In experimental science, two methods of progress are observed; first, in actual practice certain methods are adopted because they are found to be the most advantageous and useful, though we cannot explain why it is so—_i.e._, practice outstrips theory. Again, as a result of experimental investigation, certain facts are discovered which explain why the practical methods just alluded to are the best, and this in turn suggests further improvements in our practice—_i.e._, theory outstrips practice and enlarges its domain. Thus outstripping theory, the practical advance made by Lister was an example of the first. His striking results in turn stimulated scientific observers to make new discoveries of the greatest importance, and thus science immensely improved and widened our practical methods. No definite year or day can be assigned as the birth-date of Lord Lister’s antiseptic methods, as we can, for instance, for vaccination or for anæsthesia. We may assume, at least for this country, the summer of 1876 as the starting-point. During that year Lord Lister attended the International Medical Congress held in Philadelphia, and demonstrated his then methods and convinced a few surgeons of their immense advantages. Even before that date there had been very many experiments and observations, especially on the blood. In 1863 Davaine, in France, had discovered little rod-like bodies in the blood in wool-sorters’ disease, or anthrax, which he named from their shape “bacteria,” or “little rods.” This name has been adopted for all forms of germs, though many of them are not rod-like in their shape. Not until 1881 was the cause of inflammation and suppuration (the formation of pus or “matter”) discovered. In that year Ogston, of Aberdeen, published experiments which he believed demonstrated the fact that certain bacteria were the cause of suppuration. Since then this has been amply confirmed not only by experiments upon animals, but by observation in man. In 1882 Robert Koch, of Berlin, discovered the cause of tuberculosis, a little rod-like body, which is named the “bacillus” of tuberculosis. In 1883 Fehleisen discovered the germ of erysipelas, and in 1887 Nicolaier and Rosenbaum discovered the bacillus of tetanus or lockjaw. So recent have been the discoveries in bacteriology which have led to vast improvements in our methods of treatment of wounds and the performance of operations.