Louis Pasteur: His Life and Labours

by René Vallery-Radot

A few months after the publication of the results obtained by Davaine, two professors of Val-de-Grâce, MM. Jaillard and Leplat, sought to refute the preceding conclusions. After having inoculated rabbits and dogs with various putrefying liquids filled with vibrios, they could not cause the death of these animals. To bring about this result it was necessary to introduce into the blood of these dogs and rabbits several cubic centimeters of very putrid liquid. Again in this case, which only added another example to the experiments of Gaspard and Magendie upon the action of putrid liquids, they failed to generate any virulence in the blood. Davaine had no difficulty in showing that MM. Jaillard and Leplat's experiments were made under conditions totally different from his; that he, Davaine, had not made use of the vibrios or bacteria of unselected infusions, but of bacteria which had been found in the blood of sheep which had died from sang-de-rate.

Jaillard and Leplat returned to the charge, and this time with entirely new and unexpected experiments. They inoculated some rabbits, as Davaine desired, with the blood of a cow which had died of splenic fever. The rabbits died rapidly, but without showing before or after their death the least trace of bacteria. Other rabbits, inoculated with the blood of the first, perished in the same manner, but it was still impossible to discover any parasite in their blood. MM. Jaillard and Leplat offered Davaine some drops of this blood. Davaine, taking up the experiments of his opponents, confirmed the exactitude of the facts they had announced, but concluded by saying that these two professors had not employed true splenic fever blood, but the blood of a new disease, unknown up to that time, which Davaine proposed to call the cow disease.

'The blood which we used,' replied MM. Jaillard and Leplat, 'was furnished to us by the director of the knacker's establishment of Sours, near Chartres, and this director is undeniably competent as to the knowledge of splenic fever.'

Full of sincerity and conviction, MM. Jaillard and Leplat recommenced their experiments, using this time the blood of a sheep which had died of splenic fever, and which M. Boutet, the most experienced veterinary surgeon of the town of Chartres, had procured for them. Their results were the same as those obtained with the blood of the cow. Notwithstanding the replies of Davaine, which, however, added nothing to the facts already adduced on one side or the other, it was difficult to pronounce decidedly in such a debate. Unprejudiced minds received from these important discussions the impression that Jaillard and Leplat, in producing facts the exactitude of which were admitted by Dr. Davaine himself, had given a blow to the assertions of the latter, and that the subject required, in every case, new experimental studies.

In 1876, a German physician, Dr. Koch, took up the question. He confirmed the opinion of Davaine, but without in the least producing conviction, since he threw no light upon the facts adduced by MM. Jaillard and Leplat, of which, indeed, he did not even deign to speak. At the very same moment when the memoir of Koch appeared in Germany, the eminent physician Paul Bert came forward to corroborate the opinion of Jaillard and Leplat.

'I can,' said M. Paul Bert, 'destroy the bacteria in a drop of blood by compressed oxygen, inoculate with what remains, and reproduce the disease and death without any appearance of bacteria. Therefore, the bacteria are neither the cause nor the necessary effect of the disease of splenic fever. It is due to a virus.'

This was indeed the opinion of Jaillard and Leplat. Pasteur, in obedience to the necessity he felt to get at the fundamental truth of things, and also in his eager desire to discover some decisive proofs as to the etiology of this terrible disease, resolved in his turn to attack the subject.

Dr. Koch had stated in his memoir that the little filiform bodies, seen for the first time by Davaine in 1850, had two modes of reproduction—one by fission, which Davaine had observed, and another by bright corpuscles or spores. The existence of this latter mode of reproduction Pasteur had already discovered in 1865, reasserted and illustrated in 1870, as being common to the filaments of the butyric ferment, and to all the ferments of putrefaction. Was Dr. Koch ignorant of this important fact, or did he prefer by keeping silence to reserve to himself the advantage of apparent priority?

In order to solve the first difficulty which presented itself to his mind—that is to say, the question as to whether splenic fever was to be attributed to a substance, solid or liquid, associated or not associated with the filaments discovered by Davaine, or whether it depended exclusively upon the presence and the life of these filaments—Pasteur had recourse to the methods which for twenty years had served him as guides in his studies on the organisms of fermentation. These methods, delicate as they are, are very simple. When he wished, for example, to demonstrate that the microbe-ferment of the butyric fermentation was the very agent of decomposition, he prepared an artificial liquid formed of phosphates of potash, of magnesia, and of sulphate of ammonia, added to the solution of the fermentable matter, and in this medium he caused the microbe-ferments to be sown in a pure state. The microbe multiplied, and provoked fermentation. From this liquid he could pass to a second or third fermentable liquid composed in the same manner, and so on in succession. The butyric fermentation appeared successively in each. Since the year 1857 this method was supreme. In this particular research on the disease of splenic fever Pasteur proposed to isolate the microbe of the infected blood, to cultivate it in a state of purity in artificial liquids, and then to come back to the examination of its action on animals. But as, since his attack of paralysis in 1868, Pasteur had not recovered the use of his left hand, and consequently found it impossible to carry on a long series of experiments alone, he was obliged to seek for a courageous and devoted assistant. He found one in a former pupil of his at the École Normale, M. Joubert, now Professor of Physics at the Collège Rollin. If M. Joubert incurred the danger of these experiments on splenic fever, he also shared with Pasteur, in the Comptes-rendus of the Academy of Sciences, the honour of the researches and the triumph of the discoveries.