Dictionary of National Biography, 1927 supplement/Lucas, Keith

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LUCAS, KEITH (1879–1916), physiologist, was born at Greenwich 8 March 1879. He was the second son of Francis Robert Lucas, managing director of a telegraph engineering company in London, and inventor of improvements in submarine cables and cable-laying. His mother was Katharine, daughter of John Riddle, head master of Greenwich Hospital schools, and granddaughter of Edward Riddle [q.v.], both of whom were fellows of the Royal Astronomical Society and noteworthy in nautical astronomy. Educated at Rugby, where he was head of the school house, he proceeded, with a scholarship in classics, to Trinity College, Cambridge, in 1898. He gained a first class in the first part of the natural science tripos in 1901; but the death of a school friend in the South African War made him give up the second part of the tripos for the rest and change of a visit to New Zealand. There he undertook his earliest piece of research, the measuring of the depth of some hitherto unsounded lakes (Geography, July 1904). Returning to Cambridge he was elected a fellow of Trinity College in 1904, and later (1908) lecturer in science.

Between the years 1904 and 1914 Lucas undertook a series of researches, several of them in conjunction with pupils, the results of which gave a fresh impetus to the study of muscle and nerve. The contraction response of ordinary muscle fibre was shown to be of the ‘all-or-none’ type, the grading of a muscle's contraction being by additive quanta; the influence of duration on the effectiveness of an electric stimulus was measured, and further analysis of the excitability of nerve-muscle tissue was so obtained; the temperature coefficient of nerve-conduction was determined with precision; the nerve-impulse in its travel was shown to leave in its wake a phase of lessened excitability; excitability and conduction in nerve were reduced to one process; ‘magnitudes’ of nerve-impulse were discriminated by finding that range of interval between two successive impulses which is able to diminish though not to extinguish the second of them; thus subnormal impulses were recognized and the time-relations of the recovery of the nerve-fibre from its refractory phase ensuent on the impulse. In the course of this work, besides putting fundamental questions and answering them, Lucas devised for so doing instruments of remarkable ingenuity, elegance, and precision. By 1914 he was recognized as a leader in this field of science. He was appointed Croonian lecturer of the Royal Society in 1912, and was elected F.R.S. in 1913.

In 1914, on the outbreak of war, the services of Lucas, who was about to enlist as a private in an infantry battalion, were secured on 4 September for the Royal Aircraft Factory at Farnborough, ‘by a lucky stroke’, as the superintendent, Lieutenant-Colonel Mervyn O'Gorman, later wrote. There, his autographic registration of aeroplane roll, pitch, and yaw soon led to his being entrusted with further problems. For the Air Service he evolved the air-damped pendulum, improved the ‘sights’ for bomb-dropping, traced to its causes the compass disturbance which vitiated aeroplane-steering and at that time constituted an unexpected difficulty in aviation, and devised, partly in collaboration with (Sir) Horace Darwin, a type of compass which largely avoided error from this cause. Meeting with indomitable, quiet energy the ceaseless urgency for new developments of aeroplane design, and with self-effacing devotion examining and testing them against the practical conditions of flight, Lucas met his death when flying near Aldershot on 5 October 1916. He married in 1909 Alys, daughter of the Rev. Cyril Egerton Hubbard, by whom he had three sons.

[Obituary notice (by H. Darwin and W. M. Bayliss) in Proceedings of the Royal Society, vol. xc, B, 1917–1919 (portrait); personal knowledge.]

C. S. S.