a history of science-4-第47章
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inds of animals most apt to contract anthrax。 We are thus able to obtain； not only the attenuation of the virulence； but also its complete suppression by a simple method of cultivation。 Moreover； we see also the possibility of preserving and cultivating the terrible microbe in an inoffensive state。 What is it that happens in these eight days at 43 degrees that suffices to take away the virulence of the bacteria？ Let us remember that the microbe of chicken cholera dies in contact with the air； in a period somewhat protracted； it is true； but after successive attenuations。 Are we justified in thinking that it ought to be the same in regard to the microbe of anthrax？ This hypothesis is confirmed by experiment。 Before the disappearance of its virulence the anthrax microbe passes through various degrees of attenuation； and； moreover； as is also the case with the microbe of chicken cholera； each of these attenuated states of virulence can be obtained by cultivation。 Moreover； since； according to one of our recent Communications； anthrax is not recurrent； each of our attenuated anthrax microbes is； for the better…developed microbe； a vaccinethat is to say； a virus producing a less…malignant malady。 What； therefore； is easier than to find in these a virus that will infect with anthrax sheep； cows； and horses； without killing them； and ultimately capable of warding off the mortal malady？ We have practised this experiment with great success upon sheep； and when the season comes for the assembling of the flocks at Beauce we shall try the experiment on a larger scale。
〃Already M。 Toussaint has announced that sheep can be saved by preventive inoculations； but when this able observer shall have published his results； on the subject of which we have made such exhaustive studies； as yet unpublished； we shall be able to see the whole difference which exists between the two methodsthe uncertainty of the one and the certainty of the other。 That which we announce has； moreover； the very great advantage of resting upon the existence of a poison vaccine cultivable at will； and which can be increased indefinitely in the space of a few hours without having recourse to infected blood。〃＇8＇
This announcement was immediately challenged in a way that brought it to the attention of the entire world。 The president of an agricultural society； realizing the enormous importance of the subject； proposed to Pasteur that his alleged discovery should be submitted to a decisive public test。 He proposed to furnish a drove of fifty sheep half of which were to be inoculated with the attenuated virus of Pasteur。 Subsequently all the sheep were to be inoculated with virulent virus； all being kept together in one pen under precisely the same conditions。 The 〃protected〃 sheep were to remain healthy； the unprotected ones to die of anthrax； so read the terms of the proposition。 Pasteur accepted the challenge； he even permitted a change in the programme by which two goats were substituted for two of the sheep； and ten cattle added； stipulating； however； that since his experiments had not yet been extended to cattle these should not be regarded as falling rigidly within the terms of the test。
It was a test to try the soul of any man； for all the world looked on askance； prepared to deride the maker of so preposterous a claim as soon as his claim should be proved baseless。 Not even the fame of Pasteur could make the public at large； lay or scientific； believe in the possibility of what he proposed to accomplish。 There was time for all the world to be informed of the procedure； for the first 〃preventive〃 inoculationor vaccination； as Pasteur termed itwas made on May 5th； the second on May 17th； and another interval of two weeks must elapse before the final inoculations with the unattenuated virus。 Twenty…four sheep； one goat； and five cattle were submitted to the preliminary vaccinations。 Then； on May 31 st； all sixty of the animals were inoculated； a protected and unprotected one alternately； with an extremely virulent culture of anthrax microbes that had been in Pasteur's laboratory since 1877。 This accomplished； the animals were left together in one enclosure to await the issue。
Two days later； June 2d； at the appointed hour of rendezvous； a vast crowd； composed of veterinary surgeons； newspaper correspondents； and farmers from far and near； gathered to witness the closing scenes of this scientific tourney。 What they saw was one of the most dramatic scenes in the history of peaceful sciencea scene which； as Pasteur declared afterwards； 〃amazed the assembly。〃 Scattered about the enclosure； dead； dying； or manifestly sick unto death； lay the unprotected animals； one and all； while each and every 〃protected〃 animal stalked unconcernedly about with every appearance of perfect health。 Twenty of the sheep and the one goat were already dead； two other sheep expired under the eyes of the spectators； the remaining victims lingered but a few hours longer。 Thus in a manner theatrical enough； not to say tragic； was proclaimed the unequivocal victory of science。 Naturally enough； the unbelievers struck their colors and surrendered without terms； the principle of protective vaccination； with a virus experimentally prepared in the laboratory； was established beyond the reach of controversy。
That memorable scientific battle marked the beginning of a new era in medicine。 It was a foregone conclusion that the principle thus established would be still further generalized； that it would be applied to human maladies； that in all probability it would grapple successfully； sooner or later； with many infectious diseases。 That expectation has advanced rapidly towards realization。 Pasteur himself made the application to the human subject in the disease hydrophobia in 1885； since which time that hitherto most fatal of maladies has largely lost its terrors。 Thousands of persons bitten by mad dogs have been snatched from the fatal consequences of that mishap by this method at the Pasteur Institute in Paris； and at the similar institutes； built on the model of this parent one； that have been established all over the world in regions as widely separated as New York and Nha…Trang。
SERUM…THERAPY
In the production of the rabies vaccine Pasteur and his associates developed a method of attenuation of a virus quite different from that which had been employed in the case of the vaccines of chicken cholera and of anthrax。 The rabies virus was inoculated into the system of guinea…pigs or rabbits and； in effect； cultivated in the systems of these animals。 The spinal cord of these infected animals was found to be rich in the virus； which rapidly became attenuated when the cord was dried in the air。 The preventive virus； of varying strengths； was made by maceration of these cords at varying stages of desiccation。 This cultivation of a virus within the animal organism suggested； no doubt； by the familiar Jennerian method of securing small…pox vaccine； was at the same time a step in the direction of a new therapeutic procedure which was destined presently to become of all…absorbing importancethe method； namely； of so…called serum…therapy； or the treatment of a disease with the blood serum of an animal that has been subjected to protective inoculation against that disease。
The possibility of such a method was suggested by the familiar observation； made by Pasteur and numerous other workers； that animals of different species differ widely in their susceptibility to various maladies； and that the virus of a given disease may become more and more virulent when passed through the systems of successive individuals of one species； and； contrariwise； less and less virulent when passed through the systems of successive individuals of another species。 These facts suggested the theory that the blood of resistant animals might contain something directly antagonistic to the virus； and the hope that this something might be transferred with curative effect to the blood of an infected susceptible animal。 Numerous experimenters all over the world made investigations along the line of this alluring possibility； the leaders perhaps being Drs。 Behring and Kitasato； closely followed by Dr。 Roux and his associa
