From The Nineteenth Century. I. they can be weakened or increased by vaccination, so as even to confer full immunity. This being true of nearly all infectious, the attention of bacteriologists is chiefly directed now towards finding out what is the cause of the poison-resisting powers of the organism, how they are acquired, and how to strengthen them. THERE is no doubt that diphtheria has lately attained an alarming frequency in Europe. To say nothing of Russia, where the last epidemics had swept away nearly all children in many villages, we find that in Prussia no less than one-sixth to one-fourth part of all Two years ago E. Metchnikoff's inchildren dying in the age of from one genious theory of immunity was anato five years succumb to diphtheria;1lyzed in this review. According to and the same proportion must have this theory, the organism which has lately prevailed in western Europe as been successful in its struggle against well. One fully understands, therefore, | infection owes its recovery to a victory the keen interest which is taken at this which has been won by its amoeba-like moment by the general public in the white cells, or leucocytes, over the experiments of the French doctors infecting microbes. As soon as poisonRoux and Yersin, who try to cure ous bacteria are introduced into the diphtheria by means of the blood serum animal body, the free white cells — i.e., of animals previously vaccinated against the white corpuscles of the blood and that disease. However, the scientific the lymph, and the so-called wandering importance of these experiments is cells — probably attracted by the secreeven greater than their immediate tions of the bacteria, gather in imutilitarian value. Serum-therapy has a mense numbers at the spot of infection. direct bearing upon nearly all infec- There they wage a war to the intruders. tious diseases; and it touches upon If they are healthy and numerous, and some of the most burning questions if the bacteria do not multiply too relative to the fundamental problems rapidly, so as to overpower the leucoof life; while the manner in which the cytes in numbers, the latter absorb researches have been conducted is the microbes, enveloping them with such that there is hardly, in the whole their protoplasm and rendering them domain of modern science, another inoffensive. In some places the leucobranch which could better illustrate cytes actually digest the microbes the best methods of scientific investi- that is, dissolve them and absorb them gation applied to a most complicated thus fully deserving the name of subject, or better contribute to the microbe-eaters or phagocytes; in other general promotion of scientific methods cases they simply keep them envelof thought. oped in their protoplasm, and, without killing them, prevent them from casting spores and multiplying; or else, as it would appear from some recent researches, they carry them away to the liver, the lungs, and partly the spleen, where the intruders gradually decay. That diphtheria, like tetanus (or lockjaw), with which it has much in common, or like anthrax, cholera, malaria, and so on, is due to an infection of the body by special bacteria is by this time an established fact. Without an infection by either the bacteria Wonderful as these statements are, discovered by Löffler, or the poisons which they secrete, there is no diphtheria. But it is also known that the powers of different animal species, and even of different individuals, to resist infection vary a great deal, and that 1 Professor Behring, Die Geschichte der Diphtherie, mit besonderer Berücksichtigung der Immunitätslehre, Leipzig, 1893. they are facts and not theories. The leucocytes really come together in their millions at the infected spots, hastening thereto from all parts of the body; 2 and hundreds of microscopical preparations, showing to the eye how the 2 Their disappearance from the blood immediately after infection has lately been confirmed by several explorers. 1 leucocytes envelop the microbes with | ganism. Since Koch discovered his their protoplasm, have been made in tuberculin, these poisonous products of the laboratories; many of them have been figured in the works upon the subject.1 Consequently, the reality of the absorption of the microbes by the leucocytes (the phagocytosis) is now generally recognized, and the importance only of this struggle between two sets of cells, as compared with other possible means of protection against infection is now under discussion. the bacteria have been studied a great deal; and, although we are very far from a somewhat precise knowledge of their nature, we know, nevertheless, that most toxines, although deprived by filtration of all bacteria and bacteria spores, exert upon the animal body the same deadly effect as the bacteria themselves -they provoke the same discase. And, finally, there is in the Other agencies, besides the leuco- animal body another class of fermentcytes, most probably intervene, and like albumoses, also very imperfectly during the last few years a great deal known, which also develop out of the of attention has been given to these activity of bacteria, and which seem to agencies. It has become evident that meet in the body the effects of the the action of bacteria is very compli- above poisons. The British Medical cated. In some cases the poisoning Journal has proposed for them the bacteria must be associated with vari- very good name of defensive proteids.1 ous species of other micro-organisms, These anti-toxines, whatever their nainoffensive in themselves, but probably ture may be, undoubtedly develop in required to prepare some favorable the blood, and especially in the serum conditions for the multiplication and of animals which have caught certain the deadly action of the former. Without the aid of their associates the poisoning bacteria may have no effect, as has been proved several times with cholera and typhoid fever, and is well known for tetanus bacilli. Again, the bacteria may simply destroy some cells of the body this is the way of the malaria parasites, which destroy the red corpuscles of our blood 2- or they may attack the tissues of some special organs; or they will deprive the cells of the body of the plastic elements, or gases, necessary for their life, and, so to say, starve or suffocate them. But their effect may also be more indirect; they develop, also, what we call, for want of a better knowledge of the subject, some poisons some living, ferment-like toxines which affect the fluids of the body, and especially its blood, and, through it, the whole or 1 We are glad to state that Metchnikoff's "Leçons sur la pathologie comparée de l'inflammation" has by this time been translated into English by T. A. Starling and E. H. Starling. Notwithstanding its rather technical title, the reading of this little and suggestive book can safely be recommended to non-specialists. For all concerning the malaria microbes see the excellent work of Dr. Julius Mannaberg, "Die Malaria-Parasiten, auf Grund fremder und eigener Erfahrung dargestellt," Vienna, 1893. infectious diseases and have recovered from them; and, consequently, another—that is, a fourth-branch of research has grown up, the explorers of which want to know whether blood altogether, and especially its serum, as well as other liquids secreted by the body, and especially milk, do not possess immunity-conferring, or even curative, properties. This is the branch of bacteriology which interests us most at the present moment, especially as regards the applications of blood serum to the cure of diphtheria.5 3 Besides the researches of Koch and his school of works ought to be named under this head. Such into the properties of tuberculin, a wide number are the studies undertaken by Roux and Widal (at the Institut Pasteur), and Wooldridge in 1888, into the poisons secreted by the diphtheria and the tetanus bacteria; the investigations of Brieger and Fränkel into the poisonous albumines_(toxalbumines); and those of E. H. Hankin, Kanthack, and Dr. Sydney Martin into the toxines and the protective anti-toxines. See E. H. Hankin's "Report on the Conflict between the Organism and the Microbe" in British Medical Journal, July 12, 1890; also his review of Behring and Kitasato's work in Nature, December 11, 1890, xliii. 121. Indications of the corresponding literature are given in both papers. 5 Its literature is immense. Indications relative to it will be found in the quoted works and reviews. Buchner's reports to the Hygienic Congresses at London (1891) and Buda-Pesth (this ent species. But experiment, directed this way, refused to support the hypothesis. Animals whose blood showed no bactericide properties in the laboratory were found to be immune against certain diseases; while, on the other hand, animals whose blood destroyed the bacteria in a glass bottle were not always immune. Some experiments were in favor of the hypothesis, but others were dead against it, and there remained nothing but to submit to the verdict, however undesired it was.8 For many years past Doctors Richet, the different bacteria-killing properties Héricourt, and Klein, amidst general possessed by the serum in these differindifference, have advocated the use of the watery parts of blood-the serum -as a means of protecting animals against infection, and insisted upon its curative properties. However, their opinions passed unnoticed. All that preparatory work concerning the bacterial poisons and the anti-toxines which has just been mentioned had to be done before the importance of the serum could be properly understood and demonstrated. It was therefore only at the end of 1890, when the German doctor Behring and the Japanese bacteriologist Kitasato published the results of their elaborated researches, that the whole matter was put on a firm scientific basis.1 Modern serumtherapy, as acknowledged over and over again by Roux and all other explorers, dates from these memoirs. The development of Behring's ideas is extremely interesting, and it admirably illustrates the present aspects of bacteriological research. Rats, as is known, are resistent to several infective diseases, including anthrax. While mice, rabbits, guinea-pigs, sheep, and horned cattle rapidly succumb to an infection of anthrax bacteria; rats do not catch the disease. This was known years ago, and it had also been remarked, in laboratory experiments, that while anthrax bacteria thrive in the serum of the last-named animals, they rapidly degenerate in the serum of rats. It was natural, therefore, to suppose that the same takes place in the living organisms, and that the resistance of rats and the susceptibility of mice, rabbits, and so on, are due to year) are excellent reviews of the whole question, the more so as Buchner is one of the chief workers in this branch. 1 Behring and Kitasato, "Ueber das Zustandekommen der Diphtherie - Immunität und der Tetanus-Immunität bei Thieren," in Deutsche medizinische Wochenschrift, 1890, 49, p. 1113. Analyzed in Nature by Mr. Hankin, December 11, 1890, xliii. 121. 2 I follow in this sketch Behring's own description of the evolution of his ideas, as given in his introduction to his and Kitasato's memoirs, "Die Blutserumtherapie bei Diphtherie und Tetanus," in Koch and Flügge's Zeitschrift für Hygiene und Infectionskrankheiten, 1892, xii. 1-10. These negative results were arrived at at a time when Roux and Yersin, who studied diphtheria, and Kitasato, who worked on tetanus, had succeeded in obtaining, out of the secretions of the respective bacteria, such powerful poisons that it became possible to provoke both diseases by injecting the poisons alone, after all bacteria and their spores had been carefully eliminated from the injected matter. Illness and death evidently resulted in such cases, not from some action of bacteria upon the cells of the animal, but from a general poisoning, whatever that poisoning might be. Accordingly, Behring and Kitasato, and several other bacteriologists, at once began to experiment upon such substances as might paralyze the bacterial poisons, even though they might be unable to kill the bacteria themselves. Various chemicals were tried, and for some time great hopes were entertained as to the chemical treatment. But again the results were utterly disappointing. It appeared that the effects of the chemicals are mostly quite local, and that, to be of any use, they must be applied immediately after the infection takes place. Their practical value is therefore extremely limited. 3 A long series of such experiments was made in Bouchard's laboratory; so also by Behring and Nissen. 4 The limited effect of chemicals will be better illustrated by the following: Dr. Calmette, the chief of the Bacteriological Institute of Saigon, having once received from a locality infested by cobra snakes a barrel containing fourteen living specimens of the snake, utilized this opportunity for studying the means of combating the deadly Nevertheless an important point was won by such researches. Behring and Kitasato found, to their astonishment, that if the spread of tetanus in an animal had been stopped by any sort of chemical treatment, the blood of that animal, although it was unable to kill the bacteria of tetanus, paralyzed the poisons evolved by the bacteria. The animal was rendered immune against infection; and when the two doctors attempted to cure tetanus by means of the serum of such blood, they at once obtained results which went far beyond their expectations. To quote but one instance: several mice were dying from inoculated tetanus, when an injection of the serum of an immune rabbit was tried upon one of them. Improvement became apparent at once, and it was followed by recovery, while the other mice died in a few hours. The cure for tetanus was thus found, and this was what Behring and Kitasato announced in their epoch-making memoir in December, 1890. against diphtheria on larger animals It would not be possible to relate here the details of these memorable researches.1 Sufficient to say that gradually the following method was elaborated, and that it proved successful for big animals as well. Instead of introducing a deadly virus, and then trying to cure it by chemicals, an attenuated diphtheria (or tetanus) poison was used for vaccination—all bacteria and their spores having been removed by filtration from the vaccinating liquid, and the morbid properties of the poison itself having been reduced by the addition of certain chemicals.2 This attenuated poison was injected into a quite sound sheep (or horse) in such limited quantities as to obtain but a very feeble reaction of fever; and the injections were repeated until the animal was ac no more fever was provoked by subsequent injections. Then stronger doses, up to three and six cubic inches of the But now that the final aim seemed to have been reached, new difficulties arose. The first successes were not always confirmed by subsequent exper-customed, so to say, to the poison, and iments, and, in proportion as the field of research was widened, failures became more and more frequent. Then it was much more difficult to obtain a attenuated poison, were resorted to; curative serum for diphtheria cases than it was for tetanus. Moreover, large quantities of serum were required for the serum cure, and they could be obtained only by conferring immunity and when they also had no marked effect, an injection of the most virulent diphtheria poison, such as would kill outright an untrained sheep, was attempted. If it did not provoke diphtheria, the sheep or horse was considpoison. He experimented with all sorts of chem-ered immune, and the serum of its icals. It appeared, however, that although permanganate of potassium at once destroys the blood could be used to cure dipththeria cobra poison in a glass tube, and precipitates it, it in other animals. This method was has but little effect in the animal body unless it is introduced into the wound immediately after, or gradually perfected, and it was discovsimultaneously with, the inoculation of the poison. Otherwise the latter rapidly spreads through the 1 The reading of the chief original papers, body, and can be paralyzed no more either by the namely, by Behring and Kitasato, in the Zeitschrift permanganate or by ammonia. Chloride of gold | für Hygiene (1892, xii. 1–81), and by E. Roux and is but little more efficacious. If the spreading of the poison is slackened by ligatures, and injections of chloride of gold are made all round the wound, and on the way of the poison from the wound to the central parts of the body, there are some chances of recovery; but the whole must be done very quickly, in order to prevent the spreading of the poison ("Observations expérimentales du Venin de Naja tripudians ou Cobra capel," in Annales de l'Institut Pasteur, 1892, vi. 160). L. Vaillard in the Annales de l'Institut Pasteur (February, 1893, vii. 64-140), can be recommended to non-specialists as well as others. 2 Roux prefers iodine, while the German explorers prefer iodine trichloride, or a chloride of gold and sodium. Many other chemicals, including peroxide of hydrogen, were experimented with before these three were chosen. › Behring's Die Geschichte der Diphtherie, pp. 160-165. In how far the serum treatment may be relied upon for man is still a question to be solved by experiment, and upon which Roux, Behring, Kitasato, ered by Roux that the serum need not be drawn each time afresh. It may be desiccated, and kept for a long time in such state without losing its properties. The curative effects of such serum Ehrlich, and all the above-named exare really wonderful. A guinea-pig plorers, as well as Tizzoni and Cattani usually dies from inoculated diphtheria in Italy, are now busy at work. The in thirty-six to forty-eight hours. But brilliant successes announced from an injection of a very small quantity of time to time in the daily papers must serum (one five-thousandth part of the certainly be received with caution. weight of the patient), if it be made a But in view of the undoubted, though quarter of an hour after the inoculation not always infallible, successes obof the poison, prevents the appearance tained with animals, and the fair proof the disease. If the treatment begins portion of successful treatment of men, at a later period, say eight hours after we can be hopeful. In some cases the the inoculation, ten times more serum cures have been most remarkable. is required. Even twenty-four hours Moreover, we learn from statistics after the infection takes place the ani- which reach us as we write these lines mal can be saved by an injection of that Roux at Paris has obtained sevserum attaining one one-hundredth part enty-four per cent. of cures in three of the animal's weight. Its blood is hundred ascertained cases of diphrenewed ; it acquires new forces, and it theria, already treated by the serum; destroys the poisons of diphtheria and that Professor Ehrlich at Berlin which were rapidly bringing the dis- has had eighty-five per cent. of recovease to a fatal end.1 With tetanus, in- eries in the one hundred and sixtyjections of serum are effective even in three cases treated by the new method. a more advanced stage. There were only two failures out of the Moreover, as shown by Kitasato and seventy-two cases in which serum was his colleagues,2 the same method is injected during the first two days of applicable to Asiatic cholera, erysipe- the disease. Such results are more las, hog-cholera, and anthrax. Immu- than reassuring. nity at least, or, more correctly, a The theoretical value of these invesresistance to poisoning, is easily ob-tigations is self-evident. Important tained for these diseases as well; and points have been won, and new and in cholera immunity is conferred so broader vistas have been opened. rapidly-in twenty-four hours that Metchnikoff's theory of immunity has the treatment has very much the char- certainly not been overthrown by the acters of a real cure. A wide field is new discoveries. On the contrary, the thus opened for most promising discov-part played by the phagocytes in the eries. 1 Behring and Wernicke, "Ueber Immunisirung und Heilung von Versuchsthieren bei der Diphtherie," in Zeitschrift für Hygiene, 1892, xii. 10-44; also Behring's "Geschichte der Diphtherie," P. 184. struggle against. infection is fully recognized even by such promoters of the serum theory as Buchner and Roux. It has been proved, moreover, that an injection of an antitoxic serum proS. Kitasato, L. Brieger, and A. Wassermann, vokes a marked increase in the num"Ueber Immunität und Giftfestigung," in Zeit-bers of the leucocytes in blood, and it schrift für Hygiene, 1892, xii. 137-182. For immuappears probable 5 that the leucocytes nity through milk, P. Ehrlich, in same volume, p. 183, where copious bibliographical indications are given. Kitasato attenuates the bacterial poisons by cultivating the bacteria in preparations obtained 18. from the thymus gland. His researches thus join hands with the most remarkable therapeutic results obtained by Brown-Sequard and D'Arsonval, and they tread upon the ground which has been so well reviewed lately by Professor Schäfer in his presidential address before the British Association at Oxford. 8 M. A. Ruffer, in Nature, November 1, 1894, li. Roux and Vaillard recognize the fact in the above-quoted memoir, p. 91. Mademoiselle C. Everard, J. Denmoor, and J. Massart, "Sur les Modifications des Leucocytes," in Annales de l'Institut Pasteur, 1893, vii. 187-194. See also Metchnikoff's fifth memoir on immunity in the same volume. |