Born at Leigh, near Manchester, 29 January 1853, the eldest child of John Barlow, clothier, and Hannah Welsby, his wife. He was educated at Crowbent, Lancashire, at Anderson's College, Glasgow and at the Universities of Glasgow and Edinburgh, graduating from the latter in 1875, having taken the English MRCS the previous year. Barlow began his career as a pure physiologist and served as physiological assistant to Professor John Gray McKendrick, MD, FRSEd (1841-1926). He then became first Muirhead demonstrator of physiology at the Glasgow Royal Infirmary School of Medicine and subsequently professor of physiology at St Mungo's College, before its absorption by the Royal Infirmary School. He was also lecturer in physiology at the Royal Technical College, and was in demand as a lecturer to popular audiences. After some years he felt the urge to turn from academic work to practical surgery. He was elected a Fellow of Faculty in 1881 and admitted to the English Fellowship in 1885. In 1892 he was appointed visiting surgeon at the Royal Infirmary and was elected consulting surgeon on his retirement in 1913. Barlow was a fluent teacher both in physiology and surgery. He served as an examiner in physiology for the Fellowship at the Royal College of Surgeons of England in 1890, and at the Royal Faculty in Glasgow he was successively an examiner and a councillor, and served as president 1913-15. He was commissioned on 3 July 1908, when the RAMC territorial force was formed, lieutenant-colonel *à la suite* on the staff of the 14th Scottish General Hospital, Glasgow. Barlow married three times: (1) Annie Smithells, by whom he had one daughter; (2) Annie Macintyre, by whom he had two sons and three daughters, of whom one died young; and (3) seven years before his death, Agnes Strachan, who survived him. Three of his six children entered the medical profession. Of these, his daughter by his second marriage, Annie (MB Glasgow 1920), married George Thomson Mowat, FRFPS, surgeon to the Royal Infirmary; Mrs Mowat served as anaesthetist at the Glasgow Eye Infirmary. He practised at 4 Somerset Place, Glasgow and lived after his retirement at Broomfield, Callander, Perthshire, where he died on 27 December 1943, aged 90. Publications:- Physiological actions of ozonised air. *J Anat Physiol*. 1879, 13, 107. Statistics of surgical operations 1883-92. *Glasg med J*. 1892, 38, 1. Intussusception in infants treated by abdominal section. *Lancet*, 1899, 1, 291.