Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/48

34 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 concave medial surface is the auricular surface, which articulates with the sacrum. Anterior to this surface the ilium bends outward rather abruptly, terminating in a pronounced 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 body, 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 obturator 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 acetabulum. 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 iliopectineal line passes forward.