"Owing to additions made to my book upon Idiocy and Imbecility I felt warranted in giving a more comprehensive title to the work when published two years ago. This may be regarded as a third edition. By removing less important passages and shortening others, I have now managed to add the results of the most recent research without increasing the size of the volume. The principle merit of this work, probably, is that it brings together the widely scattered studies of able observers on the subjects treated. Though it is mainly intended for medical men, some parts of the book will also be found useful to those who have the care and guardianship of idiots and imbeciles, or who take a philanthropic interest in provisions for their welfare." -- Preface (page [v])