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The Tubercle Parasite

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On the 24th of March, 1882, an address of very serious public import was delivered by Dr. Koch before the Physiological Society of Berlin. It touches a questioii in which we are all at present interested - that of experimental physiology - and naay, therefore, be permifcted to give some accounts of it in the Times. The address, a copy of which lias been courteously sent to me by ils author, is entitled "The Etiology of Tubercular Disease." Koch flrst made himself knowu by the penetration, skill and Ilioroughness of his researchea on tho contaglum of splenic fever. By a process of inóculation and infection lie traced this terrible parasite through all i!s stages of' development and through ita rarious modes of actioi). 'J'hi.s masterly investigation caused tliu young physiclan to be transferred from a modest country practico, in the neighborhood of Breslau, to the post of Government Advisor to the Imperial Health Department of Berlin. From this department has lately issued a most important series of investigations on the etiology of infectivo disorders. Koch's last inquiry deals witli a disease which, in point of mortality, stands at the head of them all. 11', he says, the seriousness of a malady be measured by the number of its victima, then the mostdreaded pests whish tiave hitherto ravaged the world - plague and cholera included - must stand far behind the one now under consideration. Koch makes the starting statement that one-seventh of the deaths of the human race are due to tubercular disease, while fully onethird of thoje who die in active middle-age are carried ofE by the same cause. Prior to Koch it had been placed beyond doubt that the disease was communicable; and the aim of the Berlin physician has been to determine the precise character of the contagium which previous experiments on inoculation and inhalation had proved to be capable of indennite transfer and reproduction. He subjected the diseased organs of a great number of men and animáis to microscopio examination, and found, in all cases, the tubercles infested with a minute, rod-shaped parasite, which, by means of a special dye, he differentiated from the surrounding tissue. It was, he says, in the highest degree impressive to observe in the centre of the tubercle cell the minute organism which had created it. Transferring directly, by inoculation, the tuberculous matter from diseased animáis to healthy oue3, he in every instance reproduced the disease. To meet the objection that it was not the parasite itself, but some virus in which It was imbedded in the diseased ortjan, that was the real contagium, he cultivated his bacilli artificially, for long periods of time and through many successive generatlons. With a speek of matter, for example, from a tubercuous human lung, he infected a substance prepared, after rnuch trial, by himself, with the view of affording nutriment to the parasite. Here he sermitted it to grow and multiply. Froin this iew generation he took a minute sample and infected therewith fresh nutritivo matter, thus producing another brood. Generation afler generdtion of baccilli were developed in this way, without the intervention of disease. At the end of the process, which sometimes embraced successive cultiva;ions extending over half a year, the jurifled baccilli were introduced into ;he circulation of healthy animáis of various kinds. In every case inoculation was followed by the reproduction and spread of the parasite and the generation of the original disease. Perrriit me to give a further, though still brief and sketchy,account of Koch's experiments. Of six guinea-pigs, all in jood health, four were inoculated with jacilli deriyed originally from a human ung, which in fifty-four days had produced flve successive generations. Two of the six animáis were not infected. ín every one of the infected cases the uinea-pig sickened and lost flesh. Af;er thirty-two days one of them died, and after thirty-five days the remaining flve were killecl and examined. In the guinea-pig that died, and in the turee remaining infected ones, strongly pronounced tubercular disease had set in. Spleen, liver and lungs were found fllled with tubercles ;while in the two uninfected animáis no trace of the disease was observed. In a second experiment, six out of eight guinea-pigs were inoculated with cultivated bacilli, derived originally from the tuberculous lung of a monkey, bred and rebred for ninctyflve days, until eight generations had been produced. Every one of these animáis was attacked, while the two uninfected guinea-pigs remained fectly healthy. Similar expertments were made with cats, rabbits, rats, mice and other animáis, and without exception, ït was found that the injection of the parasite into the animal system was followed by decided and, in most cases, virulent tubercular disease. In the cases thus far mentioned inoeulation had been effected in the abdomen. The place of inoculation was afterward changed to the aqueous humor of the eye. Three rabbits received each a speek of bacillus-culture, derived originally f rom a human lung affected with pneumonia. Eighty-nine days had been devoted to the culture of the organism. The infected rabbits rapidly lost flesh, and after twenty-flve days were killed and examined. The luugs of every one of thein were found charged with tubercles. Of three other rabbits, one received an injection of pure blood-serum in the aqvieous humor of the eye, while the other two were infected, in a similar way, with the same serum, containing baccilli derived originally trom a diseased lung, and subjected to ninety-one days' cultivation. After twenty-eight days the rabbits were killed. The one which had received an injection Of pure serum was found perfectly healthy, while the lungs of the two others were found overspread with tubercle3. Other experiments are recorded in this admirable essay, from which the weightiest practical conclusions may be drawn. Koch determines the limite of temperature between which the tuber-bacillus can develop and multiply. The minimum temperature he flnds to be 86 Pahrenheit and tli8 maximum 104 . He concludes that, unlike the bacillus anthracis of splenic fever, which can flouiish freely outside the animal body, in the températe zone animal warmth is necessary for the propagation of the newly discovered organism. In a vast number of cases Koch has examined the matter expector&ted from the lungs of persons affected with phthisis and found in it swarms of baccilli, while in matter expectorated from the luiigs of persons not thus afflicted he has never found the organism. ïho expectorated matter in the former cases was highly infective, nor did drying destroy i Is virulence. (iuinea-pigs infected witb expectorated matter which had been kept dry for two, f our and eight weeks rsspeotively, were smitten with tubercular disease quite as virnlent as that produced by fresh expectoration. Koch pointa tb the grave danger of Lahaling air in which partióles of the dried sputa of consumptive patients mingles with dust of other kinds. It would le mere impertinence on my part to draw the obvious moral from these experimenta. In no other conceivable way than that pursued by Koeh could the true character of the most destructivH malady by which humanity is uow assailed be determined. And, noisy the fanaticism of the moment may be, the common sense of Englishmen will hot, in the long run, permit it to enact oruelty in the name of tenderness, or to debar us from the light and leading of such investigations as that which is here so imperfectly described.


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