From the antagonism existing between the physiological peculiarities of the splenic bacilli and the septic vibrio, it results that if, in order to inoculate an animal capable of contracting the fever, a drop of blood be taken from one that has just died of it, and if the operation is performed during the first few hours after death, it is certain to communicate to that animal splenic fever, and splenic fever only. If, on the other hand, the operation is performed after a greater number of hours—say, between twelve and twenty, according to the season of the year—then the inoculation of the blood will communicate, at one and the same time, splenic fever and septicæmia—acute septicæmia, as it may be called, because of the rapid inflammatory disorders that the septic vibrio causes in the inoculated animal. The two diseases may be developed simultaneously in the inoculated animal, but generally one precedes the other. The septic contagium is the quickest in its action; it generally causes death before the splenic fever has had time to develop itself and to produce appreciable effects.
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.
The work of M. Paul Bert, at the close of 1876, was surrounded with circumstances no less complex. To thoroughly understand them we must call to mind Pasteur's discovery as to the mode of reproducing the anaerobic germs of putrefaction. These vibrios reproduce themselves by spores. In the vibrio of acute septicæmia this is the mode of generation. Short or long jointed filaments show themselves studded with brilliant points, which are precisely the spores of which we speak. Experience proves that these spores resist perfectly the poisonous action of compressed oxygen. Inoculating an animal with blood which is at the same time septic and splenic, after the blood has been compressed, the septic germs, remaining alive, produce death, although neither bacteria nor filaments may be perceptible in its blood at the moment of death. It was likewise from Chartres that M. Paul Bert obtained his supply of splenic fever blood. The blood he had received was without doubt not only splenic but also septic. The filaments of bacteria and the filaments of septic vibrios had perished under the influence of the compressed oxygen; but the spores were there, and the great pressure of oxygen gas had not affected them. The new contagium which had appeared, and which had killed the inoculated animals, was due to these spores.
As regards the proof that this virulence in the blood of the body of an animal which has died of splenic fever is really the effect of the septic vibrio, Pasteur, assisted by Joubert and a new assistant, M. Chamberland, has given that proof, as he did in the case of the bacterium of splenic fever, by resorting to the method of successive cultivations in an artificial medium. These cultivations, however, of the septic vibrio require very special precautions and conditions. They should be carried on in as perfect a vacuum as it is possible to obtain, or in contact with carbonic acid gas without the presence of air. In contact with air the cultivations of septic vibrios would prove sterile, because the vibrio is exclusively anaerobic and air kills it. If a spore of this organism could germinate in contact with the air, the product of the germination would be at once arrested and would perish by the action of the oxygen. It is exactly the contrary with the bacilli of splenic fever, which prove sterile in a vacuum or in presence of carbonic acid gas. If one of the spores of the splenic fever bacillus (for it also produces spores) could germinate, the product of the germination, deprived of free oxygen, would at once perish. And, to mention in passing a very ingenious experiment of Pasteur's, we thus obtain a means of separating by culture the bacillus of splenic fever from the septic vibrio when they are temporarily associated together. If this mixture of pathogenic organisms is cultivated in contact with the air, the bacilli of splenic fever alone will be developed. If this same mixture is cultivated without air, either in a vacuum or in carbonic acid gas, the septic vibrio alone will be developed. This device of culture is one of the best which can be employed to demonstrate that the blood of a body dead from splenic fever possesses immediately after death a single contagium, that of splenic fever, and that twenty-four hours after death, on the contrary, there are two contagia, that of splenic fever and that of septicæmia.
Some months ago a very hot discussion arose between Pasteur and a commission formed principally of professors of the veterinary school in Turin, regarding the facts above mentioned. One experiment, in the success of which Pasteur was extremely interested, had been made at this school. Instead of employing pure splenic fever blood, free from all contagium, the Italian professors, whether from ignorance of the preceding facts or from inadvertence, employed the blood of a diseased sheep, which, from their own showing, had been dead more than twenty-four hours. Pasteur immediately wrote, pointing out that the commission had done wrong in using blood which must have been at the same time splenic and septic. The Turin professors grew angry, and affirmed that this assertion of Pasteur's was incorrect; that this sheep's blood had been studied with care, and that no filaments had been found in it except those of splenic fever; and it would, moreover, be marvellous, they added ironically, that Pasteur from the depths of his laboratory in Paris should be able to assert that this blood was mixed with septic poison, whilst they, good observers, armed with a microscope, had had this sheep's blood under their eyes. Pasteur contented himself with replying that his assertion rested upon a principle, and that he was perfectly able, without having seen the blood of the sheep, to affirm that under the conditions in which it had been collected that blood was septic. A public correspondence ensued, but no understanding could be come to. Pasteur then offered to go himself to Turin, in order to demonstrate upon as many bodies of sheep dead of splenic fever as they would like to give him, that the blood of these dead bodies—at the end of twenty-four hours if in the month of March, and in twelve or fifteen hours if in the month of June, would be found to be both splenic and septic. Pasteur also proposed, by appropriate cultures, to withdraw at pleasure the splenic fever poison or the septic poison, or the two together, at the choice of the Italians. The Italians, however, shrank from Pasteur's proposal to pay them a visit in order to convince them of their error.
The clearness and certainty of Pasteur's assertions are celebrated, but what gives such authority to all that he advances is, as M. Paul Bert once said, that Pasteur's boldness of assertion is only equalled by his diffidence when he has not experiment to back him up. He never fights except on ground with which he has made himself familiar, but then he fights with such resolution, and sometimes with such impetuosity, that one might say to his adversary, whoever he be, 'Je vous plains de tomber dans ses mains redoutables.'
'Take care!' said a member of the Academy of Sciences to a member of the Academy of Medicine, who a short time after the incident just related was proposing scientifically to 'strangle' Pasteur, 'take care! Pasteur is never mistaken.'
One day, in 1879, a professor attached to a faculty of medicine in one of the provinces announced to the Academy of Sciences that he had found, in the blood of a woman who had died in a hospital after two weeks' illness from severe puerperal fever, a considerable number of motionless filaments, simple or jointed, transparent, straight, or bent, which belonged to the genus Leptothrix. Engaged in studies on puerperal fever, and having never met with a fact of this kind in his researches, Pasteur wrote at once to this professor to ask him for a specimen of the infected blood. The blood arrived at the laboratory, and some days after Pasteur wrote to the doctor, 'Your leptothrix is nothing else than the bacterium of splenic fever.'