126 



MAMMALIAN ANATOMY 



FIG. 85. 



possesses but thirty-three vertebrae, whereof seven are cervical, twelve 

 thoracic, five lumbar, and the lower nine are coalesced into two super- 

 imposed masses, namely, the sacrum, of five vertebra?, and the 

 coccyx, or rudimentary tail, of four vertebrae. It also appears to be 

 more compact, its dorso-ventral and transverse diameters increasing 



gradually and with few irregularities from the 

 head to the sacrum. Inasmuch as it is vertical, it 

 bears the weight of the upper part of the body ; 

 hence all the vertebral bodies and all the pedicles 

 and laminae are compressed from above downward, 

 and none of the spinous processes point toward 

 the head. Owing to direct downward pressure, 

 the column describes four curves in the median 

 plane, whereof those in the cervical and lumbar 

 regions have the convexity ventral and those in 

 the thoracic and sacro-caudal regions have the 

 convexity dorsal. 



HUMAN CERVICAL VERTEBRA. 



The Sixth Cervical Vertebra (Fig. 86) com- 

 pared with the sixth of the cat is relatively wider. 

 The ends of the broad and flattened body are 

 concave transversely and scarcely bevelled. The 

 arterial canal in the transverse process is very 

 large ; the transverse process itself, however, is 

 simple, and the costal element is rounded at the 

 end. The pedicles are shorter and almost colum- 

 THE VERTEBRAL COLUMN. nar anc l incline laterally as well as dorsally. 



LATERAL VIEW. 



Exhibiting the curvatures. The laminse meet each other at a right angle, 



1 to 24, true vertebrse ; 25, 20, . . . 



false vertebra ; i to 7, cervical and the cephalic en d is emarginate. I he spinous 



vertebrae ; 8 to 19, thoracic ver- . i i r> i i i i 



tebne; 20 to 24, lumbar ver- prOCCSS IS sllOl't aild DlM at the tip, WlllCll 111- 

 tebrae ; 25, sacrum ; 26, coccyx. _.. 



clines toward the sacrum. I he cephalic articular 



surfaces (called "superior" in the illustration) face dorsally and toward 

 the head; the caudal articular surfaces (called "inferior" in the illus- 

 tration) face ventrally and toward the sacrum. The cephalic inter- 

 vertebral notches are very evident. 



The human Seventh Cervical differs from the corresponding ver- 

 tebra of the cat in having an arterial canal in its large transverse 



O O 



