326 MUSCLES AND FASCIAE. 



Remove this fascia, and the muscles of the iliac region will be exposed. 

 The Psoas Magnus (fig. 187) 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 sides of 

 the bodies, from the corresponding intervertebral substances, and from the front 

 of the bases of the transverse processes of the last dorsal and all the lumbar ver- 

 tebras. The muscle is connected to the bodies of the vertebras by five slips ; each 

 slip is attached to the upper and lower margins of the two vertebrae, and to the 

 intervertebral substance between them, the slips themselves being connected by 

 tendinous arches extending across the constricted part of the bodies, beneath which 

 pass the lumbar arteries and sympathetic nervous filaments. 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 vertebrae ; the last, to the 

 contiguous margins of the fourth and fifth lumbar, and 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 

 I 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 vertebras and the 

 Quadratus lumborum, from which it is separated by the anterior 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 its lower part. 

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

 By its inner side, with the bodies of the lumbar vertebras, the lumbar arteries, the 

 sympathetic ganglia, and its communicating branches with the spinal nerves ; the 

 lumbar glands, with 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 capsular 

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

 times 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 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 foodies 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, which is inserted into 

 the ilio-pectineal eminence, being 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. 



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 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, 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 tro- 

 chanter to the linea aspera. 



Relations. Within the Pelvis: by its anterior surface, with the iliac fascia, 

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

 nerve ; on the right side, with the cascum ; on the left side, with the sigmoid 

 flexure of the colon. By its posterior surface, with the iliac fossa. By its inner 

 border, with the Psoas magnus, and anterior crural nerve. In the Tltigli, it is in 



