Skou had taken a few years away from his clinical training in the early 1950s to study the action of local anaesthetics. He had discovered that a substance’s anaesthetic action was related to its ability to dissolve in a layer of the lipid part of the plasma membrane, the anaesthetic molecules affected the opening of sodium channels which he assumed to be protein. This, he argued, would affect the movement of sodium ions and make nerve cells inexcitable, thus causing anaesthesia.