•204 



THE A R TTCI 'LA TIOXS 



of the fjpinc and the li^raments, which fasten the sacrum to tlie ilium, are sufficient 

 to check its upward displacement. 



Tlie anterior and downward displacements of the sacrum are prc'jnted by the 

 interosseous and posterior sacro-sciatic ligaments, which pass from tne ilia to the 

 sacrum, and suspend the latter, acting somewhat in the same manner as the chains 

 of a susjiension bridge. They also bind the two bones more tightly together: the 

 greater the jtressure, the tighter the union. The suspension bridge arrangement of 

 the sacro-iliac syncliondrosis is admirably adaj)ted to give strength to the pelvis. 



{h) The 8acro-coccygeal Articulation 

 Class . — Amiph ia rtJi ro«^s■. 



The last piece of the sacrum and first })iece of the coccyx enter into this union, 

 and are bound together by the following ligaments: — 



Anterior sacro-coccygeal. 

 Posterior sacro-coccvgeal. 



Supracornual. 

 Intertransverse. 



Intervertebral suljstance. 



The intervertebral substance is a small oval disc, three-quarters of an inch 

 (about 2 (111. ) wide, and a little less from before backwards, closely connected with 

 the surrounding ligaments. It resembles the other discs in structure, but is softer 

 and more jelly-like, though the laminae of the fibrous portion are well marked. 



Fig. -209. — Lioamexts conxectixg Sacrum and Coccyx postekiorly. 



Superflcial part of 

 the supraspinous 

 ligament, turned 

 up 



Deep part of the su- 

 praspinous ligament, 

 turned up 



Intertransverse 

 ligament 



The posterior sacro-eoecy- 

 geal ligament, or the lower 

 end of the posterior com- 

 mon ligament 



Supracornual ligament eon- 

 nectiug the cornua of the 

 sacrum and coccyx, cut and 

 turned down 



The anterior sacro-coccygeal ligament is a ])rolongation of the gbstening 

 fibrous structure on the front of tlic saciuni. It is really tlu' lower extreniitv of the 

 anterior common ligament, which is thicker over this join: than over the central 

 part of either of the l»ones. 



