Ectoplasm is defined as a white, misty, liquid substance that oozes from the orifices of a medium during a seance and can be formed by spirits into a humanoid apparition. The subject of many hoaxes, it has been substantiated, photographed and described in detail by Benjamin Alexander, a former spiritualist, who was terrified by his experiences and later became a Christian evangelist. Ectoplasm is said to be light sensitive and vanishes in the presence of light.