550 MUSCLES OF THE ABDOMEN-. 



The psoas magnus t-oa, the loins, (Fig. 172,) is round, 

 long, thick, fleshy above, and arises by two planes, the 

 first fleshy from the sides of the bodies of the lumbar and 

 last one or two dorsal vertebrae, the second from the trans- 

 verse processes of all the lumbar vertebrae ; the two sets 

 unite to form an oblong muscle, which descends along the 

 lateral margin of the brim of the pelvis, beneath Poupart's 

 ligament, and about its centre, and is inserted by a tendon 

 common to it and the iliacus internus, into the trochanter 

 minor, and fleshy for about an inch below into the linea 

 aspera. A bursa is found between this tendon and the 

 trochanter, and also between it and the pubis as it passes 

 over. Function. To flex the thigh on the pelvis, or the 

 body on the thigh. It can also rotate the thigh outward. 



The psoas parvus (Fig. 1*72) has a short belly and along 

 tendon. It arises fleshy from the sides of the bodies of 

 the last dorsal and first lumbar vertebrae, and from the 

 intervertebral ligament. Its tendon begins about the fourth 

 lumbar vertebra, and passes down to be inserted into the 

 linea innominata, and by a broad aponeurotic expansion into 

 the fascia iliaca. This muscle is situated at the anterior and 

 internal edge of the psoas magnus, and is often wanting. 

 Function. To flex the body or raise the pelvis, and draw 

 up the sheath of the femoral vessels, which, it is thought, 

 in sudden flexion will lessen the liability to injury of these 

 vessels. 



The iliacus internus (Fig. 172) is situated on the outside of 

 the psoas magnus, and fills up the venter of the ilium. It 

 arises fleshy from the last lumbar vertebra by its transverse 

 process, from the ilio-lumbar ligament, inner margin of the 

 crista ilii, venter of the ilium, and intervening notch be- 

 tween the two anterior spinous processes of the ilium also 

 from the capsule of the hip joint. It unites with the tendon 

 of the psoas magnus, and is inserted along with it into the 

 trochanter minor. A large bursa is found between this 

 common tendon and the capsule of the hip joint, which 

 occasionally communicates with the cavity of the joint. 



Function. The same as the psoas magnus. 



