O'Connor, James Malachy (1886–1974), physiologist, was born in Limerick on 9 February 1886, the son of Michael Roderick O'Connor, visiting physician at Barrington's Hospital, and Kathleen O'Connor (née Bowler). He was educated at the Crescent College, Limerick, and then entered UCD, where he had a distinguished undergraduate career and took an extra two years to pursue his interest in science, philosophy, and languages, obtaining a BA (1907) and then graduating MB, B.Ch., BAO (1909). He was one of the last graduates of the RUI. After winning a travelling studentship in physiology (1910) he carried out postgraduate studies for three years at Leipzig and Heidelberg, where he worked with the physiologist R. Gottlieb at the Pharmacological Institute. As Gottlieb's assistant (1911–12) he carried out valuable work on adrenaline in the blood, which anticipated the discovery of serotonin, an important neurotransmitter. Their results were published between 1911 and 1912 in four papers in the journal Archiv für experimentelle Pathologie und Pharmakologie, but it seems the work was ahead of its time and was not well received. However, the thorough scientific and philosophical training O'Connor received in Germany informed the rest of his long career as a dedicated medical researcher and, through his teaching, a generation of Irish medical students.
On his return to Ireland O'Connor served as assistant (1912–20) to the professor of physiology at UCD, Bertram Collingwood (1871–1934). On the basis of his published work he was awarded the MD from the NUI in 1913, and when Collingwood resigned, in 1920, O'Connor succeeded him. Though a relatively young man, as professor of physiology from 1920 until 1956 he made many contributions to the organisation of teaching in the department, introducing a course in human physiology to the medical degree in 1940, the first of its kind in Ireland or Britain. In spite of heavy teaching and administrative commitments, O'Connor maintained his interest in experimental research. Working primarily on the regulation of body temperature and functioning in renal tubules, he made a substantial contribution to the understanding of auto-regulation in the kidney by showing that renal blood flow remained constant in spite of changes in perfusion pressure. He was also a popular and diligent teacher; one of his more exceptional students was Denis K. O'Donovan.
Though he never achieved an international reputation, along with his contemporary Edward Joseph Conway (qv) O'Connor was one of the brightest students of his day. Some of his colleagues believed that much of his research was undervalued, partly due to ‘his purposefully unfashionable method of presentation and his reluctance to claim the lime-light’ (O'Donovan, 464). Throughout his career he was actively involved in the regulation of the medical profession in Ireland, serving on the Medical Research Council of Ireland from its foundation until shortly before his retirement (1937–52). An able administrator, he was dean of the UCD medical faculty (1941–56), represented his university on the Medical Registration Council (1945 onwards), and was the Irish representative on the General Medical Council (1945–60). He had a reputation for efficiency and economy, and the president of UCD, Michael Tierney (qv), who was also a close personal friend, openly acknowledged his contribution to the running of the university as an active member of both the governing body and the academic council. He was awarded an honorary D.Sc. in 1956.
O'Connor published regularly throughout his career, and Harman lists his publications from 1912 to 1965, though some of his first papers published in Germany in 1911 are omitted; he is the sole author of most, but there were also collaborations with Oliver FitzGerald (qv), Conway, and O'Donovan. Many of his papers were published in the Proceedings of the Royal Irish Academy. He was an active member of the RIA: he was elected MRIA (1930), served on the ruling council (1940–44), and was vice-president twice (1949–52, 1958–63) as well as president (1955–8).
Known to his friends as James Malachy, O'Connor was a man of great integrity, modesty, and quiet intelligence, and as such was popular and well respected among his colleagues. He enjoyed exercise and eschewed the use of a car. In his recreation time he regularly hiked long distances in the Wicklow mountains with some of his students. His other great love was philosophy, and he read extensively on the subject. Such was his interest in physiology that he continued private research for over ten years after his retirement in his own laboratory, where he had a reputation for experimenting on himself and using the same laboratory rat over and over again. On the occasion of his eightieth birthday the Royal Academy of Medicine in Ireland, of which he was a fellow for some forty years, dedicated a special volume of its journal, the Irish Journal of Medical Science, to reflect the influence of his life's work.
O'Connor married (Mary) Genevieve (Gen) McGilligan (1919), and they had four sons, one of whom did not survive. James Malachy died 4 December 1974 at his home in Palmerston Villas, Rathmines, aged eighty-eight, and his wife died shortly afterwards.