4 THE SKELETON OF THE CAT. 
The vertebral arch (each half of which is sometimes called 
a neurapophysis) rises on each side from the cranial two-thirds 
of the dorsolateral angle of the centrum, as a thickened por- 
tion, the radix or pedicle (Figs. 2 and 3, ¢), which forms the 
ventral half of the lateral boundary of the vertebral canal. 
From the dorsal end of each radix a flat plate of bone, the 
lamina (/), extends caudomediad to join its fellow of the 
opposite side and form the vertebral arch. Owing to the fact 
that the radix rises from only the cranial two-thirds of the 
centrum there is left in the caudal border of the vertebral arch 
a notch bounded by the radix, the lamina, and the centrum. 
There is also a slight excavation of the cranial border of the 
radix. When the vertebre are articulated in the natural posi- 
tion, these notches form the intervertebral foramina (Fig. 4, 
ad), for the exit of the spinal nerves. 
At the junction of radix and lamina the arch is produced 
craniolaterad into a short process, the transverse process (¢), 
knobbed at the end. On the ventral face of its free end the 
transverse process bears a smooth facet, the transverse costal 
facet or tubercular facet (Fig. 4, ¢), for articulation with the 
tubercle of a rib. 
On the dorsal face ‘of each lamina at its cranial border is a 
smooth oval area, the cranial articular facet (superior articular 
facet of human anatomy) (Figs. 2 and 3, #). Its long axis is 
oblique and it looks dorsolaterad. The slight projections of 
the cranial edge of the laminz on which the facets are situated 
are the inconspicuous cranial articular processes (prezyga- 
pophyses). 
On the ventral surface of each lamina at the caudal border, 
near the middle line is a similar area, the caudal articular 
facet (inferior articular facet of human anatomy) (7); these 
occupy the ventral surfaces of two projections which form the 
caudal (inferior) articular processes (postzygapophyses) (/). 
These are separated by a median notch. When the vertebra 
are in their natural position the caudal articular facets lie dorsad 
of the cranial facets and fit against them. They thus strengthen 
the joint between contiguous vertebre, while permitting slight 
rotary motion. 
