Sir Andrew Huxley, the British researcher who shared the 1963 Nobel Prize in Physiology or Medicine for his discoveries of how nerve impulses are transmitted through cells, died May 30. He was 94.

His death was announced by the University of Cambridge's Trinity College, where he served as master from 1984 to 1990, but no details were released.

Biologists had known since the 1771 experiments of Italian physicist Luigi Galvani that giving a frog leg an electrical shock would cause it to contract, suggesting that muscle activity was electrically regulated. But it was not clear how the tissues could generate such an electrical stimulus and how it could be transmitted through cells.

Huxley and Hodgkin approached the problem by studying a squid nerve cell known as the giant axon. The giant axon, which can be up to 1 millimeter (0.04 inches) in diameter, stretches the length of the squid's body to control ejection of water for propulsion, and nerve impulses travel especially rapidly through it.

By placing tiny electrodes in the axon at various locations, they were able to measure the electrical potential inside the nerve as it transmitted an electrical current. They concluded that the current was carried by electrically charged atoms called ions. When the current reaches each cell, it causes a channel known as a sodium gate to open, allowing sodium ions to flow into the cell.

Once enough sodium is in the cell, that triggers a second set of gates on the opposite end that allow potassium ions to escape. Those ions cause the process to repeat at the next cell.

The gates themselves could not be visualized with the technology available at the time, but Huxley, working on a very primitive computer, used the laws of physics to calculate the electrical potentials that should be obtained if their model was correct. The calculated values were very close to those that were observed, confirming their hypothesis. Only much later were the ion channels actually imaged.

Huxley and Hodgkin shared their Nobel with Sir John Eccles of Australia, who explained how signals were transmitted between cells. Both Britons were knighted for their work in 1974.

Huxley later worked to explain how muscle fibers contract. For that work, he devised and built a microtome to make very thin slices of tissue for study in the electron microscope and a micromanipulator.

Andrew Fielding Huxley was born Nov. 22, 1917, in London to a celebrated family. His grandfather was biologist Thomas Henry Huxley, an early supporter of Charles Darwin's theory of evolution. His father, Leonard, was a writer who, among other things, compiled a history of Thomas Huxley. Andrew's older half-brothers were the author Aldous Huxley and biologist Julian Sorel Huxley.

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Sir Andrew Huxley dies at 94; Nobel-winning physiologist