Arm nerves. Historical anatomical artwork of the nerves (white) and muscles (red) of an upper arm. At upper right, nerves and arteries (red) are seen by the removal of part of the clavicle bone. There are several nerves branching off the spinal cord, which form a network called the brachial plexus. Next to these nerves is the subclavian artery that becomes the axillary artery as it enters the arm, and then the brachial artery in the arm proper. The brachial nerves rapidly branch into internal and external cutaneous (skin) branches, with the main (thick) nerve (the median nerve) continuing to the lower arm. Artwork from The Nerves of the Human Body (Ed. Jones Quain, London, 1839).