Celsus was not a professional doctor of medicine or a surgeon, but a practical layman whose De Medicina, written in clear and neat style, for lay Latin readers, is partly a result of his medical treatment of his household (slaves included) ...
Of all this great work there survives only the eight books on medicine (De Medicina). In Book I, after an excellent survey of Greek schools (Dogmatic, Methodic, Empiric) of medicine come sensible dietetics that will always be applicable.