278 ANATOMY OF THE RABBIT 



tions of the leg. They form the boundaries of the popHteal fossa. 



(a) The sartorius. Origin: Posterior portion of the inguinal 

 ligament, especially its sacral extension. Insertion: Medial 

 condyle of the tibia. This muscle is an extremely thin and 

 narrow band of fibres, lying on the more anterior portion 

 of the medial surface of the thigh. It is fused distally 

 with the gracilis, and is a flexor only through its connection 

 with the latter, since its position is that of a rotator. 



(b) The gracilis. Origin: The entire extent of the pubic 

 symphysis. Insertion: Through a broad tendinous expan- 

 sion ending in the fascia of the proximal portion of the 

 medial surface of the leg. The muscle forms a broad, 

 comparatively thin sheet, covering the posterior portion 

 of the medial surface of the thigh. Its insertion tendon is 

 perforated by the great saphenous artery and vein and the 

 greater saphenous nerve. 



The sartorius and gracilis should be raised from the 

 surface and divided. 



(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 tri- 

 angular 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 

 (see below). 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. 



Directions for freeing the biceps and dividing its first portion 

 have been given on page 274, this procedure being necessary to 

 expose the short thigh muscles. The freeing of the second portion 

 should now be completed, an incision first following the sciatic vein to 

 the posterior margin of the muscle, and the muscle should be divided. 



