As chairman of the Commission on the Standardization of Biological Stains, on which there are representatives of the American Medical Association and other organizations, Dr. Conn can speak authoritatively about dyes. The assistance of J. T. Scanlan, Anis P. Bradshaw, Mary A. Darrow and members of the executive committee of the commission is acknowledged. This edition marks a definite advance achieved by helpful cooperation of the commission with the American Pharmaceutical Association and the Society of American Bacteriologists. The formulas given in it, sponsored by the commission, in the National Formulary published by the association, and in the Manual of Methods for Pure Culture Study of Bacteria published by the society, have been compared and studied critically with the object of supplying identical formulas in all three places. Much confusion will thereby be avoided. This edition, like others before it, is accurate, concise and to the point. Useful information is