The title of this book has been ill-chosen. It would have been better to have called it what it really is, viz.: A Report of the Treatment of Gases at the Cassel Hospital. If the book is read from this latter point of view, the author has carried out his task in a satisfactory manner, though a considerable condensation of the tables of statistics, which comprise nearly half the book, would have been valuable to the reader. On the other hand, reports of cases, methods of treatment and their results do not constitute 'An Enquiry' into the art of foretelling the future course and termination of the neuroses.