VERTEBRAL COLUMN 



95 



laterally, ventrally, and slightly toward the head. Its caudal-dorsal 

 angle is produced into the mammillary process. The medial surface, 

 except for a small area near the base, is entirely occupied by the 

 cephalic articular surface, which is continued medially on the cephalic 

 part of the lamina. Each articular surface is circular, concave from 

 the dorsal to the ventral edge, and faces medially and dorsally. The 

 two cephalic articular processes are separated by a deep emargination 

 on the cephalic edge of the lamina?. 



The spinous process rises from the entire length of the neural 

 arch. It is thin and wedge-shaped. Its caudal edge is directed as 

 much toward the head as dorsally ; its cephalic edge is more nearly 

 vertical. The dorsal edge is short and slightly arcuate. 



The neural canal is almost square in cross-sections. 



The lumbar vertebras are so much alike that they can be distin- 

 guished from one another only by their size and by the degree of 

 development of some of their processes (Figs. 65, 66, 67, 68, 69). 



FIG. 66. 



Cephalic Articular 

 Process. 



Spinous Process. 



Accessory Process. 



Caudal Articular 

 Surface. 



t 



^~^Sfr'irst Luiiibai'^-^^^^^- 

 I Transverse Second 



Process. Lumbai 



Cephalic Epijitit/si* nf limit/, 

 articulates with Thirteenth 

 Thoracic Vertebra. 



Third 

 Lumbar. 



Caudal Epiphysis of /,'<///. 

 articulates with Fourth. 

 Lumbar. 



Intervcrtcbral 

 Fora in i a. 



FIRST THREE LUMBAR VERTEBRAE, LEFT SIDE. 



The lumbar vertebrae nearest the head resemble those thoracic 

 vertebra? nearest the tail in which the change from the thoracic type 

 to the lumbar type has already taken place ; indeed, except for the 

 presence of transverse processes and for the absence of ribs, any one of 

 the lumbars might be mistaken for a large twelfth or thirteenth thoracic. 



The change from the lumbar type to the caudal type takes place 

 mainly in those elements which coalesce to form the sacrum. 



