in.] DIVISION INTO REGIONS. 27 



been divided into five regions, the cervical, thoracic? lumbar, 

 sacral, and caudal. 



This divison is useful, especially as it is not entirely 

 arbitrary, and in most cases is capable of ready definition, 

 at least in the Mammalia ; but at the contiguous extre- 

 mities of the regions, the characters of the vertebrae of one 

 are apt to blend into those of another region, either nor- 

 mally, or as peculiarities of individual skeletons. 



i. The Cervical region constitutes the most anterior por- 

 tion of the column, or that which joins the cranium. 



The vertebrae which belong to it are either entirely 

 destitute of movable ribs, or, if they have any, these are 

 small, and do not join the sternum. 



az 



FIG. 7. Anterior surface of sixth cervical vertebra of Dog, f . s spinous process ; 

 az anterior zygapophysis ; i> vertebrarterial canal ; t transverse process ; t' its 

 inferior lamella. 



As a general rule they have a considerable perforation 

 through the base of the transverse process (the verte- 

 brarterial canal Owen), or, as it is sometimes described, 



1 Generally called dorsal, but it would be better to reserve this term 

 in morphology as relating to the upper surface of the body and opposed 

 to ventral. 



