The son of Dr McDonagh, of Ranelagh, Co Dublin; studied at Trinity College, first acted in the Cunard Ship Company's Service, then as a Civil Surgeon in the Crimea. He next lectured and demonstrated on anatomy in the School of Medicine of Apothecaries' Hall, Ireland, and was a Member of its Court of Examiners. Subsequently he was for many years in general medical practice at Hampstead and was active in local affairs and at the British Medical Association. On retiring from practice in 1889 he first lived at 64 Parliament Hill Road, and then at 23 Gloucester Road, Regent's Park, where he died on February 10th, 1899. He was twice married, and by his first wife had two sons and a daughter, one son only surviving him.