THE CERVICAL NERVES. 



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posterior arch of the atlas and the lamina of the axis ; and the eighth (the last), 

 between the last cervical and first dorsal vertebrae. 



Each nerve, at its exit from the intervertebral foramen, divides into a posterior 

 and an anterior division. The anterior divisions of the four upper cervical nerves 

 form the cervical plexus. The anterior divisions of the four lower cervical nerves, 

 together with the first dorsal, form the brachial plexus. 



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FIG. 408. Posterior divisions of the upper cervical nerves. 



Posterior Divisions of the Cervical Nerves (Fig. 408). 



The posterior division of the first cervical (suboccipitaT) nerve differs from the 

 posterior divisions of the other cervical nerves in not dividing into an internal 

 and external branch. It is larger than the anterior division, and escapes from the 

 spinal canal between the occipital bone and the posterior arch of the atlas, lying 

 beneath the vertebral artery. It enters the suboccipital triangle formed by the 

 Rectus capitis posticus major, the Obliquus superior, and Obliquus inferior, and 

 supplies the Recti and Obliqui muscles, and the Complexus. From the branch 

 which supplies the Inferior oblique a filament is given off which joins the second 

 cervical nerve. This nerve also occasionally gives off a cutaneous filament, which 



