74 OSTEOLOGY. 
passage of nutrient vessels, more particularly behind, where a depression of con- 
siderable size receives the openings of the canals through which some of the 
veins escape. Connected with the body posteriorly there is a bony arch (arcus 
vertebre) which, by its union with the body, encloses a foramen of variable 
size, the spinal or vertebral foramen (foramen vertebrale). When the vertebree 
are placed on the top of each other these foramina form with the uniting 
ligaments a continuous canal—spinal or neural canal—in which the spinal cord with 
its coverings is lodged. The arch, which is formed by the union of the pedicles and 
lamin, besides enclosing the spinal foramen, also supports a certain number of 
processes; of these, some are outstanding, and may be regarded as a series of levers 
to which muscles are attached, whilst others are articular and assist in uniting the 
different vertebrae together by means of a series of movable joints. The pedicles 
are the bars of bone which pass from the back of the body of the vertebrae on either 
side to the points where the articular processes are united to the arch. The pedicles 
are compressed laterally, and have rounded superior and inferior borders. Since 
the vertical breadth of the pedicles is not as great as the thickness of the body to 
which they are attached, it follows that when the vertebra are placed one above 
the other a series of intervals is left between the pedicles of the different vertebree. 
These spaces, enclosed in front by the bodies of the vertebrae and their inter- 
vertebral discs, and behind by the coaptation of the articular processes, form a 
series of holes communicating with the neural or spinal canal; these are called the 
intervertebral foramina (foramina intervertebralia), and allow of the transmission of 
spinal nerves and vessels. As each intervertebral foramen is bounded above and 
below by a pedicle, the grooved surfaces in correspondence with the upper and 
lower borders of the pedicles are called the upper and lower intervertebral grooves 
or notches (incisura vertebralis superior et inferior). Posteriorly, the two pedicles 
are united by two somewhat flattened plates of bone—the lamine, which converge 
towards the middle line, and become fused with the root of the projecting spinous 
process (processus spinosus). The breadth of the lamine and their sloping arrange- 
ment are such, that when the vertebrae are articulated together they leave little 
space between them, thus enclosing fairly completely the neural canal, of which 
they form the posterior wall. The edges and inner surfaces of the lamin are 
rough for the attachment of the ligaments which bind them together. 
The muscular processes are three in number, viz. two transverse processes—one 
on either side—and one central or median, the spinous process. The former 
(processus transversus) project outwards on either side from the arch at the point 
where the pedicle joins the lamina. The latter (processus spinosus) extends back- 
wards in the middle line from the point of fusion of the laminz. The spinous 
processes display much variety of length and form. - 
The articular processes (zygapophyses), four in number, are arranged in pairs— 
one superior, the other inferior; the former are placed on the upper surface of the 
arch where the pedicles and laminee j join, the latter below the arch in correspondence 
with the superior. Whilst differing much in the direction of their articular 
surfaces, the upper have generally a backward tendency, whilst the lower incline 
forwards. 
THE TRUE OR MOVABLE VERTEBRA. 
THE CERVICAL VERTEBRA. 
The cervical vertebre (vertebre cervicales), seven in number, can be readily 
distinguished from all the other vertebree by the fact that their transverse pro- 
cesses are pierced by a foramen. The two highest, and the lowest, require special 
description ; the remaining four conform to a common type. 
Their bodies, the smallest of all the true vertebra, are oblong in shape, the 
transverse diameter being much longer than the antero-posterior width. The upper 
surface, which slopes from behind forwards and downwards, is concave from side to 
side, owing to the marked projection of its lateral margins. Its anterior lip is 
rounded off, whilst its posterior edge is sharply defined. 
