The younger son of Thomas Hovell, of Wyverstone, Suffolk, who had been educated at the London Hospital and had practised at Clapton, North London. Dennis, together with his elder brother, Mark, also studied at the London Hospital, being articled to John Scott, Surgeon to the London Hospital. Both brothers held resident appointments, and Dennis in 1837 gained the Hospital Gold Medal for Surgery. Both his father and his elder brother having died, Dennis Hovell continued his father's practice at Five Houses, Clapton. He especially gave attention to midwifery, and was particularly fond of a truss after labour instead of the usual binder, for he held it as comfortable to the patient and preventive of post-partum hemorrhage. He objected to the current view of hysteria, which attributed it to uterine trouble and a defective moral sense; he attributed it to injury or shock to the nervous system. In a letter dated Feb 18th, 1888, to the President of the Hunterian Society, he recommended "the term 'neurokinesis', that is, nerve shock, or shaking, or nerve commotion", in place of the term 'neurasthenia'. He was for many years Surgeon to the Orphan Asylum, and on its removal from Clapton to Watford he became its Consulting Surgeon. He took an active interest in the Hunterian Society, of which he was Orator in 1866, President in 1870, and for many years Trustee; he also served on the Committee of the British Medical Benevolent Fund. In later years he had a consulting practice at 3 Mansfield Street, Cavendish Square, and on retiring lived at Boreham Hall, Elstree, which he had bought. He died after a fourth attack of angina pectoris on June 5th, 1888, leaving a widow and a large family. He was buried in Elstree Churchyard. His son, Mark Hovell, then in attendance on the Emperor Frederick, had to hurry back to his patient immediately after the funeral.