272 



ARTICULATIONS. 



The Posterior Occipito-atloid Ligament (Fig. 185) is a very broad but thin 

 membranous lamina, intimately blended with the dura mater. It is connected, 

 above, to the posterior margin of the foramen magnum ; below, to the upper 

 border of the posterior arch of the atlas. This ligament is incomplete at each 

 side, and forms, with the superior intervertebral notch, an opening for the 

 passage of the vertebral artery and sub-occipital nerve. It is in relation, 

 behind, with the Eecti Postici Miriores and Obliqui Superiores ; in front, with 

 the dura mater of the spinal canal, to which it is intimately adherent. 



The Lateral Occipito-atloid Ligaments are strong fibrous bands, directed ob- 

 liquely upwards and inwards, attached above to the jugular process of the 

 occipital bone; below, to the base of the transverse process of the atlas. 



The Capsular Ligaments surround the condyles of the occipital bone, and 

 connect them with the articular surfaces of the atlas ; they consist of thin and 

 loose capsules, which inclose the synovial membrane of the articulation. The 

 synovial membranes between the occipital bone and atlas communicate occa- 

 sionally with that between the posterior surface of the odontoid process and 

 transverse ligament. 



Actions. The movements permitted in this joint are flexion and extension, 

 which give rise to the ordinary forward or backward nodding of the head, 

 besides slight lateral motion to one or the other side. When either of these 

 actions is carried beyond a slight extent, the whole of the cervical portion of 

 the spine assists in its production. According to Cruveilhier, there is a slight 

 motion of rotation in this joint. 



IV. ARTICULATION OF THE AXIS WITH THE OCCIPITAL BONE. 



Occipito-axoid. Three Odontoid. 



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

 the posterior arch of the atlas, the laminas and spinous process of the axis, 



Fig. 187. Occipito-axoid and Atlo-axoid Ligaments. Posterior View, obtained by removing 

 the arches of the Vertebrae and the posterior part of the Skull. 



Mie Vertical ftorfian 



ODONTOID LICTI 



and the portion of the occipital bone behind the foramen magnum, as seen in 

 Fig. 187. 



