26 



DRY i.e., kept out of sea water. 

 Oyster 2 after 1 day . . 1,200,000 B. typhosus per oyster. 



. 175,000 



6 3 . . 42,000 



8 4 . . 3700 



10 6 . . 40,000 



12 7 . , .;-.:, 1220 



We learn from this experiment that oysters infected 

 with huge numbers of B. typhosus, then kept in clean sea 

 water changed frequently practically every day were able 

 to clean themselves and to get rid of them in a compara- 

 tively short space of time; in four days the number of 

 B. typhosus decreased to an enormous extent (320), and 

 after six days none could be found in ^ part of the oyster, 

 that is to say, less, than 10, if any, in the whole body of the 

 fish. At the same time we learn the important fact that oysters 

 of the same kind kept out of the water retained the injected 

 B. typhosus to a markedly greater extent (40,000 after six 

 days), although also under these conditions their number 

 considerably decreased. This part of the experiment, while 

 pointing out the danger attached to specifically infected 

 oysters being kept out of the water, shows at the same time 

 that the body of the oyster per se is not a soil in which the 

 typhoid bacillus is capable of multiplying ; on the contrary, 

 the tissues of the oyster distinctly acting inimically on the 

 microbe. Those oysters which were kept after infection in 

 fresh sea water might, one would perhaps be inclined to 

 conclude, have cleaned themselves of the extraneous B. 

 typhosus extraneous to the oyster on account of being 

 kept in changing water, but this evidently does not apply to 

 those oysters that were kept out of the water ; consequently 

 we are justified in, in fact are driven to, concluding that the 

 tissues of the oysters per se are endowed with the faculty of 

 devitalising this microbe. Considering that we started with 

 160 millions of B. typhosus per oyster we come down to 

 1220 in the course of seven days, during which time the 

 oysters were left entirely to themselves and without any 

 influence the surroundings could have exerted on them. 



