MUSCULO-CUTANEOUS NERVE. 609 
hallucis muscles, to the front of the leg. In its course down the leg it is deeply 
placed upon the interosseous membrane and the lower part of the tibia in company 
with the anterior tibial artery. At the ankle it les beneath the anterior annular 
ligament and the tendon of the extensor proprius hallucis, and crossing over the 
ankle-joint, it divides on the dorsum of the foot into its terminal branches. 
1. Collateral Branches (in the leg).—These are given off to the muscles between 
which the anterior tibial nerve passes: tibialis anticus, extensor proprius hallucis, 
extensor longus digitorum, and peroneus tertius. A fine articular branch supplies 
the ankle-joint. 
2. Terminal Branches (in the foot).—The terminal branches are internal and 
external. The internal branch passes along the dorsum of 
the foot on the outer side of the dorsalis pedis artery to the 
first interosseous space, where it divides into two dorsal 
digital branches for the supply of the skin of the outer 
side of the great toe and the inner side of the second toe. 
Each of these branches communicates with branches of the 
musculo-cutaneous nerve. It gives off one or two dorsal 
interosseous branches, which supply the inner tarso-metatarsal 
and metatarso-phalangeal articulations, and also enter the 
first dorsal interosseous muscle. 
The external branch passes outwards over the tarsus 
beneath the extensor brevis digitorum, and ends in a gangli- 
form enlargement (similar to the gangliform enlargement on 
the posterior interosseous nerve at the back of the wrist). 
From this enlargement muscular branches arise for the 
supply of the extensor brevis digitorum, along with branches 
for the tarsal, tarso-metatarsal, and metatarso-phalangeal 
articulations. Its dorsal interosseous branches may be as 
many as four in number. Of these the outer two, ex- 
tremely small, may only reach the tarso-metatarsal articu- 
lations. The inner two are fine branches, which, besides 
supplying the articulations, may give branches to the second 
and third dorsal interosseous muscles. 
The branches from the anterior tibial nerve to the 
interosseous muscles are probably sensory, the motor supply 
of these muscles being certainly derived from the external 
plantar nerve. 
Fig. 443.—DISTRIBUTION OF 
CuraNEOoUS NERVES ON 
Muscuto-CuTaANEous NERVE. eae DoRsUM OF THE 
The musculo-cutaneous nerve (n. peronzeus superticialis), 1.5, Internalsaphenous nerve ; 
the last of the branches of the peroneal nerve, passes uae a aes 
below the head of the fibula and beneath the upper fibres nerve: ES, External sa- 
of the peroneus longus muscle. Lying in a sheath in the phenous nerve. The ex- 
intermuscular septum, between the peronei externally ae - th Sian 
and the extensor longus digitorum internally, it proceeds reed (LP, EP). 
downwards in front of the fibula to the lower third 
of the leg, where it pierces the deep fascia in two branches, internal and external. 
Its branches are: (1) collateral muscular branches distributed to the peronei 
muscles, longus and brevis, as the nerve lies in relation to them; (2) terminal 
cutaneous branches, internal and external. 
The internal terminal branch courses downwards over the anterior annular liga- 
ment of the ankle, and after supplying offsets to the lower third of the leg and dorsum 
of the foot, divides into three branches. (1) The most internal supplies the skin 
of the dorsum of the foot and the inner side of the great toe, and communicates 
with the internal saphenous nerve. (2) The middle branch passes to the interval 
between the great toe and the second, and divides into two branches which com- 
municate with the internal branch of the anterior tibial nerve. (3) The external 
branch passes to the interval between the second and third toes, and divides into 
two digital branches to supply the adjacent sides of these toes. 
39 
