5 8 ELEMENTARY BIOLOGY. [CHAP. 



d. The unsegmented portion of the column (tiro- 

 style). 



a. Its anterior end, enlarged and bearing two ar- 

 ticular concavities. 



This region is liable to variation. 



/?. Its posterior end; tubular in the dried skeleton, 



but in the fresh state filled with cartilage which 



projects beyond it. 

 y. The prominent arch along its dorsal surface; 



getting ridge-like and disappearing posteriorly. 

 8. The small neural canal, enclosed by y. 

 t. The two minute foramina (for exit of the tenth 



pair of spinal nerves) at its extreme anterior 



end. 



3. The vertebral column, wet preparation. 

 Cf. supra, and note in addition. 



a. The great mobility of the segments upon each 

 other. Parts in articulation will be found to be 

 united by sheets {capsules) or bands (ligaments) of 

 glistening white fibrous tissue. 



b. Make a longitudinal vertical section of the entire 

 vertebral column, and examine the cut surface. 



u.. The vertebral bodies (centra). Note the shapes 

 and mode of articulation of their applied ends 

 (articular surfaces); each will be seen to be 

 capped in cartilage, the apposed faces being 

 kept moist during life. 



/?. The intra-vertebral bodies; small gelatinous 

 masses lying within the substance of a. They 

 are most marked in young specimens. 



