one of the greatest Roman medical writers, author of an encyclopaedia dealing with agriculture, military art, rhetoric, philosophy, law, and medicine, of which only the medical portion has survived. De medicina, now considered one of the finest medical classics, was largely ignored by contemporaries. It was discovered by Pope Nicholas V (1397–1455) and was among the first medical works to be published (1478) after the introduction of the printing press.

Most remarkable in Celsus' work is the apparently advanced state of medical practice (medicine, history of) at the time. He recommended cleanliness and urged that wounds be washed and treated with substances now considered to be somewhat antiseptic, such as vinegar and thyme oil. He described plastic surgery of the face, using skin from other parts of the body. He enumerated the four cardinal signs of inflammation: heat, pain, redness, and swelling.

Divided into three parts, according to the type of treatment demanded by various diseases—dietetic, pharmaceutical, and surgical—the treatise contains important accounts of heart disease, insanity, and the use of ligatures to stop arterial bleeding. Celsus also offered excellent descriptions of hydrotherapy and lateral lithotomy (for the removal of bladder stones). The historical portion of the work is of great importance; much of what is now known about Hellenistic medicine and Alexandrian anatomy and surgery comes primarily or exclusively from De medicina.