This image is part of a group of glass slides in the Garrett Collection called the “Fodor Plates.” It shows a female medium holding a séance with a group surrounding her. The slide was labeled “Wedding Veil Ectoplasm,” implying that the long piece of fabric-like material draped over her head represents ectoplasm.
Wedding Veil Ectoplasm, Fodor Plates, Box 9, Eileen J. Garrett Parapsychology Foundation collection, Collection 331, Special Collections, University of Maryland, Baltimore County (Baltimore, MD).