168 DISSECTION OF THE NECK. 



Union of the atlas with the occipital bone. The anterior ligament (oc- 

 cipito-atloid) (fig. 46, 2 ) is thin and wide, and passes from the basilar 

 process of the occipital bone, in front of the foramen magnum, to the body 

 of the atlas. The middle part of the ligament, which is fixed to the 

 tubercle on the front of the atlas, is much the thickest. 



The posterior ligament (fig. 47, *) is fixed to the occipital bone behind 

 the foramen magnum, and to the neural arch of the atlas. It is thin; and 

 at its attachment to the atlas the vertebral artery ( 3 ), and the posterior 

 primary branch of the suboccipital nerve, pass beneath it. 



The ligaments inside the spinal canal are peculiar in form, and assist 

 in retaining the skull in place during the rotatory and nodding movements 

 of the head. Between the occipital bone and the second vertebra are 



Fig. 48. 



INTERNAL LIGAMENT BETWEEN OCCIPITAL BONK AND Axis (Bourgery). 

 1 and 2. Attachments of the occipito-axoidean ligament. 



three strong ligaments a central, and two lateral or check ; and the odon- 

 toid process of the axis is fixed against the body of the atlas by a strong 

 transverse band. 



Dissection. Supposing the neural arches of the cervical vertebrae to be 

 removed except in the first three, the arches of these vertebrae are to be 

 sawn through close to the articular processes. Nextly the ring of the 

 occipital bone bounding posteriorly the foramen magnum is to be taken 

 away. Lastly, the student should detach the tube of dura mater from the 

 interior of the spinal canal ; and, on raising from below the upper part of 

 the posterior common ligament of the bodies of the vertebrae, the liga- 

 mentous band between the occipital bone and the axis (occipito-axoid) 

 will come into view. 



Union of the occipital bone with the axis. The central ligament (oc- 

 cipito-axoidean) (fig. 48, *) is a strong, thick layer beneath the posterior 

 common ligament of the bodies of the vertebra', and is rather triangular 

 in form with the base uppermost. Above it is attached to the basilar 

 process (on the cranial aspect) near the margin of the foramen magnum, 

 extending as far on each side as the insertion of the check ligaments. 

 From that spot it descends over the odontoid process, and, becoming nar- 

 rower, is inserted into the body of the axis. Occasionally a bursa is found 

 between it and the transverse ligament of the atlas. 



