The literature since the first edition has been reviewed and material from it has been inserted, with particular emphasis on experimental contributions. Major additions are made in the sections on speech abnormalities, constitutional psychopathic inferiority, behavior effects of epidemic encephalitis, and psychotherapy. The chapters on psychoneuroses now precede those on the psychoses. The revised work consists of 21 chapters and an index; bibliographies are presented in footnotes and at the ends of chapters.