Bones of the Spine. 



75 



Tuberositas sacralis 



Crista sacralis media 



. Processus articularis superior 



Basis ossis sacri 



Cornu sacrale 

 Coruu coccygeutu 



93. Sacrum and coccyx, os sacrum and os coccygis. 



From the right. 



The portions which lie lateralward from the foramina sacralia are called the partes 

 laterales ossis sacri (see also Figs. 90 92 a ); they have arisen through fusion of the trans- 

 verse processes and of rudiments of ribs (on the upper three vertebrae). The partes laterales 

 grow much narrower from above downward and present on the upper part of their free lateral 

 surfaces an uneven joint surface, fades auricularis, covered with cartilage, for union with the 

 hip bone; it is formed in the main by the first sacral vertebra, less by the second and least 

 by the third. Behind the facies auricularis lies a markedly roughened surface, tuberositas 

 sacralis, to which are attached the ligamenta sacroiliaca interossea. 



Sometimes the uppermost vertebra of the sacrum is fused laterally with the pars lateralis 

 only in one-half, while on the other half it has a shape similar to that of a lumb'ar vertebra ; 

 such a transition form is called a lumbosacral vertebra (see Fig. 96, No. 11). 



The sacrum usually presents certain differences in the two sexes. In man, it is longer, 

 relatively narrower and also more markedly curved; in woman it is shorter, relatively broader 

 and the curve is flatter (see Figs. 158 165). 



