THE VERTEBRAL COLUMN ASA WHOLE 67 



Surfaces. The anterior or ventral surface presents the bodies of the vertebra? 

 separated in the recent state by the intervertebral disks. The bodies are broad 

 in the cervical region, narrow in the upper part of the thoracic, and broadest in 

 the lumbar region. The whole of this surface is convex transversely, concave 

 from above downward in the thoracic region, and convex in the same direction 

 in the cervical and lumbar regions. 



The posterior or dorsal surface presents in the median line the spinous pro- 

 cesses. These are short, horizontal, with bifid extremities, in the cervical region. 

 In the thoracic region they are directed obliquely above, assume almost a vertical 

 direction in the middle, and are horizontal below, as are also the spines of the 

 lumbar vertebrae. They are separated by considerable intervals in the loins, 

 by narrower intervals in the neck, and are closely approximated in the middle 

 of the thoracic region. On either side of the spinous processes, extending the 

 whole length of the column, is the vertebral groove formed by the lamina? in the 

 cervical and lumbar regions, where it is shallow, and by the lamina? and transverse 

 processes in the thoracic region, where it is deep and broad. In the recent state 

 these grooves lodge the deep muscles of the back. External to each vertebral 

 groove are the articular processes, and still more externally are the transverse 

 processes. In the thoracic region the latter processes stand backward, on a plane 

 considerably posterior to that of like processes in the cervical and lumbar regions. 

 In the cervical region the transverse processes are placed in front of the articular 

 processes, and on the outer side of the pedicles, between the intervertebral 

 foramina. In the thoracic region they are posterior to the pedicles, inter- 

 vertebral foramina, and articular processes. In the lumbar region they are placed 

 in front of the articular processes, but behind the intervertebral foramina. 



The lateral surfaces are separated from the dorsal surface by the articular 

 processes in the cervical and lumbar regions, and by the transverse processes 

 in the thoracic region. These surfaces present in front the sides of the bodies of 

 the vertebra, marked in the thoracic region by the facets for articulation with 

 the heads of the ribs. More posteriorly are the intervertebral foramina, formed 

 by the juxtaposition of the intervertebral notches, oval in shape, smallest in the 

 cervical and upper part of the thoracic regions, and gradually increasing in size to 

 the last lumbar vertebra. They are situated between the transverse processes in the 

 neck, and in front of them in the back and loins, and transmit the spinal nerves. 



Base. The base of that portion of the vertebral column formed by the 

 twenty-four movable vertebra? is formed by the under surface of the body of the 

 fifth lumbar vertebra; and the summit by the upper surface of the atlas. 



Vertebral Canal. The vertebral canal follows the different curves of the verte- 

 bral column; it is largest in those regions in which the vertebral column enjoys 

 the greatest freedom of movement, as in the neck and loins, where it is wide and 

 triangular; and is narrow and cylindrical in the back, where motion is more limited. 



Surface Form. The only parts of the vertebral column which lie closely under the skin, and 

 so directly influence surface form, are the apices of the spinous processes. These are always 

 distinguishable at the bottom of a median furrow, which, more or less evident, runs down the 

 mesal line of the back from the external occipital protuberance above to the middle of the sacrum 

 below. Occasionally one of these processes deviates a little from the median line a fact to be 

 remembered in practice, as irregularities of this kind are attendant also on fracture or displace- 

 ments of the vertebral column. In the cervical region the furrow is between the Trapezii 

 muscles; in the back and loins it is between the Erector spinae muscles. In the neck the furrow 

 is broad, and terminates in a conspicuous projection, which is caused by the spinous process of 

 the seventh cervical vertebra (vertebra prominent}. Above this the spinous process of the sixth 

 cervical vertebra may sometimes be seen projecting; the other cervical spines are sunken, and 

 are not visible, though the spine of the axis can be felt, and generally also the spines of the third, 

 fourth, and fifth cervical vertebrae. In the thoracic region the furrow is shallow, and during 

 stooping disappears, and then the spinous processes become more or less visible. The markings 

 produced by these spines are small and close together. In the lumbar region the furrow is 

 deep, and the situation of the lumbar spines is frequently indicated by little pits, or depressions, 



