The fourth edition of this well known book requires little comment except to point out the changes from the previous edition. These changes are relatively slight but rather important to make in order that the new edition may be brought down to date. The sections on malaria, undulant fever, trachoma, scarlet fever, diphtheria and poliomyelitis have been changed to conform to recent knowledge and public health practice. These changes are mentioned merely as examples. It is evident that all the material has been carefully revised. Some unnecessary material has been omitted, of which the section on fumigants may be mentioned. The book has found a wide use and should continue to do so.