78 OSTEOLOGY. 
The seventh cervical vertebra, or vertebra prominens, receives the latter name 
from the outstanding nature of its spinous process, whichends in a single broad tubercle. 
This forms a well-marked surface projection at the back of the ‘root of the neck. 
The transverse processes are broad from above downwards; they project consider- 
ably beyond those of the sixth. The maximum width between their extremities 
agrees with that between the transverse processes of the atlas, these two consti- 
tuting the widest members of the cervical series. The vertebrarterial foramen is 
small. Not infrequently the costal element is separate from the true transverse 
process, thus constituting a cervical rib. 
Variations.—The vertebrarterial foramen may be absent on one or other side. 
THORACIC VERTEBRA. 
The dorsal or thoracic vertebre (vertebre thoracales), twelve in number, 
are distinguished by having facets on the sides of their bodies for the heads of the 
ribs, and in most instances also articular surfaces on their transverse processes for 
the tubercles of the ribs (Figs. 54 and 55, p. 73). 
The body is described as characteristically heart-shaped, though in the upper 
and lower members of the series it undergoes transition to the typical forms of the 
cervical and lumbar vertebre respectively. Its antero-posterior and transverse 
widths are nearly equal; the latter is greatest in line with the facets for the heads 
of the rib. The bodies are slightly thicker behind than in front, thus adapting 
themselves to the anterior concavity which the column displays in this region. 
The bodies of the second to the ninth inclusive, each possess four costal demi-facets— 
a superior pair placed on the upper margins of the body, close to the junction of the 
pedicle with the centrum, and an inferior pair situated on the lower edge, close to 
and in front of the inferior intervertebral grooves. 
When contiguous vertebrie are articulated, the upper pair of demi-facets of the lower 
vertebra coincide with the lower demi-facets of the higher vertebra, and, together with the 
intervening intervertebral disc, form an articular cup for the reception of the head of 
arib. Of these facets on the body the upper pair are the primary articular surfaces 
for the head of the rib ; the lower are only acquired secondarily. Moreover, these facets, 
though apparently placed on the body, are in reality developed on the sides of the pedicles 
behind the line of union of the pedicles with the centrum (neuro-central synchondrosis), as 
will be explained hereafter. 
The pedicles are short and thick, and directed backwards and slightly upwards. 
The superior notch is faintly marked ; the inferior notch is deep. The lamine are 
broad, flat, and sloping, having sharp upper and lower margins. When the 
vertebree are superimposed the latter overlap the former so as to form an 
imbricated arrangement. The spinal foramen is smaller than in the cervical and 
lumbar regions, and nearly circular in shape. 
The spinous processes vary in length and direction, being shorter and more 
horizontal in the upper and lower members of the series, long est and most “oblique 
in direction towards the middle of the series. All have a downward inclination, 
and are so arranged that they overlap one another. Triangular in section where 
they spring from the neural arch, they become laterally compressed towards their 
extremities, which are capped by more or less distinct tubercles. The transverse 
processes are directed backwards and outwards, and a little upwards. They 
gradually decrease in size and length from above downwards. Each has a some- 
what expanded extremity, the anterior surface of which, in the case of the upper 
ten vertebra, is hollowed out in the form of a circular facet for articulation with 
the tubercle of the rib which rests in the upper demi-facet of the vertebra to which 
the transverse process belongs. The superior articular processes are vertical and 
have their surfaces directed backwards, shehtly upwards, and a little outwards ; 
the inferior, correspondingly forwards, downwards, and inwards. 
Certain of the dorsal vertebrie display characters by which they can readily be 
recognised. These are the first, tenth, eleventh, and twelfth, and sometimes the 
ninth. 
