Born 17 April 1850 at Newark, New Jersey, the son of Alfred Lewis Dennis and Eliza Shepard, his wife. He was educated at Winchester Academy, Connecticut, where he made an intimate and lasting friendship with W H Welch, afterwards professor of pathology at the Johns Hopkins University. From Winchester Academy he went to the Phillips Academy at Andover, Massachusetts, and from there to Yale University where he graduated in 1872. He received his medical degree from the Bellevue Hospital Medical College, New York in 1874, and in 1876-77 took postgraduate medical courses at Heidelberg and under Von Langenbeck in Berlin and Lister in Edinburgh. He was admitted MRCS in 1877. Returning to the United States he was appointed instructor in surgery at the Bellevue Hospital Medical College, becoming professor of surgery there from 1883 to 1898. During this period he was instrumental in persuading Andrew Carnegie to found the Carnegie Pathological Laboratory in the Bellevue Hospital Medical College. He was selected to act as professor of clinical surgery at Cornell University in 1898, and retired from office in 1910 with the title of emeritus professor. He was president of the American Association of Surgeons, a founder of the Harlem Hospital, a Fellow of the Clinical Society of London, and a member of the German Surgical Congress. Dennis was a great surgeon and a great teacher, who did much to popularize the practice and teaching of Lister in the United States. He died on 8 March 1934 at 1136 Fifth Avenue, New York, aged 83. Publications:- *The American Textbook of Surgery*. Philadelphia, 1892; 2nd edition, 1895. (Editor) *A System of Surgery*, in 4 vols. Philadelphia, 1895-6. (Editor) *A Memoir of James R Wood, MD*. New York, 1884; 24 pages with portrait; and again the same year: 31 pages with portrait. *Selected Surgical Papers*, 2 vols., with portrait and bibliography. New York, 1934.