118 



THE SKELETON. 



are flattened and of equal depth ; the former is placed on a lower level than 

 the latter, and its inferior border is prolonged downwards so as to overlap the 

 upper and fore part of the vertebra below. Its upper surface is concave trans- 

 versely, and presents a projecting lip on each side; its lower surface being 

 convex from side to side, concave from before backwards, and presenting late- 

 rally a shallow concavity, which receives the corresponding projecting lip of 

 the adjacent vertebra. The pedicles are directed obliquely outwards, and the 

 superior intervertebral notches are deeper, but narrower, than the inferior. 

 The laminse are narrow, long, thinner above than below, and overlap each 

 other ; inclosing the spinal foramen, which is very large, and of a triangular 

 form. The spinous processes are short and bifid at the extremity, to afford 

 greater extent of surface for the attachment of muscles, the two divisions being 

 often of unequal size. They increase in length from the fourth to the seventh. 

 The transverse processes are short, directed downwards, outwards, and forwards, 

 bifid at their extremity, and marked by a groove along their upper surface, 

 which runs downwards and outwards from the superior intervertebral notch, 

 and serves for the transmission of one of the cervical nerves. The transverse 

 processes are pierced at their base by a foramen, for the transmission of the 

 vertebral artery, vein, and plexus of nerves. Each process is formed by two 

 roots : the anterior root arises from the side of the body, and corresponds to 

 the ribs : the posterior root springs from the junction of the pedicle with the 

 lamina, and corresponds with the transverse processes in the dorsal region. It 

 is by the junction of the two that the foramen for the vertebral vessels is formed. 

 The extremities of each of these roots form the anterior and posterior tubercles of 

 the transverse processes. The articular processes are oblique ; the superior are 

 of an oval form, flattened and directed upwards and backwards ; the inferior 

 downwards and forwards. 



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

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

 the form of the atlas and axis are designed to admit of the nodding and rota- 

 tory movements of the head. 



The Atlas (Fig. 69) (so named from supporting the globe of the head). The 



Fig. 69. 1st Cervical Vertebra, or Atlas. 

 Tubercle- 



Pro 



for 

 Vertebral Art?. 



Groove cr VfrPtt. Art ? 

 Cerv.Nerve 



Rudimentary Spin, 

 a. Diagram of Section of Adontoid Process. b. Diagram of Section of Transverse Ligament. 



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 pass in 

 front, and join to form the anterior arch. The atlas consists of an anterior 

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

 one-fifth of the bone ; its anterior surface is convex, and presents about its 

 centre a tubercle, for the attachment of the Longus Colli muscle ; posteriorly 



