48 



MAMMALIAN AX ATOMY 



on the adjoining vertebrae intervertebral foramina for the exit of the 

 spinal nerves from the neural canal. 



The body of the vertebra is in general cylindrical. Its cephalo- 

 caudal length is greater than its transverse width, which in turn is 

 always greater than the dorso-ventral height. The body consists of 

 three parts, a middle part, the centrum proper or diaphysis, and two 

 thin disks, one at each end, namely, the anterior or cephalic and 

 posterior or caudal epiphyses. The body presents for examination 

 cephalic, caudal, dorsal, and ventral surfaces, and lateral borders. 



The ventral surface of the body (Fig. IS) is quadrate and flattened, 

 or strongly convex, transversely. It is limited at the ends by the 



Fir,. 18. 



Transverse Process. 



Articular facet on 

 under Surface of Trans- 

 verse Process for Tuber- 

 cle of ib. 



Cephalic Articular Surface. 

 A THORACIC VERTEBRA, VENTRAL ASPECT. 



straight or arcuate ventral borders of the cephalic and caudal surfaces. 

 On each of the remaining edges are the lateral border and the root of 

 the transverse process, with the ventral surface of which the ventral 

 surface of the body may be continuous. The ventral surface of the 

 body is slightly concave from the cephalic to the caudal end, and the 

 middle line is often elevated into a decided keel, separating shallow 

 excavations. Near each end is an irregular transverse line which 

 indicates the junction of the diaphysis with the epiphysis. 



The dorsal surface of the body (Fig. 19) forms the floor of the 

 neural canal. It is limited at each end by the dorsal edges of the 

 cephalic and caudal surfaces, and at each side by the medial surface of 

 the ventral end of the pedicle, and by the small lateral border. While 

 the surface is in general flat, the middle line commonly presents a 

 flattened ridge wider at the ends than in the middle. On each side 

 of this ridge is a shallow depression, the two together forming most 

 of the dorsal surface. Close to the middle of the median ridge, on 

 each side, is a vascular foramen. These two foramina come together 



