

BACK OF THE THIGH 249 



expanded insertion of the sartorius. A bursa mucosa lies 

 between the three tendons and the tibial collateral ligament 

 of the knee-joint. 



M. Semimembranosus. The semimembranosus muscle 

 arises from the lateral impression on the proximal part of the 

 tuberosity of the ischium (Fig. 74, p. 200). The tendon of 

 origin is broad at its attachment to the bone, and narrows as 

 it passes medially beneath the origin of the biceps femoris ; 

 it then expands again, and, passing distally and medially 

 anterior to the semitendinosus, is folded in such a manner 

 as to form a groove, in which the latter muscle lies. The 

 tendon of insertion is chiefly inserted into the groove on the 

 back of the medial condyle of the tibia, under cover of the 

 tibial collateral ligament of the knee-joint. Three additional 

 attachments, however, require to be noted. These are 

 effected by aponeurotic extensions from the tendon of in- 

 sertion (i) to the back of the knee-joint, forming a consider- 

 able part of the oblique popliteal ligament; (2) to the surface 

 of the popliteus muscle, which is covered by the expansion ; 

 and (3) to the tibial collateral ligament of the knee-joint. 



Nervus Ischiadicus (O.T. Great Sciatic Nerve). This large 

 nerve commences at the distal border of the great sciatic 

 foramen, and usually terminates about the middle of the 

 thigh by dividing into the tibial nerve and common peroneal 

 nerve. Its relations in the glutseal region have already been 

 studied. In the thigh it lies on the posterior surface of the 

 adductor magnus muscle, and is covered by the long head 

 of the biceps femoris. It gives branches to both heads of 

 the biceps, to the semitendinosus, to the semimembranosus, 

 and to the adductor magnus ; the branches to the two last- 

 named muscles arise by a common trunk. In a few cases it 

 may be observed to give off a long articular twig, which 

 enters the fossa poplitea and takes the place of the lateral 

 superior articular nerve which, as a rule, comes from the 

 common peroneal nerve. 



Dissection. To bring the adductor magnus more fully into view, and 

 to facilitate the cleaning of its posterior surface, and at the same time to 

 follow the terminal parts of the perforating arteries, the hamstring muscles 

 should be detached from their origins and thrown distally. First detach 

 the common tendon of the biceps femoris and semitendinosus from the 

 tuber ischiadicum. When this has been done the exact attachment of the 

 semimembranosus is displayed, and after this muscle has been again 

 examined, under the present more advantageous circumstances, it also 



