12 • A MANUAL OF ANATOMY 



present, above and below, the superior and inferior vertebral notches. 

 The spinous process is formed by the fusion of the two laminae in 

 the median line posteriorly. The transverse processes project out- 

 wards, one at either side, from the neural arch at the junction of 

 the pedicle and lamina. The articular processes, two superior and 

 two inferior, project upwards and downwards from the junction of 

 the pedicle and lamina at either side, and they are covered by 

 cartilage. The spinal or neural foramen is enclosed by the body 

 and neural arch. It is bounded in front by the posterior surface 

 of the body, on either side by a pedicle and lamina, and behind by 

 the fusion of the laminae to form the spinous process. 



Structure of a Vertebra. — The body is composed of cancellated 

 tissue, covered by a thin layer of compact bone. The chief lamellae 

 are disposed in almost vertical curves, the convexities of which are 

 directed towards the periphery. Crossing these there are horizontal 

 lamellae, which are nearly parallel with the superior and inferior 

 surfaces. The cancellated tissue is permeated by venous channels 

 which converge to the two large foramina on the posterior surface 

 of the body. The neural arch and its processes are chiefly com- 

 posed of compact bone, the amount of cancellated tissue being for 

 the most part small. 



The Cervical Vertebrae. 



The cervical vertebrae are seven in number, and they occupy 

 the region of the cervix or neck. The distinctive character of all 

 cervical vertebrae is the presence of an aperture at either side of 

 the body, called the costo-transverse foramen. The first or atlas, 

 the second or axis, and the seventh or vertebra prominens have 

 such pronounced characters that they require a special description. 

 A Typical Cervical Vertebra.— The body is small and elongated 

 from side to side. The superior surface presents at either side an 

 antero-posterior. lip, the inner surface of which is sloped towards the 

 superior surface, and embraces the corresponding bevelled lateral 

 border of the inferior surface of the body above. The whole 

 surface is thus concave from side to side, and the posterior lip is 

 on a slightly higher level than the anterior. The inferior surface 

 is bevelled laterally, and its anterior lip is on a lower level than 

 the posterior. The inferior surface is convex from side to side, 

 and concave from before backwards. The superior and inferior 

 surfaces give attachment to the intervertebral discs. The anterior 

 surface is convex from side to side, and concave from above down- 

 wards. It is covered by the anterior common ligament, and it 

 presents a number of nutrient foramina. The posterior surface is 

 , flat, and presents several nutrient foramina, two of which, one at 

 [ either side of the middle line, are large, for the escape of the venae 

 ' basis vertebrae. The posterior surface is related to the posterior 

 common ligament. Each lateral surface forms the inner boundary 

 of. the costo-transverse foramen. 

 The pedicles spring at either side from the posterior part of the 



