208 ANATOMY OF THE RABBIT 



of the acetabulum, the pubis being excluded through the develop- 

 ment in the acetabular depression of a small triangular element,, 

 the OS acetabuli. Although completely coalesced in the adult 

 condition, and showing but few traces of their original separation, 

 the three chief elements are nevertheless described as if distinct. 



The ilium (os ilium) is the anterior, also somewhat dorsal, 

 portion of the bone; that part extending forward from the ace- 

 tabulum. It comprises a basal portion, the body (corpus oss. 

 ilium), which includes the anterior portion of the acetabulum and 

 the cylindrical part of the bone in front of it, and an expanded 

 portion, the iliac wing (ala oss. ilium), for muscle attachment and 

 articulation, with the sacrum. The body is somewhat triangular 

 in transverse section, its surface being divided into three areas, 

 which are respectively medial, or sacral, ventrolateral, or iliac, 

 and dorsolateral, or gluteal. The corresponding borders are re- 

 spectively ventral, or pubic, lateral, or acetabular, and dorsal, or 

 ischial. The acetabular border terminates a short distance in front 

 of the acetabulum in an abruptly truncated projection, the inferior 

 anterior spine (spina anterior inferior), which is the origin of an 

 extensor muscle of the leg (second portion of the rectus femoris). 

 The ischial border forms the anterior half of a long depression of 

 the dorsal surface of the coxal bone, the greater sciatic notch 

 (incisura ischiadica major) over which pass the sciatic nerve and 

 artery as well as the piriformis muscle. The pubic border presents 

 on its medial side a faint, ridge-like elevation, the iliopectineal 

 line (linea iliopectinea), which connects the sharp anterior border 

 of the pubis with the articular surface for the sacrum. 



The wing of the ilium forms a shovel-like expansion, the natural 

 position of which is almost sagittal. Its lateral surface provides 

 a fairly extensive area for the origin of the gluteal muscles. Its 

 medial surface is a muscle surface only in its anterior portion, the 

 posterior portion being occupied by the roughened auricular sur- 

 face (facies auricularis), for connection with the sacrum. The 

 dorsal margin is thin and straight. Posteriorly, where it is asso- 

 ciated with the greater sciatic notch, there is a small projection, 

 the inferior posterior spine (spina posterior inferior), also termed 

 the tuber sacrale. Anteriorly it passes by a broad angle into the 

 anterodorsal margin of the bone, the latter forming the projecting 



