THE POSTERIOR LIMB 223 
by the great saphenous artery and vein and the greater saphenous 
nerve. 
(c) 
(d) 
The sartorius and gracilis should be raised from the surface and 
divided. 
The biceps femoris: Origin in two portions: 
First portion (caput breve): Spinous processes of three 
posterior sacral and three anterior caudal vertebrae. This 
portion is triangular in shape, the distal end, or apex of the 
triangle, passing into a thin flat tendon which is inserted on 
the lateral margin of the patella. 
Second portion (caput longum): Dorsal surface of the 
ischial tuberosity, fused with the adductor magnus, and the 
lateral process, fused with the second, or deep portion of 
the semimembranosus. This portion is also triangular, the 
base being distal and providing a broad insertion on the 
fascia of the proximal third of the lateral surface of the 
leg. The first, or superficial head of the semimembranosus, 
covers this portion at its origin, which is also crossed by the 
sciatic vein. 
To free the biceps and divide it: Incision along the apon- 
eurotic line joining the tip of the great trochanter with the 
sacrum; also distad along the intermuscular septum of the 
lateral surface of the thigh from the great trochanter to the 
knee. An incision along the first portion of the sciatic 
vein will free the superficial head of the semimembranosus 
from the biceps. Raise the biceps slightly by working the 
handle of the scalpel under its distal portion. Divide the 
muscle from its posterior margin, being careful not to injure 
the slender tensor fasciae cruris muscle and the branches of 
the sciatic nerve which lie beneath it. The first head of the 
biceps may be separated and reflected in order 40 €xpose the 
short muscles of the thigh. . 
The tensor fasciae cruris. Origin: By a long, slender 
tendon, from the transverse process of the fourth sacral 
vertebra. Insertion: Lateral fascia of the leg. This slender 
muscular slip underlies the biceps femoris. 
