This comprehensive work is the culmination of many years of labor by the author and undertakes an exhaustive review of the entire field and a discussion of the various theories that have been advanced from time to time to account for hallucinations. At the end there are gathered together a section on depersonalization and the instinct life, the author's conception of engrams and mechanics, and his final conclusions. A masterly presentation, but one which leans too much from the reviewer's point of view to the organic side. In working in these borderland fields, especially where the psyche is so deeply involved, one recalls over and over again the thought of Claude Bernard expressed by saying that “some day a real science of medicine will have been born when the physiologist, the philosopher and the poet shall speak the same language and understand each other.”