610 A MANUAL OF ANATOMY. 



and in flexion to rotate the leg inward (pronation). (2) 

 Upon the thigh, it has the same action as the semitendi- 

 nosus. (3) Upon the body, the muscle acts as the semi- 

 tendinosus. 



The Great Sciatic Nerve. Figs. 112, 114, 126, 127. 



This is the largest nerve in the body. It is formed 

 within the pelvis but close to the great sacrosciatic foramen, 

 by the convergence of the lumbosacral cord, the first, 

 second, and third sacral nerves (anterior branches, see page 



553). 



It emerges through the great sacrosciatic foramen being 

 below the pyriformis muscle, and descends into the thigh 

 until at its lower third, when it divides into the external and 

 internal popliteal nerves. In its course the great sciatic 

 nerve lies between the tuberosity of the ischium and the 

 great trochanter, and crosses the gemellus superior, tendon 

 of the obturator internus, gemellus inferior (tendon of the 

 obturator externus), the quadratus femoris, and adductor 

 magnus muscles. 



It lies under the gluteus maximus, and long head of the 

 biceps muscles, and is covered by the fascia lata, superficial 

 fascia and the integument. 



In the upper part of its course it is accompanied by the 

 arteria comes nervi ischiadici. 



Branches. (i) Muscular, to the biceps, semitendinosus, 

 semimembranosus, and adductor magnus. (2) Articular, 

 to the hip and knee joints. The latter through the internal 

 and external popliteal branches. 



The Internal Pudic Nerve. See page 413. 



The Nerve to the Obturator Internus. 



This branch of the sacral plexus arises from the second 



