PSOAS. PECTINEUS. 259 



continuous with the synovial membrane of the articulation. By its 

 inner border with the psoas magnus and crural nerve. 



The PSOAS MAGNUS (^, lumbus, a loin), situated by the side of 

 the vertebral column in the loins, is a long fusiform muscle. It arises 

 from the intervertebral substances, part of the bodies and bases of the 

 transverse processes, and from a series of tendinous arches, thrown 

 across the constricted portion of the last dorsal and four upper lumbar 

 vertebrae. These arches are intended to protect the lumbar arteries 

 and sympathetic filaments of nerves from pressure, in their passage 

 beneath the muscle. From this extensive origin the muscle passes 

 along the margin of the brim of the pelvis, and beneath Poupart's li- 

 gament, to its insertion. The tendon of the psoas magnus unites with 

 that of the iliacus, and the conjoined tendon is inserted into the poste- 

 rior part of the trochanter minor, a bursa being interposed. 



Relations. By its anterior surface with the ligamentum arcuatum 

 internum of the diaphragm, the kidney, the psoas parvus, genito-crural 

 nerve, sympathetic nerve, its proper fascia, the peritoneum and colon, 

 and along its pelvic border with the common and external iliac artery 

 and vein. By its posterior surface with the lumbar vertebrae, the 

 lumbar arteries, quadratus lumborum, from which it is separated by 

 the anterior layer of the aponeurosis of the transversalis, and with the 

 crural nerve, which near Poupart's ligament gets to its outer side. 

 The lumbar plexus of nerves is situated in the substance of the 

 posterior part of the muscle. In the thigh the muscle is in relation 

 with the fascia lata in front ; the border of the pelvis and hip-joint, 

 from which it is separated by the synovial membrane, common to 

 it and the preceding muscle, behind ; with the crural nerve, and 

 iliacus to the outer side ; and with the femoral artery, by which it is 

 slightly overlaid to the inner side. 



The PECTINEUS is a flat and quadrangular muscle ; it arises from 

 the pectineal line (pecten, a crest) of the os pubis, and from the sur- 

 face of bone in front of that bone. It is inserted into the line leading 

 from the anterior intertrochanteric line to the linea aspera of the 

 femur. 



Relations. By its anterior surface with the pubic portion of the 

 fascia lata, which separates it from the femoral artery and vein and 

 internal saphenous vein, and lower down with the profunda artery. 

 By its posterior surface with the capsule of the hip-joint, and with the 

 obturator externus and adductor brevis, the obturator vessels being 

 interposed. By its external border with the psoas, the femoral artery 

 resting upon the line of interval. By its internal border with the 

 outer edge of the adductor longus. Obturator hernia is situated di- 

 rectly behind this muscle, which forms one of its coverings. 



The ADDUCTOR LONGUS (adducere, to draw to), the most superfi- 

 cial of the three adductors, arises by a round and thick tendon from 

 the front surface of the os pubis, immediately below the angle ; and, 

 assuming a flattened and expanded form as it descends, is inserted into 

 the middle third of the linea aspera. 



