ARTICULATION OF THE AXIS WITH THE OCCIPITAL BONE 277 



Complexus, Splenius, and upper fibres of the Trapezius. The Recti laterales are concerned in 

 the lateral movement, assisted by the Trapezius, Splenius, Complexus, and the Sternomastoid 

 of the same side, all acting together. According to Cruveilhier, there is a slight amount of rota- 

 tion in this joint. 



IV. Articulation of the Axis with the Occipital Bone. 



The ligaments of this articulation are the 



Occipito-axial. Three Odontoid. 



To expose these ligaments the vertebral canal should be laid open by removing 

 the posterior arch of the atlas, the lamina? and spinous process of the axis, and 

 the portion of the occipital bone behind the foramen magnum, as seen in Fig. 227. 



The vertical portion of 



ODONTOID LIGAMENTS. 



5CCIPITO f OAPSULAR LIGAMENT 

 TLANTALl OIM * < 



(. membrane. 



TLANTO f CAPSULAR LIGAMENT 



AXIAL '} andsynovial 

 (_ membrane. 



FIG. 227. Occipito-axial and atlanto-axial ligaments. Posterior view, obtained by removing the arches of 

 the vertebrae and the posterior part of the skull. 



The posterior occipito-axial ligament (membrana tectoria) (Figs. 227 and 228) 

 is situated within the vertebral canal. It is a broad, strong band, which covers 

 the odontoid process and its ligaments, and appears to be a prolongation upward 

 of, or a membrane due to fusion with, the posterior common ligament of the spine. 

 It is attached, below, to the posterior surface of the body of the axis, and, becom- 

 ing expanded as it ascends, is inserted into the basilar groove of the occipital 

 bone, in front of the foramen magnum, where it becomes blended with the dura 

 of the skulL 



Relations. By its anterior surface with the transverse ligament; by its posterior surface 

 with the posterior common ligament. 



The lateral odontoid ligaments (ligamenta alaria) (Figs. 227 and 228) are 

 strong, rounded, fibrous cords, which arise one on either side of the upper part of 



