THE MUSCLES OF THE LOWER LIMB. 623 



THE MUSCLES OF THE LOWER LIMB. 



In describing the muscles of the lower limb a classification similar to that which 

 was employed for the upper limb muscles will be followed. Owing, however, to the 

 firm articulation of the innominate bones to the sacrum, the muscles extending 

 between the axial skeleton and the pelvic girdle are greatly reduced, and those 

 (such as the psoas) which might be included in this group are continued to the 

 femur, and for present purposes are more conveniently grouped with the muscles 

 extending from the girdle to the femur. 



There is also, in the lower limb, a greater number of muscles passing over two 

 joints ; indeed, many of the muscles which are inserted into the upper portions of 

 the leg bones take their origin from the pelvic girdle. Most of these seem to be, 

 primarily, members of the femoral group of musfles and will be so classified in the 

 succeeding pages, but one (the gracilis), at least, appears to belong to the group 

 extending from the girdle to the femur. 



THE MUSCLES EXTENDING FROM THE PELVIC GIRDLE 



TO THE FEMUR. 



(a) THE PRE-AXIAL MUSCLES. 



I. Psoas Magnus (Fig. 598). 



Attachments. — This muscle (m. psoas major) arises from the sides of the 

 bodies of the twelfth thoracic and all the lumbar vertebrae and from the transverse" 

 processes of the lumbar vertebrae. Its fibres pass directly downward and slightly 

 forward over the superior ramus of the pubis and are mserted by a tendon, in com- 

 mon with the iliacus, into the lesser trochanter of the femur. 



Nerve-Supply. — By branches from the lumbar plexus from the second, third, 

 and fourth lumbar nerves. 



Action. — To bend the spinal column laterally and to flex the body and pelvis 

 upon the femur. Acting from above, it flexes the thigh and rotates it outward. 



Relations. — The psoas magnus lies along the side of the lumbar vertebrae, 

 resting upon their transverse processes and the medial portion of the quadratus 

 lumborun-^ Extending as high as the last thoracic vertebra, it passes beneath the 

 internal arcuate ligament, or medial lumbo-costal arch, of the diaphragm, and below 

 it passes beneath Poupart's ligament to reach the thigh. In its abdominal portion 

 it is in relation ventrally with the peritoneum, on the right side with the ascending 

 colon and duodenum, and on the left side with the descending colon and pancreas. 

 The inner border of the kidney overlaps the lateral portion of the muscle, and the 

 ureter and spermatic (or ovarian) arteries descend obliquely along it. The inferior 

 vena cava lies in front of the right muscle. The nerves formed by the lumbar 

 plexus perforate the muscle, and the genito-crural nerve passes down on its anterior 

 surface. In the pelvis the external iliac vessels lie along its medial border, and it is 

 crossed, just before it passes beneath Poupart's ligament, by the vas deferens. In 

 the thigh it forms a portion of the floor of the femoral or Scarpa's triangle, and lies 

 between the iliacus and pectineus muscles, behind the femoral vessels. As the ten- 

 don which is common to it and the iliacus passes over the hip-joint it rests upon a 

 rather large bursa (bursa iliopectinea) ; just above the insertion a second bursa (bursa 

 iliaca subtendinea) intervenes between the tendon and the femur. 



