June 2, 1910] 



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bacillus would grow luxuriantly only at the body tem- 

 perature, Koch found it necessary to obtain some solid 

 medium that would not melt at that temperature, and, 

 going- on the principle that the fluids of the body 

 would probably afford the best nutrient medium for 

 an organism that grows so readily in the tissues, he 

 took the blood serum of sheep, calves, &c., which not 

 only contained the necessan,^ nutrient elements for the 

 bacillus, but was consolidated by heat, and he found 

 that if the consolidation were effected at a sufTiciently 

 low temperature, the medium retained most of its 

 nutrient properties. Here again was a tremendous 

 advance, and his paper, read on March 24, 1882. 

 before the Berlin Physiological Society, and published 

 in the report of the Imperial Board of Health, was 

 received with acclamation on every hand, and although 

 criticism of all kinds was directed against his find- 

 ings, Koch maintained his thesis against all comers. 

 .After this work on tuberculosis, Koch was naturally 

 looked to, not only by his own countrymen, but by 

 scientific men of all countries, as the man most likely 

 to solve the questions bound up in the causation of 

 cholera. In 1883 he went out to Egypt on a quest 

 for the causa causans of cholera, and in 1884 acted 

 as chairman of the Germap Cholera Commission, 

 which carried out much of its work in India. His 

 works on cholera, one volume published in 1884 and a 

 second in 1894, must be looked upon as classical mono- 

 graphs, and from 1884 onwards the cholera vibrio, or 

 comma bacillus, became indissolubly associated with 

 cholera as its prime etiological factor. 



In 1885 Koch was appointed professor of hygiene in 

 the faculty of medicine in Berlin University, and his 

 classroom and laboratory became the resort of students 

 from all parts of the world, as they had already been 

 at the Gesundheitsamte, though on a smaller scale. 

 His pupils there trained took up many of the 

 problems for the consideration of which he had neither 

 time nor energ\\ In 1890, at the tenth International 

 Medical Congress, he announced the discover}- of 

 tuberculin, and. in a series of admirable experiments, 

 demonstrated the action of tuberculin as an immunis- 

 ing agent, an aid to diagnosis, and even as a curative 

 when injected into animals already suffering from 

 tuberculosis. The announcement of this treatment 

 seemed to give hope of prolonged life to thousands of 

 tuberculous patients, many of whom clamoured to be 

 treated. The method, however, had not been suffi- 

 cientlv fuUv developed, and there can be little doubt 

 that it fell into disrepute, not because it failed to 

 accomplish what had been claimed for it by Koch, 

 but because it failed to give such results as had taken 

 form in the imagination, alike of patients and of 

 medical men, who could not understand the limitations 

 of such a method of treatment — a method still in its 

 infancv. Those, however, who really studied the 

 tuberculin treatment never lost heart, and in 1897 

 Koch reported a new tuberculin, with which much 

 more satisfactory curative results have since been 

 obtained. There can be little doubt that some modi- 

 fication of this method must form the basis of anv 

 specific curative treatment. 



In 1891 Koch was appointed director of the mag- 

 nificent new Institute for the Study and Treatment of 

 Infective Diseases, and here, with his band of 

 workers, in which were men whose reputation is now 

 world-wide, continued to work out some of the 

 problems in which he was now interested. In 1896 

 he was called to .South .Africa to studv rinderpest, a 

 disease which, with the assistance of Kolle and 

 Turner, he traced to its cause and for which he de- 

 vised a method of immunisation. As the result of 

 these observations, on which were built up investiga- 

 tions by later workers, rinderpest has become a 



NO. 2 II 8, VOL. 83I 



manageable disease. At this lime Koch first took up 

 the question of sleeping sickness, but, like most other 

 observers, he failed at the outset to find any organism 

 that he could associate causally with the disease. 

 From this he turned his attention to the bubonic 

 plague, studying it in India and German East Africa. 

 Following up the observations of Yersin and Lowson, 

 and tracking down the bacillus of plague, he found 

 that it was really conveyed by rats, and that, however, 

 it was endemic in Mesopotamia, in Hunan in China, 

 in Tibet and Mecca, and in Kissiba, Victoria Nyanza. 

 As a result of his observations, he expressed the hope 

 and assurance that in time these plague centres might 

 be cleansed, and when the reservoirs and carriers of 

 the disease could be localised, plague might gradually 

 be exterminated. How far these prognostications mav 

 be realised it is still early to state, but the continuation 

 of this line of research and the tracking down of 

 the flea as a further carrier have undoubtedly brought 

 this period nearer. 



In 190 1 Koch exploded his great bombshell at the 

 International Congress on Tuberculosis in London 

 when he said, " I feel justified in maintaining that 

 human tuberculosis differs from bovine and cannot be 

 transmitted to cattle." That he wished further 

 evidence, however, is evident from the fact that to this 

 statement succeeds the following : — '" It seems to me 

 very- desirable, however, that these experiments should 

 be repeated elsewhere in order that all doubts as to 

 the correctness of my assertions may be removed." 

 As regards infection of the human subject by the 

 material from tuberculous cattle, he said : — • I should 

 \ estimate the extent of infection by the milk and flesh 

 j of tuberculous cattle and the butter made of their 

 j milk as hardly greater than that of hereditary trans- 

 I mission, and I therefore do not deem it advisable to 

 I take any measures against it." It was this last state- 

 ment to which special objection was made, as it in- 

 volved such a complete alteration in our method of 

 procedure in connection with milk and milk products 

 from tuberculous cattle. It is not necessarv here to 

 repeat what has been now before the public for so 

 long in the Interim Reports of the Royal Commission 

 on Tuberculosis and of the German Commission on 

 Tuberculosis, the Transactions of the International 

 Congress on Tuberculosis at Washington, and many 

 papers by individual workers. Moreover, there seems 

 some reason to believe that latterly Koch had modified 

 his views somewhat, in so far that in his interview 

 with the Times correspondent in Berlin during the 

 early part of last year he stated that the " Diff^erences 

 still unsolved between my critics in the Roval Com- 

 mission and myself have been greatly reduced by 

 further examination, and are now \exy slight." As 

 shortly before his death Koch was making a verv 

 thorough search for the bacillus of bovine origin in 

 cases of pulmonary- tuberculosis, it is to be hoped that 

 his colleagues and literary executors will give the 

 world the results of his investigations. 



In 1903, still in search of fresh fields to conquer, 

 he returned to South Africa to study on the spot coast 

 fe\er (allied to Texas fever), a condition due, appar- 

 ently, to the presence of protozoal parasites in the 

 blood. At this period his investigations were occupy- 

 ing so much of his time that in order to devote himself 

 to them more thoroughly he retired from his position 

 as director of the Institute for the Study and Treat- 

 ment of Infectious Diseases. In 1905 he was awarded 

 the Xobel prize in recognition of his great services 

 to medicine, an award approved bv all. 



In 1906, returning to East Africa, he continued his 

 studies on sleeping sickness, especially in relation to 

 its treatment by atoxyl. At one time it appeared as 

 though he had obtained a drug specific for this 



