COPYRIGHT 1992 The Economist Newspaper Ltd. All rights reserved.WHEN the commonplaces of one discipline are applied to an unrelated field,they can prove curiously fruitful. In 1952 two British physiologists, AlanHodgkin and Andrew Huxley, managed just such a fruitful crossover, applyingtextbook physics to living tissue. They were both later knighted, andshared a Nobel prize in 1963. The experimental method they pioneeredremains fundamental to research into the behaviour of nerve cells.As anyone who has ever had an electric shock knows, electricity haspowerful effects on living matter. Luigi Galvani found in 1771 thatelectricity could make the muscles from frogs' legs contract; soonafterwards, physiologists came to suspect that all sensation and movementdepended upon electric pulses in nerve and muscle. But how does electricitypass through living things?By the time Dr Hodgkin and Dr Huxley (as they then were) came to thesequestions, other researchers had discovered various things about nervecells. One of the most intriguing was that messages down nerves are as loudwhen received as they were when transmitted--unlike messages sent downcables, which attenuate with distance. Physiologists thought that thisactive transmission had something to do with sudden and short-lived changesin the electrical resistance of a nerve fibre's outer membrane. The linkbetween transmission and changing resistance was the subject of decades ofincreasingly intense speculation.Progress was slow because the nerves were not, as the police put it,assisting in the inquiries. Nerve fibres are made of axons, which arehairlike protrusions that grow out of nerve cells. They are small anddelicate, unforgiving of rough treatment. The surges in the voltage acrossthe cell membrane, now called action potentials, are complex events lastingonly a couple of milliseconds. Difficulties with delicacy and speed oftenthwarted the physiologists working on nerves before the second wor...
