Caudad of the third vertebra for a considerable distance, each centrum bears on each lateral face at its cranial end a short anterior transverse process, and on its ventral face at its cranial end a pair of rounded tubercles, hæmal processes (c), which articulate with a small pyramidal chevron bone (d) so as to enclose a canal. These structures disappear caudad.
Cervical Vertebræ. Vertebræ cervicales
([Fig. 10]).—The cervical vertebræ number seven. The first two of these are so peculiar as to require a separate description, so that the last five may be first considered.
Passing craniad from the fourth thoracic vertebra to the third cervical there is a gradual transition. The centra of the cervical vertebræ are broader and thinner than those of the thoracic vertebræ, while the vertebral arches and vertebral canal are larger ([Fig. 11]). The caudal end of each centrum is concave and looks dorsocaudad when the centrum is held with its long axis horizontal. The cranial end of the centrum is convex and looks ventrocraniad when the centrum is horizontal. These peculiarities are more marked in the third vertebra than in the seventh. The spinous processes grow rapidly shorter as we pass craniad; the fifth, sixth, and seventh are directed dorsocraniad, the third and fourth dorsad.
[Fig. 10].—Cervical Vertebræ, Side View.
![[Fig. 10]](#3418956513767812439_illo012lg.jpg.id-4816605871391558034.wrap-0.html.html){kind=link}
a, spinous processes; b, cranial articular processes; c, caudal articular facet; d, intervertebral foramina; e, transverse process proper; f, processus costarius; g, wing of the atlas; h, dorsal arch of the atlas; i, atlantal foramen.
The caudal articular processes are situated at the junction of the radices and laminæ; their facets ([Fig. 10], c) look ventrocaudolaterad. The cranial articular processes also become more prominent than is the rule in the thoracic vertebræ; they are borne at the junction of radix and lamina and have their facets ([Fig. 11], b) directed dorsomediad. The cranial and caudal articular processes of each side are joined by a prominent ridge which is most pronounced in the third, fourth, and fifth vertebræ.
The characteristic feature of the cervical vertebræ is their transverse process, so called. In each of them it arises by two roots, one from the centrum and one from the arch. These two roots, which are broad and thin, converge and unite so as to enclose a canal or foramen, the foramen transversarium ([Fig. 11], g), for the vertebral artery. Laterad of the foramen the two parts of the process are, in the third cervical, almost completely united, the dorsal part being, however, distinguishable as a tubercle at the caudolateral angle of the thin plate formed by the process as a whole. This dorsal component is the transverse process proper ([Figs. 10] and [11], e), while the ventral portion represents a rib, and is hence known as the processus costarius (f). The expanded plate formed by the union of these two processes is directed nearly ventrad and somewhat craniad in the third, fourth, and fifth vertebræ. The two components of the process gradually separate as we pass caudad; in the fourth and fifth vertebræ the part which represents the transverse process proper forms a very prominent tubercle at the caudolateral angle of the plate formed by the processus costarius. In the sixth ([Fig. 11]) the two parts are almost completely separated; the dorsal part forms (e) a slender knobbed process, while the processus costarius is divided into two portions (f and f′) by a broad lateral notch. In the seventh the ventral part (processus costarius) is usually quite lacking, though sometimes represented by a slender spicule of bone. In the former case the foramen transversarium is of course likewise lacking.
