VERTEBRAE 



in shape ; the sides and upper and lower surfaces are slightly 

 concave. Posteriorly, two short, stout processes the pedicles 

 are formed; these support flattened laminge, which fuse in the 

 middle line ; thus, the posterior surface of the body, the 

 pedicles, and the laminse form a bony canal through which the 

 spinal cord runs. The pedicles are not as deep vertically as the 

 bodies, so that between the pedicles of two adjacent vertebras 

 there are spaces left the intervertebral foramina through 

 which the spinal nerves emerge. Immediately in front of the 

 pedicles are other processes the transverse, to which the 

 muscles of the back are attached, and on the upper and lower 

 surfaces of the pedicles are articular processes (four in all) for 

 the articulation of the vertebrae one with another. At the 

 junction of the laminae a third process is developed, called the 

 spine, for the attachment of muscles. 



PRINCIPAL VARIATIONS IN VERTEBRAE OF DIFFERENT REGIONS. 



The Sacral vertebrae are all fused together into one bone, 

 called the sacrum. 



The Sacrum is a triangular bone formed of the five sacral 

 vertebra?, whose bodies and transverse processes have become 

 fused together, distinct ridges being seen at the line of fusion on 

 the anterior surface. 



The anterior surface is concave from above downwards, and 

 has four foramina on each side of the middle line for the 

 passage of nerves. These are homologous with the inter- 

 vertebral foramina, and, through the fusion of the transverse 

 processes with one another, appear both anteriorly and pos- 



