The doctrine of signatures in the medieval and Ottoman Levant.

This study traces the use of the Doctrine of Signatures among medieval and Ottoman physicians and its subsequent appearance in the pharmacological literature of the Levant. Close examination of the historical sources of the Levant seems to support the claim that although this theory did not originate in the region, it was certainly practised there. These sources have revealed 23 substances with medicinal uses based on the Doctrine, bearing witness to the extent of its influence at the time. The main categories of the Doctrine uncovered were: similarity between the substance used and the human organ; resemblance in shape or behaviour to a specific animal; correlation between the colour of a substance and the colour of the symptoms; similarities between the substance and the patient's symptoms and the use of a substance that might produce symptoms of a particular disease in a healthy person to remedy those same symptoms in one who is sick.