34 ANATOMY OF THE RAT 



on to the ischium. Its anterior border is the posterior 

 inferior spine. The iliopectineal line on the ventral side 

 of the body connects the sharp anterior border of the pubis 

 with the wing of the ilium. The wing is the broad, flat, 

 anterior part of the ilium. The posterior part of its con- 

 cave medial surface is the auricular surface, which articu- 

 lates with the sacrum. Anterior to this surface the ilium 

 bends outward rather abruptly, terminating in a pro- 

 nounced tuberosity at right angles to the long axis of the 

 bone. The thickened anterodorsal margin of the bone is the 

 iliac crest. 



The ischium (os ischium), the most posterior component 

 of the coxal bone, has three parts: a Ijody, a superior 

 ramus, and an inferior ramus. The anterior end of the 

 bone forms the posterior side of the acetabulum. The body 

 expands posteriorly, giving off dorsally the superior and 

 ventrally the inferior ramus. This part of the ischium is 

 concave medially, and convex laterally. The inferior 

 ramus joins the pubis at the ventral extremity of the ob- 

 turator foramen. There is a longitudinal depression along 

 the dorsolateral surface of the ischium. This depression is 

 bounded ventrally by a longitudinal ridge, terminating 

 posteriorly in a thickening, the sciatic tuber. The upper 

 edge of the ischium is convex, while the posterior edge is 

 nearly a straight line. These two edges meet at almost a 

 right angle. 



The pubis (os pubis) is the ventral branch of the coxal 

 bone. Its superior ramus extends ventrally from the ace- 

 tabulum. The inferior, or symphyseal, ramus passes back 

 along the symphysis pubis to join the inferior ramus of 

 the ischium. The body is located at the region of union 

 of the two rami. The sharp anterior edge of the bone 

 bears the iliopectineal eminence. From this the iliopectin- 

 eal line passes forward. 



