10 PREFACE. .; ' The aim has been to describe only such bacteria" fB can be proven pathogenic 'by the lesions .or -toxins which they engender, and, while considering them, to mention as fully as is necessary the species with which they may be confounded. The book, of course, will find its proper sphere of usefulness in the hands of medical students ; its pages, however, will be found to contain much that will be of interest and profit to those practitioners of medicine who graduated before modern science had thrown its light upon the etiology of disease. In writing this work the popular text-books have r been drawn upon. Hiippe, Fliigge, Sternberg, Prankel, Gunther, Thoinot and Masselin, and others have been freely consulted. The illustrations are mainly reproductions of the best the world affords, and, being taken from the great stand- ards, are surely superior to anything new covering the same ground. Credit has carefully been given for each illustration. J. McF. PHILADELPHIA, Feb. i, 1896.