OSTEOLOGY. 61 



The posterior superior spinous process, for the oblique band 

 of the sacro-iliac ligament, and part of the multifidus spinae 

 muscle, below which is 



The posterior inferior spinous process, for attachment of 

 the great sacro-sciatic ligament. 



Between the superior and inferior spinous processes, both 

 anteriorly and posteriorly, is a notch,, the former for partial at- 

 tachment of the sartorius and passage of the external cutaneous 

 nerve. 



The internal concave surface, or venter, presents 

 The internal iliac fossa, lodging the iliacus muscle, and hav- 

 ing a nutrient foramen at its lower part ; 



Ilio-pectineal line,- limiting the fossa below, and separating 

 the false from the true pelvis ; 



Rough surface, divided into two parts an upper part for 

 posterior sacro-iliac ligaments, and lower auricular surface for 

 articulation with sacrum. 



THE ISCHIUM forms the outer back part of pelvis, and con- 

 sists of a body, tuberosity, and ascending ramus. 



The external surface of the body forms a little more than 

 two-fifths of the acetabulum, and presents 



A groove below, for the tendon of the obturator externus. 

 The internal surface is concave and smooth, and forms the 

 lateral wall of the true pelvis. 



The posterior border presents 



The spine of the ischium, projecting downward, backward, 

 and inward, from below the centre, for attachment of the gemel- 

 lus superior, coccygeus, and levator ani muscles, and lesser sacro- 

 sciatic ligament; 



Great sacro-sciatic notch, a deep notch above the spine con- 

 verted into a foramen by the lesser sacro-sciatic ligament, trans- 

 mitting the pyriformis muscle, superior gluteal nerve, gluteal 

 vessels, sciatic vessels and nerves, and the internal pudic vessels 

 and nerves; 



Lesser sacro-sciatic notch, below the spine, and between it 

 and the tuberosity, converted into a foramen by the great sacro- 

 sciatic ligament, transmitting the obturator internus muscle and 

 nerve, the internal pudic vessels and nerves. The lowest portion 

 of the body presents : 



Tuberosity (tuber ischii), with 



An outer lip, for attachment of part of adductor magnus, 

 and quadriceps femoris; 



Inner lip, for part of great sacro-sciatic ligament, erector 

 penis, and transvrrsus pcriim-i : 



Groove, on inner lip, for internal pudic vessels and nerve; 



