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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-oi-ganisms 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 cidtivated outside the body, and separated 

 from all the morbid materials, and the disease has been produced 

 by the inti'oduction 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 



