Henry Hamilton Green (later known as Harry Green) received his schooling in Glasgow and then studied at the West of Scotland Agricultural College, Royal Technical College, and University of Glasgow. He obtained a BSc degree in chemsitry in 1910, and the next year continued his studies in physiological chemistry at the University of Glasgow. In 1912 he was awarded an 1851 Exhibition Research Scholarship and went to the University of Leipzig where he worked on industrial and soil bacteriology during 1913. He was one of the pioneers of the new discipline of biochemistry, and received the degree Doctor of Science (DSc) from the University of Glasgow in 1916.
Green came to South Africa in February 1914 to join the research staff at the Onderstepoort Veterinary Research Institute. There he started a biochemistry laboratory and initiated a study of vitamin deficiencies, thought to possibly play a role in lamsiekte (botulism). When phosphate deficiency was identified as a key factor in the development of this disease he switched to studying mineral deficiencies, a field in which he remained until he left Onderstepoort in 1927. His work resulted in a number of publications in collaboration with Arnold Theiler*, P.J. du Toit* and others in the annual Reports of the Director of Veterinary Research, including two on lamsiekte and a series of seven under the general title "Studies in mineral metabolism". During 1920-1921 he spent a year at Yale University in the United States in preparation for his duties as professor of biochemistry in the newly established Faculty of Veterinary Science (of the Pretoria University College) at Onderstepoort, a post to which he was appointed in 1920. For a short period he also lectured on general bacteriology. During the next few years he published several papers in the South African Journal of Science, on "The toxic principles of Adenia digitata (1923, Vol. 20, pp. 273-274, with W.H. Andrews), "A bacterium decomposing nicotin" (1923, Vol. 20, pp. 274-275, with Ida Loustein), and "Mineral requirements of farm stock" (1926, Vol. 23, pp. 196-7). He was a person of marked creative ability, also an extremely hard worker, but suffered a mental breakdown in 1927. As a result he returned to Britain with his family that year.
Following extended treatment Green made a remarkable recovery in 1930 and subsequently enjoyed a second career at the Veterinary Laboratory at Weybridge, Surrey. There he worked on a much improved type of tuberculin that came to be know as purified protein derivative (PPD) which is still in use today. He headed the Biochemistry Department at Weybridge from 1933 to 1953.
Green was active in a number of local and British scientific societies. Soon after his arrival he became a member of the Transvaal Biological Society, read three papers before it, and was its president when it amalgamated with the South African Ornithologists' Union in 1916 to form the South African Biological Society. He served as president of the latter in 1923 and received its Senior Captain Scott Memorial Medal three years later. He was elected a Fellow of the Royal Society of South Africa in 1925. After becoming a member of the South African Association for the Advancement of Science in 1915 he was elected a member of its council, served as president of Section B in 1919, and was awarded the association's South Africa Medal (gold) in 1928 in recognition of his brilliant biochemical research. He became a member of the South African Association of Analytical Chemists (from 1921 the South African Chemical Institute), in 1919, served on its council from 1921, as vice-president for 1922/3, and as president for 1923/4.