VERTEBEAL COLUMN <s; . 



and presents a strong, rounded, cephalic tuberosity and a long, pointed, 

 caudal spine. 



The Tenth Thoracic Vertebra (Figs. 50, 52, 54) differs from all 

 the thoracics so far considered, except the first, in having distinct 

 caudal articular processes whereof the articular surfaces face laterally 

 as well as ventrally and thus become visible when the bone is viewed 

 from the side. Only a fourth of the height of the vertebra lies dorsal 

 to the caudal articular surfaces. 



The spinous process is very short, and lias a less inclination toward 

 the tail than the spinous process of the ninth vertebra. 



This is the last thoracic vertebra possessing true transverse pro- 

 cesses which articulate with the ribs. They are very different, how- 

 ever, from the transverse processes of the preceding vertebrae. Each 

 is greatly elongated from head to tail, and its end bears distinct 

 cephalic and caudal processes which are separated by a more or 

 less well-defined dorso- ventral depression. These secondary processes 

 are known as the mammillary 1 and accessory 2 processes. The 

 mammillary is the cephalic process, and is smaller and more rounded. 

 The accessory is the caudal process, and is longer and more pointed. 

 The costal facet on the ventral surface of the transverse process is 

 borne on a distinct elevation, and faces ventrally and laterally and 

 toward the head. The body is more massive, and the neural canal is 

 wider. 



The Eleventh Thoracic Vertebra (Figs. 54, 55, 5<>) is known at 

 once by its very small triangular spinous process, which points 

 directly dorsally. This process marks the point where a change in 

 the direction of the spinous processes takes place; the spinous pro- 

 cesses of the remaining thoracic and of all the lumhar vertebra- point 

 toward the head. The eleventh thoracic is therefore known as the 

 anticlinal" vertebra, a term borrowed from geology, in which it is used 



O O/ ' 



to denote the line from which strata dip in opposite directions. 



This vertebra has distinct cephalic articular processes, where. .!' 

 the articular surfaces face dorsally and medially. 



The mamrnillary process has a more dorsal origin, and now spriii-- 

 from the lateral side of the cephalic articular process. The accessory 

 process is all that is left of the transverse process. It springs from 



1 From mamma, the breast, teat-like. ' 2 From accessvm. a<Mc<l. 



s From (Gr.) anti, against, and kli.no, to loan. 



