Lucas, Keith (1879–1916)

English neurophysiologist who investigated the transmission of nerve impulses. He demonstrated that the contraction of muscle fibres follows the ‘all or none’ law: a certain amount of stimulus is needed in order to induce a nerve impulse and subsequent muscle contraction. Any stimulus below that threshold has no effect regardless of its duration.

Lucas showed that when two successive stimuli are given, the response to the second stimulus cannot be evoked if the first nerve impulse is still in progress. He also demonstrated that following a contraction there is a period of diminished excitability during which the muscle cannot be induced to contract again. This is due to the chemical transmission of impulses over synaptic clefts (the junction between two individual neurons).

Lucas was born in Greenwich, London and graduated from the University of Cambridge in natural sciences. He joined the staff of Cambridge in 1903 and began his work on the structure and function of nerves and muscles.

By the outbreak of World War I, Lucas had developed highly sensitive technology for measuring the electrical currents in individual neurons. They characteristically have very long fibrelike extensions called processes which can extend over large distances in the body and conduct messages. Unfortunately, after enlisting in 1914 and being trained as a pilot, he was killed in an air crash, before he was able to fully apply his new experimental techniques. However, they became invaluable tools for post-war neurophysiologists.