A. Cornelius Celsus was author, probably during the reign of the Roman Emperor Tiberius (14–37 CE), of a general encyclopaedia of agriculture, medicine, military arts, rhetoric, philosophy, and jurisprudence, in that order of subjects. Of all this great work there survives only the 8 books on medicine (De Medicina or On Medicine).

Celsus was not a professional doctor of medicine or a surgeon, but a practical layman whose On Medicine, written in a clear and neat style, for lay readers, is partly a result of his medical treatment of his household (slaves included) and partly a presentation of information gained from many Greek authorities. From no other source can we learn so much of the condition of medical science up to his own time.

Book 1: after an excellent survey of Greek schools (Dogmatic, Methodic, Empiric) of medicine come sensible dietetics or health preservation which will always be applicable. Book 2 deals with prognosis, diagnosis of symptoms (which he stresses strongly), and general therapeutics. Book 3: internal ailments: fevers and general diseases. Book 4: local bodily diseases. Next come two pharmacological books, Book 5: treatment by drugs of general diseases; and Book 6: of local diseases. Books 7 and 8 deal with surgery; these books contain accounts of many operations, including amputation.