This idea of employing bacteria as executioners was not original, for Pasteur had already in 1888 suggested to the Intercolonial Rabbit Commission in Australia that chicken-cholera microbes should be employed for destroying the rabbits, which then, as now, are such a source of difficulty and pecuniary loss to the country. No active measures appear to have been taken, however, to carry out this suggestion, one of the principal objections raised being the undesirability of introducing a disease which was at that time believed to be a stranger to the colony. Recently the idea has been revived by Mr. Pound, the Government bacteriologist at Brisbane, in consequence of his discovery that chicken-cholera, far from not existing in Australia, has infested poultry yards more or less extensively for several years past, although it has only lately been accurately diagnosed as such. This chicken-cholera microbe is particularly well suited for the work in question, inasmuch as, whilst extremely fatal to rabbits, it produces, like Loeffler's bacillus, no ill effect whatever on farm-stock of various kinds, and is perfectly harmless to man, so that its handling by the uninitiated is not attended with any personal danger. This brings us to what may be designated the human side of bacteriology, _i.e._ its relation to disease and its prevention. In these important departments of life the services already rendered by this infant prodigy of science can as yet be only approximately appreciated. Anthrax, tuberculosis, cholera, typhoid, plague, influenza, tetanus, erysipelas, are only a few of the diseases the active agents of which bacteriology has revealed to us. Bacteriology has, however, not been content to merely identify particular micro-organisms with particular diseases, it has striven to devise means by which such diseases may be mastered, and one of the most glorious achievements of the past sixty years is the progress which has been made in the domain of preventive medicine.