We are now in a position to explain all the contradictory results obtained by MM. Jaillard and Leplat on one side, and by Davaine on the other. In a country which splenic fever had made famous, the Département d'Eure-et-Loir, they had asked for a little splenic fever blood. Now, what takes place in a farm where an animal has died of this disease? The dead body is thrown upon a dungheap, or into some shed or stall, until the knacker's cart happens to pass. The knacker takes his own time, and the body often remains there twenty-four or forty-eight hours. The blood taken from this animal is more or less invaded by putrefaction, and vibrios are mingled with the bacteria of splenic fever, the development of which is arrested the moment the animal dies. In short, it may be easily conceived that an experimenter writing to Chartres to procure some splenic fever blood might, without his knowledge, or the knowledge of his correspondent, receive blood at the same time both splenic and septic. And this septicæmia is sometimes manifold, for a special septicæmia may be said to correspond to every sort of vibrio of putrefaction. Such were the circumstances which, without their being aware of it, accompanied Jaillard and Leplat's researches upon splenic fever infection. This impression will be derived from reading the successive notes laid by them before the Academy of Sciences. The blood of the cow which had died of splenic fever, sent from the knacker's establishment of Sours, and the blood of the sheep sent by M. Boutet, must both have been taken from the bodies of animals which had been dead a sufficient number of hours to render their blood both splenic and septic; and it was septicæmia, so prompt in its action, that had killed the rabbits of Jaillard and Leplat. As the examination of the blood of these animals showed no signs of bacteria, they had concluded, with great apparent truth, that the inoculation of splenic blood could cause death without any appearance of these organisms, even while the blood used for inoculation was full of them. The presence of _septic_ vibrios in the blood of the inoculated rabbits escaped their notice. When Davaine replied that Jaillard and Leplat had not worked with pure splenic blood he had hit upon the truth, but he could not give plausible reasons for it. The contest was carried on by experiments in which, on both sides, truth and error were closely blended.