Though a professor at the Alfort Veterinary School, M. Delafond, did point out to his pupils as far back as 1838 that charbon blood contained “little rods,” as he called them; it was only looked upon by himself and them as a curiosity with no scientific importance. Davaine, when he--and Rayer as well--recognized in 1850 those little filiform bodies in the blood of animals dying of splenic fever, he too merely mentioned the fact, which seemed to him of so little moment that he did not even report it in the first notice of his works edited by himself. It was only eleven years later that Davaine--struck, as he himself gladly acknowledged, by reading Pasteur’s paper on the butyric ferment, the little cylindrical rods of which offer all the characteristics of vibriones or bacteria--asked himself whether the filiform corpuscles seen in the blood of the charbon victims might not act after the manner of ferments and be the cause of the disease. In 1863, a medical man at Dourdan, whose neighbour, a farmer, had lost twelve sheep of charbon in a week, sent blood from one of these sheep to Davaine, who hastened to inoculate some rabbits with this blood. He recognized the presence of those little transparent and motionless rods which he called bacteridia (a diminutive of bacterium, or rod-shaped vibriones). It might be thought that the cause of the evil was found, in other words that the relation between those bacteridia and the disease which had caused death could not be doubted. But two professors of the Val de Grâce, Jaillard and Leplat; refuted these experiments. They had procured, in the middle of the summer, from a knacker’s yard near Chartres, a little blood from a cow which had died of anthrax, and they inoculated some rabbits with it. The rabbits died, but without presenting any bacteridia. Jaillard and Leplat therefore affirmed that splenic fever was not an affection caused by parasites, that the bacteridium was an epiphenomenon of the disease and could not be looked upon as the cause of it. Davaine, on repeating Jaillard and Leplat’s experiments, found a new interpretation; he alleged that the disease they had inoculated was not anthrax. Then Jaillard and Leplat obtained a little diseased sheep’s blood from M. Boutet, a veterinary surgeon at Chartres, and tried that instead of cow’s blood. The result was identical: death ensued, but no bacteridia. Were there then two diseases?