THE BONES OF THE LOWER LIMB 223 



forms the iliac fossa, which lodges the iliacus muscle. The iliac 

 portion of the ilio-pectineal line gives attachment to the fascia 

 iliaca, and for about an inch posteriorly to the parietal pelvic fascia. 

 It may also give partial insertion to the psoas parvus near the 

 ilio-pectineal eminence. The posterior division is subdivided into 

 auricular, ligamentous, and muscular portions. The auricular 

 division, anteroinferior in position, is broad in front and narrow 

 behind, where it extends over the inner aspect of the posterior 

 inferior spine. It is covered by cartilage in the recent state, and 

 articulates with the auricular surface of the sacrum. The liga- 

 mentous division, situated above and behind the auricular, presents 

 an elevation, called the tuberosity, for the posterior sacro-iliac 

 ligament, its surface being marked by several pits. The muscular 

 division, placed superiorly, gives origin to fibres of the multifidus 

 spinae. 



The ischium forms the lower and back part of the bone, and 

 is divisible into a body, tuberosity, and ramus. The body con- 

 tributes rather more than two-fifths to the acetabulum, and 

 forms the greater portion of its non-articular part. It is some- 

 what triangular, the truncated apex being directed downwards, and 

 its surfaces are internal, external, and posterior. The internal 

 surface extends from near the centre of the ilio-pectineal line 

 to the ischial spine, and is narrow above, but widens inferiorly 

 before reaching the spine. Its place of junction with the ilium is 

 indicated by a line passing from the Uio-pectineal eminence back- 

 wards and downwards to a point a little below the deepest part of the 

 great sciatic notch. Its junction with the superior pubic ramus 

 is marked by a line passing from the ilio-pectineal eminence down- 

 wards to the posterior margin of the obturator foramen about 

 I inch below its upper end. This surface gives origin to part 

 of the obturator intemus. The external surface enters into the 

 acetabulum, and between that cavity and the tuberosity it presents 

 an obturator groove for the tendon of the obturator externus. The 

 upper part of this groove gives attachment to the ischio- capsular 

 ligament. The posterior surface is limited externally by the brim of 

 the acetabulum, behind by the posterior border, and below by the 

 upper border, of the tuberosity. At the lower part it presents a 

 portion of the obturator groove, and it supports the pyriformis, and 

 the sciatic nerves and vessels. 



The borders, like the surfaces, are internal, external, and 

 posterior. The internal border forms a portion of the posterior 

 margin of the obturator foramen, and is sharp for the obturator 

 membrane. It separates the internal from the external surface. 

 The external border forms the posterior part of the margin of the 

 acetabulum, and gives attachment to a part of the cotyloid 

 ligament. The posterior border is continuous with that of the 

 ilium. Superiorly it forms the lower part of the great sciatic 

 notch, below which it presents a projection, called the spine, which 

 has an inward curve towards the pelvis, and gives attachment to the 



