Enclosed is a short excerpt about the "dancing mania" that broke out various times and places in medieval Europe: The dancing mania, especially as described in Aix-la-Chapelle, may have had a physical cause. The descriptions of the symptoms of some of the sufferers leads to another hypothesis, that the manic dancers (at least some of them) were victims of ergot poisoning, or ergotism. Ergotism, which was known in the Middle Ages as "St. Anthony's Fire", is a toxic condition in humans and ani- mals which inadvertently eat rye and other grasses parasitized by Claviceps purpurea (ergot). This small brown fungus produces an amazing array of dangerous chemicals, including lysergic acid diethylamide (LSD). Symptoms of ergotism may include psychotic delusions, nervous spasms, spontaneous abortion, convlusions, and gangrene. LSD in particular causes intensely colored hallucinations, perhaps explaining the visions of some of the dancers, like those who claimed to have seen the heavens open up to reveal Christ enthroned with the Virgin Mary. Ergotism is also frequenly fatal, and could have been the cause of the death of the dancers described in the early 17th C. Straussburg Chronicle.