Normal arborization of the deep branch of the ulnar nerve into the interossei and lumbricals.

Ten adult hands were dissected to reexamine in new detail the distribution of the deep branch of the ulnar nerve from its origin in the ulnar tunnel to its termination in the first dorsal interosseous muscle. The relationships of the subdividing branches to each other and to the muscle bellies were clarified. The palmar interossei along with the first and second dorsal interossei were all innervated within the middle third of their corresponding metacarpal. The third and fourth dorsal interossei were innervated within the proximal third of their corresponding metacarpals, and the third lumbrical was innervated within the middle third whereas the fourth lumbrical was innervated along its distal third.