504 THE MUSCLES AND FASCIA. 



corresponding to the point where the femoral vessels pass into the thigh, this fascia 

 descends behind them, forming the posterior Avail of the crural sheath. This 

 portion of the iliac fascia which passes behind the femoral vessels is also attached 

 to the ilio-pectineal line beyond the limits of the attachment of the conjoined 

 tendon ; at this part it is continuous with the pubic portion of the fascia lata of 

 the thigh. The external iliac vessels lie in front of the iliac fascia, but all the 

 branches of the lumbar plexus behind it ; it is separated from the peritoneum by a 

 quantity of loose areolar tissue. 



The Psoas magnus (Fig. 326) is a long fusiform muscle placed on the side of 

 the lumbar region of the spine and margin of the pelvis. It arises from the front 

 of the bases and lower borders of the transverse processes of the lumbar vertebrae 

 by five fleshy slips ; also from the sides of the bodies and the corresponding 

 intervertebral substances of the last dorsal and all the lumbar vertebrae. The 

 muscle is connected to the bodies of the vertebrae by five slips ; each slip is attached 

 to the upper and lower margins of two vertebrae, and to the intervertebral substance 

 between them, the slips themselves being connected by the tendinous arches which 

 extend across the constricted part of the bodies, and beneath which pass the lumbar 

 arteries and sympathetic nerves. These tendinous arches also give origin to 

 muscular fibres, and protect the blood-vessels and nerves from pressure during the 

 action of the muscle. The first slip is attached to the contiguous margins of the 

 last dorsal and first lumbar vertebrae ; the last to the contiguous margins of the 

 fourth and fifth lumbar, and to the intervertebral substance. From these points 

 the muscle passes down across the brim of the pelvis, and, diminishing gradually 

 in size, passes beneath Poupart's ligament, and terminates in a tendon which, 

 after receiving the fibres of the Iliacus, is inserted into the lesser trochanter of 

 the femur. 



Relations. In the lumbar region : by its anterior surface, which is placed 

 behind the peritoneum, with the iliac fascia, the ligamentum arcuatum internum, 

 the kidney, Psoas parvus, renal vessels, ureter, spermatic vessels, genito-crural 

 nerve, and the colon ; by its posterior surface, with the transverse processes of the 

 lumbar vertebrae and the Quadratus lumborum, from which it is separated by the 

 anterior lamella of the lumbar fascia. The anterior crural nerve is at first 

 situated in the substance of the muscle, and emerges from its outer border at the 

 lower part. The lumbar plexus is situated in the posterior part of the substance 

 of the muscle. By its inner side the muscle is in relation with the bodies of the 

 lumbar vertebras, the lumbar arteries, the ganglia of the sympathetic nerve, and 

 their branches of communication with the spinal nerves ; the lumbar glands ; the 

 vena cava inferior on the right and the aorta on the left side, and along the brim 

 of the pelvis with the external iliac artery. In the thigh it is in relation, in front, 

 with the fascia lata ; behind, with the capsular ligament of the hip, from which it 

 is separated by a synovial bursa, which frequently communicates with the cavity 

 of the joint through an opening of variable size; by its inner border, with the 

 Pectineus and the femoral artery, which slightly overlaps it : by its outer border, 

 with the anterior crural nerve and Iliacus muscle. 



The Psoas parvus is a long slender muscle placed in front of the Psoas magnus. 

 It arises from the sides of the bodies of the last dorsal and first lumbar vertebrae 

 and from the intervertebral substance between them. It forms a small flat muscular 

 bundle, which terminates in a long flat tendon inserted into the ilio-pectineal 

 eminence, and, by its outerfborder, into the iliac fascia. This muscle is often 

 absent, and, according to Cruveilhier, sometimes double. 



Relations. It is covered by the peritoneum, and, at its origin, by the ligamentum 

 arcuatum internum ; it rests on the Psoas magnus. 



The Iliacus is a flat, triangular muscle which fills up the whole of the iliac 

 fossa. It arises from the upper two-thirds of this fossa and from the inner margin 

 of the crest of the ilium ; behind, from the ilio-lumbar ligament and base of the 

 sacrum ; in front, from the anterior superior and anterior inferior spinous processes 

 of the ilium, from the notch between them, and by a few fibres from the capsule 



