Having entered Cambridge in 1935, Huxley graduated with a bachelor's degree in 1938. In 1939,
Alan Lloyd Hodgkin returned from the US to take up a fellowship at Trinity College, and Huxley became one of his postgraduate students. Hodgkin was interested in the transmission of electrical signals along nerve fibres. Beginning in 1935 in Cambridge, he had made preliminary measurements on frog
sciatic nerves suggesting that the accepted view of the nerve as a simple, elongated battery was flawed. Hodgkin invited Huxley to join him researching the problem. The work was experimentally challenging. One major problem was that the small size of most
neurons made it extremely difficult to study them using the techniques of the time. They overcame this by working at the
Marine Biological Association laboratory in
Plymouth using the
giant axon of the longfin inshore squid (
Doryteuthis (formerly Loligo) pealeii), which have the largest neurons known. The experiments were still extremely challenging as the nerve impulses only last a few milliseconds, during which time they needed to measure the changing electrical potential at different points along the nerve. Using equipment largely of their own construction and design, including one of the earliest applications of a technique of
electrophysiology known as the
voltage clamp, they were able to record ionic currents. In 1939, they jointly published a short paper in
Nature reporting on the work done in Plymouth and announcing their achievement of recording action potentials from inside a nerve fibre. Then
World War II broke out, and their research was abandoned. Huxley was recruited by the British Anti-Aircraft Command, where he worked on radar control of anti-aircraft guns. Later he was transferred to the Admiralty to do work on naval gunnery, and worked in a team led by
Patrick Blackett. Hodgkin, meanwhile, was working on the development of radar at the Air Ministry. When he had a problem concerning a new type of gun sight, he contacted Huxley for advice. Huxley did a few sketches, borrowed a lathe and produced the necessary parts. Huxley was elected to a research fellowship at Trinity College, Cambridge, in 1941. In 1946, with the war ended, he was able to take this up and to resume his collaboration with Hodgkin on understanding how nerves transmit signals. Continuing their work in Plymouth, they were, within six years, able to solve the problem using equipment they built themselves. The solution was that nerve impulses, or action potentials, do not travel down the core of the fiber, but rather along the outer membrane of the fiber as cascading waves of sodium ions diffusing inward on a rising pulse and potassium ions diffusing out on a falling edge of a pulse. In 1952, they published their theory of how
action potentials are transmitted in a joint paper, in which they also describe one of the earliest computational models in biochemistry. This model forms the basis of most of the models used in neurobiology during the following four decades. In 1952, having completed work on action potentials, Huxley was teaching physiology at Cambridge and became interested in another difficult, unsolved problem: how does muscle contract? To make progress on understanding the function of muscle, new ways of observing how the network of filaments behave during contraction were needed. Prior to the war, he had been working on a preliminary design for
interference microscopy, which at the time he believed to be original, though it turned out to have been tried 50 years before and abandoned. He, however, was able to make interference microscopy work and to apply it to the problem of muscle contraction with great effect. He was able to view muscle contraction with greater precision than conventional microscopes, and to distinguish types of fiber more easily. By 1953, with the assistance of
Rolf Niedergerke, he began to find the features of muscle movement. Around that time,
Hugh Huxley and
Jean Hanson came to a similar observation. Authored in pairs, their papers were simultaneously published in the 22 May 1954 issue of
Nature. Thus the four people introduced what is called the
sliding filament theory of muscle contractions. Huxley synthesized his findings, and the work of colleagues, into a detailed description of muscle structure and how muscle contraction occurs and generates force that he published in 1957. In 1966 his team provided the proof of the theory, and has remained the basis of modern understanding of muscle physiology. In 1953, Huxley worked at
Woods Hole,
Massachusetts, as a Lalor Scholar. He gave the
Herter Lectures at
Johns Hopkins Medical School in 1959 and the Jesup Lectures at
Columbia University in 1964. In 1961 he lectured on
neurophysiology at
Kiev University as part of an exchange scheme between British and Russian professors. He was an editor of the
Journal of Physiology from 1950 to 1957 and also of the
Journal of Molecular Biology. In 1955, he was elected a
Fellow of the Royal Society and served on the Council of the
Royal Society from 1960 to 1962. Huxley held college and university posts in Cambridge until 1960, when he became head of the Department of Physiology at
University College London. In addition to his administrative and teaching duties, he continued to work actively on muscle contraction, and also made theoretical contributions to other work in the department, such as that on
animal reflectors. In 1963, he was jointly awarded the
Nobel Prize in Physiology or Medicine for his part in discoveries concerning the ionic mechanisms of the nerve cell. He was also a fellow of
Imperial College London in 1980. From his experimental work with Hodgkin, Huxley developed a set of differential equations that provided a mathematical explanation for nerve impulses—the "action potential". This work provided the foundation for all of the current work on voltage-sensitive membrane channels, which are responsible for the functioning of animal nervous systems. Quite separately, he developed the mathematical equations for the operation of myosin "cross-bridges" that generate the sliding forces between actin and myosin filaments, which cause the contraction of skeletal muscles. These equations presented an entirely new paradigm for understanding
muscle contraction, which has been extended to provide understanding of almost all of the movements produced by cells above the level of bacteria. Together with the Swiss physiologist Robert Stämpfli, he evidenced the existence of
saltatory conduction in
myelinated nerve fibres. ==Awards and honours==