238 POSTERIOR TIBIAL REGION. 



(the body supported on the tibia) in the middle, and the power (these 

 muscles) at the other extremity. 



They are, therefore, the walking muscles, and perform all move- 

 ments that require the support of the whole body from the ground, 

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

 steady the leg upon the foot. 



Deep layer. 



Popliteus, 



Flexor longus pollicis, 

 Flexor longus digitorunv 

 Tibialis posticus. 



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

 be found bound down by an inter-muscular 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 tightjy 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 often called, from being the limit of inser- 

 tion 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 

 articulation of the knee-joint and with the upper part of the tibia. 



The Flexor longus pollicis is the most superficial of the three next 

 muscles. It arises from the lower two-thirds of the fibula, 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 intermuscular 

 fascia, which separates it from the soleus and tendo Achillis. By 

 its deep surface with the tibialis posticus, fibula, fibular vessels, inter- 

 osseous 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 pol- 

 licis 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 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 



