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E. G. PRYOR
Such wild speculation may well have created a fatalistic attitude to the inevitability of the plague as a natural phenomenon and consequently limited an awareness of the need to search in other directions. However, the desperate need to find a solution prompted a considerable amount of inquiry and reflection by a number of independent observers and some of these researchers deserve a fuller mention.
Dr. Gomes da Silva, the Principal Medical Officer of Macau gave an account of the disease which affected the Portuguese colony in 1895. He records that during a visit to Canton he had observed a strange disease that attacked "only Chinese ..... and rats" and that the same disease spread from Hong Kong to Macau in 1895. In drawing attention to the association of the plague with rats Dr. da Silva also described the general sanitary condition of Canton which he concluded was a further causal factor. He records that house refuse was usually thrown into the streets where it accumulated until such time as the torrential summer rains and the overflow of the Pearl River cleared it away. However, between May and September 1894 it did not rain to any great extent with the consequence that large quantities of rubbish accumulated and reached an advanced state of putrefaction. These conditions were paralleled by outbreaks of plague. Conversely, Dr. da Silva observed that when the summer rains were early and abundant the disease seldom occurred.
It is now not difficult to establish the chain of events that must have occurred, namely that during prolonged dry spells when refuse piled up in the streets colonies of rats thrived on the nourishment so carelessly provided. As the rats multiplied, so did the fleas and from but one source of infection carried by the fleas the disease spread like a forest fire first through the population of rats and then to homo-sapiens.
However, amidst the wild speculation of how the disease was communicated to man scientific researches undertaken by Alexandre Yersin in Hong Kong established in June 1894 that the bacillus, pasteurella pestis, was the direct cause of plague. This was subsequently confirmed by two Japanese doctors, Professors Kitasato and Aoyama, who were also pursuing researches in the colony. Conclusive evidence was obtained by injecting animals with a virus preparation. Notwithstanding, the means of transmission of the