The portion covering the Psoas is thickened above to form the medial lumbocostal arch, which stretches from the transverse process of the first lumbar vertebra to the body of the second. Medially, it is attached by a series of arched processes to the intervertebral fibrocartilages, and prominent margins of the bodies of the vertebræ, and to the upper part of the sacrum; the intervals left, opposite the constricted portions of the bodies, transmit the lumbar arteries and veins and filaments of the sympathetic trunk. Laterally, above the crest of the ilium, it is continuous with the fascia covering the front of the Quadratus lumborum (see page 419), while below the crest of the ilium it is continuous with the fascia covering the Iliacus.
The portions investing the Iliacus (fascia iliaca; iliac fascia) is connected, laterally to the whole length of the inner lip of the iliac crest; and medially, to the linea terminalis of the lesser pelvis, where it is continuous with the periosteum. At the iliopectineal eminence it receives the tendon of insertion of the Psoas minor, when that muscle exists. Lateral to the femoral vessels it is intimately connected to the posterior margin of the inguinal ligament, and is continuous with the transversalis fascia. Immediately lateral to the femoral vessels the iliac fascia is prolonged backward and medialward from the inguinal ligament as a band, the iliopectineal fascia, which is attached to the iliopectineal eminence. This fascia divides the space between the inguinal ligament and the hip bone into two lacunæ or compartments, the medial of which transmits the femoral vessels, the lateral the Psoas major and Iliacus and the femoral nerve. Medial to the vessels the iliac fascia is attached to the pectineal line behind the inguinal aponeurotic falx, where it is again continuous with the transversalis fascia. On the thigh the fasciæ of the Iliacus and Psoas form a single sheet termed the iliopectineal fascia. Where the external iliac vessels pass into the thigh, the fascia descends behind them, forming the posterior wall of the femoral sheath. The portion of the iliopectineal fascia which passes behind