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 tlie 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 11, c), 

 while the ventral portion represents a rib, and is hence known 

 as the processus costarius (/). The expanded plate formed 

 by the union of these two processes is directed nearly ventrad 

 and somewhat craniad in the third, fourth, and fifth vertebrae. 

 The two components of the process gradually separate as we 



Fig. II. — Sixth Cervical Verte- Fig. 12. — Atlas, Ventral View. 



BRA, Cranial End. 



Fig. II. — a, spinous process; b, cranial articular facet; c, lamina; d, radix or 

 pedicle; e, transverse process proper; /, /', processus costarius; g, foramen trans- 

 versarium; h, centrum; ?', vertebral canal. 



Fig. 12. — a, ventral arcli ; /', tuberculum anterius; c, lateral masses; d, trans- 

 verse processes; e, cranial articular facets; f, groove connecting the foramen trans- 

 versarium with the atlantal foramen; g, allantal foramen; /:, caudal articular 

 facets. 



pass caudad ; in the fourth and fifth vertebra; 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 [c) a slender 

 knobbed process, while the processus costarius is divided into 

 two portions (/" 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. 



