THE VERTEBRAL COLUMN. 13 
These two roots, which are broad and thin, converge and unite 
so as to enclose a canal or foramen, the foramen transver- 
sarium (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, dis- 
tinguishable as a tubercle at the caudolateral angle of the thin 
plate formed by the process as a whole. This dorsal compo- 
nent is the transverse process proper (Figs. 10 and II, e), 
while the ventral portion represents a rib, and is hence known 
as the processus costarius (7). The expanded plate formed 
by the union of these two processes is directed nearly ventrad 
and somewhat craniad in the third, fourth, and fifth vertebra. 
The two components of the process gradually separate as we 
Fic. 11.—S1IxTH CERVICAL VERTE- Fic. 12.—ATLAS, VENTRAL VIEW. 
BRA, CRANIAL END. 
Fig. 11.—a, spinous process; 4, cranial articular facet; c, lamina; d, radix or 
pedicle; ¢, transverse process proper; /, /’, processus costarius; g, foramen trans- 
versarium; 4, centrum; 2, vertebral canal. 
Fig. 12.—a, ventral arch; 4, tuberculum anterius; ¢, lateral masses; .d, trans- 
verse processes; ¢, cranial articular facets; 7, groove connecting the foramen trans- 
versarium with the atlantal foramen; g, atlantal foramen; 4, caudal articular 
facets. 
pass caudad; in the fourth and fifth vertebre 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 (¢) a slender 
knobbed process, while the processus costarius is divided into 
two portions (f and /’) 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. 
