102 



MAMMALIAN ANATOMY 



directed from the cephalic end toward the tail and the median line. 

 Caudal to the cephalic third the margin is flat and emarginate, but 

 opposite the second ventral sacral foramen it presents a swelling. The 

 caudal border is straight and transverse in the middle, but deeply 

 emarginate on each side. 



The cephalic margin is likewise straight and transverse for most of 

 its extent, but at each side it curves toward the head and laterally. 

 The cephalic third of the ventral surface is strongly concave from side 

 to side. The middle of the concavity is flattened, and is the promon- 

 tory. On each side of this area the surface is convex in a cephalo- 

 caudal line. In the caudal two-thirds the ventral surface is in general 

 slightly concave in the same direction, except where it is convex at the 

 region of junction of the vertebral bodies. It is convex from side to 

 side in the middle line. On each side of this median convexity the 

 ventral surface is flattened or slightly concave in the cephalic part and 

 slightly convex in the caudal part. 



The ventral surface is pierced by four ventral sacral foramina, 

 which are arranged in two pairs, placed approximately at the junctions 



Cephalic Articular Process. 



United Articular Processes. 

 First Dorsal Sacral Foramen. 



Auricular Surface, with Ilium. 



Transverse Process. 



Second Dorsal Sacral Foramen. \ Body of Third Sacral Vertebra, 

 Caudal Articular Surface. with, First Caudal. 



THE SACRUM, POSTERIOR OR CAUDAL VIEW. 



of the end thirds with the middle third and a little nearer the lateral 

 margin than the median line. They pierce the bone obliquely from 

 the lateral side toward the cephalic end and the median line. The 

 cephalic pair are circular and larger and placed further apart than 

 the caudal pair, which are oval, with the long diameter of the oval 

 directed obliquely from the median line laterally and toward the head. 

 The caudal surface (Fig. 73) comprises the middle caudal surface 

 of the third sacral vertebra, and is transversely oval and continued on 

 each as the thin, concave, caudal edge of the inferior sacral angle. 



