, 
elbow, between the biceps and brachio- radials, and terminates in cutaneous 
branches for the supply of the outer side of the forearm. 
The branches of the nerve are muscular and cutaneous. The muscular branches 
are supphed to the two heads of the biceps and the brachialis anticus, as the nerve 
lies between the muscles. The nerve to the coraco-brachialis (usually meorporated 
with the trunk of the musculo-cutaneous nerve) has an independent origin from 
the seventh cervical nerve. It is usually double, one branch entering each portion 
of the muscle. The cutaneous branches are anterior and posterior (Fig. 452, p. 586). 
The anterior branch descends along the front of the outer side of the forearm to the 
wrist, and supplies an area extending inwards to the middle line of the forearm 
anteriorly, and downwards so as to include the ball of the thumb. It communicates 
above the wrist with the radial nerve and supplies branches to the radial artery. The 
posterior branch passes backwards and downwards over the extensor muscles and 
supplies the skin on the outer aspect of the forearm posteriorly in its upper three- 
fourths, communicating with the cutaneous branches of the musculo-spiral nerve. 
MEDIAN NERVE. 585 
In addition to the above branches, the musculo-cutaneous nerve supplies in many 
cases the following small twigs in the arm: (1) a medullary branch to the humerus; (2) 
a periosteal branch to the lower end of the humerus on its anterior surface; and (3) a 
branch to the brachial artery. 
MEDIAN NERVE. 
The median nerve (n. medianus) arises by two roots—one from the outer 
cord, the other from the inner cord of the brachial plexus. The outer head, from 
the (fifth), sixth, and seventh nerves, descends along the outer side of the axillary 
artery; the inner head, from the eighth cervical and first thoracic nerves, crosses 
the end of the axillary artery or the beginning of the brachial artery, to join the other 
head at the upper part of the arm. Descending along the outer side of the brachial 
artery, the nerve crosses over it obliquely in the lower half of the arm. In the 
hollow of the elbow, it lies internal to the brachial artery, beneath the bicipital 
fascia and the median basilic vein. It passes into the forearm between the two 
heads of the pronator radii teres muscle, separated from the ulnar artery by the 
deep origin of that muscle. Extending down the middle of the forearm, between 
the superficial and deep muscles to the wrist, it enters the palm of the hand on the 
outer side of the flexor tendons of the fingers beneath the anterior annular 
ligament. In the hand it spreads out at the lower border of the annular ligament 
beneath the palmar fascia and superficial palmar arch, and separates into its six 
terminal branches. In the forearm a small artery accompanies it,—the comes nervi 
mediani. Above the wrist it is comparatively superficial, lying on the outer side of 
the flexor tendons and directly beneath the tendon of the palmaris longus. 
Communications.—(1) The median nerve, in some cases, receives a communicating 
branch from the musculo-cutaneous inthe arm. (2) It communicates in some cases, in 
the upper part of the forearm, with the ulnar nerve beneath the flexor muscles. (3) It 
communicates by means of its cutaneous branches with the ulnar nerve in the palm of 
the hand. 
Branches.—The median nerve usually gives off no branches in the upper arm. 
Branches in the Forearm.—(1) Articular Branches.—Minute articular fila- 
ments are distributed to the front of the elbow joint. 
(2) Muscular Branches.—Just below the elbow a bundle of nerves arise which 
is distributed to the following muscles: pronator radii teres, flexor carpi radialis, 
palmaris longus, flexor sublimis digitorum. Nerves are also generally traceable 
from this bundle to the upper fibres of the flexor longus pollicis and flexor pro- 
fundus digitorum. The nerve to the pronator radii teres often arises independently 
in the hollow of the elbow. ‘ 
(3) The anterior interosseous nerve arises from the back of the median nerve 
in the forearm, descends in front of the interosseous membrane along with the 
anterior interosseous artery, passes behind the pronator quadratus muscle, and 
terminates by supplying articular filaments to the radio-carpal articulation. In its 
course the nerve supplies muscular branches to the flexor longus pollicis, the outer 
