112 MAMMALIAN ANATOMY 



an increase in length from the first to the tenth and eleventh, beyond 

 which there is a gradual decrease in both length and width. From 

 the beginning to the sixth or the seventh there are cephalic articular 

 surfaces. The second vertebra has a distinct cephalic angle on the 

 cephalic edge of the transverse process. This angle may appear on 

 the first, usually, however, as a trace only, and also less commonly on 

 the third. The tip of the transverse process is slightly bifid on the 

 third, fourth, and fifth or on some one of the three. The cephalic 

 transverse process begins at the sixth, and the caudal articular 

 surfaces cease at the fifth or the sixth. The chevron bones usually 

 become paired ossicles at the eighth. The cephalic and caudal 

 parts of the transverse process have attained equal size at about the 

 eighth. 



The neural canal disappears between the seventh and the ninth. 



THE ENTIRE VERTEBRAL COLUMN. 

 DORSAL ASPECT. 



When the vertebral column is viewed from the dorsal side the 

 variations in its width are plainly visible. It is wide at the atlas, 

 contracts abruptly and strikingly at the axis, then rapidly widens to 

 the mid-cervical region, whence it gradually and regularly narrows to 

 the eleventh thoracic vertebra ; at this point it again begins to widen, 

 and reaches its greatest width at the caudal end of the lumbar region. 

 It narrows again from the cephalic end of the sacrum to the beginning 

 of the caudal region, where, enlarging again slightly, it diminishes in 

 width to the tip of the tail. It will be observed, therefore, that caudal 

 to the atlas the column can be said to be made up of four long 

 truncated pyramids, the first and third with their bases directed toward 

 the tail, and the second and fourth with their bases directed toward the 

 head. 



In the middle line of the dorsal aspect of the vertebral column is 

 the crest formed by the row of spinous processes, whereof the variation 

 in height and direction can be best seen on the lateral aspect of the 

 column. 



On each side of this crest is a long strip, narrow and more or less 

 level. In the cervical region it is formed by the lamina? of the ver- 

 tebrae, and is flat, except where raised by the laminar tubercles. In 



