Others made observations in their turn. It occurred to a young German physician, Dr. Koch, who in 1876 was beginning his career in a small village in Germany, to seek a culture medium for the bacteridium. A few drops of aqueous humour, collected in the eyes of oxen or of rabbits, seemed to him favourable. After a few hours of this nutrition the rods seen under the microscope were ten or twenty times larger than at first; they lengthened immoderately, so as to cover the whole slide of the microscope, and might have been compared to a ball of tangled thread. Dr. Koch examined those lengths, and after a certain time noticed little spots here and there looking like a punctuation of spores. Tyndall, who knew how to secure continuous attention by a variety of comparisons, said at a scientific conference in Glasgow a few months later that those little ovoid bodies were contained within the envelope of the filament like peas in their pods. It is interesting to note that Pasteur, when he studied, in connection with silkworm diseases, the mode of reproduction of the vibriones of flachery, had seen them divide into spores similar to shining corpuscles; he had demonstrated that those spores, like seeds of plants, could revive after a lapse of years and continue their disastrous work. The bacterium of charbon, or _bacillus anthracis_ as it now began to be called, reproduced itself in the same way, and, when inoculated by Dr. Koch into guinea-pigs, rabbits and mice, provoked splenic fever as easily and inevitably as blood from the veins of an animal that had died of the disease. Bacilli and spores therefore yielded the secret of the contagion, and it seemed that the fact was established, when Paul Bert, in January, 1877, announced to the _Société de Biologie_ that it was “possible to destroy the bacillus anthracis in a drop of blood by compressed oxygen, to inoculate what remained, and to reproduce the disease and death without any trace of the bacteridium ... Bacteridia,” he added, “are therefore neither the cause nor the necessary effect of splenic fever, which must be due to a virus.”