128 MAMMALIAN ANATOMY 



The costal element is shorter than the transverse element. The groove 

 on the side of the body for the vertebral artery is short and deep, and 

 the foramen for the artery and the first spinal nerve is a canal in the 

 pedicle. The cephalic articular surfaces are less cup-shaped than the 

 corresponding surfaces on the cat's atlas; the caudal articular surfaces 

 encroach to a great extent upon the lumen of the neural canal, offering 

 medial roughened surfaces for the attachment of ligaments. 



HUMAN THORACIC VERTEBRAE. 



The Sixth Thoracic Vertebra in man (Fig. 89) differs from 

 the corresponding vertebra in the cat principally in the relative 

 decrease in the cephalo-caudal diameters of all its parts and in the 



greater inclination of the spinous process. The 

 dorso-ventral diameter of the body is greater 

 than the transverse diameter, the cephalic and 

 caudal surfaces are cordiform, or heart-shaped, 

 and their edges are margined by an elevated 

 band. The dorsal surface is not keeled. The 

 neural canal is round. The cephalic articular 

 processes are more distinct than on the cat's 

 A THORACIC VERTEBRA. vertebra. The transverse processes are longer 



1, centrum; 2, articular facets aild 11101*6 sleildei*, aild the Cllds ai'6 11 Ot CX- 

 for ribs ; 3, arch ; 4, 5, intervene- 111 ji i i j> j* 



brai notches; e, spinous process; paneled ; hence the ventral articular facet for 



7, transverse process; 8, superior i f i -1-1 



articular processes; 9, inferior the tubercle 01 til 6 I'lD IS l6SS COllSplCUOUS. 



articular processes. . . 



lliey have, however, a decided dorsal inclina- 

 tion. The spinous process is relatively short, and the tip is obliquely 

 truncated. 



When the other human thoracic vertebrae (Fig. 85) are examined, 

 the student will observe that they are all very similar and that the 

 characters which serve to distinguish the different thoracic vertebrae 

 of the cat are here of less value. 



The bodies increase in size gradually from the first vertebra to the 

 last, which has the shape and most of the characters of a lumbar 

 vertebra. 



In the first and second vertebras the transverse diameter of the 

 body is greater than the dorso-ventral diameter ; from the third to 

 the seventh, approximately, the dorso-ventral diameter is the greater ; 

 in the remaining thoracic vertebrae the two diameters are at first nearly 



