36 



THE SKELETON. 



long, thinner above than below, and overlap each other, enclosing the spinal 

 foramen, which is very large, and of a triangular form. The sptnous process is 

 short, and bifid at the extremity to afford greater extent of surface for the attach 

 ment of muscles, the two divisions being often of unequal size. Ihey increase m 

 length from the fourth to the seventh. The articular processes are flat, oblique, 

 and of an oval form : the superior are directed backward and upward ; the 

 inferior forward and downward. The transverse processes are short, directed 

 downward, outward, and forward, bifid at their extremity, and marked by a 

 groove aloncr their upper surface, which runs downward and outward from the 

 superior intervertebral notch, and serves for the transmission of one of the cer- 

 vical nerves. They are situated in front of the articular processes and on the 

 outer side of the pedicles. The transverse processes are pierced at their base by 

 a foramen, for the transmission of the vertebral artery, vein, and plexus of nerves. 



Anterior tubercle of trans- 

 verse process. 



Foramen for vertebral 

 artery. 



Posterior tubercle o 

 transverse process, 



Transverse process. 



^-Superior articular 



process. 

 Inferior articular process. 



Spinuus] 

 I process. 



FIG. 1. Cervical vertebra. 



Each process is formed by two roots : the anterior root, sometimes called the 

 costal process, arises from the side of the body, and is the homologue of the rib 

 in the dorsal region of the spine; the posterior root springs from the junction of 

 the pedicle with the lamina, and corresponds with the transverse process in the 

 dorsal region. It is by the junction of the two that the foramen for the vertebral 

 vessels is formed. The extremity of each of these roots forms the anterior and 

 posterior tubercles of the transverse processes. 1 



The peculiar vertebrae in the cervical region are the first, or Atlas ; the second, 

 or Axis ; and the seventh, or Vertebra prominens. The great modifications in the 

 form of the atlas and axis are designed to admit of the nodding and rotatory 

 movements of the head. 



The Atlas (Fig. 2) is so named from supporting the globe of the head. The 

 chief peculiarities of this bone are that it has neither body nor spinous process. 

 The body is detached from the rest of the bone, and forms the odontoid process of 

 the second vertebra; while the parts corresponding to the pedicles join in front to 

 form the anterior arch. The atlas is ring-like, and consists of an anterior arch, 

 a posterior arch, and two lateral masses. The anterior arch forms about one-fifth 

 of the ring: its anterior surface is convex, and presents about its centre a tubercle, 

 for the attachment of the Longus colli muscle ; posteriorly it is concave, and 

 marked by a smooth, oval or circular facet, for articulation with the odontoid 

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

 occipito-atlantal and the anterior atlanto-axial ligaments, which connect it with 

 the occipital bone above and the axis below. The posterior arch forms about 

 two-fifths of the circumference of the bone ; it terminates behind in a tubercle, 



1 The anterior tubercle of the transverse process of the sixth cervical vertebra is of large size, 

 and is sometimes known as "Chassaignac's" or the "carotid tubercle." It is in close relation with 

 the carotid artery, which lies in front and a little external to il so that, as was first pointed out by 

 Chassaignac, the vessel can with ease be compressed against it. 



