2io THE MUSCLES. 



M. peroneus tertius (Fig. 90, r~). A slender fusiform 

 muscle beneath the peroneus longus (g). 



Origin by fleshy fibres from about the second quarter of the 

 lateral surface of the fibula. The muscle ends in a slender 

 tendon (>'), which passes with that of the peroneus brevis (s) 

 through the groove on the ventral border of the lateral mal- 

 leolus. The groove is converted into a canal by a transverse 

 ligament. Emerging from it, the tendon turns and passes along 

 the outer margin of the foot. In passing the sesamoid at the 

 base of the first phalanx of the fifth digit it is united to it by a 

 band which passes from the sesamoid to the tendon. 



The insertion is finally into the lateral border of the extensor 

 tendon of the fifth digit as it passes from the first to the second 

 phalanx. 



Relations. Outer surface with the peroneus longus (q}, the 

 soleus (o), and the superficial fascia. Ventral border with the 

 soleus (<?) and flexor longus hallucis (Fig. 91, ;//). Inner sur- 

 face with the peroneus brevis (Fig. 90, s). 



Action. Extensor and abductor of the fifth digit and flexor 

 of the foot. 



M. peroneus brevis (Fig. 90, s) lies beneath the other 

 peronei. 



Origin by fleshy fibres from the distal half of the surface of 

 the fibula, which it embraces. At the lateral malleolus the 

 muscle ends in a thick tendon which passes through the canal 

 on the ventral surface of the malleolus. In the canal it is 

 enlarged and surrounded by a synovial bursa. It then turns 

 onto the foot and passes over the dorsal surface of the calcaneus 

 on its lateral side and has its 



Insertion into the tubercle on the lateral side of the base of 

 the fifth metatarsal. 



Relations. Outer surface with the peronei longus (q] and 

 tertius (f). Inner surface with the bone. 



Action. Extensor of the foot. 



M. extensor digitorum longus (Fig. 90, /). A fusiform 

 muscle which lies beneath the tibialis anterior (;z), against the 

 interosseous membrane, and between the tibialis anterior and 

 the peronei. 



