This volume was written with the interests of the general reader particularly in mind; for this reason the subject matter has been treated in a more or less popular style. With a view toward aiding sufferers from nervous affections, as well as toward promoting a better understanding of various normal and abnormal mental processes, an effort has been made to make the book as practical as possible.

In preparing the work it was, of course, necessary to refer to the writings of others. The sources from which the present writer has drawn are generally mentioned in the proper places. In giving references, it was deemed best to favor those books and periodicals which are suitable for general reading, and which are available. The dates of publication of the works referred to are mentioned so that the reader unfamiliar with them may be able to separate the older literature from the more recent. The publishers of the later books, as well as of other literature likely to be obtained from their respective publishers, are also mentioned.

To the authors and publishers of the works from which I have obtained aid I express my thanks. To my wife, and my brother, Francis M. Walsh, I am very grateful for aid in procuring much of the literature consulted, and for help in typing the manuscript. Through Dodd, Mead & Co. several suggestions were received which, I hope, will enhance whatever value the work may have.

William S. Walsh.

Providence, Rhode Island, U. S. A. Feb., 1920.