Born in Dublin on January 19th, 1845, the second son of Henry Yeo, of Ceanchor, Howth, JP, clerk of the rules, Court of Exchequer, by his wife Jane, daughter of Captain Ferns. Educated at the Royal School, Dungannon, and at Trinity College, Dublin, where he graduated Moderator in natural science 1866, proceeding MB and MCh in 1867. He gained the Gold Medal of the Dublin Pathological Society in 1868 with an essay on renal disease. He then studied for a year in Paris, a year in Vienna, and a year in Leipzig and Berlin, took the MD at the University of Dublin in 1871 and the LRCSI in the following year. He first acted as Demonstrator of Anatomy at Trinity College, Dublin, and then taught physiology in the Carmichael School of Medicine in Dublin from 1872-1874. In 1877 he was appointed Professor of Physiology at King's College, London, and Assistant Surgeon to the Hospital. Here he did excellent work in conjunction with Sir David Ferrier - then Professor of Neuropathology - on the cerebral localization in monkeys. The experiments were done using the antiseptic measures of Lister, and were in that respect an advance in cerebral surgery. They were later noted by Victor Horsley (qv). Yeo was elected in 1889 a FRS. He resigned his chair in 1890 and received the title of Emeritus Professor. At the Royal College of Surgeons Yeo was Arris and Gale Lecturer on Anatomy and Physiology, 1880-1882; a Member of the Examining Board of Anatomy and Physiology for the Fellowship, 1884-1885 and 1887-1892; and a Member of the Examining Board in England, 1884-1885. The subjects of his Arris and Gale Lectures were: (1) "Application of the Graphic Method to the Study of Muscle Contraction", and (2) "Relation of Experimental Physiology to Practical Medicine". He retired to Totnes, Devonshire, in 1889, and later to Fowey, where, having a competence, he devoted himself to yachting, fishing, and gardening. He married: (1) In 1878 Charlotte, only daughter of Isaac Kitchin, of Rock Ferry, Cheshire, who died in 1884 without issue; (2) In 1886 Augusta Frances, second daughter of Edward Hunt, of Thomastown, Co Kilkenny, and by her had one son. He died at Austin's Close, Harbertonford, Devonshire, on May 1st, 1909. Yeo was a fluent speaker with a rich brogue, good-natured, impetuous, generous, and full of common sense. Although he was appointed Assistant Surgeon to King's College Hospital, he never took the duties seriously, for his whole interests were centred in the physiological laboratory. He was an experimentalist and acknowledged Karl Ludwig as his master. In conjunction with Professor Krönecker, of Berne, he inaugurated the international physiological congresses which were held triennially, the first meeting being in Berne in 1891. He did good service to English physiologists by founding the Physiological Society in March, 1876. It was at first a dining club with a carefully chosen and limited membership, Yeo being the Secretary. He conducted the affairs with tact and energy until his resignation in 1889, when he was presented with a valuable souvenir of plate. A small woodcut, which is a good likeness, is inserted in the Supplement to the *Journal of Physiology* for December, 1927, p 32. Publication: *Manual of Physiology for the Use of Students of Medicine*, London, 8vo, 1884; 2nd ed, 1887. It was a useful and popular text-book.