The revised edition of Tredgold's valuable book contains a new chapter dealing with mental tests and case-taking which is interesting and scientific. Many chapters have been entirely rewritten, bringing the work up to date. The subject of mental deficiency in its various phases, including the sociologic and medicolegal aspects, has been handled with great skill and conservatism. An admirable feature of the book is the willingness to give credit to those who deserve it, regardless of nationality. In common with most English authors, Tredgold makes use of simple phraseology, intelligible alike to specialist and general practitioner. We commend this work as one of the best short text-books on the subject in any language.