Caniff was a Union surgeon during the American Civil War. This work was entirely based on his lectures on general pathology and surgery at Victoria College. In 1868, Caniff became professor of surgery and sub-dean of the medical faculty at Victoria and the following year was appointed to the staff of theToronto General Hospital. In 1870, he became a consulting surgeon to the Toronto Eye and Ear Infirmary and eventually became dean of the medical faculty at Victoria. He was appointed president of the Canadian Medical Association in 1880 and, in 1883, became Toronto's first medical health officer, promoting sanitation and disease control. His major work was The Medical Profession in Upper Canada, 1783-1850, published in 1894.