Sir Alan Lloyd Hodgkin was an English biophysicist and a physiologist who received the Nobel prize in Physiology or Medicine along with Sir John Eccles and Andrew Fielding Huxley for discovering the chemical processes which controlled the transmission of electrical impulses from one nerve cell in the brain to another though nerve fibers. He and his fellow scientists introduced microelectrodes into the giant nerve fibers of a squid and showed that the electrical potential of a nerve fiber transmitting an impulse is higher than a nerve fiber which remains at rest. This discovery was in contradiction to the earlier hypothesis that nerve membranes break down when an impulse was transmitted. This theory formulated by Hodgkin and Huxley is known as the ‘voltage clamp’. They found that a large amount of potassium ions is concentrated inside a nerve fiber while the solution which surrounds the fibers has a large concentration of sodium ions. They proved with the help of experiments that nerve fibers allow only potassium ions to pass through the membrane when they are at rest while only sodium ions are allowed passage when the fibers are excited. The continuous sequence of depolarization that occurs to the nerve cell membranes discovered by him is known as the ‘Hodgkin Cycle’.