SACRUM. 



69 



The Lumbar Vertebrae (Fig. 21) are the largest of all 

 the movable vertebrse and have no ribs attached to them. 

 Their spines are short and stout and lie in a more horizontal 



Aa Fas 



Ta 



Ma 



Frt 



Pat 



FIG. 19. 



FIG. 20. 



FIG. 19. The atlas. FIG. 20. The axis. Aa, body of atlas; D, odontoid pro- 

 cess; Fas, facet on front of atlas with which the skull articulates; and in Fig. 20, 

 anterior articular surf ace of axis; L, transverse ligament; Frt, vertebral fora- 

 men ; Ap, neural arch ; Tp, spinous process. 



plane than those ot the vertebrae in front. The articular 

 and transverse processes are also short and stout. 



The Sacrum, which is represented along with the last 

 lumbar vertebra in Fig. 22, consists in the adult of a single 

 bone; but cross-ridges on its ventral surface indicate the 



Pas 



Pni 



Pa 



Ti Pai 



FIG. 21. A lumbar vertebra seen from the left side. Ps. spinous process; 

 Pas, anterior articular process; Pai t posterior articular process ; Pt, transverse 

 process. 



limits of the five separate vertebrae of which it is composed 

 in childhood. It is somewhat triangular in form, its base 

 being directed upwards and articulating with the under 



