370 CHORDATA. 
The vertebral column consists of a great number of 
vertebrae which are known as cervical, or neck-vertebre, 
thoracic, lumbar, sacral and caudal. Of these the cervical 
are numerous, forming a very flexible neck; the thoracic 
Fig. 262. — LATERAL VIEW OF CERVICAL VERTEBRA OF 
THE PIGEON. (Ad nat.) 
Posterior Zygapophysis. Anterior Zygapophysis. 
Cervical Rib. 
Heteroccelous Articulation. Vertebrarterial Canal. 
are largely fused together and rigid, while a great number 
of the caudal are also fused. 
The fourteen cervicals have (except the first two) cervical 
ribs fused on to them, and as the ribs have two heads their 
fusion with the vertebra forms a canal on each side, called 
Fig. 263.—A RIB OF THE PIGEON. (dd nat.) 
(Slightly magnified). 
Tuberculum. Uncinate 
Process. 
Capitulum. 
Vertebral Part. 
Sternal Part. 
the vertebrarterial canal because it transmits the vertebral 
artery. The vertebrae are called /eterocelous to describe 
their peculiar articulations with each other, which are convex 
in one direction and concave the other, like a saddle. The 
