PREVERTEBRAL REGION 269 



Vena Vertebralis. Only the first part of the vertebral 

 artery is accompanied by a definite vertebral vein. There 

 are no accompanying veins with the fourth part of the artery, 

 but a plexus is formed round the commencement of the 

 third part, by the union of tributaries from the venous plexus 

 in the vertebral canal and from the plexus of veins in the 

 sub-occipital triangle. The plexus accompanies the second 

 part of the artery through the transverse processes of the 

 cervical vertebrae ; it anastomoses with the venous plexuses in 

 the vertebral canal ; and it terminates, below, as one or two 

 vertebral veins. The vertebral veins accompany the first 

 part of the artery and end in the posterior aspect of the 

 commencement of the innominate vein. 



Dissection. The muscles must now be completely removed, 

 .in order that the vertebral and cranio- vertebral joints, and the 

 ligaments in connection with the cervical portion of the verte- 

 bral column, may be examined. 



THE JOINTS OF THE NECK. 



The epistropheus, atlas, and occipital bone present a series 

 of articulations in which the uniting apparatus is very different 

 from that of the vertebras below. 



Articulations of the Lower Five Cervical Vertebrae. The 

 lower five cervical vertebrae are united together very much 

 upon the same plan as the vertebrae in other regions of the 

 vertebral column. The bodies and the vertebral arches are 

 connected by distinct articulations and special ligaments. 



Three separate joints may be said to exist between the 

 opposed surfaces of the bodies of two adjacent cervical 

 vertebrae viz., a central synchondrosis and two small col- 

 lateral diarthrodial joints. 



The synchondrosis occupies by far the greatest part of 

 the interval between the vertebral bodies, and it presents 

 the usual characters of such an articulation. The opposed 

 bony surfaces are coated with a thin layer of hyaline or 

 encrusting cartilage, and are connected together by an inter- 

 posed disc of fibro- cartilage. The intervertebral fibro- 

 cartilages are distinctly deeper anteriorly than posteriorly, 

 and upon that circumstance the cervical curvature of the 

 column in great measure depends. 



The two diarthrodial joints are placed, one on each side, 



