392 THE MUSCLES 



Nerve-supply. — From the anterior til)ial nerve l)y small filaments wl)icli enter 

 the deep surface of the muscle near its inner border as it crosses the cuhoiil and 

 external cuneiform Ijones. 



Action. — (1) To extend the four inner toes. In the case of the outer toes the 

 two last phalanges will be chietl}' extended, and the obliquity of its insertion, by 

 causing it to draw the toes somewhat outwards at the same time that it extends 

 them, will enaljle it to correct the opposite tendency of the long extensor. (2) 

 The innermost tendon will act as an adductor of the first jjludanx of the great toe. 



Relations. — Superficially, the tendons of the extensor longus digitorum and 

 peroneus tertius; deeply, the tarsal and tarso-metatarsal joints; and, in the case of 

 the tendon to the great toe, the dorsalis pedis vessels and the termination of the 

 anterior tibial nerve. 



Variations. — The number of tendons may be diminished or increased. Sometimes a tendon 

 is given to the little toe. Accessory bundles maybe derived from some of the tarsal or mt_'t;i- 

 tarsal bones, and slii)S have been found running to the dorsal interossei ; and also a small slip 

 between the first and second bellies, going to the inner side of the second toe or its metatarsal 

 bone. 



MUSCLES Oy THE OUTER SIDE OF THE LEG 



These are two muscles — the peroneus longus and Ijrevis — situated upon the outer 

 side of the fil^ula in a compartment of quadrilateral section, bounded internally 

 by the fibula, in front and behind by intermuscular septa, and externally by the 

 deep fascia of the leg. 



1. PERONEUS LONGUS 



The peroneus longus (figs. 292 and 296) — named from its l^eing the longer of 

 the two filjular muscles — is long and fusiform. 



Origin. — (1) The outer tuberosity of the tibia by a few fibres; (2) the front of 

 the head of the fibula; (3) the upper two-thirds of the outer (or peroneal) surface 

 of the fibula, occupying the whole of this surface above, and the posterior half of 

 it below; (4) the inner surface of the deep fascia of the leg, and the opjoosed sur- 

 faces of the two external intermuscular septa. 



Insertion. — (1) The low^er part of the outer surface of the base of the first 

 metatarsal bone; (2) the lower part of the outer surface of the internal cuneiform 

 bone close to its articulation with the first metatarsal bone. 



Structure. — This is a strong penniform muscle, the short fleshy fibres of which 

 pass downwards, and for the most part forwards, to be inserted into the tendon 

 Avhieh, beginning al)out three inches (7 "5 cm.) below^ the head of the fii^ula, runs 

 along the front of the outer surface of the muscle, and becomes free in the lower 

 third of the leg. It then passes behind the outer ankle, beneath the external 

 annular ligament, in a special sheath with the tendon of the i^eroneus l)revis, which 

 lies in front of it. On the outer surface of the calcaneum, it runs forwards and 

 downwards in a s])ecial compartment of the external annular ligament below the 

 comi)anion tendon. At the outer border of the foot it again changes its direction, 

 and i)asses obliquely inwards and forwards across the sole of the foot, in a canal 

 formed by the long plantar ligament beneath, and by the groove in the cuboid bone 

 above, to its insertion near the inner side of the sole. In the upper two-thirds of 

 the leg the peroneus longus almost entirely conceals from view the peroneus l)revis, 

 Avhieh lies beneath and slightly anterior to it. 



The synovial tube which it enters at the outer ankle is common to it and the 

 peroneus brevis, and bifurcates to accompany the two tendons Avhere they are 

 separated by the jx'roneal tul)ercle of the os calcis. A second sheath envelopes the 



