6 



THE VERTEBRAL COLUMN. 



with cartilage, in the superior pair look backwards, and in the inferior forwards, so 

 that the former face the latter in adjoining vertebras. 



The foramen is bounded anteriorly by the body, posteriorly and laterally by the 

 arch. The series of rings thus formed, united by ligaments, constitutes the spinal 

 or neural canal, which lodges the spinal cord. 



Texture. The bodies of the vertebrae are almost entirely composed of spongy substance, 

 the principal lamellae being vertical : on the surface is a thin layer of compact tissue. 

 Venous canals, commencing at the larger foramina behind, traverse the cancellated structure. 

 The arch and processes contain a much smaller proportion of spongy substance, being covered 

 with compact tissue of considerable density in some places. 



INF. ARTIC.PROC. 



SUP.ARTIC.PROC. 



GROUPS OF VERTEBRJE. 



The vertebrae are divided into five groups, named from the regions which they 

 occupy, cervical, dorsal, lumbar, sacral, and coccygeal. 



Cervical vertebrae. These are seven in number ; they are the smallest of the 



moveable vertebras, and are spe- 

 cially characterized by the pre- 

 sence of foramina in the trans- 

 verse processes. The first and 

 second are so peculiar in form, 

 as to require a separate descrip- 

 tion. The following are the 

 common characters of a cervical 

 vertebra. 



The lody is small, and much 

 broader from side to side than 

 from before backwards ; in depth 

 nearly the same in front and 

 behind. Its upper surface is trans- 

 versely concave from the upward 

 projection of its lateral margins, 

 and is sloped down in front. The 

 under surface, on the contrary, 

 is rounded off at the sides, while 

 its anterior margin forms a marked 

 projection downwards. 



The pedicles spring from the 

 body about midway between the 



upper and lower borders, and are directed outwards and backwards ; the lamina are 

 slender, long and flat. The superior and inferior notches are nearly equal in depth. 

 The spinous process is short, only slightly depressed, and bifid. 

 The tranverse processes are short, and present at their extremities two tubercles, 

 anterior and posterior. Each process is deeply grooved above for a spinal nerve, and 

 its base is perforated vertically by a round foramen (vertebrarterial), through which 

 in the upper six the vertebral artery and vein pass. It is united with the rest of the 

 vertebra by two parts ; by the posterior, at the place of junction of the pedicle and 

 lamina, like a dorsal transverse process ; by the anterior, to the body of the vertebra, 

 in the same position as the heads of the ribs. 



The articular processes are placed at the extremities of a short, stout, vertical 

 column of bone ; their articular surfaces are nearly flat and oblique, the superior 

 looking backwards and upwards, the inferior forwards and downwards. 



NF. VERTEBRAL NOTCH 



Fig. 2. FOURTH CERVICAL VERTEBRA : A, FROM ABOVE 

 B, FROM THE RIGHT SIDE. (Drawn by D. Gunn. ) 



