He clearly demonstrated that spinal nerves carry both sensory and motor functions and that sensory fibers traverse the posterior roots whereas the motor fibers run through the anterior (Bell’s Law).
He also demonstrated that the cranial nerve V was sensory to the face and motor to mastication whereas cranial nerve VII controlled muscles of expression. The eponyms of the respiratory nerve of Bell and Bell’s Palsy perpetuate his name.
Born in Scotland, Charles Bell studied anatomy and medicine at the University of Edinburgh. Bell left Edinburgh for London after he and his brother John were rejected by the Edinburgh Royal Infirmary. He lived and worked in London for thirty years before returning to Scotland, where he ended his career as professor of surgery at the University of Edinburgh. Bell was an expert surgeon: he served as a surgeon with the British army at the famous Battle of Waterloo in 1815. His fame, however, rests on medical illustration and neurology. His Essays on the anatomy of expression in painting (1806) is a classic of art history.
An Exposition of the Natural System of the Nerves of the Human Body is a collection of Bell's observations on the nerves.