This book is devoted to the problems of the reaction of the organism to the administration of antigens of whatever derivation. The chemical aspects of the mechanisms of the reactions concerned are stressed. Throughout, military comparisons of attack and defense are emphasized rather excessively and perhaps not always very felicitously. The various aspects of immunity are discussed quite thoroughly, as are its relation to allergy and the clinical implications. The limitations of existing theories are duly considered, so that it is made clear that the riddle of immunity is not solved completely. Some omissions are unavoidable, and some attention may be paid to the Shwartzman phenomenon in further editions. The book constitutes a very palatable review of the problems of immunity.