FLEXOR DIGITORUM LONGUS 



2? 17 



489 



36 i 



D 



externally by the laciniate (internal annular) ligament. In the sole the tendon of 

 the long flexor of the big toe passes under (deeper than) the tendon of the flexor 

 digitorum, to which it gives a slip, and is inserted into the terminal phalanx of 

 the big toe. The tendon of the long flexor of the toes passes obliquely across the 

 sole, is joined by the quadratus plantae (flexor accessorius), and gives rise to a 

 tendon for the terminal phalanx of each of the four lateral toes. From these 

 tendons the lumbrical muscles arise. The tibiahs posterior has an extensive 

 insertion on the plantar surface of the tarsus. 



The long flexors act chiefly on the toes. Together with the tibiahs posterior 

 they invert and extend the foot. 



The long flexors of the toes probably represent the flexor profundus and the flexor poUicis 

 longus of the forearm. The tendons of the deep flexors of the forearm do not, however, cross 

 like those of the long flexors of the toes. In the lower mammals there is much variation in the 

 toes to which the tibial and fibular flexors are distributed. The tibialis posterior has no certain 

 representative in the forearm. The rare ulno-carpeus may represent it. 



The flexor digitorum longus (figs. 416, 420). — Origin. — From the popHteal Une, the medial 

 side of the second quarter of the dorsal surface of the tibia, the fibrous septum between the 

 muscle and the tibialis posterior, and the fascia covering its proximal extremity. 



Structure and insertion. — From these areas of origin the fibre-bundles run obliquely to be 

 inserted in a penniform manner on a tendon which begins in the proximal quarter of the 

 muscle as a narrow septum, and more distally becomes a strong band on the medial margin. 

 The insertion of the fibre-bundles continues nearly to the medial malleolus. From here the 

 tendon passes behind the medial malleolus, dorso-lateral to the tendon of the tibiahs posterior, 

 crosses the posterior talo-tibial ligament, and passes along the medial margin of the sustenta- 

 culum tah into the sole of the foot. Here it crosses the tendon of the flexor hallucis longus, 

 from which it receives a tendinous slip, and divides into four parts, which pass to the second to 

 the fifth toes. Each tendon is bound to the phalanges of the toe to which it passes by a fibrous 

 sheath. Superficial to it in the sheath lies a tendon of the flexor digitorum brevis, which the 



