THE LOWER EXTREMITY, ANTERIOR. 589 



Tibialis Anticus. Figs. 123, 124. 



Origin. From the under surface of the external tuber- 

 osity of the tibia, from the upper half or two-thirds of the 

 outer surface of the tibia, from the adjacent portion of the 

 interosseous membrane, from the upper third of the inner 

 surface of the deep fascia covering the muscle, and from 

 the intermuscular septum between the extensor longus digi- 

 torum and itself. 



Insertion. Into the adjoining portions of the inner and 

 lower surfaces of the internal cuneiform and first metatarsal 

 bones. 



Nerve Supply. The anterior tibial branch of the external 

 popliteal nerve. 



Action. To flex the foot upon the leg, to raise (invert) 

 the inner border of the foot, to adduct the anterior part of 

 the foot. 



Extensor Longus Dig-itorum. Figs. 123, 124, 



Origin. From the external tuberosity of the tibia, from 

 the front of the head of the fibula, from the upper three- 

 fourths of the anterior surface of the fibula, from the upper 

 third of the interosseous membrane, and for the same extent 

 from the inner surface of the deep fascia covering the leg, 

 and from the intermuscular septa between it and the border- 

 ing muscles. 



Insertion. Into the four outer toes by separate tendons 

 which divide into three slips. The middle slip in each case 

 being inserted into the base of the second phalanx, the 

 other two tendons passing around the middle one to be in- 

 serted into the bases of the third phalanx. 



From the margins of each tendon slips pass to the lateral 

 ligaments of the metacarpophalangeal articulations. 



The tendons of the interossei, lumbricales, and extensor 



