52 ATLAS AND AXIS VERTEBRA PROMINENS. 



The intervertebral notches are peculiar, from being situated behind the 

 articular processes, instead of before them as in the other vertebrae. The 

 transverse processes are remarkably large and long, and pierced by the 

 foramen for the vertebral artery. The articular processes are situated upon 

 the most bulky and strongest part of the atlas. The superior are oval and 

 concave, and look inwards, so as to form a kind of cup for the condyles 

 of the occipital bone, and are adapted to the nodding movements of the 

 head ; the inferior are circular, and nearly horizontal, to permit of the ro- 

 tatory movements. Upon the inner face of the lateral mass which sup- 

 ports the articular processes, is a small tubercle at each side, to which the 

 extremities of the transverse ligament are attached, a ligament which di- 

 vides the ring of the atlas into two unequal segments ; the smaller for 

 receiving the odontoid process of the axis, and the latter to give passage 

 to the spinal cord and its membranes. 



The Axis (vertebra dentata) is so named from having a process upon 

 which the head turns as on a pivot. The body is of large size, and sup- 

 ports a strong process, the odontoid, which rises perpendicularly from its 

 upper surface. The odontoid process presents two articulating surfaces ; 

 one on its anterior face, to articulate with the anterior arch of the atlas ; 

 the other on its posterior face, for the transverse ligament; the latter sur- 

 face constricts the base of the process, which has given rise to the term neck 

 applied to this part. Upon each side of its apex is a rough depression, for 

 the attachment of the alar ligaments ; and running down from its base on 

 Fiff lg the anterior surface of the body of the vertebra a 



vertical ridge, with a depression at each side for 

 the attachment of the longus colli muscle. The 

 lamina, are large and strong, and unite posteriorly 

 to form a long and bifid spinous process, which is 

 concave beneath. The transverse processes are 

 quite rudimentary, not bifid, and project only so 

 far as to enclose the vertebral foramen, which is 

 directed obliquely outwards instead of perpendicu- 

 larly as in the other vertebra. The superior articulating processes are 

 situated upon the body of the vertebra on each side of the odontoid process, 

 They are circular and nearly horizontal, having a slight inclination out- 

 wards. The inferior articulating processes look downwards and forwards, 

 as do the same processes in the other cervical vertebra. The superior in- 

 tervertebral notch is remarkably shallow, and lies behind the articular pro- 

 cess as in the atlas. The lower surface of the body is convex, and is 

 received into the concavity upon the upper surface of the third vertebra. 



The Vertebra prominens, or seventh cervical, approaches in character 

 to the upper dorsal vertebrae. It has received its designation from having 

 a very long spinous process, which is single and terminated by a tubercle, 

 and forms a considerable projection on the back part of the neck ; to the 

 extremity of this process the ligamentum nuchse is attached. The trans- 

 verse processes are but slightly grooved along the upper surface, have 



* A lateral view of the axis. 1. The body; the figure is placed on the depression 

 which gives attachment to the longus colli. 2. The odontoid process. 3. The smooth 

 facet on the anterior surface of the odontoid process which articulates with the anterior 

 arch of the atlas ; the facet for the transverse ligament is beneath No. 2, where the 

 constriction called the neck of the odontoid process is seen ; the bulk of the process be- 

 tween 2, 3, would represent its head. 4. The lamina. 5. The spinous process. 6 

 The transverse process, pieced obliquely by the vertebral foramen. 7. The superior 

 articular surface. 8. Thb inferior articular process 



