POSTERIOR FEMORAL REGION. 261 



ternal saphenous vein crosses it lying superficially to the fascia lata. 

 By its outer or deep surface with the adductor longus, brevis, and mag- 

 nus, and the internal lateral ligament of the knee-joint, from which it 

 is separated by a synovial bursa common to the tendons of the gracilis 

 and semi-tendinosus. 



Actions. The iliacus, psoas, pectineus, and adductor longus muscles 

 bend the thigh upon the pelvis, and, at the same time, from the obli- 

 quity of their insertion into the lesser trochanter and linea aspera, 

 rotate the entire limb outwards ; the pectineus and adductors adduct 

 the thigh powerfully ; and from the manner of their insertion into the 

 linea aspera, they assist in rotating the limb outwards. The gracilis 

 is likewise an adductor of the thigh ; but contributes also to the flexion 

 of the leg, by its attachment to the inner tuberosity of the tibia. 



Posterior Femoral Region. 



Biceps, 



Semi-tendinosus, 



Semi-membranosus. 



Dissection Remove the integument and fascia on the posterior 

 part of the thigh by two flaps, as on the anterior region, and turn 

 aside the gluteus maximus from the upper part ; the muscles may then 

 be examined. 



The BICEPS FEMORIS (bis, double, x.i$o.\^ head) arises by two 

 heads, one by a common tendon with the semi-tendinosus ; the other 

 muscular and much shorter, from the lower two thirds of the external 

 border of the linea aspera. This muscle forms the outer hamstring, and 

 is inserted by a strong tendon into the head of the fibula ; a portion of 

 the tendon is continued downwards into the fascia of the leg, and 

 another is attached to the outer tuberosity of the tibia. 



Relations. By its superficial or posterior surface with the gluteus 

 maximus and fascia lata. By its deep or anterior surface with the 

 semi-membranosus, adductor magnus, vastus externus, the great sciatic 

 nerve, popliteal artery and vein, and near its insertion with the exter- 

 nal head of the gastrocnemius, and plantaris. By its inner border with 

 the semi-tendinosus, and in the popliteal space with the popliteal ar- 

 tery and vein. 



The SEMI-TENDINOSUS, remarkable for its long tendon, arises in 

 common with the long head of the biceps, from the tuberosity of the 

 ischium ; the two muscles being closely united for several inches below 

 their origin. It is inserted into the inner tuberosity of the tibia. 



Relations. By its superficial surface with the gluteus maximus, 

 fascia lata, and at its insertion with the synovial bursa which separates 

 its tendon from the expansion of the sartorius. By its deep surface 

 with the semi-membranosus, adductor magnus, internal head of the 

 gastrocnemius, and internal lateral ligament of the knee-joint, the sy- 

 novial bursa common to it and the tendon of the gracilis being inter- 



