40 



ANATOMY FOE, NUESES. 



[CHAP. IV. 



solid portion or body, and a posterior portion or arch. The 

 bodies of the vertebrae are piled one upon another, forming a 

 solid, strong pillar, for the support of the cranium and trunk, 

 the arches forming a hollow cylinder behind for the protection 

 of the spinal cord. Each arch has seven processes : four 

 articular, two transverse, and one spinous process. The dif- 

 ferent vertebrae are connected together by means of the articu- 

 lar processes, and by disks of intervertebral fibro-cartilage 

 placed between the vertebral bodies, while the transverse and 

 spinous processes serve for the attachment of muscles which 

 move the different parts of the spine. In the cervical region of 



the vertebral column 

 the bodies of the ver- 

 tebrae are smaller than 

 in the dorsal, but the 

 arches are larger ; the 

 spinous processes are 

 short, and are often 

 cleft in two, or bifid. 

 The first and second 

 cervical vertebrae 

 differ considerably 

 from the rest. The 

 first, or atlas, so 

 named from support- 

 ing the head, has 

 practically no body, 

 and may be described as a bony ring divided into two sections 

 by a transverse ligament. The dorsal section of this ring 

 contains the spinal cord, and the ventral or front section 

 contains the bony projection which arises from the upper sur- 

 face of the body of the second cervical vertebra, or axis. This 

 bony projection, called the odontoid process, represents the 

 body of the atlas. Around this peg the atlas rotates when 

 the head is turned from side to side, carrying the skull, to 

 which it is firmly articulated, with it. The bodies of the dorsal 

 vertebrae are larger and stronger than those of the cervical ; 

 they contain depressions for the reception of the vertebral 

 ends of the ribs. The bodies of the lumbar vertebrae are the 

 largest and heaviest in the whole spine. The sacrum, formed 



FIG. 40. A CERVICAL VERTEBRA. Inferior sur- 

 face. 1, spinous process, slightly bifid ; 4, transverse 

 process ; 5, articular process, inferior surface. Below 

 the arch, or hollow portion, is seen the solid portion, 

 or body. 



