THE VERTEBRAL COLUMN. n 



the fused transverse processes of the second and third sacral 

 vertebrae. 



Caudal Vertebrae. Vertebrae caudales (Fig. i, y, and 

 Figs. 8 and 9). The caudal vertebrae (21-23 m number) 

 decrease gradually in size to the last one. Caudad they 

 become longer and more slender 

 and lose the character of verte- 

 brae. They become finally re- 

 duced to mere centra, slender fff 

 rods of bone knobbed or enlarged 



at their two ends (Fig. 8). The 



v . j ' FlG - 8 - FlG - 9- 



last one IS more pointed than the Fig . 8. Caudal Vertebra, from near 



others and bears at its caudal end the caudal end of the tail - 



. Fig. 9. Fourth Caudal Vertebra, 



a small separate conical piece, ventral view, a, transverse processes; 



the rudiment of an additional *' cranial articular processes; ,, haemal 



processes; a, chevron bone, 

 vertebra. 



The parts of a typical vertebra vertebral arch, transverse 

 processes, cranial and caudal articular processes may be 

 recognized in the vertebrae as far back as the eighth or ninth. 

 The transverse processes (Fig. 9, a) are directed caudad and 

 decrease rapidly in length. They are very small on the ninth 

 vertebra, but may be recognized for a considerable distance 

 back of this. The spinous process disappears at about the 

 fourth caudal vertebra, and the vertebral canal becomes 

 gradually smaller caudad, until on the eighth or ninth vertebra 

 it becomes merely a groove open dorsad. 



Caudad of the third vertebra for a considerable distance, 

 each centrum bears on each lateral face at its cranial end a 

 short anterior transverse process, and on its ventral face at its 

 cranial end a pair of rounded tubercles, haemal processes (c), 

 which articulate with a small pyramidal chevron bone (</) so 

 as to enclose a canal. These structures disappear caudad. 



Cervical Vertebrae. Vertebrae cervicales (Fig. 10). The 

 cervical vertebrae number seven. The first two of these are so 

 peculiar as to require a separate description, so that the last five 

 may be first considered. 



Passing craniad from the fourth thoracic vertebra to the 

 third cervical there is a gradual transition. The centra of the 



