88 PRACTICAL ANATOMY. 



is a well-marked groove for the passage of the vertebral 

 artery. The lateral masses present the superior and in- 

 ferior articular surfaces. The superior articular surfaces 

 are strongly concave, oval or reniform ; their axes are 

 directed forward and outward ; they receive the condyles 

 of the occipital bone. The inferior articular surfaces are 

 flat, directed downward and slightly inward to articu- 

 late with the axis. Projecting inward from the inner 

 borders of the lateral masses are the tubercles for the 

 attachment of the transverse ligament, which passes be- 

 hind the odontoid process of the axis, holding it in place 

 against the anterior arch of the atlas ; posterior to the 



FIG. 37. THE Axis. 



transverse ligament is the spinal foramen for the trans- 

 mission of the cord. The transverse processes project 

 from the outer border of the lateral mass and are broad 

 and strong. 



The axis is distinguished by a strong, pivot-like 

 process, the odontoid, which projects upward from its 

 body. This process is, in fact, the detached body of the 

 atlas joined to the body 6f the axis. It forms the axis 

 on which the atlas, and with this the head, rotates. The 

 body presents anteriorly a ridge, and on each side of the 

 ridge a depression for the attachment of muscles. It is 

 prolonged below into a prominent lip, which overlaps the 

 anterior part of the body of the vertebra below. Pos- 



