THE BONES OF THE POSTERIOR LIMB 209 



end of the wing, which is distinguished as the iliac crest (crista 

 iUaca). This portion is considerably thicker than the related 

 dorsal and ventral margins, and also bears on its medial side a 

 somewhat hook-shaped process. Its anteroventral angle is the 

 superior anterior spine (spina anterior superior) or tuber coxae. 

 The ventral margin is slightly longer than the dorsal margin, and 

 is also concave. It is associated with the pubic border of the body 

 of the ilium, and is not connected with the inferior anterior spine. 

 The anterior elongation of the ilium is an adaptation to the powerful 

 anterior thrust of the hind limb in progression. 



The ischium (os ischii) extends backward from the acetabulum, 

 its axis continuing that of the ilium. It consists of a basal portion, 

 or body (corpus oss. ischii), a superior ramus, and an inferior 

 ramus. The body of the ischium is for the most part cylindrical. 

 It forms the posterior part of the acetabulum and presents in 

 connection with the latter a deep acetabular notch (incisura ace- 

 tabuli), which tends to interrupt the articular surface. The 

 acetabular notch leads forward into a depression of the centre of 

 the articular basin, the acetabular fossa (fossa acetabuli). In the 

 natural condition the combined depressions serve for the attach- 

 ment of the round ligament of the head of the femur. The dorsal 

 margin of the bone, belonging in part to the body and in part to 

 the superior ramus, bears a short hook-like projection, the ischial 

 spine (spina ischiadica), a point of muscle origin (p. 275). The 

 spine divides this margin into two parts, one of which forms the 

 posterior half of the greater sciatic notch, already described, while 

 the other forms a similar, and, in the rabbit, scarcely less extensive, 

 posterior depression, the lesser sciatic notch (incisura ischiadica 

 minor). Through both notches pass muscles which move the 

 femur (p. 275). 



The superior or acetabular ramus of the ischium is the con- 

 tinuation backAvard of the body of the bone. It is a somewhat 

 flattened plate of bone, the thicker dorsal portion of which ter- 

 minates in two blunt projections. ^ One of these, the ischial 

 tuberosity (tuber ischiadicum), forms the posterior end of the bone, 

 while the other extends in a lateral direction and is described as 

 the lateral process (processus lateralis). The inferior or sym- 

 physeal ramus is that part of the ischium which extends from 



