Denis was educated at the Edinburgh Academy and at Christ’s College, Cambridge, where he spent two years in medical study. He completed his curriculum in Edinburgh, gaining distinction in pathology and surgery, and graduated in 1906. In 1910 he was elected a Fellow of the Royal College of Surgeons, Edinburgh, and took a seat as a Fellow during his father’s occupancy of the presidential chair. He was house surgeon under the Professor Annandale, and on he Continent and in London and Liverpool studied surgery, especially in its orthopedic aspects, in which he intended to specialize. On his return to Edinburgh Denis began practice as a surgeon, whilst acting as tutor in clinical surgery, and in 1913 was appointed an assistant surgeon to the Royal Infirmary. Denis entered the war in France on the 1st December 1914 with the British Red Cross, attached to No 11 Stationary Hospital at Rouen. He remained there until January 1918, when he resigned this appointment and joined the R.A.M.C., gaining a commission at the rank of Lieutenant, and was sent to serve with No 50 Casualty Clearing Station at Bohain, France. He died there of pneumonia following influenza. Denis was the eldest son of Lieutenant-Colonel Joseph Montague Cotterill, C.M.G. (consulting surgeon to Edinburgh Royal Infirmary) and Mary Jane Cotterill; and the husband of Emily J Cotterill of Ardnacraggan, Callander, Perthshire - married in 1908, they had two sons.