BRANCHES OF PROFUNDA ARTERY. 599 



tendon. The muscle is attached above to the highest impression on the 

 back of the tuber ischii, above and external to the semitendinosus and 

 biceps ; and it is inserted below into the hinder and inner part of the head 

 of the tibia. 



The muscle is thick and fleshy inferiorly, where- it bounds the popliteal 

 space. On it lies the semitendinosus, which is lodged in a hollow in the 

 upper tendon; and beneath it is the adductor magnus. Along the outer 

 border lie the great sciatic, and internal popliteal nerves. Between its 

 tendon and the inner head of the gastrocnemius is a large bursa. The 

 insertion of the muscle will be dissected with the knee-joint. 



Action. This hamstring is united with the preceding in its action, for 

 it bends the knee and rotates in the tibia ; and with the knee straight it 

 will limit flexion of the hip, or extend this joint after the femur has been 

 carried forwards. 



When the foot rests on the ground, the semimembranosus acts altogether 

 on the pelvis. 



The GREAT SCIATIC NERVE (fig. 203, 2 ) lies on the adductor magnus 

 muscle below the buttock, and divides it into the two popliteal nerves 

 about the middle of the thigh, though its point of bifurcation may be car- 

 ried upwards as far as the pelvis. In this extent the nerve lies along the 

 outer border of the semimembranosus, and is crossed by the long head of 

 the biceps. 



Branches. At the upper part of the thigh it supplies large branches to 

 the flexor muscles, and a small one to the adductor magnus. 



SMALL SCIATIC NERVE (fig. 203, x ). Between the gluteus maximus and 

 the ham this small nerve is close beneath the fascia ; but it becomes cuta- 

 neous below the knee, and accompanies the external saphenous vein for a 

 short distance. 



Small cutaneous filaments pierce the fascia of the thigh ; and the largest 

 of these arises near the popliteal space. 



Dissection. To see the posterior surface of the adductor magnus, and 

 the branches of the perforating and muscular arteries, the hamstring 

 muscles must be detached from the hip bone and thrown down ; and the 

 branches of arteries and nerves they receive are to be dissected out with 

 care. All the parts are to be cleaned. 



ADDUCTOR MAGNUS MUSCLE (fig. 203, c ). At its posterior aspect the 

 large adductor is altogether fleshy, even at the opening for the femoral 

 artery ; and the fibres from the pubic arch appear to form a part almost 

 distinct from those connected with the tuberosity of the hip bone. In 

 contact with this surface are the hamstring muscles and the great sciatic 

 nerve. 



Ending of the perforating arteries (fig. 203, c, d, e). These branches 

 of the profunda appear through the adductor magnus close to the femur, 

 and are directed out through the short head of the biceps and the outer 

 intermuscular septum to the vasti muscles ; but as the first branch is 

 placed higher than the attachment of the biceps, it pierces the gluteus 

 maximus in its course. In the vasti they anastomose together, and with 

 the descending branches of the external circumflex artery. 



Muscular branches are furnished by the perforating arteries to the 

 heads of the biceps ; and a cutaneous offset is given by each to the tegu- 

 ments of the outer part of the thigh, along the line of the outer inter- 

 muscular septum. 



