into the spinal canal. A considerable part of the arch 



is lower than the body. • i i , 



The spinous process is a flat projection extending nearly straight backward, 

 with two lateral surfaces and a superior, inferior, and posterior border. The last is 

 rough and thickened below, with occasionally a tendency to become bifid. 



The transverse processes, which are solely for muscular attachments, and 



Fig. 146. 



Superior articular procesa 



Mammillary process' 

 Transverse process 



Accessory process 

 -Inferior articular process and facet 



Third lumbar vertebra from the side. 



therefore not heavy, project outward and somewhat backward. They are thin, 

 having an anterior and a posterior surface and a blunt end. 



The articular processes are large, very nearly vertical, and curved. The 

 superior, facing somewhat backward but chiefly inward, are concave and embrace 

 the inferior ones of the vertebra above, which are convex, and face in the opposite 

 direction. 



Superior articular process and facet 



Mammillary process 



Accessory process 



Inferior articular process 



Spinous process Lamina 

 Third lumbar vertebra from behind and the side. 



The mammillary processes form on either side a rounded lateral projection 

 on the posterior border of the superior articular process. Additional tubercles, the 

 accessory processes, appear as inconspicuous elevations at the junction of the 

 posterior border of the transverse with the superior articular processes. The details 

 and the morphological significance of the mammillary and the accessory processes 

 are discussed later (page 123). 



