FLEXOR LONGUS DIGITORUM. 



265 



The three remaining muscles of this group are bound down, together by a deep 

 fascia, which extends between the tibia and fibula, and separates them from the 

 soleus. 



The flexor longus digitorum pedis muscle, or flexor perforans, arises from 

 the inner portion of the posterior surface of the tibia (see p. 126), its attachment 



Fig. 258.- 



-DEEP POSTERIOR MUSCLES OF THE LEO. (Allen 

 Thomson. ) J 



, popliteal surface of the femur ; 6, surface of the upper third 

 of the fibula, from which the soleus muscle has been removed ; c, 

 internal malleolus ; d, external malleolus ; e, tuberosity of the os 

 calcis, with a part of the tendo Achillis inserted into it, and the 

 plantaris on its inner side ; 1, inner head of the gastrocnemius, 

 cut short ; 2, outer head ; 3, plantaris ; 4, tendon of the semi- 

 membranosus muscle near its insertion, seen spreading in three 

 portions, viz., to the tibia, to the popliteal fascia, and to the 

 posterior ligament ; 5, tendon of the biceps inserted into the head 

 of the fibula ; 6, popliteus muscle ; 7, upper part of the origin of 

 the soleus from the fibula, cut short ; 7', line of its tibial origin ; 

 between these figures is seen the perforation in the upper part of 

 the interosseous membrane ; 8, tibialis posticus ; 8', its tendon, 

 passing between the flexor longus digitorum and the tibia ; 9, flexor 

 longus digitorum; 9' its tendon, with that of the tibialis posticus, 

 passing behind the internal malleolus ; 10, flexor longus hallucis ' r 

 10', placed beside its tendon, where it passes over the tibia and 

 astragalus ; 11, peroneus longus ; 11', its tendon behind that of 

 the peroneus brevis, passing down behind the external malleolus ; 

 12, peroneus brevis. 



extending over the middle two-fourths of the length 



of the bone ; it likewise receives fibres from a thin 



aponeurosis which covers the tibialis posticus, and is 



attached to the inner border of the fibula, and from 



which the flexor longus hallucis also takes origin. Its 



tendon descends behind the internal malleolus, lying 



outside that of the tibialis posticus, and invested by 



a distinct fibrous and synovial sheath ; it is then 



directed obliquely forwards and outwards into the sole 



of the foot, crossing superficially the tendon of the 



flexor longus hallucis, to which it is connected by 



a tendinous slip ; it there divides into four parts, 



which pass forwards to be inserted into the terminal 



phalanges of the four smaller toes. Each digital 



tendon enters a fibrous sheath on the toe to which it 



belongs, perforates the corresponding tendon of the 



flexor brevis digitorum, and is invested with synovial 



membrane and connected by vincula accessoria to the " \y LiQ% 



phalanges ; the whole arrangement being essentially 



the same as that which has been already described in 



the fingers (see p. 228). 



Relations. The belly of the muscle rests upon the tibia 

 and upon the tibialis posticus, crossing- the latter obliquely 

 in the lower third of the leg 1 . It is covered at the upper part 



by the soleus and inferiorly by the aponeurosis of the leg. Upon it also lie the posterior 

 tibial vessels and nerve. 



Varieties. A supplementary head, flexor accessories longus digitorum, is not unfrequently 

 found arising from the fibula, or the tibia, or the deep fascia, and ending in a tendon which, 

 after passing beneath the internal annular ligament, joins the tendon of the long flexor, or 



