F THE MUSCLES ON THE FRONT OF THE LEG AND FOOT. 357 
lower part of the anterior annular ligament. On the dorsum of the foot the 
tendon is placed on the inner side of the dorsalis pedis artery. 
The extensor longus primi internodii and extensor ossis metatarsi hallucis are occasional 
separate slips of this muscle inserted into the bones of the great toe. 
The extensor brevis digitorum arises on the dorsum of the foot from a special 
impression on the upper surface of the greater process of the os calcis. 
It usually gives rise to four fleshy bellies, from which narrow tendons are 
directed forwards and inwards, to be inserted into the four inner toes. The three 
outer tendons join those of the long extensor muscle to form the membranous 
expansions on the dorsum of the toes. The innermost tendon is inserted separately 
into the base of the first phalanx of the great toe. 
The muscle is covered by the lower band of the anterior annular ligament, and 
by the tendons of the extensor longus digitorum and peroneus tertius ; the slip 
of the muscle passing to the great toe crosses the dorsalis pedis artery. 
THE MUSCLES ON THE OUTER SIDE OF THE LEG. 
The muscles on the outer side of the leg comprise the peronei—longus and brevis. 
The peroneus longus arises from the upper two-thirds of the outer surface of 
the fibula, from intermuscular septa on either side, and from the fascia over it. 
It forms a stout tendon, which hooks round 
the external malleolus, crosses the outer side ee oe cemoucs Hauer 
of the os calcis, and passing through the 
groove on the cuboid bone, is directed across 
the sole of the foot, to be inserted into the 
internal cuneiform and the base of the first 
metatarsal bones. The muscle is placed super- 
ficially in the leg, between the extensor longus 
digitorum and peroneus brevis in front and 
the soleus and flexor longus hallucis behind. 
It partially conceals the peroneus brevis, along 
with which it passes beneath the external 
annular ligament, invested by a common 
synovial sheath. As it enters the sole of the 
foot a fibro-cartilage is formed in the tendon, 
which plays over a smooth tubercle on the 
cuboid bone, a bursa intervening. In its pas- 
sage across the foot the tendon is enclosed 
in a fibrous sheath derived from the inferior 
calcaneo-cuboid ligaments and the tibialis 
posticus tendon, and is concealed by the first 
three layers of the muscles of the sole. 
The peroneus brevis arises from the 
lower two-thirds of the outer surface of the F! 262.—TuE Insertions Or THE PERONEUS 
c LONGUS AND TIBIALIS Posticus MUSCLES 
fibula, and from an intermuscular septum jy ae Sone or tax Ricut Foor. 
along its anterior border. Its tendon passes 
over the back of the external malleolus and the outer side of the os calcis, to be 
inserted into the base of the fifth metatarsal bone. In the leg the peroneus brevis 
lies behind the extensor longus digitorum and peroneus tertius, and in front of the 
peroneus longus, which partially overlaps it. The tendon les directly behind the 
external malleolus beneath the external annular ligament, invested by a synovial 
sheath common to it and the peroneus longus. 
INSERTION OF 
PERONEUS 
LONGUS 
INSERTION OF 
TIBIALIS 
POSTICUS 
FLEXOR LONGUS 
DIGITORUM 
FLEXOR LONGUS 
HALLUCIS 
The peroneus longus and brevis may be fused together, or additional slips may be present, as 
peroneus accessorius, peroneus quinti digiti, peroneo- -calcaneus externus, and peroneo-cuboideus. 
THE MUSCLES ON THE BACK OF THE LEG. 
The muscles on the back of the leg are divisible into two layers: (1) a 
superficial set, consisting of the oastrocnemius and soleus (the so-called triceps 
