Barcroft, Henry (1904–98), physiologist, was born 18 October 1904 in Cambridge, the elder of two sons of Sir Joseph Barcroft (qv), an eminent physiologist and professor at Cambridge university, and his wife, Mary Agnetta (1875–1961), daughter of Sir Robert Ball (qv), astronomer royal of Ireland. His childhood was steeped in the scientific milieu of his father's career, which frequently spilled over into their family home. Educated at first by a German governess, he was fluent in German by the age of ten and continued his education at the choir school at King's College, Cambridge (1912–18), and Marlborough College (1918–23). In the summer of 1923, before starting his university studies at King's College, he assisted his father in performing laboratory experiments that resulted in two joint publications in influential journals. At Cambridge he obtained a double first (1925 and 1927) in the natural sciences tripos. Having started postgraduate studies in physiology at Cambridge in 1927, he eventually opted to complete his medical training at St Mary's Hospital, London, in 1928. He qualified MRCS, LRCP (1932), and completed the MB B.Chir. degree at Cambridge the following year. In 1932 he obtained an appointment as a lecturer in physiology at University College, London, and worked with many of the giants in the subject, pursuing his research interests with single-minded determination.
Appointed to the Dunville chair of physiology at QUB, Barcroft moved to Belfast in 1935, receiving his MD in the same year. Although the appointment was difficult, not least because of sparse facilities and a huge teaching load, he remained at QUB for thirteen years, during which time he revitalised the department and spearheaded the introduction of research to what had been an almost exclusively clinical medical degree. With his enthusiastic and authoritative lecturing he inspired undergraduates, influencing a new generation of medical students such as Robert Ford Whelan (qv) to pursue research careers. While at Queen's his personal research interests changed. Having realised the limitations of his previous work on animal physiology, he began to focus on human peripheral circulation, using himself as the subject of his experiments – a practice that became a tradition among physiologists at Queen's. At this time he made one of his greatest contributions to science when, with Otto Edholm, he succeeded in making instantaneous measurements of venous blood flow, which paved the way for their highly respected work on the nervous and chemical control of blood circulation in human limbs. Returning to London and St Thomas's Hospital when he was appointed the Sherrington professor of physiology (1948), he continued much of the research begun at QUB, and at St Thomas's too raised the profile of clinical research. He retired in 1971; shortly before his death the Physiological Society celebrated his contributions to physiology in a special lecture held in London, which he attended.
Greenfield and Roddie prepared a bibliography of his published work (2000): the papers published while he was in Belfast and the monograph Sympathetic control of human blood vessels (1953, with H. J. C. Swan) are regarded as significant. The latter was the first in a series published by the Physiological Society and it remains a classic work of reference on the subject. Despite a lack of interest in administrative responsibility, he received many scientific honours, including election to fellowship of the Royal Society (1953) and honorary membership of the Physiological Society (1974).
Barcroft was an energetic and resourceful man, who combined great intellectual capacity with a talent to inspire others through his genuine warmth and modesty. Maintaining an active interest in research throughout his career, he eschewed academic politics and emerged from the shadow of his father to demonstrate the key importance of physiology to clinical medicine. In 1933 he married Bridget Mary (Biddy) Ramsey (d. 1990), also a medical doctor, and they had four children together. He died 11 January 1998 at his home, 73 Erskine Hill, Hampstead, London, aged ninety-three.