544 DISSECTION OF THE PELVIS. 



into view, the dissector may consult the directions already given for the 

 dissection of the ligaments of the vertebrae (p. 346). 



The common ligaments for the bodies of the two bones are an anterior 

 and a posterior, with an intervening h'bro-cartilaginous substance. Be- 

 tween the neural arches lie the ligamenta subflava; and between the 

 spines the supra and interspinous bands are situate. The articular pro- 

 cesses are united by capsular ligaments with synovial membranes. 



The sacro-vertebral ligament is a rather strong bundle of h'bres, which 

 reaches from the under surface of the tip of the transverse process of the 

 last lumbar vertebra to the lateral part of the base of the sacrum. Widen- 

 ing as it descends, the ligament joins the fibres in front of the articulation 

 between the sacrum and the innominate bone. 



SACRO-COCCYGEAL ARTICULATION. The sacrum and coccyx are 

 united at the centre by a fibro-cartilage, and by an anterior and posterior 

 common ligament. And there is a separate articulation for the cornua of 

 the bones. 



Dissection. Little dissection is needed for these ligaments. When 

 the areolar tissue has been removed altogether from the bones, the liga- 

 ments will be apparent. 



The anterior ligament (sacro-coccygeal) consists of a few fibres that 

 pass between the bones in front of the fibro-cartilage. 



The posterior ligament is wide at its attachment to the last piece of the 

 sacrum, but narrows as it descends to be inserted into the coccyx. 



The Jibro-cartilage resembles that between the bodies of the other ver- 

 tebras, and is attached to the surfaces of the bones. 



Articulation of the cornua. The cornua of the first piece of the coccyx 

 are united with the cornua of the last sacral vertebra by ligamentous bands, 

 and not by joints as in the articular processes of the other vertebrae. 



Movement. Whilst the coccyx remains separate from the sacrum, a 

 slight antero-posterior movement will take place between them. 



SACRO-ILIAC ARTICULATION. The irregular surfaces by which the 

 sacrum and the innominate bone articulate, are united by cartilage (syn- 

 chondrosis), and are maintained in contact by anterior and posterior sacro- 

 iliac ligaments. Inferiorly the bones are further connected, without being 

 in contact, by the strong sacro-sciatic ligaments. 



Dissection. To see the posterior ligaments, the mass of muscle at the 

 back of the sacrum is to be removed on the side on which the innominate 

 bone remains. The anterior bands will be visible on the removal of some 

 areolar tissue. The small sacro-sciatic ligament will be brought into view 

 by removing the coccygeus; and the large ligament is dissected with the 

 lower limb. 



The anterior sacro-iliac ligament consists of a few thin scattered fibres 

 between the bones, near their articular surfaces. 



The posterior ligaments (sacro-iliac) are much stronger than the ante- 

 rior, and the fibres are collected into bundles : these ligaments pass from 

 the rough inner surface, at the posterior end of the innominate bone, to 

 the first two pieces of the sacrum. One bundle, which is distinct from 

 the others, and more superficial, is named the oblique or long posterior 

 ligament ; it is attached to the posterior upper iliac spinous process, and 

 descends almost vertically to the third piece of the sacrum. 



Articular cartilage. Between the irregular surfaces of the bones is a 

 thin uneven layer of cartilage (fig. 189, a). It fits into the inequalities 

 of the osseous surfaces, uniting them very firmly together. On separating 



