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very largely increased. The water of the Seine above 

 Paris contains 300 organisms to the cubic centimetre, 

 while below Paris the number has increased to 200,000 

 per cubic centimetre. We have also shown from our 

 experiments at Port Erin that in oysters purposely placed 

 near the outlet of the drain the number of organisms 

 increased enormously. All estuaries, however, are not 

 polluted, and the deleterious effects of sewage do not 

 extend far, consequently there should be no great difficulty 

 in finding perfectly suitable localities for oyster culture if 

 a careful study is made of the matter. Tides and other 

 currents, depth, specific gravity and temperature of the 

 water all affect the distribution of the sewage in an 

 estuary, and their influence should be carefully enquired 

 into in connection with the site of any proposed shellfish 

 cultivation. 



Some of our experiments have shown that the oyster 

 can purify polluted water in a most remarkable degree, 

 but that property may have a bad as well as a good result. 

 The good side of the matter is that the oyster in obtaining 

 its nutriment from the water is able to convert useless 

 and deleterious products of decomposition into excellent 

 human food. The bad side of the matter is that if there 

 happen to be any disease germs in the water the oyster 

 may possibly strain out and store them up in its own 

 body. And it even seems probable that other microbes 

 associated with disease germs may play some part in 

 causing" or modifying disease. 



It is re-assuring, however, to find as we do from our 

 own investigations as well as from the consideration of 

 the work of others that the typhoid organism {Bacillus 

 typhosus) dies off very rapidly in ordinary sea water as 

 one passes either in distance or time from the source of 

 supply. 



