Visual hallucinations in the 19th century: research in a medical archive.

The authors have gathered and analyzed the visual hallucinations described in the mid- to late-19th century from archived medical records of the former psychiatric hospital "Osservanza" in Imola, northern Italy. Though the investigation was not intended as a statistical survey, the principal aim being to classify the hallucinations according to their outward characteristics, the authors have tried to locate the possible sources of these phenomena in folklore and religious iconography.