Bones of the Trunk. 



53 



V. Lumbar vertebra, 



t.rv.t, Coccyx 



68, The Sacral Bone. Os sacrum, anterior view. 



The sacrum consists of 5 vertebrae united with each other; it has 

 a base, an anterior and a posterior surface and 2 lateral 

 borders. The base is articulated with the Y. lumbar vertebra. 

 The anterior surface is concave, and has 4 pairs of foramina, 

 Foramina sacralia antcriora ; each pair is connected by a horizontal ridge; 

 external to these are the lateral masses, Massae laterales ossis sacri. The 

 lateral borders which are articulated at their upper parts with the 

 Ossa innominata, approach each other inferiorly, and form the apex below ; 

 this serves for articulation with the coccyx; near this apex the lateral 

 borders present a semilunar notch, Incisura sacro-coccygea. 



