THE LOWER LIMB 521 



the posterior tibial vessek and ner\'e, are covered by the posterior 

 or transverse intermuscular septum. 



Popliteus — Origin. — (i) By a narrow round tendon from the 

 front part of the horizontal portion of the popliteal groove on the 

 outer surface of the external condyle of the femur, and (2) slightly 

 from the posterior ligament of the knee-joint. 



Insertion. — (i) The popliteal surface of the tibia, and (2) the 

 popliteal fascia which covers the muscle. 



Nerve-supply. — ^The internal popliteal nerve. The branch from 

 this ner\e descends over the posterior surface of the muscle, and, 

 turning round its lower border, enters the deep or anterior surface 

 in its lower part. 



Action. — ^The muscle is a feeble flexor of the leg upon the thigh, 

 and, when the knee-joint has been flexed, it acts as an internal 

 rotator of the leg. 



The tendon of origin is within the capsular Ugament, and beneath 

 the long external lateral hgament, of the knee-joint. Whilst within 

 the joint it is in contact with the posterior and outer aspect of the 

 external semilunar fibro-cartilage, which it grooves. It then 

 pierces the capsule, and the fleshy 'ibres spread out in the manner 

 of a fan as they diverge do^vn wards and inwards. The popliteal 

 "fascia, which covers the muscle, represents part of the insertion of 

 the semimembranosus muscle, and it is attached to the oblique or 

 popliteal line of the tibia. 



Flexor Longus Digltorum (flexor perforans) — Origin. — (i) The 

 inner division of the posterior surface of the shaft of the tibia, 

 commencing at the oblique or popliteal line, and extending down- 

 wards over the middle two-fourths of the bone ; (2) the posterior 

 intermuscular septum which covers the muscle ; and (3) the inter- 

 muscular septum bet\veen it and the tibiahs posticus on its outer 

 side. 



Insertion. — By means of four tendons which go to the four outer 

 toes, where each is inserted into the plantar surface of the base or 

 proximal end of the distal phalanx. 



Nerve-supply. — ^The jxjsterior tibial nerve. 



Action. — (i)The muscle acts as a flexor of the distal phalanges 

 of the four outer toes, and (2) when these have been flexed, it acts 

 as an extensor of the foot upon the leg. 



The muscle crosses behind the tibiahs posticus obliquely from 

 within outwards in the lower third of the leg. The tendon passes 

 behind the internal malleolus and beneath the internal annular 

 I ligament, Mng behind and slightly external to the tendon of the 

 i tibialis posticus, and occupying a special, purely fibrous compart- 

 ; ment, in which it is invested by a distinct synovial sheath. It 

 I then enters the sole of the foot, where it passes for\s'ards and out- 

 i wards to the middle line, crossing beneath the tendon of the flexor 

 1 longus hallucis, from which it receives a slip. On reaching the 

 i middle hne it gives insertion to the flexor or musculus accessorius, 

 ] and immediately afterwards it divides about the centre into four 



to 



