Adductor pollicis. The missing interosseous

This paper highlights the many similarities between the adductor pollicis and the palmar interossei. In particular it compares their anatomy, innervation and function. It suggests that adductor pollicis should be considered as the first palmar interosseous and that this view simplifies the teaching of hand anatomy and the tests of ulnar nerve function. Further support for the view that adductor pollicis is the thenar counterpart of the second, third and fourth palmar interossei is gained from studies of the literature on hand evolution, in particular published details of fossil records and dissection of primate hands.