THE CERVICAL VERTEBRA 



51 



oval facet (fovea dentis), covered with cartilage, for articulation with the odontoid 

 process of the axis. The upper and lower borders give attachment to the anterior 

 occipitoatlantal and the anterior atlantoaxial ligaments, which connect it with 

 the occipital bone above and the axis below. The posterior arch (arcus posterior) 

 forms about two-fifths of the circumference of the bone; it terminates behind 

 in a tubercle (tuberculum posterius), which is the rudiment of a spinous process, 

 and gives origin to the Rectus capitis posticus minor. The diminutive size of 

 this process prevents any interference in the movements between the atlas and the 

 cranium. The posterior part of the arch presents above and behind a rounded 

 edge for the attachment of the posterior occipitoatlantal ligament, while in front, 

 immediately behind each superior articular process, is a groove (sulcus arteriae 

 vertebral is), sometimes converted into a foramen by a delicate bony spiculum, 

 which arches backward from the posterior extremity of the superior articular 

 process. These grooves represent the superior intervertebral notches, and are 

 peculiar in that they are situated behind the articular processes, instead of in 

 front of them, as in the other vertebra?. They serve for the transmission of the 

 vertebral artery, which, ascending through the foramen in the transverse process, 

 winds around the lateral mass in a backward and inward direction. They also 

 transmit the suboccipital (first spinal) nerve. On the under surface of the poste- 



Tiiberde. 



Transverse 



Diagram of section of odontoid, 

 process. 



Diagram of section of 

 transverse ligament. 



Foramen for 

 rertebral artery. 



Groore for vertebral artery 

 and 1st cervical nerve. 



Rudimentary spinous process. 



FIG. 16. First cervical vertebra, or atlas. 



rior arch, in the same situation, are two other grooves, placed behind the lateral 

 masses, and representing the inferior intervertebral notches of other vertebrae. 

 They are much less marked than the superior. The lower border also gives 

 attachment to the posterior atlanto-axial ligament, which connects it with the 

 axis. The lateral masses (rnassae laterales) are the most bulky and solid parts 

 of the atlas, in order to support the weight of the head; they present two articulating 

 surfaces above and two below. Each represents one-fifth of the ring. Each 

 superior process (fovea articularis superior) is of large size, oval, concave, and ap- 

 proaches its companion in front but diverges from it behind; it is directed upward, 

 inward, and a little backward, forming a kind of cup for the corresponding 

 condyle of the occipital bone. The two processes are admirably adapted to the 

 nodding movements of the head. Not infrequently they are partially subdivided 

 by a more or less deep indentation, which encroaches upon each lateral margin. 

 Each inferior articular process (fades articularis inferior) is circular in form, 

 flattened or slightly concave, and directed downward and inward, articulating 

 with the axis. The inferior processes permit the rotatory movements. Just 

 below the inner margin of each superior articular surface is a small tubercle, 

 for the attachment of the transverse ligament, which, stretching across the ring 

 of the atlas, divides it into two unequal parts or arches; the anterior or smaller 



