BONES. 



The middle curved line begins at the crest, an inch and a half 

 behind the anterior superior spine, and runs toward the upper 

 and back part of the great sciatic notch. The superior (pos- 

 terior) curved line begins at the crest, two and a half inches 

 in front of the posterior superior spine, and descends just in 

 front of the posterior inferior spine. [215] 



The internal surface has two parts. The posterior (sacral) 

 part presents anteriorly a smooth, articular surface for the 

 sacrum; and above and behind this an elevated, irregular 

 area (tuberosity) . The anterior part is smooth and subdivided 

 by an oblique ridge (ileo-pectineal line) which runs from the 

 most prominent part of the articular surface toward the inner 

 side of an (ileo-pectineal) eminence. The part above the ridge 

 forms the iliac fossa, and the part below helps form the true 

 pelvis. [217] 



Ischium. This is the lower and hinder part and consists of 

 a body and two rami. The body forms a little more than the 

 inferior two-fifths of the acetabulum. The superior ramus, 

 which runs downward and backward from the body, is a three- 

 sided bar from whose lower end the inferior ramus, a flattened 

 bar, runs forward at an angle. On the outer aspect of the 

 ischium, superiorly, the acetabular surface is marked off by a 

 prominent margin which is deficient in front, forming the floor 

 of the cotyloid notch. Below the acetabular margin there is 

 a well-marked groove. The postero-external surface of the 

 ischium forms the convex surface on the back of the acetab- 

 ulum; a pointed process (spine) springs from its sharp inner 

 border, opposite the lower edge of the acetabulum; lower 

 down the surface narrows and its inner border is hollowed 

 (small sciatic notch) out. A rough pyriform mass (tuberosity), 

 with prominent inner and outer lips, caps the lower part of this 

 surface and the angle between the rami; an oblique ridge di- 

 vides it into two areas, supero-external and infero-external. 

 The inner surface of the body and superior ramus helps form 

 the wall of the true pelvis and is widest opposite the spine; 



[185] 



