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xx] a great epidemic spread to Calcutta, and to many other parts of India, where it still prevails. The mortality from the current epidemic is numbered in millions.

Soon after its appearance in India, plague became extensively epidemic in Mauritius, where it still prevails at certain seasons. Mombasa and British East Africa (including Nairobi), the West African colonies, Madagascar, Delagoa Bay, Cape Town, Port Elizabeth in Cape Colony, and Durban; also Sydney and Brisbane in Australia, and Alexandria in Egypt, have all been invaded.

Until its recent appearance in Brazil, the Argentine and other South American countries, in San Francisco and Mexico, plague had never invaded the western hemisphere. Etiology. The micro-organism.— The proofs are now complete that the specific cause of plague is the cocco- bacillus which was discovered first by Kitasato and afterwards, independently, by Yersin during the Hong Kong epidemic in 1894. This microbe occurs in great profusion in the characteristic buboes —generally in pure culture, although towards the later stages it is often associated with the streptococci and staphylococci of suppuration. It is present, besides, in great abundance, in the spleen, intestines, lungs, kidneys, liver, and other viscera, and also, though in smaller numbers, in the blood. In the pneumonic type of the disease it is present in the sputum in enormous numbers. It occurs also in the urine and fæces; in the latter, though detectable by inoculation and by cultivation, the bacillus may be hard to find by direct observation. Towards the termination of rapidly fatal cases it may become so abundant in the blood as to be readily observed there with the microscope. The plague bacterium (Fig. 66), as seen in smearings or scrapings from the pulp of the buboes, or from any of the inflamed lymphatic glands, or from the viscera, is a short, thick cocco-bacillus (1.5 to 2 μ and 0.5 to 0.7 μ) with rounded ends, very like that of chicken cholera. Gordon says it has one