66 



MAMMALIAN ANATOMY 



edge. The articular surface is pear-shaped and cup-like. It faces 

 toward the skull and the middle line, and articulates with the condyle 

 of the occipital bone. 



FIG. 41. 



Neural Arch. 



RECTUS POSTICUS MINOR. 



TYansrcrxr 

 Process. 



Body. 

 THE ATLAS, ANTERIOR OR CEPHALIC ASPECT. 



The neural canal appears to be round, but is divided into two parts 

 by a transverse ligament, which arises on each side from a tubercle 

 and depression (Fig. 42) situated just caudal to the cephalic articular 

 surface, decidedly ventral to the middle of the medial wall of the 

 arch. The dorsal of the two canals thus formed is the neural canal 

 proper, and its outline is a little more than a half-circle. The ventral 

 canal receives the odontoid process of the second vertebra. Its outline 

 is less than half of a smaller circle. The dorsal surface of the ventral 

 bar is smooth for articulation with the odontoid process, which is held 

 firmly in place by the transverse ligament and by the check liga- 

 ments which run from its tip to the occipital bone of the skull. The 

 medial surface of the arch, dorsal to the tubercle, is smooth, and 



FIG. 42. 



Divided Neural Arch. 



L 



Arterial Opening. 



Cephalic Articular Surface. 



Dorsal Surface of Ven- 

 tral Arch. 



Opening into Arterial Canal. 



Transverse Process. 



Arterial Canal. 

 Caudal Articular Surface. 

 ~~ Tubercle for Ligament. 



Divided Ventral Arch. 

 ATLAS. LONGITUDINAL VERTICAL SECTION. 



exhibits, dorsal to the cephalic articular surface, the large opening 

 for the vertebral artery, and, just dorsal to the tubercle, the smaller 

 opening into the arterial canal. The atlas has a greater range of 

 motion than any other vertebra except the terminal caudals. In 



