Part 17

'For a long period,' he said, 'the mucus of the bladder was regarded as the agent of the alkaline decomposition of urine. It was supposed that, in consequence of the distension produced by the retention of the liquid, the irritated bladder produced a larger quantity of mucus, and this mucus was regarded as the ferment which brought about the decomposition of urea, by an innate chemical force. This opinion (which was that of Liebig) cannot hold its ground in presence of the researches of Pasteur. This investigator has demonstrated, in the most decisive manner, that alkaline fermentation, like alcoholic and acetic fermentation, is produced by living organisms, the pre-existence of which in the liquid is the sine quâ non of the process.' And Dr. Traube, citing some facts which confirmed the doctrine of Pasteur, concluded thus: 'Notwithstanding the long retention of the urine, its alkaline fermentation is not produced by an increased secretion of mucus or of pus; it only begins to develop from the moment when the germs of vibrios find access to the bladder from without.

The opposite doctrines of Liebig and Pasteur are here brought into clear juxtaposition; and thus was their mutual and reciprocal influence established in dealing with the etiology of one of the most serious diseases of the bladder. So far back as 1862, Pasteur, in his memoir on spontaneous generation, had announced, contrary to all the notions then held, that whenever urine becomes ammoniacal, a little microscopic fungus is the cause of this alteration. Later on he established that in affections of the bladder ammoniacal urine was never found without the presence of this fungus; and in order to show how in these studies therapeutic application often runs hand in hand with scientific discovery, Pasteur, having proved, with his assistant, M. Joubert, that boracic acid is antagonistic to the development of the ammoniacal ferment, advised Dr. Guyon, Clinical Professor of Urinary Diseases in the Faculty of Paris, to combat the dangerous ammoniacal fermentation by injection of boracic acid into the bladder. The celebrated surgeon hastened to follow this advice, and with the most happy results. While attributing to Pasteur the honour of this discovery, M. Guyon, in one of his lectures, said:--

'Boracic acid has this immense advantage, that it can be applied in large doses--3 to 4 per cent.--without causing the slightest pain. It has therefore become, in our practice, the agent continually and successfully used for injections. I also have recourse to a solution of boracic acid to produce large evacuations after the operation of breaking up stones in the bladder (lithotrity). I never omit to use this antiseptic agent in operations where breaking up is required, and I never wash the bladders of lithotritised patients with any other substance. I have also had good results from copiously washing the bladders and the wounds of patients on whom lithotomy has been performed with boracic acid. I always finish the operation by prolonged irrigations with a solution of from 3 to 4 per cent.'

It was not only into France and Germany that Pasteur's ideas penetrated; in England, surgery borrowed from Pasteur's researches important therapeutic applications. In 1865 Dr. Lister began in Edinburgh the brilliant series of his triumphs in surgery by the application of his antiseptic method, now universally adopted. In the month of February 1874 in a letter which does honour to the sincerity and modesty of the great English surgeon, he wrote to Pasteur as follows:--

'It gives me pleasure to think that you will read with some interest what I have written about an organism which you were the first to study in your memoir on lactic fermentation. I do not know whether you read the 'British Medical Journal;' if so, you will from time to time have seen accounts of the antiseptic system which for the last nine years I have been trying to bring to perfection. Allow me to take this opportunity of sending you my most cordial thanks, for having, by your brilliant researches, demonstrated to me the truth of the germ theory of putrefaction, thus giving me the only principle which could lead to a happy end the antiseptic system.'

Pasteur followed with lively interest the movement of thought and the successful applications to which his labours had given rise. It was a realisation of the hopes he had ventured to entertain. Already, in 1860, he expressed the wish that he might be able to carry his researches far enough to prepare the way for a profound study of the origin of diseases. And, as he gradually advanced in the discovery of living ferments, he hoped more and more to arrive at the knowledge of the causes of contagious diseases.

Nevertheless, he hesitated long before definitely engaging himself in this direction. 'I am neither doctor nor surgeon,' he used to repeat with modest self-distrust. But the moment came when, notwithstanding all his scruples, he could no longer be content himself to play the part of a simple spectator of the labours started by his studies on fermentation, on spontaneous generation, and on the diseases of wines and beer. The hopes to which his methods gave rise, the eulogies of which they were the object, obliged him to go forward. In February 1876 Tyndall wrote to him thus:--

'In taking up your researches relating to infusorial organisms, I have had occasion to refresh my memory of your labours; they have revived in me all the admiration which I felt on first reading them. It is my intention to follow up these researches until I shall have dissipated every doubt that has been raised as to the unassailable exactitude of your conclusions.

'For the first time in the history of science we are able to entertain the sure and certain hope that, in relation to epidemic diseases, medicine will soon be delivered from empiricism, and placed upon a real scientific basis. When this great day shall come, humanity will recognise that it is to you the greatest part of its gratitude is due.'

Pasteur approached the study of viruses by seeking to penetrate into all the causes of the terrible malady called splenic fever (charbon, Germ. Milzbrand). Each year this disease decimates the flocks not only in France but in Spain, in Italy, in Russia, where it is called the Siberian plague, and in Egypt, where it is supposed to date back to the ten plagues of Moses. Hungary and Brazil pay it a formidable yearly tribute; and to come back to France, the losses have amounted in certain years to from fifteen to twenty millions of francs. For centuries the cause of this pest has eluded all research; and further, as the malady did not always exhibit the same symptoms, but varied according to the kind of animal that was smitten by it, the disease was supposed to vary with the species that was attacked by it. The splenic fever of the horse was distinct from that of the cow; the splenic fever of horse and cow were again different from that of the sheep. In the latter, splenic fever was called sang-de-rate; in the cow, it was maladie du sang; in the horse, splenic fever; in man, malignant pustule.

It was not until 1850 that trustworthy data were first collected regarding the nature of the malady, its identity with and difference from other maladies. From 1849 to 1852 a commission of the Medical Association of Eure-et-Loir made a great number of inoculations, applied other tests, and proved that the splenic fever of the sheep is communicable to other sheep, to the horse, to the cow, and to the rabbit; that the splenic fever of the horse is communicable to the horse and to the sheep; that the splenic fever of the cow is communicable to the sheep, to the horse, and to the rabbit. As for the malignant pustule in man, no doubt remained that it must arise from the same cause as splenic fever in animals. What class of men is it that the malignant pustule most frequently attacks? Shepherds, cowherds, cattle breeders, farm servants, dealers in hides, tanners, wool cleaners, knackers, butchers--all who derive their living from domestic animals. In handling contaminated subjects the slightest excoriation or scratch of the skin is sufficient to allow the virus to enter. When others besides the class that we have named become infected, it is because they live in the neighbourhood of herds smitten with splenic fever. There are also certain flies which transport the virus. Suppose one of these flies to have sucked the blood of an animal which has died of splenic fever, a person stung by that fly is forthwith inoculated with the virus.

At the very time (1850) when these first experiments were being made by the Medical Association of the Eure-et-Loir, Dr. Rayer, giving an account in the 'Bulletin de la Société de Biologie de Paris' of the researches he had made, with his colleague, Dr. Davaine, on the contagion of splenic fever, wrote:--'In the blood are found little thread-like bodies about twice the length of a blood corpuscle. These little bodies exhibit no spontaneous motion.'

This is the date of the first observation on the presence of little parasitic bodies in splenic fever, but, strange to say, no attention was paid to these minute filaments. Rayer and Davaine also paid no attention to them. This indifference lasted for thirteen years; it would have lasted longer still, if the parasitic origin of communicable diseases had not been brought before the mind by each new publication of Pasteur's. From 1857 to 1860 it will be remembered that he had demonstrated lactic fermentation, like alcoholic fermentation, to be the work of a living ferment; in 1861 he had discovered that the agent of butyric fermentation consisted of little moving thread-like bodies, of dimensions similar to those of the filaments discovered by Davaine and Rayer in the blood of splenic fever patients; in 1861 he had announced that no ammoniacal urine existed without the presence of a microscopic organism; in 1863 he had established that the bodies of animals in full health are sealed against the introduction of the germs of microscopic organisms; that blood drawn with sufficient precaution from the veins and the arteries, and urine taken direct from the bladder, could be exposed to the contact of pure air without putrefaction, and without the appearance of living thread-like organisms of any kind whatever, mobile or immobile. It was all these facts which in 1863 brought back the attention of Davaine, as he himself has acknowledged, to the observation which he had made in 1850.

'M. Pasteur,' said M. Davaine in a communication made to the Academy of Sciences, 'published some time ago a remarkable memoir on butyric fermentation, which consists of little cylindrical rods, possessing all the characteristics of vibrios or of bacteria. The thread-like corpuscles which in 1850 I saw in the blood of sheep attacked with sang-de-rate, having a great analogy with these vibrios, I was led to examine whether filiform corpuscles, analogous to or of the same kind as those which determined the butyric fermentation, would not, if introduced into the blood of an animal, equally act the part of a ferment. Thus would be easily explained the alteration, and the rapid infection of the mass of the blood, in an animal which had received accidentally or experimentally into its veins a certain number of these bacteria--that is to say, of this ferment.'

But two summers passed before M. Davaine was able to procure a sheep affected with the sang-de-rate. It was only in 1863 that he first recognised the constant presence of a parasite, in the blood of sheep and rabbits which had died from successive inoculations with blood taken after death or in the last hours of life. He further proved that the inoculated animal, in the blood of which no parasites were as yet visible with the microscope, had every appearance of health, and that in these conditions the blood could not communicate splenic fever.

'In the present state of science,' Davaine concluded, 'no one would think of going beyond these corpuscles to seek for the agent of the contagion. This agent is visible, palpable; it is an organised being, endowed with life, which is developed and propagated in the same manner as other living beings. By its presence, and its rapid multiplication in the blood, it without doubt produces in the constitution of this liquid, after the manner of ferments, modifications which speedily destroy the infected animal.' 'For a long time,' he repeated, 'physicians and naturalists have admitted theoretically that contagious diseases, serious epidemic fevers, the plague, &c., are caused by invisible animalculæ, or by ferments, but I do not know that these views have ever been confirmed by any positive observations.'

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.

On April 30, 1877, Pasteur read to the Academy of Sciences, in his own name and in that of his fellow-worker, a note in which he demonstrated, this time in a completely unanswerable manner, that the bacilli called bacteria, bacterides, filaments, rods, in a word the bacilli discovered by Davaine and Rayer in 1850, constituted the only agent of the malady.

A little drop of splenic fever blood, sown in urine or in the water of yeast, previously sterilised--that is to say, rendered unputrescible by contact with air free from all suspended germs--produces in a few hours myriads of bacilli or of bacteria. A little drop of this first cultivation sown in a second flask containing the same liquid as the first and prepared with the same precautions as to sterility and purity, shows itself no less fertile. Finally, after ten or twenty similar cultures the parasite is evidently freed from the substances which the initial drop of blood might carry with it; yet, if a very small quantity of the last culture is injected under the skin of a rabbit or a sheep, it kills them in two or three days at most, with all the clinical symptoms of natural splenic fever.

It might be objected that the parasite was associated in the cultivating liquid with some dissolved substance that it had produced during its life and which acted as a poison. Pasteur accordingly transported some cultivating tubes into the cellars of the Observatory, where a temperature absolutely constant reigned, a circumstance which permits of the deposit of all the parasitic filaments at the bottom of the tubes. Inoculating afterwards both with the clear upper liquid and with the deposit at the bottom, he found that the latter alone produced disease and death. It is, then, the bacteria which cause splenic fever. The proof was given and no further doubt remained.