SACEO-ILIAC ARTICULATION. 



IGl 



occur till a more advanced age ; the pieces of the coccyx uniting one to another 

 in the fii'st place, and the joint between the sacrum and coccj-x not ossifyino- till 

 old age. The mobility seems to increase during pregnancy. 



The sacko-iliac ARTicuLATioi>r, often named the sacro-iliac syn- 

 chondrosis, is formed between the aui'icular snrfaces of the sacrum and 

 ilimn, -^-hich are bound together by a plate of cartilage, and by strong 

 ligaments (see fig. 148). 



The auricular cartilaginous plate unites the bones with great firm- 

 ness. When the ilium and sacrum are forcibly torn asunder,"this plate 

 usually separates into two layers, one of which adheres to the surface of 

 each bone. In some instances a small cavity naturally exists between 

 these two plates of cartilage, and in advanced life small spaces con- 

 taining glairy fluid are liable to be formed between them. Even when 

 separate in part, however, these plates are very closely applied, and 

 admit only a limited amount of movement. The cavity of this articu- 

 lation becomes more apparent, and the ligaments somewhat looser before 

 parturition. 



The posterior sacro-iliac ligament consists of a large number of 

 strong irregular fibres extending across the interval between the pos- 



Fig. 146. 



6 ^<^^0i 



ing. l4o. — Ligaments of the Pelvis and Hip-Joint- seen from behind, from a 

 Female Subject. (A. T.) i 



1, ilio-himbar ligament : above it the last lumbar intertransverse ligament ; 2, posterior 

 sacro-iliac ligaments, the short and the oblique ; 3, great sacro-sciatic ligament ; 4, lesser 

 sacro-sciatic ligament ; 5, obturator membrane ; 6, posterior hgament of symphysis 

 pubis ; 7, 7, continuation of supraspinous ligaments from the lower lumbar vertebra 

 over the sacral sj)ines ; 8, transverse j^rocess of last lumbar vertebra, to which from 

 above is seen descending the last intertransverse ligament, and from below ascending tlie 

 sacro-vertebral ligament ; 9, posterior surface of the capsular ligament of the hip- 

 joint. The posterior ligaments passing between the sacrum and coccyx are also partiaUy 

 shown. 



VOL. I. M 



