8 THE SKELETON OF THE CAT. 
The cranial articular processes (Fig. 5, @) are prominent 
and directed craniodorsad; they have the facets on their 
medial surfaces, while their dorsolateral surfaces bear the 
mammillary processes (4) as prominent tubercles. The caudal 
articular processes (c) are likewise large; their facets look 
laterad. When the vertebrz are articulated they are received 
between the medially directed cranial processes. 
The accessory processes (@) are well developed on the 
first vertebra, diminish in size to the fifth or sixth, and are 
absent on the seventh and sometimes on the sixth. 
The transverse processes (more properly pseudo-transverse 
processes) (¢) arise from the lateral surface of the centra; are 
flat and are directed ventrocraniolaterad. The first is small, 
and they increase in length and breadth from the first to the 
sixth, those of the last being slightly smaller than in the sixth. 
The free ends of the last four are curved craniad. 
The spinous processes (/) are flat and directed cranio- 
dorsad. They increase in length to the fifth and then decrease. 
The first five are knobbed at the end. In a dorsal view the 
spinous process and cranial articular processes of each vertebra 
are seen to interlock with the caudal articular processes and 
accessory processes of the preceding vertebra in such a way as 
to prevent rotary motion, and this arrangement may be traced 
craniad as far as the eleventh thoracic vertebra. 
Sacral Vertebre. Vertebre sacrales (Figs. 6 and 7).— 
The three sacral vertebre are united in the adult into a single 
bone, the os sacrum, or sacrum. Ina kitten the three verte- 
bre are separate, while in an animal almost mature the first 
two are united and the third is still separate. The sacrum lies 
between the last lumbar and the first caudal vertebrze and 
articulates laterally with the two innominate bones. It is 
pyramidal, with the base of the pyramid directed craniad, and 
is perforated by a depressed longitudinal canal, the sacral 
canal, which is a continuation of the vertebral canal, and by 
four large foramina dorsally and four ventrally. It may be 
described as having a cranial end or base and a caudal end or 
apex, a dorsal, a ventral, and two lateral surfaces. 
"The base is slightly oblique and presents a smooth trans- 
