Born at Croydon in 1870 he was educated at Chatham House College, Ramsgate, and at Charing Cross Hospital, London. Here he was house physician, house surgeon, assistant demonstrator of anatomy, acid surgical registrar. He then proceeded to Newcastle, where he was appointed assistant demonstrator of anatomy in the Durham University, and from there migrated to Canada, where he practised as a doctor for a short time. In 1902 he was appointed demonstrator of anatomy at the Medico-Chirurgical College, Philadelphia. From Philadelphia he passed in 1907 to the Syracuse University, returned to the Wistar Institute as professor of anatomy and biology, settling finally at New York in 1910 as a professor of anatomy and director of the anatomical laboratories in the New York University. He was a vice-president of the American Anatomical Association for the year 1922-23, and was for many years associate editor of the *American Journal of Anatomy*. He married in 1901 Jean Hedley of Halifax, Nova Scotia, and died in the French Hospital, New York on 6 August 1938. It was said of Professor Senior that "he followed to the end the British tradition of teaching anatomy by personal supervision of his pupils, as opposed to the American method which made the student a responsible person requiring but little personal attention, abundant equipment and a numerous staff, with insistence upon personal research". He was a great teacher of individuals, who found time to carry out much good work on the development of the blood vessels in relation to their genetic factors. For this work he was given an honorary DSc and was awarded a gold medal by the University of Durham in 1918.