LIGAMENTS OF THE SPINE. 



135 



Fig 



nal occipital protuberance to the spine of the seventh cervical, separating the 

 muscles of the two sides. The free border is 

 continuous with the supraspinous ligament, but, 

 instead of touching the cervical spines, it lies 

 in the superficial layer of muscles, and is rein- 

 forced below by radiating fibres from each of the 

 spinous processes of the cervical region. It is 

 inseparably blended with the origin of the trapezii 

 and with the fasciae between the muscular layers, 

 especially with that covering the semispinalis and 

 the short suboccipital muscles. • In the region of 

 the axis it is a thick median membrane ; in the 

 lower cervical region it is of little importance. 

 In man it contains but a small proportion of elas- 

 tic fibres, in marked contrast to what is found 

 in many quadrupeds in which the structure con- 

 sists principally of elastic tissue, since in these 

 animals the ligamentum nuchae forms an important 

 organ for the support of the head at the end of 

 the horizontal vertebral axis. 



The intertransverse ligaments (Fig. 

 162) are trifling collections of fibres between the 

 transverse processes, although occasionally distinct round cords in the thoracic 

 region. 



Fig. 165. 



Anterior occipito-atlantal ligament 



Mastoid process 



Intervertebial 



disk 



Cut surface of 

 pedicle 



Posterior 

 common 

 ligament 



Posterior surface of bodies of vertebrae 

 shown after removal of arches by cutting 

 through the pedicles. 



Lateral occipito-atlantal 

 ligament 



Anterior tubercle of atlas 



Atlanto-axial ligament and joint 



Anterior common ligament 



Anterior ligaments of upper end of spine. 



ARTICULATIONS OF THE 



OCCIPITAL 

 THE AXIS. 



BONE, THE ATLAS, AND 



The arrangement here differs in some points considerably from that of the rest 

 of the spine in order to provide for the security and the free movement of the head. 

 The ligaments effecting this union consist of three groups : 

 I. Those connecting the Atlas and the Axis, including the 



Anterior Atlanto-Axial ; Transverse ; 



Posterior Atlanto-Axial ; Two Capsular. 



