The subject with which this book is concerned is one of vast extent and enormous importance. It covers wide tracts of territory in physiology and medicine. All life processes, as Prof. Wolfgang Ostwald has summarily said, take place in a colloidal system, and that is true both of the normal ?uids and secretions of the organism and of the bacterial toxins, as well as, in large measure, of the reactions which confer im munity. If this is so, it would seem to be an obvious desidemtum that the drugs employed to combat disease should be in the colloidal state, i.e. In a form in which they may be isomorphic and isotonic with the elements of the body. Only so can they be expected to exert their full potency. The task of thus bringing their remedial virtue to its highest point is not an easy one, for colloidal substances, unless prepared with consummate skill and meticulous care, lack stability, and are prone to precipitation when brought into contact with the electrolytes normally present in the body tissues and ?uids. That it is not beyond the resources of scientific chemistry is clearly shown in this book. A measure of success has, in fact, been achieved which leaves no doubt of the brilliant future which lies before drugs in the colloidal form.