74 



Bones of the Spine. 



Crista sacralis media 



/ 

 Canalis sacralis 



Crista sacralis articularis 



Processus articularis superior 



Incisura vertebralis superior 



Pars lateralis 



92. Sacrum, os sacrum, from above. 



Foramen intervertebrale 

 Foramen sacrale postering \ 



- Crista sacralis media 



Canalis sacralis 



Pars lateralis 



Foramen sacrale anterius 



92 a . Transverse section through the sacrum 



at the level of the second pair of foramina sacralia. 



The anterior upper surface of the sacrum, basis ossis sacri (see also Figs. 90, 91 

 and 95) contains in the middle a somewhat projecting, transversely oval, flat surface with 

 which the body of the fifth lumbar vertebra is connected by means of an intervertebral disc. 

 Behind this lies the upper, triangular opening of the canalis sacralis which passes through 

 the sacrum as a flattened, triangular canal from above downward and reaches its lower ex- 

 tremity in the hiatus sacralis on the posterior surface, a little above the apex ; within the bone 

 at the junctions of the vertebrae sacrales going off from it on each side are four short canals 

 (foramina intervertebralia) which are continued H-shaped into the foramina sacralia anteriora 

 and posteriora. Lateralward from the upper opening of the canalis sacralis the processus arti- 

 cular es superior es (see p. 73) project upward; in front of them lie the incisurae vertebrales 

 superior es. The lateral portions of the basis ossis sacri are smooth, somewhat concave and 

 form the anterior, upper limiting surfaces of the partes laterales ossis sacri. 



Through the union of the fifth lumbar vertebra with the sacrum there arises, at the 

 site of junction in front, an angle projecting somewhat downward and forward, the promon- 

 torium (0. T. sacrovertebral angle) (see Figs. 164 and 165). 



