17 



was a pure cul ture of our laboratory B. typhosus. Under these 

 conditions, therefore, the presence of any B. typhosus in the 

 oysters or in the sea water could be determined readily and 

 at once numerically by means of Drigalski plates, since 

 all colonies of the colour and appearance resembling those 

 of B. typhosus could, without hesitation, be declared as 

 those of B. typhosus. The other tests : microscopic exami- 

 nation in the hanging drop, agglutination with typhoid 

 serum, subcultures in MacConkey fluid, neutral red broth, 

 litmus milk, streak and shake gelatine culture, would fully 

 confirm the diagnosis. We shall have later an opportunity to 

 describe experiments with oysters of a certain locality 

 experiments made not with B. typhosus but with B. coli in 

 which the Drigalski plates revealed the presence of microbes 

 whose colonies in their blue colour and general appearance 

 bore a great resemblance to those of B. typhosus, but which 

 by microscopic tests and by subculture in the various 

 media could be recognised as different; but in our experi- 

 ments (except Experiment IV) of testing the vitality of the 

 B. typhosus in oysters, cockles, and mussels, no such dis- 

 turbing microbes were present at starting, and under the 

 conditions above stated none could have been afterwards 

 present to disturb the simplicity of the procedure. This can 

 in no way interfere with the general results obtained, since 

 our object was to determine how far and to what degree and 

 in what manner living oysters, cockles, and mussels as such 

 have the power to deal with the B. typhosus that have 

 had access to them. Whether other microbes are present 

 in the oysters or whether other additional microbes are 

 introduced with the B. typhosus are questions which do not 

 materially alter the simple and fundamental problem, viz. 

 can, and to what degree do shellfish deal with the B. 

 typhosus? and, therefore, the simpler the conditions for 

 elucidating it, the more accurate, it may be expected, will be 

 the result. There is one further point which, at the outset, 

 has to be stated here this is the character of the B. typhosus 

 on Drigalski medium in surface plates. We mentioned 

 above that it was by this method that we analysed the shell- 



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