LIGAMENTS OF THE PELVIS. 131 



ilium which surmounts the sacro- iliac articulation. It is triangular 

 in form. 



10. The Articulations of the Pelvis. The ligaments belonging to the 

 articulations of the pelvis are divisible into four groups : 1. Those 

 connecting the sacrum and ilium ; 2. those passing between the 

 sacrum and iscliium ; 3. between the sacrum and coccyx ; and 4, be- 

 tween the two pulic bones. 



1st, Between the sacrum and ilium. 

 Sacro-iliac anterior, 

 Sacro-iliac posterior. 



2nd, Between the sacrum and ischium. 

 Sacro-ischiatic anterior (short), 

 Sacro-ischiatic posterior (long). 



3rd, Between the sacrum and coccyx. 

 Sacro-coccygean anterior, 

 Sacro-coccygean posterior. 



4th, Between tlie ossa pubis. 

 Anterior pubic, 

 Posterior pubic, 

 Superior pubic, 

 Sub-pubic, 

 Interosseous fibro-cartilage. 



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

 ment 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 

 between the rough surfaces in the posterior half of the sacro-iliac arti- 

 culation, and constitute the principal bond of connection 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 

 interosseous ligament. The anterior or auricular half is coated with 

 cartilage, which is thicker on the sacrum than on the ilium. The sur- 

 face of the cartilage is irregular, and provided with a very delicate 

 synovial membrane, 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- 

 ischiatic 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 



