Canniff was rapidly promoted to Professor of Surgery, however, he resigned his position in 1863 following a conflict with his colleague, John Rolph.[2] Canniff returned to the Victoria School in 1868 and remained there until its closure in 1874. During his brief departure from Victoria College, Canniff authored the first Canadian textbook on pathology, A manual of the principles of surgery: based on pathology for students, Philadelphia: Lindsay & Blakiston, 1866.[1] Canniff became a founding member of the Canadian Medical Association in 1867 and the Ontario Medical Association in 1880.