Celsus, a layman, provides in On Medicine more information about the condition of medical science up to his own time (probably first century CE) than any other author. Book I is on Greek schools of medicine and dietetics; Book II on prognosis, diagnosis, and general therapeutics; Book III on internal ailments; Book IV on local bodily diseases.

Celsus, a layman, provides in On Medicine more information about the condition of medical science up to his own time (probably first century CE) than any other author. Book V is on treatment by drugs of general diseases, Book VI on treatment by drugs of local diseases.