Produced by Bryan Ness, Stephanie Eason, and the Online Distributed Proofreading Team at http://www.pgdp.net. (This file was produced from images generously made available by The Internet Archive/American Libraries.) The greater part of the first three chapters of this book appeared in the _Journal of Abnormal Psychology_ in the December-January number of 1915-16 and the February-March number of 1916. This material is reprinted here by the kind permission of the Editor of that Journal. This part of the subject is chiefly historical and the data here given is accessible as indicated by the references throughout the text, although many of these books are difficult to secure or are out of prin…
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