FLEXOR LONGUS POLLICIS. 267 



dancing, leaping, &c. Taking their fixed point from below, they 

 steady the leg upon the foot. 



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 dis- 

 sected 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 side of the external condyle of the femur, beneath 

 the external 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 popliteus 

 muscle, the popliteal line. 



Relations. By its superficial surface with a thick fascia which 

 separates it from the two heads of the gastrocnemius, the plantaris, 

 and the popliteal vessels and nerve. By its deep surface with the sy- 

 novial 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 con- 

 verted by tendinous fibres into a distinct sheath lined by a synovial 

 membrane, 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 intermuscular fascia, 

 which separates it from the soleus and tendo Achillis. By its deep sur- 

 face with the tibialis posticus, fibula, fibular vessels, interosseous mem- 

 brane, 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 sur- 

 face of the tibia, immediately below the popliteal line. Its tendon 

 passes through a sheath common to it and the tibialis posticus behind 

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

 connected with a groove in the astragalus and os calcis, into the sole of 

 the foot, where it divides into four tendons, which are inserted into the 

 base of the last phalanx of the four lesser toes, perforating the tendons 

 of the flexor brevis digitorum. 



Relations. By its superficial surface with the intermuscular fascia, 

 which separates it from the soleus, and with the posterior tibial vessels 



