CERVICAL VERTEBRA. 35 



pillar for the support of the cranium and trunk ; the arches forming a hollow 

 cylinder behind the bodies for the protection of the spinal cord. The different 

 vertebrae are connected together by means of the articular processes and the 

 intervertebral fibro-cartilages; while the transverse and spinous processes serve 

 as levers for the attachment of muscles which move the different parts of the 

 spine. Lastly, between each pair of vertebrae apertures exist through which the 

 spinal nerves pass from the cord. Each of these constituent parts must now be 

 separately examined. 



The Body or Centrum is the largest part of a vertebra. Above and below, it 

 is flattened; its upper and lower surfaces are rough for the attachment of the 

 intervertebral fibro-cartilages, and present a rim around their circumference. 

 In front, it is convex from side to side, concave from above downward. Behind, 

 it is flat from above downward and slightly concave from side to side. Its ante- 

 rior surface is perforated by a few small apertures, for the passage of nutrient 

 vessels ; whilst on the posterior surface is a single large, irregular aperture, or 

 occasionally more than one, for the exit of veins from the body of the vertebra 

 the vena* basis vertebra 1 . 



The Pedicles are two short, thick pieces of bone, which project- backward, 

 one on each side, from the upper part of the body of the vertebra, at the 

 line of junction of its posterior and lateral surfaces. The concavities above 

 and below the pedicles are the intervertebral notches ; they are four in number, 

 two on each side, the inferior ones being generally the deeper. When the 

 vertebrae are articulated the notches of each contiguous pair of bones form the 

 intervertebral foramina, which communicate with the spinal canal and transmit 

 the spinal nerves and blood-vessels. 



The Laminae are two broad plates of bone which complete the neural arch by 

 fusing together in the middle line behind. They enclose a foramen, the spinal 

 foramen, which serves for the protection of the spinal cord; they are connected 

 to the body by means of the pedicles. Their upper and lower borders are rough, 

 for the attachment of the ligamenta subflava. 



The Spinous Process projects backward from the junction of the two laminae, 

 and serves for the attachment of muscles and ligaments. 



The Articular Processes, four in number, two on each side, spring from the 

 junction of the pedicles with the laminae. The two superior project upward, their 

 articular surfaces being directed more or less backward; the two inferior project 

 downward, their articular surfaces looking more or less forward. 1 



The Transverse Processes, two in number, project one at each side from the 

 point where the lamina joins the pedicle, between the superior and inferior 

 articular processes. They also serve for the attachment of muscles and ligaments. 



Character of the Cervical Vertebrae (Fig. 1). 



The Cervical Vertebrae are smaller than those in any other region of the spine, 

 and may readily be distinguished by the foramen in the transverse process, which 

 does not exist in the transverse process of either the dorsal or lumbar vertebrae. 



The Body is small, comparatively dense, and broader from side to side than 

 from before backward. The anterior and posterior surfaces are flattened and of 

 equal depth ; the former is placed on a lower level than the latter, and its inferior 

 border is prolonged downward, so as to overlap the upper and fore part of the 

 vertebrae below. Its upper surface is concave transversely, and presents a pro- 

 jecting lip on each side ; its lower surface is convex from side to side, concave 

 from before backward, and presents laterally a shallow concavity which receives 

 the corresponding projecting lip of the adjacent vertebra. The pedicles are 

 directed outward and backward, and are attached to the body midway between 

 the upper and lower borders, so that the superior intervertebral notch is as deep 

 as the inferior, but it is, at the same time, narrower. The lamince are narrow, 



1 It may, perhaps, be as well to remind the reader that the direction of a surface is determined by 

 that of a line drawn at right angles to it. 



