452 PELVIC VERTEBRAE. 



all smooth, funnel-shaped, and have their orifices looking 

 outward. The anterior projecting edge of the upper l><>m' 

 of the sacrum is called its promontory. 



The posterior surface is 

 rough and convex ; on its 

 middle line four promi- 

 nences are observed cor- 

 responding to spinous 

 processes, which are not 

 unfrequently seen united 

 into a single ridge or 

 crest. The fourth and 

 fifth spines are generally deficient, leaving a triangular 

 space which is simply closed by ligaments, and in place 

 of the spine, presenting, on either side, two tubercles 

 styled comua, which unite with similar cornua from the 

 coccyx, forming foramina for the passage of the last sacral 

 nerve. 



On either side of the spinous processes four foramina 

 are seen, smaller than those in front, transmitting the pos- 

 terior sacral nerves. External to these foramina, a row of 

 five tubercles is noticed, though indistinct, corresponding to 

 the transverse processes of the true vertebrae ; and internal 

 to these foramina, between them and the spinous processes, 

 another row of indistinct tubercles is seen, regarded as 

 analogous to the oblique processes. 



The lateral or iliac surfaces are rough, irregular, and 

 triangular, having their superior portions broad and cov- 

 ered with cartilage to articulate with the ilium. Their 

 inferior surfaces are thin, and give attachment to the 

 greater and lesser sacro-ischiatic ligaments. 



Fio. 130, A represents a front view of the Sacrum. 1 Superior articular 

 process. 2 Superior surface of first sacral vertebra. 3 Lateral side of sa- 

 crum. 4 Anterior surface of the bodies of the sacral vertebra. 5 Grooves 

 leading to the anterior sacral foramina. 16 Apex of last sacral vertebra. 



Fio. 130, B represents a side view of the Sacrum. 1 Superior articular 

 process. 2 Sacro vertebral angle. 3 Hollow of the sacrum. 4 Termination 

 of sacral canal. 5 Articular surface for coccyx. 888 Spinous processes, or 

 crest. 



