In vain. Irrepressible and hot-tempered John could not sit down quietly to study dead languages. Back he came from Oxford in haste, to study dead bodies in his brother's dissecting room, and serve as demonstrator to his course of lectures, simultaneously with his study of living bodies at St. George's Hospital, where in a comparatively short time he became house-surgeon.
His appointment as staff-surgeon to our troops on foreign service marked the six intervening years before he settled down to practise in London. He had laboured ten years on human anatomy, and had dissected a number of the lower animals, laying the foundation of his collection of comparative anatomy. Even while on foreign service he had amused himself with studying the digestive faculties of snakes and lizards when in a torpid state, and many were the contributions he sent home to his brother's museum.
His return to London, as a teacher of surgery and anatomy, was a marked success, though private practice had to grow. In 1776, he was appointed surgeon extraordinary to His Majesty George III., but eleven years prior to this was admitted a Fellow of the Royal Society, slightly in advance of his elder brother. Then in 1768, the bachelor, William, shifted himself and his museum from Jermyn Street to Windmill Street, and resigned the lease to John, thus securing independent action to the latter, and facilities for creating a natural-history museum of his own.
Hitherto, the brothers had worked together in unison, but now John committed the unpardonable offence of bringing home to Jermyn Street "a tocherless bride," fourteen years younger than himself, endowed only with beauty and accomplishments, and a faculty for filling the house with assemblies of wit and fashion, which blunt-spoken John designated "kick-ups," no doubt with an irreverent big D as a prefix, swearing being as characteristic as hard work.
And work hard he did, early and late, not merely to maintain his extensive and lucrative practice, but to provide and prepare subjects for the museum in the rear of his town house, and for the valuable and original lectures he delivered in language forcible and clear, if neither refined nor academic.
His chief workshop, so to speak, was at his country "Box" at Earl's Court, the grounds of which he had converted into a zoological garden, so many wild animals were there kept for study. There is a story told of his facing an escaped lion and flicking him back to his den with his pocket handkerchief, showing his fearlessness and his knowledge of leonine nature.