THE LOWER EXTREMITY, ANTERIOR. 565 



abduct the thigh, to rotate the thigh inward ; through the 

 iliotibial band, to flex the leg, to rotate the leg outward, 

 when flexed. 



Acting from below it preserves the horizontal position of 

 the pelvis upon the femur (in this connection acting with 

 the gluteus maximus), and rotates it to the same side. 



Bectus Femoris. Fig. 1 1 7. 



Origin. By the straight (anterior) tendon from the ante- 

 rior inferior spine of the ilium, by the reflected (posterior) 

 tendon from the outer surface of the ilium just above the 

 acetabulum. 



Insertion. Into the upper border of the patella. 



Nerve Supply. The anterior crural. 



Action. To extend the leg on the thigh, or vice versa ; 

 to flex the thigh on the abdomen or the reverse. 



Pectineus. Figs. 117, 120. 



Origin. From the iliopectineal line and the triangular 

 surface of bone in front of it, between the iliopectineal 

 (pubal) eminence and the spine of the pubes. From the 

 under inner surface of the fascia lata covering the muscle. 



Insertion. Into a line extending from the back of the 

 lesser trochanter to the linea aspera of the femur. 



Nerve Supply. The obturator, anterior crural (constant), 

 and the accessory obturator (when present). 



Action. To flex the thigh, to adduct the thigh, to rotate 

 the thigh slightly externally when it is partially flexed, but 

 if the thigh is kept extended it will rotate it internally in the 

 same way that the iliopsoas muscle does. The explanation 

 is this : the centre of motion is at the hip-joint ; the mus- 

 cular attachments are to the shaft of the femur two inches 

 external to the centre of motion ; flexion being resisted the 



