MUSCLES OF THE PELWC LIMBS. 211 



Origin by a thin flat tendon from the lateral surface of the 

 lateral epicondyle of the femur just dorsad of the origin of the 

 popliteus. The tendon becomes narrower and thicker and 

 passes through the capsule of the knee-joint and over a slight 

 groove on the tibia just dorsad of the head of the fibula. The 

 belly of the muscle extends the entire length of the tibia, pass- 

 ing beneath the transverse ligament (s) along with the tendon 

 of the tibialis anterior (). At the ankle it runs through a 

 fibrous loop which is attached to the dorsal surface, of the 

 calcaneus (the annular ligament of the calcaneus) ; it then turns 

 and passes onto the dorsum of the foot. The muscle ends in 

 four slender tendons, the two middle of which begin at the 

 transverse ligament, while the others begin at the fibrous loop. 

 The tendons diverge to the four digits. Each tendon is con- 

 nected with the fibrous sheath surrounding the base of the first 

 phalanx, and each has a synovial bursa beneath it at this point. 

 Near the distal end of the first phalanx the tendon is united on 

 the lateral side to the conjoined tendon of the extensor brevis 

 digitorum and an interosseus muscle, and on the medial side 

 to the tendon of the interosseus. The lateral side of the most 

 lateral tendon is not thus united, but is joined on the outer side 

 by the tendon of the peroneus tertius. 



Insertion. The tendon thus formed on the dorsum of each 

 phalanx by the junction of the two or three tendons above 

 mentioned is firmly attached to the base of the second phalanx 

 at its proximal end in the middle of its dorsal surface. In 

 crossing the joint between the first and second phalanges the 

 tendon forms a fibrous pad which protects the dorsum of the 

 joint and glides over it. It then continues to be inserted into 

 the base of the terminal phalanx. 



Relations. Outer surface with the tibialis anterior () and 

 the superficial fascia. Inner surface with a part of the tibialis 

 anterior, with the bones, the interosseous membrane, and the 

 peroneus brevis (s}. 



Action. Extensor of the phalanges. 



M. tibialis anterior (Fig. 90, ). This is the superficial 

 muscle covering the lateral side of the tibia. 



Origin by fleshy fibres from the proximal one-sixth of the 



