Barcroft, Sir Joseph (1872–1947), physiologist, was born at The Glen, Newry, Co. Down, second of five children of the quakers Henry Barcroft (qv), DL, and Anna (Richardson) Barcroft, daughter of David Malcomson of Melview, Co. Tipperary. Educated at the Friends’ School, York, and the Leys School, Cambridge (1889–92), he received a London University B.Sc. (1891) while still a schoolboy. He entered King's College, Cambridge (1893), graduated (1897), and became a fellow (1899) and lecturer (1909). His work – at Carlingford, Co. Louth, later at Tenerife (1910) and Monte Rosa (1911) – on the oxygen dissociation curve of haemoglobin and the physiology of life at differing altitudes is summarised in The respiratory function of the blood (1914). In 1917 Barcroft joined the war office chemical-warfare committee and became chief physiologist at Porton, studying the effects of gases on the respiratory and circulatory systems, with himself as a subject. He returned to Cambridge as reader in physiology (1919) and became Fullerian professor of physiology of the Royal Institution (1923–6) and professor in physiology at Cambridge (1926–37). His research concentrated on cardiovascular and respiratory physiology. His The architecture of physiological function (1934) attempted to find the central integrating principle of bodily functions. In 1941 he became head of the Agricultural Research Council Unit in Animal Physiology; its pioneering work on foetal physiology is described in Researches in pre-natal life (1946). Editor or author of over 300 publications, member and president of many societies, he received numerous honours from institutions throughout the world, including honorary degrees from QUB (1931), NUI (1933), Harvard (1936), and Dublin (1937). He was made FRS (1910), CBE (1918), and a knight (1935), and received the Copley medal of the Royal Society (1944). International conferences were held in Cambridge to commemorate his pioneering work on haemoglobin (1948), and a centenary symposium on foetal and neonatal physiology (1972). Mount Barcroft, site of the University of California high-altitude laboratory, was named in his honour (1952). Barcroft spent most of his life in England, but maintained strong personal and professional links with Ireland, which he frequently visited. He died in Cambridge 21 March 1947.
He married (1903) Mary Agnetta, daughter of the astronomer Sir Robert S. Ball (qv); they had two sons, Henry (physiologist and FRS) and Robert.