16 A MANUAL OF ANATOMY 



presents a shallow vertebral notch, which lies behind the inferior 

 articular process. The centre of the posterior arch presents the 

 posterior tubercle, which is the only representative of a spinous 

 process. At either side of this tubercle the rectus capitis posticus 

 minor arises. The upper aspect of the posterior arch gives attach- 

 ment to the posterior occipito-atlantal hgament, and the lower 

 aspect to the posterior atlanto axial ligamen*^. 



The lateral masses support the superior and inferior articular pro- 

 cesses, and laterally the transverse and costal processes spring from 

 them. The anterior surface of each gives partial origin to the rectus 

 capitis anticus minor. The in ternal surface of each presents anteriorly 

 a tubercle for the transverse ligament. The superior articular pro- 

 cesses are oval and deeply concave, to articulate with the con- 

 dyles of the occipital bone. Their long axes are directed backwards 



Anterior Arch 



Inferior Articular 

 Process \ 



\ 



Inferior Vertebral 

 Notch 



Posterior Arch 



Fig. 9. — The Atlas (Inferior View). 



and outwards, so that they converge in front and diverge behind. 

 Anteriorly they reach as far as the anterior arch, and posteriorly 

 they overhang the vertebrarterial grooves on the posterior arch 

 to a slight extent, but they do not extend farther back than 

 about the centre of the ring. The plane of each is sloped down- 

 wards and inwards, and the direction of the surface is upwards 

 and inwards. The movement between them and the occipital 

 condyles is one of flexion and extension, or nodding. Some- 

 times one or both of them may be divided by a groove into two 

 circular facets. The inferior articular processes are circular and 

 slightly concave. The plane of each is sloped upwards and in- 

 wards, and the direction of the surface is downwards and inwards. 

 They articulate with the superior articular })rocesses of the axis, 

 and the movement allowed i? rotation. The articular processes 

 of the atlas, being placed in front of the points of exit of the spinal 



