180 HEALTH AND DISEASE 



prominences varying in form and size in different parts. In all they 

 serve for the attachment of muscles, in addition to which those of the 

 dorsal vertebrae are also united to the ribs, with which they have a 

 synovial articulation. In the neck an opening passes through the trans- 

 verse processes of the first six vertebrae, while in the loins these processes 

 are very long and flat, and some of them behind have synovial articula- 

 tions by which they are joined together. 



The oblique processes are situated on the anterior and posterior parts 

 of the arch. They form joints with corresponding parts on the bones in 

 front and behind them by broad synovial surfaces, the two anterior of 

 which look upward and inward, while the two posterior look downward 

 and outward. 



The Body is the thick solid base on which the arch rests, and which 

 forms the floor of the spinal canal. Its anterior extremity is round or 

 convex, and fits into a corresponding hollow or concavity in the bone 

 before it. Its posterior extremity is concave, and receives the rounded 

 end of the vertebra which follows it. These convexities and concavities 

 are much greater in the cervical vertebrae than in other regions, on account 

 of which the neck is able to move with exceptional freedom in all direc- 

 tions. On either side, in front and behind, a small depression exists on 

 the bodies of the dorsal vertebrae for the accommodation of the heads of 

 the ribs, which fit in between them to form a synovial articulation. 



The Neural Arch is formed by two plates of bone which spring from 

 the upper surface of the body on either side, and unite above to form 

 the spinal canal. In the anterior and posterior borders of the neural 

 arch above the body of each vertebra are two notches which, with cor- 

 responding notches in the vertebrae before and behind it, form openings, 

 termed the intervertebral foramina, through which the spinal nerves leave 

 the spinal canal. 



The False Vertebrae are those of the sacrum, the several pieces of 

 which are firmly joined together by bony union, and the coccygeal bones, 

 from which some of the parts above described are wanting or exist only 

 in a rudimentary form. 



PARTICULAR VERTEBRA 



The first vertebra or Atlas (fig. 1, Plate XXXVIII), so described 

 because in the human family it supports the head, differs in a striking 

 manner from the typical vertebra, being a mere ring of bone, having two 

 broad wings or transverse processes jutting out from the sides. In front 

 it presents two deep concave surfaces, which articulate with corresponding 



