108 



OSTEOLOGY 





processes, which are named the sacral cornua, and are connected to the cornua 

 of the coccyx. Lateral to the articular processes are the four posterior sacral 

 foramina; they are smaller in size and less regular in form than the anterior, and 

 transmit the posterior divisions of the sacral nerves. On the lateral side of the 

 posterior sacral foramina is a series of tubercles, which represent the transverse 

 processes of the sacral vertebrae, and form the lateral crests of the sacrum. The 

 transverse tubercles of the first sacral vertebra are large and very distinct; they, 

 together with the transverse tubercles of the second vertebra, give attachment 

 to the horizontal parts of the posterior sacroiliac ligaments; those of the third 

 vertebra give attachment to the oblique fasciculi of the posterior sacroiliac liga- 

 ments; and those of the fourth and fifth to the sacrotuberous ligaments. 





Sacrospinulis 



Latissimus 

 dor si 



Sacrospinalis 



Upper half of fifth 

 posterior sacral foramen 



FIG. 96. Sacrum, dorsal surface. 



Lateral Surface. The lateral surface is broad above, but narrowed into a thin 

 edge below. The upper half presents in front an ear-shaped surface, the auricular 

 surface, covered with cartilage in the fresh state, for articulation with the ilium. 

 Behind it is a rough surface, the sacral tuberosity, on which are three deep 

 and uneven impressions, for the attachment of the posterior sacroiliac ligament. 

 The lower half is thin, and ends in a projection called the inferior lateral angle; 

 medial to this angle is a notch, which is converted into a foramen by the trans- 

 verse process of the first piece of the coccyx, and transmits the anterior division of 

 the fifth sacral nerve. The thin lower half of the lateral surface gives attachment 

 to the sacrotuberous and sacrospinous ligaments, to some fibers of the Glutseus 

 maximus behind, and to the Coccygeus in front. 



Base (basis oss. sacri). The base of the sacrum, which is broad and expanded, 

 is directed upward and forward. In the middle is a large oval articular surface, 



