His pioneer experiments made modern surgery possible. In this year also, Pasteur was sent to investigate a disease, Pebrine, which was destroying the silkworms in Southern France. He showed the cause to be a protozoan which had been seen previously by Cornalia and described by Nägeli under the name _Nosema bombycis_ and devised preventive measures. This was the _first infectious disease_ shown to be _due to a protozoan_. In 1866 Rindfleisch observed small pin-point-like bodies in the heart muscle of persons who had died of wound infection. Klebs, in 1870-71, published descriptions and names of organisms he had found in the material from similar wounds, though he did not establish their causal relation. Bollinger, in 1872, discovered the spores of anthrax and explained the persistence of the disease in certain districts as due to the resistant spores. In 1873 Obermeier observed in the blood of patients suffering from recurrent fever long, flexible spiral organisms which have been named _Spirochæta obermeieri_. Lösch ascribed tropical dysentery to an ameba, named by him _Amœba coli_, in 1875. Finally, Koch, in 1876, isolated the anthrax bacillus, worked out the life history of the organism and reproduced the disease by the injection of pure cultures and recovered the organism from the inoculated animals, thus establishing beyond reasonable doubt its causal relationship to the disease. This was the _first instance of a bacterium_ proved to be the cause of a _disease in animals_. Pasteur, working on the disease at the same time, confirmed all of Koch’s findings, though his results were published the next year, 1877. Bollinger determined that the _Actinomyces bovis_ (_Streptothrix bovis_) is the cause of actinomycosis in cattle in 1877. Woronin in the same year discovered a protozoan (_Plasmodiophora brassicæ_) to be the cause of a disease in cabbage, the _first proved instance of a unicellular animal causing a disease in a plant_. In 1878 Koch published his researches on wound infection in which he showed beyond question that microörganisms are the cause of this condition, though Pasteur in 1837, had suggested the same thing and Lister had acted on the theory in preventing infection. These discoveries, especially those of Koch, immediately attracted world-wide attention and stimulated a host of workers, so that within the next ten years most of the bacteria which produce disease in men and animals were isolated and described. It is well to remember that the first _specific_ disease of man proved to be caused by a _bacterium_ was _tuberculosis_, by Koch in 1882. Progress was greatly assisted by the introduction of anilin dyes as suitable stains for organisms by Weigert in 1877, by Koch’s application of special technic and gelatin cultures for isolation and study, 1881, and the great improvements in the microscope by Prof. Abbé, of Jena.