VII TROPICAL DISEASES DR. C. J. MARTIN, M.B., D.Sc., F.R.S., July 10 and 17, 1907 DR. MARTIN, Director of the Lister Institute, Chairman of the Anti-Typhoid Inoculation Committee appointed by the Secretary of State for War, Member of the Plague Committee, and Member of the Tropical Diseases Committee of the Royal Society, gave evidence on behalf of Prof. Starling's Committee. (See also Chap. IV.) Plague Asked by the Commissioners to give an account of plague, he answered that plague was a disease of great antiquity. The constant association of deaths of rats and mice with outbreaks of plague among human beings. had been observed for ages, but was not understood till Yersin and Kitasato, in 1894, found the germs of the disease, grew them on artificial media, and reproduced the disease in animals by inoculation with these pure cultures. "Once the cause of the disease was known, it was easy to determine that the disease from which rats and mice simultaneously suffered was also plague. All the conditions, favourable and unfavourable to the existence of the infective agent, could now be studied; and the means, whereby the infection leaves the bodies of persons or animals dead of the disease, could be determined. The relationship in time and space between human outbreaks and disease in rodents could be worked out, and the influence of epidemics amongst rats, in the spread of the disease amongst human beings, determined. The relationship of rat plague to human plague has been found to be of such a character as (taking into consideration the small extent to which bubonic plague is infectious from man to man) to indicate in the strongest manner that the spread of the disease in man is conditioned almost entirely by the occurrence of plague amongst rats in his vicinity. The Commission at present investigating the question of the spread of plague in India have, by extensive experiments on animals, succeeded in showing that the infection is carried from rat to rat by the agency of the fleas infesting these animals. By the same agency they have been able to produce epidemics amongst other animals, guinea-pigs and monkeys; whereas all other means failed to give rise to the epidemic spread of the disease. The Indian rat flea also feeds upon man when his natural prey is not available: so that a possible, and indeed probable, means whereby the infection is carried from rats suffering from the disease to mankind has been The accompanying chart is reproduced from the pamphlet " Plague in India, Past and Present," by Colonel Bannerman, 1.M.S., Director of the Bombay Bacteriological Laboratory. The pamphlet is published by the Research Defence Society. The chart shows the number of plague-infected rats found among the hundreds daily caught and destroyed in the city of Bombay during a time of plague, and the number of human deaths from plague during the same period. The dotted line shows the number of brown rats (M. decumanus) found infected; the thin line shows the number of black rats (M. rattus) found infected; the thick line shows the number of human deaths from plague. Oct. Nov. Jan. Feb.1 July. Dec. RATS AND PLAGUE. established. Further experiments carried out in houses or huts, where many cases of plague occurred, have shown that animals (guinea-pigs or monkeys) are attacked by the disease when placed in such infected huts without protection from fleas; but if the simplest means are adopted to prevent the fleas from reaching the animals, by a gauze covering, or a layer of sticky paper wider than a flea can jump, or by suspending the cage at a distance from the floor greater than a flea can leap, they have in no case contracted plague. . . . It need hardly be insisted upon that the complete comprehension of the spread of the disease under natural conditions is essential to successfully devise preventive measures. Without such knowledge our efforts will, in all probability, be misdirected. A knowledge of the causation of plague has enabled a useful method of protective inoculation to be devised. Efforts towards the production of a curative serum have unfortunately, so far, been disappointing, as the means employed have not produced an anti-serum of sufficient potency." Asked about Haffkine's preventive treatment, he referred to Pasteur's discovery that animals could be protected against chicken cholera and anthrax by inoculation with attenuated cultures of the organisms which cause the diseases; and to Gamaleia's discovery, in 1888, that it was not essential, for the production of protection, to use living germs, since some degree of immunity could be induced by the use of the chemical products contained in dead germs. This discovery made by Gamaleia had been extended to the protective treatment against cholera, typhoid, and plague. "In 1896, plague broke out in Bombay, and spread throughout the city, and extended to neighbouring places. The general sanitary measures employed proved powerless to prevent the spread of the disease. Haffkine therefore turned his attention to the problem. of preventive inoculation against plague, in the hope of arriving at a useful method which could be applied upon a large scale to man. After numerous experiments with cultures of the plague bacillus, which had been killed by a variety of means, Haffkine decided upon a broth culture of the organism, sterilised by heating to 65° C. Having tested the vaccine by inoculating first himself and then the personnel of his laboratory, the first extensive trial of the efficacy of this vaccine was made in January, 1897, upon the inmates of the Byculla Jail, where plague had broken out. The submission to inoculation was voluntary. The jail contained 337 adults of both sexes, who were not obviously infected with plague; 154 offered themselves for inoculation. Three of these were, however, in the incubation stage of plague, for they developed plague the same evening. For the purpose of arriving at an estimate of the value of the preventive inoculation, these persons in the incubating stage of the disease must be eliminated from the calculation, as also many cases amongst the uninoculated, who also developed plague upon the day the injections were made; leaving 177 uninoculated and 151 inoculated. The result of this experiment was as follows: "In December, 1897, an outbreak of plague occurred in another jail in Bombay (Umkardi), thus affording a further opportunity of testing the efficacy of Haffkine's |