The most notable feature of this edition is the part devoted to the protozoa. Hitherto textbooks on bacteriology have failed to recognize the importance of animal organisms in the causation of disease. Obviously it is advisable that these organisms should be discussed together with the vegetable organisms. Sixty pages are devoted to the discussion of the ameba, trypanosomes, the spirochetes of relapsing fever and syphilis, the malarial organisms and the protozoan-like bodies found in smallpox and allied diseases. In the appendix the author discusses the aggressins, the hemolysins, the diplobacillus of Morax-Axenfeld and the relation of the stegomyia to yellow fever. The part on bacteria also has been revised carefully, thus making the work a valuable summary of the present-day knowledge in this field of medicine.