THE FIRST CERVICAL VERTEBRA. 



The foramen is triangular, with rounded angles, and larger than in the dorsal or 

 lumbar vertebras. 



The first cervical vertebra, or atlas, differs remarkably from the others in 

 the absence of a body and spinous process, having the form merely of a large ring 

 with articular and transverse processes. 



The interior of the ring is wider behind than in front. Its posterior part cor- 



ODONTOID PROCESS 



TIC. PROCESS 



RANSV. PROC. 



TRANSV. PROC. 



INF. ARTIC. PROCESS 



Fig. 3. ATLAS AND AXIS, FROM BEFORE. (Drawn by D. Gunn.) 



responds to the foramina of the other vertebrae ; its narrower anterior part is 

 occupied by the odontoid process of the axis, and in the recent state is separated 

 from the posterior by the transverse ligament. In front of the ring is the anterior 

 arch, on the anterior aspect of which is a small tubercle, and on the posterior a 

 smooth surface for articulation with the odontoid process. At the sides of the ring 

 are the lateral masses, which are thick and strong, bearing the articular processes 

 above and below, and extending outwards into the transverse processes. The articular 



POSTERIOR ARCH 



ERTEBRAL GROOVE 



SUP. ARTIC. PROC. 



FOR TRANSV. 

 LIGAMENT 



TUBE 



ANTERIOR ARCH 

 ARTIC. SURF. FOR ODONTOID PROC 



Fig. 4. ATLAS, FROM ABOVE. (Drawn by D. Gunn.) 

 The position of the transverse ligament is indicated by dotted lines. 



processes differ from those of other vertebrae in being situated in front of the places 

 of exit of the nerves. The superior, larger than the inferior, are oval, and converge 

 in front ; their articular surfaces are concave for the reception of the condyles of 

 the occipital bone, and look upwards and inwards ; they are frequently divided by a 

 transverse groove into two. Below the inner margin of each, towards the front, is a 

 smooth rounded tubercle, to which the transverse ligament is attached. The inferior 

 articular processes are smaller than the superior, flat, nearly circular, looking down- 

 wards and slightly inwards. 



The posterior arch presents in the middle line a rough elevation, the rudiment of 

 a spinous process ; at its junction with the lateral masses, it is hollowed out above 



