Born in Newry, County Down into a Quaker family, he was the son of Henry Barcroft DL and Anna Richardson Malcomson of The Glen, Newry – a property purchased for his parents by his mother's uncle, John Grubb Richardson and adjoining his own estate in Bessbrook. He was initially educated at Bootham School, York and later at The Leys School, Cambridge. He married Mary Agnetta Ball, daughter of Sir Robert S. Ball, in 1903.
In 1936 he was nominated, unsuccessfully, by Professor Arthur Dighton Stammers, Professor of Physiology in the University of the Witwatersrand, for the Nobel Prize in Physiology or Medicine, for his work on the respiratory function of the blood and the functions of the spleen.[5]
In the course of his research, he did not hesitate to use himself as a test subject. For example, during the First World War, when he was called to Royal Engineers Experimental Station (near Salisbury) to carry out experiments on asphyxiating gas, he exposed himself to an atmosphere of poisonous hydrogen cyanide. On another occasion he remained for seven days in a glass chamber in order to calculate the minimum quantity of oxygen required for the survival of the human organism, and another time he exposed himself to such a low temperature that he collapsed into unconsciousness.
He also studied the physiology of oxygenation at extreme altitudes, and for this purpose he organized expeditions to the peak of Tenerife (1910), to Monte Rosa (1911), and to the Peruvian Andes (1922).
Between 1902 and 1905 he was a Governor of Leighton Park School, the Quaker School in Reading. From 1925 to 1937 he held the chair of physiology at Cambridge. His final research, begun in 1933, concerned fetalrespiration.
