THE VERTEBRAL COLUMN. 15 
The attached margin of each is about two-thirds the length of 
the thinner free margin. The somewhat thicker caudal end 
of the transverse process projects further caudad than any other 
part of the vertebra and is separated by a slight notch from the 
caudal articular facet. From the bottom of this notch the 
foramen transversarium extends craniad and opens at the 
middle of the ventral face of the transverse process. 
Epistropheus or Axis (Fig. 10, 2; Fig. 13).—The second 
cervical vertebra (epistropheus or axis) is not so wide as the 
atlas but is much longer. Craniad the centrum is continued 
into a slender conical, toothlike projec- 
tion, the dens or odontoid process (Fig. 
13, @) which represents the centrum of the 
atlas. The dens is smooth below for 
articulation with the ventral arch of the 
atlas. It is rougher above. Laterad of 
the dens the centrum bears a pair of large Fic. 13.—Axis or Epis- 
crania] articular facets (4) which look T®OFHEUS, Sipe View. 
craniolaterad. These have each the form Pa ay spot ger ah 
of a right-angled triangle with rounded gee Fes Teele tnee 
angles, one side of the triangle being «, transverse process; /, 
nearly horizontal. Each is separated from ‘r#men transversarium, 
the articular face of the dens by a roughened groove. The 
spinous process (c) runs the length of the vertebral arch. It 
extends craniad of the vertebral arch nearly as far as the dens, 
as a flat rounded projection. Caudad of the vertebral arch it 
projects for a short distance as a stout triangular spine. The 
caudal articular facets (@) are borne on thickenings of the 
caudolateral portions of the arch; they face almost directly 
ventrad. The transverse process (¢) is slender and triangular 
and directed nearly caudad. Its apex reaches no farther than 
the caudal or articular face of the centrum. Its base is traversed 
by the foramen transversarium (/). 
Differential Characters of the Cervical Vertebre.—It is 
possible to identify each of the cervical vertebra: 
The first by the absence of the centrum. 
The second by the dens or odontoid process. 
The third by the small spinous process and slightly marked 
