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Feast through the summer; but, when Scale yonder beetling cliffs, where now the

From The Nineteenth Century.
RECENT SCIENCE.

I.

they can be weakened or increased by vaccination, so as even to confer full immunity. This being true of nearly

Two years ago E. Metchnikoff's ingenious theory of immunity was ana

THERE is no doubt that diphtheria all infections, the attention of bacterihas lately attained an alarming fre-ologists is chiefly directed now towards quency in Europe. To say nothing of finding out what is the cause of the Russia, where the last epidemics had poison-resisting powers of the organswept away nearly all children in many ism, how they are acquired, and how villages, we find that in Prussia no less to strengthen them. than one-sixth to one-fourth part of all children dying in the age of from one to 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 amœba-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 subject, or better contribute to the general promotion of scientific methods of thought.

thus fully deserving the name of microbe-eaters or phagocytes; in other cases they simply keep them enveloped in their protoplasm, and, without That diphtheria, like tetanus (or killing them, prevent them from castlockjaw), with which it has much in ing spores and multiplying; or else, as common, or like anthrax, cholera, ma- it would appear from some recent relaria, and so on, is due to an infection | searches, they carry them away to the of the body by special bacteria is by liver, the lungs, and partly the spleen, this time an established fact. Without where the intruders gradually decay. an infection by either the bacteria Wonderful as these statements are, discovered by Löffler, or the poisons they are facts and not theories. The which they secrete, there is no diph-leucocytes really come together in their theria. But it is also known that the millions at the infected spots, hastenpowers of different animal species, and ing thereto from all parts of the body; even of different individuals, to resist and hundreds of microscopical preparainfection vary a great deal, and that tions, showing to the eye how the

1 Professor Behring, Die Geschichte der Diphtherie, mit besonderer Berücksichtigung der Immunitätslehre, Leipzig, 1893.

2

2 Their disappearance from the blood immediately after infection has lately been confirmed by several explorers.

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 the bacteria have been studied a great been figured in the works upon the deal; and, although we are very far subject. Consequently, the reality of from a somewhat precise knowledge of the absorption of the microbes by the their nature, we know, nevertheless, leucocytes (the phagocytosis) is now that most toxines, although deprived generally recognized, and the impor- by filtration of all bacteria and bacteria tance only of this struggle between two spores, exert upon the animal body sets of cells, as compared with other the same deadly effect as the bacteria possible means of protection against themselves - they provoke the same infection is now under discussion. disease. And, finally, there is in the animal body another class of fermentlike albumoses, also very imperfectly known, which also develop out of the activity of bacteria, and which seem to meet in the body the effects of the

Other agencies, besides the leucocyles, most probably intervene, and during the last few years a great deal of attention has been given to these agencies. It has become evident that 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. With-infectious diseases and have recovered out the aid of their associates the from them; and, consequently, anpoisoning 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.

2 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.

other-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 into the properties of tuberculin, a wide number

of works ought to be named under this head. Such 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

pothesis. 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.3

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 ent species. But experiment, directed the watery parts of blood—the serum this way, refused to support the hyas 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.

Ill

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 The development of Behring's ideas poisons alone, after all bacteria and is extremely interesting, and it admi- their spores had been carefully elimrably illustrates the present aspects of inated from the injected matter. bacteriological research. Rats, as is ness and death evidently resulted in known, are resistent to several infec- such cases, not from some action of tive diseases, including anthrax. While bacteria upon the cells of the animal, mice, rabbits, guinea-pigs, sheep, and but from a general poisoning, whatever horned cattle rapidly succumb to an that poisoning might be. Accordingly, infection of anthrax bacteria; rats do Behring and Kitasato, and several not catch the disease. This was known other bacteriologists, at once began to years ago, and it had also been re-experiment upon such substances as marked, in laboratory experiments, might paralyze the bacterial poisons, 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.

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