588 THE NERVOUS SYSTEM. 
The superficial branch is purely cutaneous; it passes downwards beneath the 
palmar fascia, and subdivides into an inner and an outer branch. The inner 
branch courses 
| along the inner 
border of the little 
ee finger, which it 
—~< supplies on its 
r palmar aspect. The 
outer branch  be- 
T3 comes superficial at 
T4 the cleft between 
Ts the fourth and fifth 
=a fingers, between 
7 the slips of the 
= palmar fascia, and 
subdivides into two 
branches which 
supply the adjacent 
sides of these fingers 
on their palmar 
aspect. It com- 
municates with the 
adjacent digital 
branch of the 
median nerve. 
The deep branch 
is purely muscular. 
It separates from 
the superficial 
branch, and passes 
> deeply between the 
flexor brevis and 
“ abductor =minimi 
digiti muscles; it 
supplies these 
muscles and the 
opponens minimi 
digiti, and, turning 
Fic. 433.—THE DIsTRIBUTION OF CUTANEOUS NERVES ON THE BACK OF THE outwards along the 
6G Voge Lite SRE Pate, line of the deep 
(A) represents the distribution of the several nerves, the letters indicating their palmar arch and 
nomenclature. AcR, Acromial branches (cervical plexus) ; Crrc, Cutaneous 
branch of circumflex nerve ; Ms.E.C.s, Ms.B.C.i, Superior and inferior external under cover of the 
cutaneous branches of musculo-spiral nerve ; M.C, Musculo-cutaneous nerve ; deep flexor tendons, 
15% Radial nerve ® M, Branches of meman nerve to fingers ; U, Ulnar nerve 5 if supplies branches 
I.C, Internal cutaneous nerve ; Ms.1I.C, Internal cutaneous branch of musculo- A 
spiral nerve; L.I.C, Lesser internal cutaneous nerve (Wrisberg) ; I.H, Inter- to the following 
costo-humeral ; T.1, 2, 3, 4, 5, 6, Lateral and posterior branches of upper muscles: the in- 
uboTacle Melves: terossel, two inner 
(B) is a schematic representation of the areas supplied by the above nerves, the (third and fourth) 
lettering indicating the spinal origin of the branches of distribution to each l nice 
area. D.A.L, Dorsal axial line. u ten VrICales (on 
their deep sur- 
faces), the adductores, obliquus and transversus, and deep part of the flexor brevis 
pollicis. 
INTERNAL CUTANEOUS NERVE. 
The internal cutaneous nerve (n. cutaneus brachii medialis) arises from 
the inner cord of the brachial plexus, from the eighth cervical and first thoracic 
nerves (Figs. 432 and 435). In the axilla and upper half of the arm it lies superficial 
to the main arteries. It becomes cutaneous by piercing the deep fascia about the 
middle of the inner side of the upper arm, and, accompanying the basilic vein 
