122 



PELVIS. 



the innominate bone posteriorly; and a 

 single joint in front, uniting the innominate 

 bones to each other. The three latter joints 

 are of the kind usually denominated " sym- 

 physis" and considered by many as included 

 also in the class " amphi-arthrosis." 



The sacro-iliac joints, however, most fre- 

 quently presenting two contiguous surfaces and 

 two separate plates of incrusting cartilage,ought 

 rather, as Albinus remarked, to be considered 

 as "arthrodial" forms of articulation, while the 

 pubic symphysis occupies an intermediate or 

 transitional position between the fibro-carti- 

 laginous. or mixed, and the arthrodial joints. 



The sacro-coccygeal joint is composed of a 

 fibro-cartilaginous disc, and an anterior and 

 posterior ligament. The fibro-cartilaginous 

 disc is a miniature of the intervertebral, inter- 

 vening between and adherent to the opposed 

 articular surfaces of these bones, being, how- 

 ever, less evidently pulpy in the centre. Ac- 

 cording to Cruveilhier, there is sometimes 

 found a synovial membrane in the centre of 

 this joint. The anterior sacro-cocoygeal liga- 

 ment consists of a thin layer of fibres passing 

 from one bone to the other in front of the 

 joint, and spreading over the whole coccy- 

 geal surface. The posterior sacro-cocci/geal 

 ligament is much stronger and more developed. 



It springs from the edges of the notched in- 

 ferior opening of the sacral canal by a thick 

 band of fibres, which includes also, as an in- 

 vesting capsular ligament, lined by a synovial 

 membrane, the articular extremities of the 

 sacral horns, and, gradually narrowing down- 

 wards, is attached to, and extends over, the 

 whole posterior surface of the coccyx and its 

 articular processes, covering in the inferior 

 aperture of the sacral canal, and connecting 

 the several pieces of the coccyx when they 

 remain separate. In the latter case also are 

 found intra-coccygeal articulations, small fibro- 

 cartilaginous discs intervening between the 

 several bones. This, according to Levret, is 

 most constant between the first and second 

 pieces of the coccyx, where it is sometimes 

 met with in advanced age. 



The motions of this joint, and those of the 

 coccygeal bones, are simply antero-posterior 

 flexure, and are sometimes, especially in females 

 and young subjects, very extensive, forming, 

 Cruveilhier says, a complete anterior projecting 

 angle. This anatomist also mentions having 

 seen many times anterior sacro-coccygean mus- 

 cles ; other anatomists also mention posterior 

 sacro-coccygean muscles blended with the 

 fibres of the ligament. 



The sacro-iliac joints {Jig. 80. I .), one on 



Fig. 80. 



Anterior view of the full-grown male pelvis with its ligaments. 



1, sacro-iliac symphyses; 2, pubic symphysis. a, superior sacro-iliac ligaments; b, anterior sacro iliac 

 ligaments ; c, ilio-lumbar ligaments ; d, anterior pubic ligament ; e, superior pubic ligament ; /, subpubic 

 or arcuate ligament ; g, obturator membrane ; h, sacro -sciatic ligaments ; i, sacro-lumbar fibro-cartilage, 

 forming the sacral promontory. 



each side, are composed of an anterior or 

 inferior portion, in which the opposing bones 

 are covered with cartilages of an auricular 

 or angular shape, and a posterior or superior 

 portion where they are united by powerful 



inter-osseous ligaments, which fill up the re- 

 tiring angle left by the cartilages. These 

 are inclosed by anterior, posterior, and superior 

 sacro-iliac investing ligaments. 



The cartilages lining these articulations differ 



