If anyone runs into information about multiplicity in history, this is the section for it. How multiplicity was viewed in the Middle Ages (see also possession), for example.
Mary Reynolds Uses Reynolds' case to prove that multiplicity exists outside of iatrogenic, therapist-created delusions.
Before Eve This goes clear back to Gmelin's Syndrome, without however mentioning his theory that multiplicity could be a "royal road" to understanding how personality is formed in the first place.
Mollie Fancher: the Brooklyn Enigma Was Mollie a medium or a multiple, or both? In the 1860s, the two were considered practically interchangeable.
The Passion of Ansel Bourne: Multiple Personality in American Culture Excellently researched scholarly text.
The writings of William James are always a good place to start, particularly his study of Ansel Bourne. - Jay Young
Just added a couple of links, 1/12/05. Astraea^Bluejay