Born on January 17th, 1851, at Dufftown, Banffshire, the son of a banker interested in farming, who handed on to his son a love of outdoor life. He was educated at the Milne Institution, Fochhaber, then at the University of Aberdeen, being the only student in attendance wearing the kilt. After graduating in Natural Science with Honours in 1871, he proceeded to Charing Cross Hospital for his clinical studies under the influence of Dr Mitchell Bruce, who knew him from boyhood and was then teaching anatomy. Cantlie became House Surgeon and then Demonstrator and Lecturer on Anatomy (1872-1887), and in 1877, having become FRCS he was appointed Assistant Surgeon to Charing Cross Hospital, becoming Surgeon in 1886 and resigning his office in 1888. Cantlie first became interested in the work of the St John Ambulance Association and later in that of the Red Cross when in 1878 Surgeon Major Peter Shepherd, AMS, left with Mitchell Bruce and Cantlie the proofs of his *First Aid to the Wounded*. Shepherd had been ordered to the war in Zululand, where he fell at Isandlwana. It was in 1883 that Cantlie commenced the classes at Charing Cross Hospital which developed into the systematic framing of the RAMC Territorial Force. In 1883 he was one of twelve young medical men who were sent to Egypt to assist in dealing with the epidemic of cholera introduced by pilgrims from Mecca. In a lecture he delivered at the Parkes Museum of Hygiene on Jan 27th, 1887, entitled “Degeneration amongst Londoners”, his mildly extravagant statements directed to the encouragement of exercise in fresh air met with a good deal of cheap ridicule in the public Press, generally epitomized in the statement that Londoners die out in the third generation. He had just become full Surgeon to the hospital when he accepted Patrick Manson’s invitation to join him at Hong Kong and become Dean of the Chinese School of Medicine. At the same time he engaged in a large surgical practice. Among the students at the College of Medicine was Sun Yat Sen, who subsequently was concerned in converting the Empire into a Republic. And when Sen in October, 1896, was held captive in the London Chinese Legation, Cantlie was instrumental in getting him released. He also inquired into the distribution of leprosy in China and adjacent parts of the East Indies, and in 1894 encountered an outbreak of plague. He returned to London in 1897 and set to work to advocate a Tropical Medical School in London, a Tropical Section at the Annual Meeting of the British Medical Association, and a Tropical Medical Journal published in London. Backed up by Sir Patrick Manson, then Medical Adviser to the Colonial Office, he read a paper at the Imperial Institute urging a School of Tropical Medicine for medical officers going to the Tropics. A Committee was formed at Manson’s house, Mr Joseph Chamberlain’s interest was secured, and he presided at a dinner with the result that £16,000 was collected and the London School of Tropical Medicine was opened in 1899. The British Medical Association Section of Tropical Medicine was inaugurated at the Edinburgh Meeting in 1898; and Manson, the President, read out the telegram from Sir Ronald Ross announcing the discovery of the malaria parasite in the mosquito. Cantlie was Secretary of the section, and at subsequent meetings Vice-President and President. The first number of the *Journal of Tropical Medicine and Hygiene*, with Cantlie and Professor Sir William Simpson as editors, appeared in 1898; Manson and later Cantlie were Presidents of the Royal Society of Tropical Medicine, and Cantlie presented the gold chain and insignia for the President. He contributed many articles on tropical surgical affections, but gradually his attention concentrated itself upon ambulance work. On the formation of the Territorial Armies he became Hon Colonel RAMC (TF), 1st London Division. He held classes and lectured at the Polytechnic on first aid to the wounded. From that he passed on to found the College of Ambulance for the training of both men and women. The training of VADs started in 1908, but with the outbreak of war in 1914 it was greatly developed under Lady Cantlie. Among numerous inventions which are owing to his genius and untiring exertion are a portable X-ray apparatus, and exercises graduated for people of mature age; he attacked the Eton jacket for exposing the loins, also the ‘baby’s comforter’ as the transmitter of infection. At the Newcastle Meeting of the British Medical Association in 1921 Cantlie was President of a special section of Ambulance. The same year, 1921, marked the decline of his active career owing to the death of Lady Cantlie. In private life Cantlie was a delightful and entertaining companion and host, abounding in Scotch humour, whilst the faculty of imitation and the instincts of a born actor made him an admirable after-dinner speaker and singer. He started a Students’ Dinner, and presided over the dinner of the Caledonian Society. He preached at St Martin’s Church on Hospital Sunday, and addressed a Jewish audience on the hygiene of Moses. After prolonged retirement and ill health, latterly accompanied by mental disturbance, he died in London on March 25th, 1926. Cantlie married in 1884 Mabel Brown, daughter of Robert Barclay Brown, and there were four sons. His wife was his great helper in all private and public work. To her he was entirely indebted for the management of his finances. Upon her too fell the severe work of conducting the training of the VADs in ambulance work, and her death in 1921 was an irreparable loss. Publications:– *Degeneration amongst Londoners*, London, 1885. *Leprosy in Hong Kong*, Hong Kong, 1890. *Report on the Conditions under which Leprosy occurs in China*, etc., London, 1897. *Plague and how to Recognize and Treat Plague*, London, 1901. *Physical Efficiency: A Review of the Deleterious Effects of Town Life upon the Population of Britain*. Preface by Sir Lauder Brunton; Foreword by Sir James Crichton Browne, London, 1906. *First Aid Manuals*, revised 1915, 1926, etc. A great number of other publications.