Pasteur Koch Controversy

An acrimonious dispute arose between Pasteur and Koch and Koch’s colleagues triggered by the latter’s harsh criticism of Pasteur’s work on attentuation of viruses.  The documents on this page present the positions of Pasteur and Koch as interpreted in editorials appearing in 1883 in the Boston Medical and Surgical Journal.  View the full text of Pasteur’s reply to Koch  and Koch’s critique of Pasteur’s research on Anthrax inoculation.  A summary of this controversy and a surprising interpretation of events leading up to it are presented in our translation of a 1983 article by Molleret.


[Editorial: Boston Medical and Surgical Journal, January 18, 1883, Vol. CVIII, No. 3]

The day appointed for the first general meeting of the last International Congress of Hygiene at Geneva was looked forward to as the great occasion of the Congress. M. Pasteur was announced as prepared not only to expound his previously published investigations concerning the modification and protective inoculation of disease-poisons, but to disclose new examples of modification of such poisons by the oxygen of the air, and to prove that we have really reached a general method for the modification of certain poisons, whose application has only to be varied according to the physiological characteristics of the various microbions. It was also known that Dr. Robert Koch would be present as representing the Imperial German Health Board and the German school of investigators, from which criticisms of Pasteur’s work had already emanated, criticisms which Pasteur resented in the course of his remarks before the Congress.

The assembled savants were disappointed in their expectations. Pasteur, it is true, did present himself in the role of the “second Jenner,” but he adduced nothing new in support of his previous observations, and the two new instances of inoculation with modified virus, namely, the inoculation of rabbits with culture-liquids containing microbions taken from the nasal discharge of horses dead from the so-called typhoid fever of horses, and of rabbits again with culture-liquids of microbions taken from the saliva of a child supposed to have died from hydrophobia; these instances were, for several sufficient reasons, not very satisfactory. Moreover, Koch refused to discuss Pasteur’s statements or to support his previous criticisms on the legitimate ground that as each expressed himself but very imperfectly in the other’s language, science could derive little benefit from such a debate. He promised, however, to put in print with as little delay as possible whatever he had to say on the subjects of Pasteur’s communication, and Pasteur, recognizing the propriety of Koch’s course, promised that his reply to such a publication should not be long in appearing. With this the scientific quidnuncs of the Congress were forced to content themselves; but if they lost a sensation it seems as if scientific medicine will make a more important gain.

Koch’s arraignment — for it is hardly less — of Pasteur has been published, and is now in our hands. It is a very able and interesting paper, and we give as brief an abstract as possible of the principal points taken up by the writer. Koch thinks Pasteur goes much too fast and too far in proclaiming the discovery and development of a general method of protective inoculation against infectious disease, and denounces the two latest examples cited by Pasteur in favor of such a position not merely as absolutely valueless in that respect, but as admirably exhibiting Pasteur’s false methods of investigation, and the way in which they inevitably lead to false conclusions. Koch states the point of view from which he himself regards the investigation of infectious diseases thus: It is not yet proved that all infectious diseases are caused by parasitic microorganisms, and proof must therefore be found in each separate case of the parasitic nature of a disease. The careful examination of all parts of the body affected by the disease for the presence of parasites, a knowledge of their relative frequency in the affected organs, and of their relation to the tissues, constitutes the first step toward such proof, and all the aids which the microscopical technique of the present day offer are to be brought to bear upon such an examination. Only then can one expect to prove that such microorganisms are of a pathological nature, and that they are the specific cause of the disease in question. For this purpose they must be propagated in unmixed cultures, and when in this manner they have been freed from all adherent substances of the affected body they are then to be inoculated, if possible, upon the same species of animal as that originally attacked, or at least upon such animals as are well known by unmistakable symptoms to be subject to the disease in question. Such was the procedure pursued by Fehleisen in regard to erysipelas, and such that of Koch himself in isolating his bacillus of tuberculosis. Koch next states how far he believes Pasteur’s methods depart from the rules here laid down, and how both the methods and results are unreliable on account of the absence of proper microscopical research, on account of the inoculation of mixed substances, and on account of the selection of unsuitable animals for the experiments. Pasteur not being a physician, Koch thinks it less justifiable to reproach him with his mistaken interpretation of pathological processes and symptoms of disease.

All these sources and kinds of error Koch finds exhibited in Pasteur’s reports of his experiments in inoculating rabbits with the nasal secretion of horses dying from so-called typhoid fever and with the saliva of a child dying from hydrophobia. The rabbits died in both cases, Koch thinks, and supports his opinion pretty strongly, not from typhoid fever or from rabies, but from the well-known septicaemia to which they are especially prone, the symptoms and the microbion of which had been previously thoroughly studied and described by Davaine and others. Moreover, the so-called typhoid fever of horses has nothing in common with the typhoid of men, but belongs, according to Schütz, to the group of erysipelatous processes. No characteristic microbion was found in horses to begin with, the substances for inoculation were not taken from characteristic organs, the materials used for inoculation were not unmixed, the malady from which the rabbits died did not even present any of the general symptoms of typhoid, and rabbits were not the proper animals for the test. Almost the same remarks are applicable to the inoculation of the other rabbits with the saliva from the hydrophobic child, and in regard to this Sternberg has shown how full even the saliva of a healthy person is of various microbions.

In regard to the claim of Pasteur for the discovery and enunciation of a general law for the modification of their poisons and for the protective inoculation of infectious diseases, Koch considers that splenic fever (anthrax, ed.) is the only infectious disease which can as yet be properly accepted in favor of such a claim; that even in this one disease the results are thus far limited to sheep, and both the strength of the virus to be used for the first and second
inoculations and the length and degree of protection secured are still very uncertain, much more uncertain than Pasteur has acknowledged ; that the danger of the inoculation itself for the subject and for other animals and men is increased in direct proportion to the efficacy of the virus employed. As another objection to Pasteur’s claim that he has discovered a general law, Koch recalls the fact that it was Toussaint of the Veterinary School at Alfort who first inoculated the modified virus of splenic fever, the virus being modified by the addition of a one per cent carbolic solution, or by raising the temperature to 55° C. (150° F.); that although Pasteur’s method for modifying the virus is much better than Toussaint’s, his interpretation of the process by which the modification is brought about is incorrect, for it is not, as his own experiments show, the direct action of oxygen which produces the modification, but the presence of products evolved by the microbions themselves, – an evolution favored by oxygen, by elevation of temperature, and replaced by the presence of carbolic compounds.

In regard to Pasteur’s “chicken-cholera” Koch believes no practical use of the modified virus has been made by poultrymen, and thinks that the existence of a specific pathological microbion of such a disease has yet to be demonstrated.

Koch thinks that the general principle of preventive inoculation with artificially modified virus should not be triumphantly proclaimed as established until we have succeeded in modifying and transforming into protective inoculation-material bacteria belonging to diseases of men, of which he thinks we know the bacilli of tuberculosis, of leprosy, of typhoid fever, the micrococci of erysipelas, and the spirochaete of relapsing fever. In none of these diseases, it will be remarked, is one attack protective against a second. Koch acknowledges the modification of the bacillus of splenic fever as an established fact and as a very important step in the right direction, and desires to give Pasteur proper credit for his contributions toward this result, but thinks Pasteur should not make a secret of his processes, and should have more regard for truth and scientific accuracy in his statements, and that all future workers in this department should proceed with greater “objectiveness,” and with a more conscientious self-criticism.

Pasteur’s reply to this brochure of Koch’s will be awaited with much interest and some impatience


            [Editorial: Boston Medical and Surgical Journal, March 1, 1883, Vol. CVIII, No. 9]

THE Revue Scientifique (January 20, 1883,) contains Pasteur’s reply to Koch’s criticism of his methods and results in regard to the micro-organisms of disease and the value of attenuated virus for inoculative purposes. Pasteur’s reply is preceded by his critic’s remarks translated into French. A summary of Koch’s attack was published in the JOURNAL of January 18th.

It is to be regretted that abstract questions of scientific truth or error cannot be divorced from the personalities of discoverers and wrangling over priority, that ” such anger should possess celestial minds.” The expanse of the unknown is broad enough for all voyagers to pursue their way without collision. Such discussions seem to be the inevitable accompaniment of every discovery, and we should, perhaps, rather regard them in the light of the shifting wind, necessary to clear away fog banks, and make plain all the details of new and hitherto but fitfully illumined surroundings, or, to change the metaphor, they may be regarded as the reagent needed to clear up a cloudy liquid.

We must confess, however, that any advantages to be derived from the discussion by abstract science would have been quite as attainable had it been started by Koch on a somewhat different key, excellent though his brochure was as a mere polemical effort. The form which the dispute has taken is tinged with a certain acrimony, borrowed in part, perhaps, from the difference in nationalities, and in part from the difference in ages.

All will recognize that Pasteur has done some remarkable work – we may even, in the German fashion, call it epoch-making work – in the province of scientific medicine, and he duly invites attention to it in his reply to Koch. If the latter accomplishes as much more in twenty years from the date of his first publication in 1876 he may well congratulate himself. The science and the profession which they serve, and the public whom they benefit, will know how to honor both investigators. To Pasteur we must, probably, accord the full credit of solving the riddle of the nature of the ferment in what were formerly known as zymotic diseases, and of teaching the possibility and developing a method – if not the best method – of the attenuation and inoculation of the virus. Koch himself already acknowledges that the secret of splenic fever (anthrax, ed.) has been forced, and he now confesses that Pasteur must be credited with working out the attenuation of the active principle of disease ferments. In these respects at least Pasteur is a genuine “path-breaker,” and has enabled Koch to make his own brilliant discovery of the bacillus tuberculosis.

The action of micro-organisms as ferments or tissue destroyers, and the attenuation of their virulence, are to be regarded as far-reaching principles acquired for science. There have been and will be mistakes in regard to the significance of this or that particular microbion, and the manner in which attenuation of a virus is brought about- whether directly by oxygen and temperature, or indirectly by these, and directly by increased activity in the organisms themselves – may have been misinterpreted; generalizations have been at times too hasty. These considerations should not be allowed to obscure the great principles involved.

Let Koch and his fellow-workers in this field continue, by absolutely pure cultures, to enlarge the number of infectious diseases having a demonstrable connection with a given microbion, by a more exact interpretation of the processes taking place to develop better methods of attenuation of virus, by greater experience to arrive at surer and safer methods of inoculation. There is work here for the time and energies and ingenuity of all interested in these questions, and there are still absolutely unknown regions in the domain of science for the bolder spirits who must be always in the vanguard, and are impatient of a neighbor however distant. There is no excuse here for the elbowing and crowding attendant upon upon long occupation.

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