Aulus Cornelius Celsus ( 25 BC 50 AD) was a Roman encyclopaedist, known for his extant medical work, De Medicina, which is believed to be the only surviving section of a much larger encyclopedia. The De Medicina is a primary source on diet, pharmacy, surgery and related fields, and it is one of the best sources concerning medical knowledge in the Roman world. The lost portions of his encyclopedia likely included volumes on agriculture, law, rhetoric, and military arts. He made contributions to the classification of human skin disorders in dermatology, such as myrmecia, and his name is often found in medical terminology regarding the skin, e.g., kerion celsi and area celsi. Life Nothing is known about the life of Celsus. Even his praenomen is uncertain; he has been called both Aurelius and Aulus, with the latter being more plausible. Some incidental expressions in his De Medicina suggest that he lived under the reigns of Augustus and Tiberius; which is confirmed by his reference to the Greek physician Themison as being recently in his old age. It is not known with any certainty where he lived. He has been identified as the possible dedicator of a gravestone in Rome, but it has also been supposed that he lived in Narbonese Gaul, because he refers to a species of vine (marcum) which, according to Pliny, was native to that region. It is doubtful whether he practised medicine himself, and although Celsus seems to describe and recommend his own medical observations sanctioned by experience, Quintilian says that his volumes included all sorts of literary matters, and even agriculture and military tactics. Works De Medicina Of the numerous volumes of his encyclopedia published before 47 CE, only one remains intact, his celebrated treatise On Medicine (De Medicina). "The work’s encyclopedic arrangement follows the tripartite division of medicine at the time as established by Hippocrates and Asclepiades — diet, pharmacology, and surgery." It is divided into eight books. Book 1 – The History of Medicine (includes references to eighty medical authors, some of whom are known only through this book) Book 2 – General Pathology Book 3 – Specific Diseases Book 4 – Parts of the Body Book 5 and 6 – Pharmacology Book 7 – Surgery Book 8 – Orthopedics In the "Prooemium" or introduction to De Medicina there is an early discussion of the relevance of theory to medical practice and the