It is usual for the median nerve to innervate 41/2 muscles of the hand (opponens pollicis, abductor pollicis brevis, first and second lumbricals, and the superficial head of the flexor pollicis brevis); the remaining are supplied by the ulnar nerve. From the above it would appear that the management of peripheral nerve lesions, affecting the small muscles of the hand, would be a simple one. Actually the contrary is true, as physicians dealing in the diagnosis and repair of these nerve lesions often encounter striking variations with regard to the innervation of the intrinsic muscles of the hand. As long ago as 1886, Brooks1 discovered the existence of two heads of the flexor pollicis brevis and also of their varied nerve supply. He dissected 30 cadavers in which he found that the flexor pollicis brevis was supplied by the ulnar nerve alone in five cases and by the median