Because the very wicked serpent shall direct every worship to himself.
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In Africa the chief centre of serpent worship was Dahomey.
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Among the chiefdoms of this land were inhabitants that proliferated serpent worship before the common era.
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Serpent worship was well known in ancient Europe.
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Serpent and ancestral worship are also practiced.
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In Africa the chief centre of serpent worship was Dahomey, but the cult of the python seems to have been of exotic origin, dating back to the first quarter of the 17th century.
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Possibly at Delphi and other places there was an old serpent-worship ousted by that of Apollo, which may account for expiation for the slaying of Python being considered necessary.