148 Anatomy of the Rabbit. 



(c) 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. 



To free the biceps and divide it : Incision along the aponeurotic 

 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. 

 The sciatic vein lies on the lateral surface towards the ischial 

 tuberosity. An incision along it will free the superficial 

 head pf 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 to expose the short muscles of the thigh. 



(d) 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. 



(e) The semimembranosus. Origin in two portions: 



First (superficial) portion : Fascia covering the first head of the 



biceps. ' 



Second (deep) portion : Lateral process of the ischial tuberosity. 

 Insertion: In common with the gracilis on the fascia of the 

 proximal portion of the medial surface of the leg. This 

 fascia is contracted into two ligaments, one of which carries 

 • the insertion of the muscle to the distal end of. the tibial 

 tuberosity, the other to the distal end of the leg, where it joins 

 the tendon of the heel (tendo calcaneus). 



(f) The semitendinosus. Origin: Ischial tuberosity. Insertion: 

 Medial condyle of the tibia. The muscle is completely en- 

 closed by the adductor magnus, which must be split to 

 expose it. 



