404 MUSCLES AND FASCIAE. 



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 

 bloodvessels 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 

 vertebra ; 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 behind 

 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 ligamentum arcuatum internum, the kidney, 

 Psoas Parvus, renal vessels, ureter, spermatic vessels, genito-crural nerve, the 

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

 and vein. By its posterior surface, with the transverse processes of the lumbar 

 vertebra and the Quadratus Lumborum, from which it is separated by the an- 

 terior lamella of the aponeurosis of the Transversalis. 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 vertebrae, the lumbar arteries, the sympathetic 

 ganglia, and their branches of communication with the spinal nerves; the 

 lumbar glands ; the vena cava on the right, and the aorta on the left side. In 

 the thigh it is in relation, in front, with the fascia lata ; behind, with the cap- 

 sular ligament of the hip, from which it is separated by a synovial bursa, which 

 sometimes 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 preceding. 

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

 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 continuous, by its outer border, with the iliac fascia. 

 This muscle is present, according to M. Theile, in one out of every twenty 

 subjects examined. 



Delations. It is covered by the peritoneum, and at its origin by the liga- 

 mentum arcuatum internum ; it rests on the Psoas Magnus. 



The Iliacus is a flat radiated muscle, which fills up the whole of the internal 

 iliac fossa. It arises from the iliac fossa, and 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 of the hip- 

 joint. The fibres converge to be inserted into the outer side of the tendon of 

 the Psoas, some of them being prolonged into the oblique line which extends 

 from the lesser trochanter to the linea aspera. 



Relations. 11V////// ///< pelvis: by its anterior surface, with the iliac fascia, which 

 separates the muscle from the peritoneum, and with the external cutaneous 

 nerve; on the ri.irlit side, with the caecum; on the loft side, with the sigmoid 

 ili-xure of the colon. By its posterior surface, with the iliac fossa. By its inner 

 />.- /</</-, with the Psoas Magnus, and anterior crural nerve. In the thigh, it is in 

 relation, by its anterior surface, with the fascia lata, Rectus and Sartprius ; be- 

 hind, with the capsule of the hip-joint, a synovial bursa common to it and the 

 Psoas Magnus being interposed. 



Nerves. The Psoas is supplied by the anterior branches of the lumbar 

 nerves, the Iliacus by the anterior crural. 



