THE MUSCLES OF THE LOWER EXTREMITY. 175 



muscular part of the biceps is superseded by a strong, 

 round tendon, wliich, passing down between the muscles 

 of the fleshiest part of the upper and outer side of the 

 leg, becomes attached to a tuberosity on the external 

 aspect of the shaft of the fibula, about two centimetres 

 below its head. 



Thus this muscle becomes a powerful flexor of the leg 

 upon the thigh, but it has associated with it another 

 contrivance, so that when the leg is flexed the weight of 

 the posterior moiety of the body is in part transmitted 

 to the lower third of the femur. 



This contrivance consists in a tendinous loop, the 

 longer and at the same time the inner end of which is 

 attached just above the outer condyle of the femur, while 

 the shorter end merges with the fascia of the supcro- 

 median aspect of the outer head of the gastrocnemius, and 

 the deeper muscles immediately beneath it. The tendon of 

 insertion of the biceps passes through the bight of this 

 exquisite little arrangement, and, in addition to the use 

 already assigned to it, as Owen says, it enables the 

 biceps to effect a more rapid and extensive inflection of 

 the leg than it otherwise could have produced by the 

 simple contraction of its fibres. 



Coming to consider these muscles (the biceps flexor 

 cruris, vastus internus, and the extensor femoris), in such 

 a form as Geococcyx calif ornianus, I have elsewhere re- 

 marked that " the hiceps flexor cruris (Fig. 63 his) arises 

 by carneous fibres upon quite an extensive portion of the 

 under surface of the over-curled part of the ilium behind 

 the acetabulum, and by a long tendinous slip w^hich comes 

 off from the free anterior margin of this part of the ilium. 

 The fibres converge as they pass downwards, and unite to 

 form a somewhat flattened muscle. Opposite the head 

 of the tibia, the biceps terminates in a round tendon, of 



