LIGAMENTS OF THE PELVIS. 147 



inv the sacrum and ilium ; 2. those passing between the sacrum and is- 

 chium , 3. between the sacrum and coccyx ; and 4. between the tyvo pubic 

 bones. 



1st, Between the sacrum and ilium. 

 Sacro-iliac anterior, 

 Sacro-iliac posterior. 



2d, Between the sacrum and ischium. 

 Sacro-ischiatic anterior (short), 

 Sacro-ischiatic posterior (long). 



3d, Between the sacrum and coccyx. 

 Sacro-coccygean anterior, 

 Sacro-coccygean posterior. 



4th, Between the ossa pubis. 

 Anterior pubic, 

 Posterior pubic, 

 Superior pubic, 

 Sub-pubic, 

 Interosseous fibre-cartilage. 



1. Between the Sacrum and Ilium. The anterior sacro-iliac ligament 

 consists of numerous short ligamentous fibres, which pass from bone to 

 bone on the anterior surface of the joint. 



The posterior sacro-iliac or interosseous ligament is composed of nu- 

 merous strong fasciculi of ligamentous fibres, which pass horizontally be- 

 tween the rough surfaces in the posterior half of the sacro-iliac articulation, 

 and constitute the principal bond of connexion between the sacrum and 

 the ilium. One fasciculus of this ligament, longer and larger than the 

 rest, is distinguished, from its direction, by the name of the oblique sacro- 

 iliac ligament. It is attached, by one extremity, to the posterior superior 

 spine of the ilium ; and, by the other, to the third transverse tubercle on 

 the posterior surface of the sacrum. 



The surfaces of the two bones forming the sacro-iliac articulation are 

 partly covered with cartilage, and partly rough and connected by the in- 

 terosseous ligament. The antetior or auricular half is coated with carti- 

 lage, which is thicker on the sacrum than on the ilium. The surface of 

 the cartilage is irregular, and provided with a very delicate synovial mem- 

 brane, which cannot be demonstrated in the adult ; but is apparent in the 

 young subject, and in the female during pregnancy. 



2. Between the Sacrum and Ischium. The anterior or lesser sacro-ischi- 

 atic ligament is thin, and triangular in form ; it is attached by its apex to 

 the spine of the ischium, and by its broad extremity to the side of the sa- 

 crum and coccyx, interlacing its fibres with the greater sacro-ischiatic 

 ligament. 



The anterior sacro-ischiatic ligament is in relation in front with the coc 

 cygeus muscle, and behind with the posterior ligament, with which its 

 fibres are intermingled. By its upper border it forms a part of the lower 

 boundary of the great sacro-ischiatic foramen, and by the lower, a part of 

 the lesser sacro-ischiatic foramen. 



