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Ectoplasm

Ectoplasm is an attempt to describe the substance which ghosts are made of.

It should be mentioned that it has never been possible to physically examine ectoplasm.
Ectoplasm is in spiritual circles a solid proof of the presence of a ghost or a spirit. During seances it is reported that ectoplasm can ooze from all orifices of spiritual mediums. This ectoplasm may take the form of a body, face or an entire body. Numerous photos are taken are seances, of this substance. However, is has never been possible to produce this substance under controlled laboratory conditions.

Ectoplasm photographed under seance in the 19th century. Note the small face.
Ectoplasm photographed under seance in the 19th century. Note the small face. As many of such pictures, the validity is discussed. Remember  picture-editing was also possible at that time.