Harry was educated at the Irvine Royal Acadamy, at Anderson's College, and at the University of Glasgow, where he graduated in medicine, with commendation in 1905. He was described as a "scratch" golfer, representing his Universities in several matches and winning many cups and other prizes. After qualifying he held the posts of resident house surgeon and house physician at the Glasgow Western Infirmary and assistant medical officer at the Brook Fever Hospital under the Metropolitan Asylum Board. He joined the R.A.M.C. in January 1909, taking first place at the entrance examination and retaining this place at the examination during the probationary course. He also gained the Tulloch medal, the medal for military medicine, the medal and prize for tropical medicine, the De Chaumont prize in hygiene and the prize of £20 for grand aggregate of marks in all examinations during the probationary course, open to the R.A.M.C. and the I.M.S. From 1919 to 1911 Harry was stationed in London under the Eastern Command, and during this period was assistant to Sir William Leishman at the Royal Army Medical College and to Dr H G Plimmer in the Brown Institute, and engaged himself in research work, particularly in connexion with sleeping sickness. In 1910 he obtained the M.R.C.P. diploma, and in the following year passed the examination for captaincy with special certificate and was promoted Captain in July 1912. During these years he contributed, jointly with Major W B Fry and Dr Plimmer, several important papers on trypanosomiasis, which were published in the Proceedings of the Royal Society. From August 1911, until June 1914, he transferred to the Egyptian Army and served as a member of the Soudan Government Sleeping Sickness Commission, and was in charge of the camp at Yei in the Lado enclave, Western Mongalla. He was described as a keen big game shot in the Soudan. He went home on leave in July 1914 and volunteered for war service, he was restored to the British establishment in August 1914 and entered the war in France with the Expeditionary Force on 12th August 1914. Harry was awarded the Croix de Chevalier of the Legion of Honour (France) for gallant conduct during the operations from 21st to 30th August 1914. One month later his bravery resulted in his being awarded the Victoria Cross and in his death. His citation reads "For tending wounded in the trenches under rifle and shrapnel fire at Hautevesnes on 19th September and on 20th September continuing to attend to wounded after his thigh and leg had been shattered." The Times History of the War Pt. 41, p.44 says "It is a safe statement that no man ever won the Victoria Cross more nobly than did Capt. Harry Sherwood Rankin R.A.M.C. Capt Rankin was severely wounded in the leg whilst attending to his duties on the battlefield. He arrested the bleeding from this, and bound it up, and then continued to dress the wounds of his men, sacrificing his chances of salvation to their needs. When finally he permitted himself to be carried to the rear, his case had become almost desperate. He died within a short period." Lieut Robinson of 8th Field Ambulance wrote in his narrative for 23rd September 1914 - “It was on one of these days at Braisne that I came across that very gallant fellow Captain Rankin, R.A.M.C. When I saw him he was lying on a stretcher on Braisne Station platform; he was smoking a cigarette and talking with animation. He had recently had his leg amputated somewhere above the knee, but had said he was in no pain and was quite comfortable and well. We were horribly shocked to hear a day or two later that he had died suddenly of Embolism; but he had already received the award of the V.C. for his work at the time when he received his injuries.” Col Northey commanding 1st Bn. King's Royal Rifle Corps, and several other of his brother officers, wrote to his parents of their personal loss and the loss to the whole Battalion. The PMO of the Egyptian Army regarded his death as a great loss to science. Sir William Leishman deplored the loss of a friend and wrote of him as a man who thought nothing of doing three men's work. Additionally, the Lancet wrote "The bare record of his scientific and professional career shows that he was a man of unusual ability with a special leaning towards research, and his early and heroic death robs the RAMC of one of its most promising and accomplished junior officers. Harry was the elder son of the Reverend Henry Ranken, B.D., minister of Irvine parish, and Helen Morton Ranken of The Manse, Irvine, Ayrshire.