HAMSTRING MUSCLES. 5J7 



the knee joint. After supplying filaments to the vessels, the nerve enters 

 the articulation through the posterior ligament. 



The lymphatic glands of the popliteal space are situate around the 

 large arterial trunk. Two or three are ranged on the sides ; whilst one is 

 superficial to, and another beneath the vessel : they are joined by the deep 

 lymphatic vessels, and by the superficial set with the saphenous vein. 



THE BACK OF THE THIGH. 



Dissection (fig. 203). Now the popliteal space has been examined, the 

 student may proceed with the dissection of the back of the thigh. The 

 piece of skin between the buttock and the popliteal space should be di- 

 vided, and reflected to the sides. In the fat on the sides of the limb fine 

 offsets of the internal and external cutaneous nerves of the front of the 

 thigh may be found ; and along the middle line some filaments from the 

 small sciatic nerve pierce the fascia. 



Remove the deep fascia of the limb, taking care of the small sciatic 

 nerve and its artery. Lastly, clean the hamstring muscles ; trace out the 

 perforating arteries to the front of the thigh, and clean the branches of 

 the great sciatic nerve and profunda artery to the muscles. 



MUSCLES. The muscles behind the femur act mainly as flexors of the 

 knee joint. They extend from the pelvis to the bones of the leg, and are 

 named hamstrings from their cord-like appearance on the sides of the ham : 

 they are three in number, viz., biceps, semitendinosus, and semimembra- 

 nosus. The first of these lies on the outer, and the others on the inner 

 side of the popliteal space. 



The BICEPS (fig. 203, D ) has two heads of origin, long and short, which 

 are attached to the pelvis and the femur. The long head arises from an 

 impression on the back of the ischial tuberosity, in common with the 

 semitendinosus muscle. The short head is fixed to the femur below the 

 glutens maximus, viz., to all the linea aspera, to nearly the whole of the 

 line leading inferiorly to the outer condyle, and the external iritermuscular 

 septum. The fibres end inferiorly in a tendon, which is inserted into two 

 prominences on the head of the fibula by slips which embrace the exter- 

 nal lateral ligament ; and a slight piece is prolonged to the head of the 

 tibia. 



The muscle is superficial, except at the origin, where it is covered by 

 the gluteus : it rests on the upper part of the semimembranosus, and on 

 the great sciatic nerve and the adductor magnus muscle. On the inner 

 side is the semitendinosus as far as the ham. Its tendon gives offsets to 

 the deep fascia of the limb. 



Action. It can bend the knee if the leg-bones are not fixed, and after- 

 wards rotate out the tibia; and the long head, which passes upwards 

 beyond the femur, will extend the bent hip joint when the knee is straight. 



The leg being supported on the ground, the long head will assist in 

 balancing and erecting the pelvis ; and the short head will draw down the 

 femur so as to bend the knee in stooping. 



The SEMITENDINOSUS (fig. 203, E ) is a slender muscle and receives its 

 name from appearance. It arises from the tuberosity of the hip bone 

 with the long head of the biceps, and by fleshy fibres from the tendon of 

 that muscle. Inferiorly it is inserted into the inner surface of the tibia, 

 close below the gracil's, and for a similar extent. 



Tais muscle, like the biceps, is partly covered by the gluteus maximus. 



