Cyclopedia of Biblical, Theological and Ecclesiastical Literature
a class of mystical ceremonies performed at a very early period in the history of Greece. The followers of Orpheus (q.v.) devoted themselves to the worship of Dionysus, not, however, by practicing the licentious rites which usually characterized the Dionysia or Bacchanalia, but by the maintenance of a pure and austere mode of life. These devotees were dressed in white linen garments, and partook of no animal food, except that which was taken from the ox offered in sacrifice to Dionysus.
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McClintock, John. Strong, James. Entry for 'Orphic Mysteries'. Cyclopedia of Biblical, Theological and Ecclesiastical Literature. http://www.studylight.org/encyclopedias/tce/o/orphic-mysteries.html. Harper & Brothers. New York. 1870.