Among medical historians, Thomas Laycock¹ is best known for his determining influence on the young Hughlings Jackson. Laycock’s interests were the nervous system and psychology.^2,3

Thomas Laycock was the son of a Wesleyan minister. In Bedale, a pretty Yorkshire village just one mile off the Great North road (A1), he trained as an apprentice surgeon-apothecary. He attended the University College, London, furthering his training in Paris for two years, under Alfred Armand Velpeau (1795–1867) and the pathologist, Pierre Louis (1787–1872) an initiator of statistics. In Göttingen, he received his doctorate degree, summa cum laude. He returned to the York County Hospital, receiving preferment as lecturer at York Medical School and physician to the York Dispensary.

In 1852 Laycock encountered Hughlings Jackson, a new student; he also taught Jonathan Hutchinson whom Jackson was to meet in 1859 and share a house with at 14 Finsbury Circus, London for three years. Hutchinson was to become surgeon to the London Hospital (1863), President of the Royal College of Surgeons (1889), and FRS (1881). In 1848 he wrote:

“Dr Laycock: a real treat to listen to—some good observations against materialism.”

He later acknowledged, that Dr Laycock had taught him about heredity.

Laycock taught in York from 1846 and worked with Daniel Hack Tuke who had studied treatment in psychiatric disorders. He published an acclaimed and lasting Manual of Psychological Medicine in 1858.⁴ Tuke took the young Jackson to visit his mentally ill patients at The Retreat. Laycock’s studies led to papers on periodic illness (proleptics),⁵ in the Lancet, since he considered an understanding of periodicities essential for the treatment ofdiseases.⁶ The concept probably anticipates modern ideas of biological clocks and diurnal rhythms. He wrote articles on hysteria and on reflex function of the brain,⁷ and systemic disorders.⁸

Following Robert Whytt, and Marshall Hall, Laycock emphasised that the nervous system must be seen as one continuous series of structures obeying one law, that of the reflex.⁹

He extended the studies of Johann August Unzer (1727–1799) and Jirí Procháska (1749–1820), which he translated.¹⁰ Unzer’s book Erste Gründe einer Physiologie der eigentlichen thierischen Natur thierischer Körper was a system of physiological metaphysics introducing reflex action, afferent or “external sensory impression” and efferent or “internal impression” paths, but wrongly localised the central part of the reflex. Procháska termed the central mechanism of the reflex the sensorium commune lying in the spinal root ganglia and peripheral plexuses.

Laycock stated⁷:

“The brain, although the organ of consciousness, was subject to the laws of reflex action and in this respect it did not differ from other ganglia of the nervous system.”

He concluded that the entire nervous system was the seat of reflex function in which the mind played no part.¹¹ This revolutionary idea was later supported by the experiments of Sechenov and were the foundation for the work of Pavlov, Ferrier, and Sherrington. Laycock’s role in such a fundamental aspect of the history of the study of mind and brain has perhaps been neglected.¹² In 1855, Laycock became Professor of Medicine in Edinburgh.¹³ There he met David Ferrier and orientated him towards neurology. Laycock published Mind and Brain in 1860,containing one volume on philosophy, one on physiology.