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These micro-organisms in various forms seem to take part in the destructive changes, with which we are familiar in the animal and vegetable world, they are found in connection with certain diseases, and some of them have their home in the circulatory apparatus. Is it not then peculiarly fitting that on an occasion like this some reference should be made to these micro-organisms 1 We can rightly commemorate and rejoice over the work which has been done in this direction, whilst we feel at the same time how much there is still unsettled and obscure. The knowledge gained from the experimental observations on animals is as yet applicable only within very narrow limits to the human subject. Nay more, the results of clinical observation are altogether inconsistent in many cases with what these experiments would suggest; and yet how fruitful and full of promise does the territory seem from our present stand-point! Is it not one to which I may point encouragingly and ask you to explore it, and bid you, in Harvey's words, "search out its secrets by way of experiment"?
Let me briefly remind you of some of the facts which have been made out regarding these bodies.
There can be little doubt that in some disorders these organisms in their various forms, round, corkscrew or straight-rod shaped, are the causal connection, the virus, of the disease. The bacilli are constantly present in the affected parts, the organisms have been cultivated outside the body, and separated from all the morbid materials, and the disease has been produced by the introduction of these cultivated organisms into healthy animals. As examples of such disorders we have, as described by Koch, anthrax or splenic fever, a septicaemia in mice due to bacteria, and a septicaemia in rabbits due to micrococci. An
