INTERNAL FEMORAL REGION. 249 



similarity of action. They extend the leg upon the thigh, and obtain a 

 great increase of power by their attachment to the patella, which acts as a 

 fulcrum. Taking their fixed point from the tibia, they steady the femur 

 upon the leg, and the rectus, by being attached to the pelvis, serves to 

 balance the trunk upon the lower extremity. 



Internal Femoral Region. 



Iliacus internus, Adductor brevis, 



Psoas magrms, Adductor magnus, 



Pectineus, Gracilis. 

 Adductor longus, 



Dissection. These muscles are exposed by the removal of the inner 

 flap of integument recommended in the dissection of the anterior femoral 

 region. The iliacus and psoas arising from within the abdomen, can only 

 be seen in their entire extent after the removal of the viscera from that 

 cavity. 



The ILIACUS INTERNUS is a flat radiated muscle. It arises from the 

 whole extent of the inner concave surface of the ilium ; and, after joining 

 with the tendon of the psoas, is inserted into the trochanter minor of the 

 femur. A few fibres of this muscle are derived from the base of the sa- 

 crum, and others from the capsular ligament of the hip joint. 



Relations. By its anterior surface, within the pelvis, with the external 

 cutaneous nerve, and with the iliac fascia, which separates the muscle 

 from the peritoneum, on the right from the caecum, and on the left from 

 the sigmoid flexure of the colon ; externally to the pelvis with the fascia 

 lata, rectus, and sartorius. By its posterior surface with the iliac fossa, 

 margin of the pelvis, and with the capsule of the hip joint, a synovial 

 bursa of large size being interposed, which is sometimes continuous with 

 the synovial membrane of the articulation. By its inner border with the 

 psoas magnus and crural nerve. 



The PSOAS MAGNUS (-^oa, 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 trans- 

 verse 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 ligament, to its insertion. The 

 tendon of the psoas magnus unites with that of the iliacus, and the con- 

 joined tendon is inserted into the posterior part of the trochanter minor, a 

 bursa being interposed. 



Relations. By its anterior surface, with the ligamentum arcuatum in- 

 ternum 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 ar- 

 teries, quadratus lumborum, from which it is separated by the anterioi 

 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 tlte posterior part of the muscle 



