As to his actual legacy to the world, let us sum it up briefly. There is the impulse which he gave, after the successful organization of his own Institute, to the establishment in other countries of similar laboratories of preventive medicine, and, one may also say, of experimental evolution. There is his educative work at Strasburg and Lille, at the Ecole Normale and the Sorbonne, and, above all, in the smaller yet world-wide circle of his immediate disciples. To general biology his chief contribution has been the demonstration of the part which bacteria play, not only in pathological and physiological processes, but in the wider drama of evolution. To the chemist he has given a new theory of fermentation; to the physician many a suggestive lesson in the etiology [inquiry into the causes] of diseases, and a series of bold experiments in preventive and curative inoculation, of which Roux's treatment of diphtheria and Professor Fraser's new remedy for snake-bite are examples at present before the public; to the surgeon a stable foundation, as Lister acknowledged, for antiseptic treatment; to the hygienist a multitude of practical suggestions concerning water-supply and drainage, disinfection and burial. On brewer, distiller, and wine-maker he has forced the microscope and its results; and he has shown both agriculturist and stock-breeder how some, at least, of their many more than ten plagues may be either averted or alleviated. TUBERCULOSIS AND ITS PREVENTION T. MITCHELL PRUDDEN, M.D. [Dr. Prudden is Professor of Pathology in the College of Physicians and Surgeons, New York. He has bestowed especial attention upon the means of preventing disease: in that important field he has written three capital manuals, all published by G. P. Putnam's Sons, New York:--"Story of the Bacteria," "Dust and Its Dangers," "Water and Ice Supplies." His other works, intended for the professional reader, are of the highest authority. The article here given appeared in _Harper's Magazine_, March, 1894; copyright by Harper & Brothers, who have granted permission to reprint. In May, 1902, these pages were revised by Dr. Prudden.]