THE VERTEBRAE 



21 



loiitifular-shaped cartilage. During the second year a nucleus appears at the tij) 

 of the odontoid process; it joins the main mass at the fourth year. An epiphysial 

 meniscus Ioy the inferior and superior surfaces of the centrum of the axis appears 

 ahout the seventeenth year. As a rule, the superior meniscus is represented Ity 

 a few earthy granules. 



Fig. 24.— Immaturk Atlas. (Third year.) 



The sixth and seventh vertebrae. — In the cervical vertebrae the pedicles, or 

 anterior extremities of the neural arches, take a much larger share in forming the 

 centrum than is the case Avith the remaining vertebrae. The sixth, seventh, and 

 possir)ly other cervical vertebrae present an additional centre on each side of the 

 neural arch for the costal process; it appears before birth. The costal processes of 



Fig. 25. — Development of the .Axis. 



Suspensory ligament 



NUCLEUS FOR TIP OF OOONTOIO PROCESS 



LATERAL CENTRES FOR OOONTOIO PROCESS 



EPIPHYSIAL PLATE OR DISC 

 PEDICLE 



CENTRUM OR BODY 

 EPIPHYSIAL PLATE 



the seventh cervical not infrequently fail to ankylose with the vertebra; when this 

 is the case, the processes l)ecome cervical riljs. Sometimes these ribs are of large 

 size. 



The lumbar vertebrae. — In the lumVnir vertebra?, two additional centres make 



Fig. 26.— The Axis (from an Adilt) in Section. 



OOONTOIO PROCESS 



CARTILAGE REPRESENTING THE INTER- 

 VERTEBRAL DISC BETWEEN THE ODON- 

 TOID PROCESS AND THE BODY OF THE 

 AXIS 



BODY OF AXIS 



their appearance, about puberty, namely, for the mammillary tubercles on the 

 jjosterior aspect of each superior articular process. 



The fifth lumbar occasionally diff(>rs in the mode of ossification of its arch; in 

 many skeletons this arch is derived from four nuclei. There is a nucleus on each 

 side for the pedicle, the transverse pnxess, and the superior articular process; and 



