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FLEXOR LONGUS DIGITORUM. 



Deep Layer. 



Popliteus, 



Flexor longus pollicis, 

 ^ Flexor longus digitorum, 

 </Tibialis posticus. 



Dissection. After the removal of the soleus, the deep layer will be found 

 bound down by an intermuscular fascia which is to be dissected away ; 

 the muscles may then be examined. 



The POPLITEUS muscle (poples, the ham of the leg) forms the floor of 

 the popliteal region at its lower part, and is bound tightly down by a strong 

 fascia derived from the middle slip of the tendon of the semi-membranosus 

 muscle. It arises by a rounded tendon from a deep groove on the outer 

 Fig. 134.* side of the external condyle of the femur, beneath the ex- 

 ternal lateral ligament ; and spreading obliquely over the 

 head of the tibia, is inserted into the surface of bone above 

 its oblique line. This line is called, from being the limit 

 of insertion of the popliteal muscle, the popliteal line. 



Relations. By its superficial surface with a thick fascia 

 which separates it from the two heads of the gastrocne- 

 mius, the plantaris, and the popliteal vessels and nerve. 

 By its deep surface with the synovial membrane of the knee 

 joint and with the upper part of the tibia. 



The FLEXOR LONGUS POLLICIS is the most superficial 

 of the next three muscles. It arises from the lower two- 

 thirds of the fibula, and passes through a groove in the 

 astragalus and os calcis, which is converted by tendinous 

 fibres into a distinct sheath lined by a synovial mem- 

 brane, into the sole of the foot ; it is inserted into the base 

 of the last phalanx of the great toe. 



Relations. By its superficial surface with the intermus- 

 cular fascia, which separates it from the soleus and tendo 

 Achillis. By its deep surface with the tibialis posticus, 

 fibula, fibular vessels, interosseous membrane, and ankle 

 joint. By its outer border with the peroneus longus 

 and brevis. By its inner border with the flexor longus 

 digitorum. In the foot, the tendon of the flexor longus 

 pollicis is connected with that of the flexor longus 

 digitorum by a short tendinous slip. 



The FLEXOR LONGUS DIGITORUM (perforans) arises 

 from the surface of the tibia, immediately below the popliteal line. Its 

 tendon nasses through a sheath common to it and the tibialis" posticus be- 

 hind the inner malleolus ; it then passes through a second sheath which is 



* The deep layer of muscles of the posterior tibial region. 1. The lower extremity 

 of the femur. 2. The ligamentum posticum Winslowii. 3. The tendon of the semi- 

 membranosus muscle dividing into its three slips. 4. The internal lateral ligament of 

 -he knee joint. 5. The external lateral ligament. 6. The popliteus muscle. 7. The 

 flexor longus digitorum. 8. The tibialis posticus, 9. The flexor longus pollicis. 1". 

 The peroneus longusmuscle. 11. The peroneus brevis. 12. The tendo Achillis divided 

 near its insertion into the os calcis. 13. The tendons of the tibialis posticus and flexor 

 longus digitorum muscles, just as they are about to pass beneath the internal annular 

 ligament of the ankle; the interval between the latter tendon and the tendon of the 

 flexor longus pollicis is occupied by the posterior tibial vessels and nerve. 



