The Scottish anatomist and surgeon Sir Charles Bell (1774-1842), considered to be the father of modern neurophysiology. Bell learned surgery from his elder brother John and at Edinburgh University. In 1804 he moved to London where he became a well known surgeon and lecturer on surgery. From 1807 he showed that nerves are not single units but consist of separate fibres within a common sheath. He proved that a fibre transmits either sensory or motor stimuli, but not both, and that a muscle must be supplied with both types of fibre. He discovered the long thoracic nerve (Bell's nerve) and showed that lesions of the seventh cranial nerve produce facial paralysis.