CHAPTEH X. 



PELVIS. 



OSTEOLOGY. 



Sacrum. — Formed by the union of the five sacral ver- 

 tebrae. Division : Two faces, two borders, a base, an 

 apex and a central canal. Faces : Superior presents 

 the spinous processes forming the sacral spine, bent 

 backwards and diminishing in length posteriorly; it 

 offers on each side the four supra-sacral foramina. 

 The inferior face is smooth and shows the lines of sep- 

 aration of the vertebrae, and on each side the four sub- 

 sacral foramina. The borders are thick and concave, 

 rough posteriorly, having forward a broad, rough au- 

 ricular surface, to articulate with the ossa innominata. 

 The base offers on the median line the anterior orifice 

 of the sacral canal and the anterior articular head of 

 the body of the first sacral vertebrae ; on the sides the 

 articular processes and the anterior notches of that ver- 

 tebrae, and outside the two large facets for articulation 



