THE LEG 347 



comes to the surface. It takes origin posterior to the extensor 

 digitorum longus, from an extremely narrow strip of the 

 anterior part of the medial surface of the body of the fibula, 

 in its middle two-fourths, and also from the adjoining part of 

 the interosseous membrane. Its tendon passes deep to the 

 transverse ligament, crosses in front of the distal part of the 

 anterior tibial artery, and passing distally in front of the ankle 

 joint reaches the dorsum of the foot deep to the cruciate 

 ligament (Fig. 342). It is inserted into the dorsal aspect of 

 the base of the ungual phalanx of the great toe. 1 It is not 

 joined by the most medial tendon of the extensor digitorum 

 brevis. The extensor hallucis longus is supplied by the 

 deep peroneal nerve. It is an extensor of all the joints of the 

 great toe and a dorsi-flexor of the foot. 



M. Peronseus Tertius. The peronseus tertius is a small 

 muscle which is continuous at its origin with the extensor 

 digitorum longus. It arises from the distal fourth of the 

 anterior part of the medial surface ot the fibula, and from a 

 corresponding extent of the interosseous membrane. It 

 receives fibres also from the distal part of the anterior 

 fibular septum, which intervenes between it and the peronaeus 

 brevis. Its slender tendon is inserted into the dorsal surface 

 of the expanded base of the fifth metatarsal bone. It is 

 supplied by the deep peroneal nerve. It is a dorsi-flexor of 

 the ankle joint and an evertor of the foot. 



Arteria Tibialis Anterior. The anterior tibial artery is 

 the smaller of the two terminal branches of the popliteal. 

 It takes origin in the posterior region of the leg, at the distal 

 border of the popliteus muscle, and at the level of the 

 tuberosity of the tibia (see Fig. 135). It enters the anterior 

 crural region by passing forwards through the opening in the 

 proximal part of the interosseous membrane. As it passes 

 forwards it lies close to the medial side of the neck of the 

 fibula, where it appears in the present dissection. In the 

 anterior part of the leg it takes a straight course distally 

 to the ankle joint. Then it reaches the dorsum of the 

 foot, and receives the name of dor sails pedis. 



In the proximal two-thirds of the leg the anterior tibial 

 artery is very deeply placed. It lies upon the interosseous 

 membrane, in the interval between the tibialis anterior on the 

 medial side, and the extensor digitorum longus and the 



1 In most cases it gives a slip to the base of the proximal phalanx also. 



