I30 



HUMAN ANATOMY. 



This represents a costal element which fuses with the front of the pedicle. Those ot 

 the first two sacrals appear shortly before birth (Bade). The line of union can still 

 be seen at seven years on the top of the first vertebra. The time at which the laminae 



Fig. 158. 



D 



Costal element 



Illustrating homology of costal element (c. e.). ^, sixth cervical vertebra; ^, seventh cervical; C, fifth thoracic; 

 D, second lumbar ; E, fifth lumbar ; F, sacrum in transverse section. 



meet in the middle is uncertain ; the arch of the first vertebra is sometimes complete 

 at seven, those below it being still open. The five distinct sacral vertebrae which are 

 thus formed remain separate for some time, the bodies being separated by interver- 



FiG. 159. 



Fig. 160. 



Superior and anterior surfaces of young sacrum 

 of about five years. 



Sacrum and coccyx of about seventeen years. 



tebral disks. A thin plate appears in the upper and lower parts of these disks which 

 fuses with the bodies before the latter unite. The union of the vertebrae begins below 

 and proceeds upward in a very irregular manner. 



Probably union generally occurs first in the lateral masses, between the laminae 



