210 THE MUSCLES. 
M. peroneus tertius (Fig. 90, v).—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 (r’), 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 zzsertéon 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 (g), the 
soleus (0), and the superficial fascia. Ventral border with the 
soleus (¢) and flexor longus hallucis (Fig. 91, 7). 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 (g) and 
tertius (7). Inner surface with the bone. 
Action. —Extensor of the foot. 
M. extensor digitorum longus (Fig. 90, 4).—A fusiform 
muscle which lies beneath the tibialis anterior (), against the 
interosseous membrane, and between the tibialis anterior and 
the peronei. 
