8 THE SKELETON OF THE CAT. 



The cranial articular processes (Fig. 5, a) are prominent 

 and directed craniodorsad ; they have the facets on their 

 medial surfaces, while their dorsolateral surfaces bear the 

 mammillary processes (b] as prominent tubercles. The caudal 

 articular processes (<:) are likewise large; their facets look 

 laterad. When the vertebrae are articulated they are received 

 between the medially directed cranial processes. 



The accessory processes (d} 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) (e) 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 Vertebrae. Vertebrae sacrales (Figs. 6 and 7). 

 The three sacral vertebras are united in the adult into a single 

 bone, the OS sacrum, or sacrum. In a kitten the three verte- 

 brae 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 vertebrae 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- 



