THE LOWER EXTREMITY, POSTERIOR. 631 



third. From the intermuscular septa and deep fascia of the 

 leg. 



Insertion (see Dorsum of Foot). Into the prominent 

 base of the fifth metatarsal bone. The tendon of the 

 muscle lies in front of that for the peroneus longus ; 

 as the two pass behind the external malleolus, one synovial 

 sheath here encloses them both. 



Nerve Supply. The musculocutaneous. 



Action. To extend the foot, to abduct the foot, to raise 

 the outer border of the foot. In all its actions it is much 

 inferior to the peroneus longus. 



The Posterior Tibial Nerve. Figs. 128, 130, 131. 



This is the continuation of the internal popliteal nerve 

 from the lower border of the popliteus muscle to the mid- 

 point between the internal malleolus and the point of the 

 heel, where it terminates by dividing into the external and 

 internal plantar nerves. 



The posterior tibial nerve lies first at the inner side of the 

 corresponding artery, but crosses behind the artery (just 

 after -the peroneal branch is given off) to the outer side, 

 which position it keeps for the rest of its course. 



Branches. (i) Muscular to the tibialis posticus, flexor 

 longus digitorum, and flexor longus hallucis. (2) Articu- 

 lar, one or more filaments to the ankle joint. (3) Cuta- 

 neous, internal calcanean (calcaneoplantar). Pierces the 

 internal annular ligament and supplies the integument over 

 the inner side of the heel, and back part of the sole. 



The Anterior Tibial Artery. See page 593. 



The Posterior Tibial Artery. Figs. 130, 131. 



This is the continuation of the popliteal, of which it is 

 the larger terminal branch, from the lower border of the 



