SEA-FISHERIES LABORATORY. 187 



bacteriological results. The topographical observations 

 and the laboratory work ought always to be considered 

 together, and must be regarded as parts of the same 

 investigation conducted by the one authority. The 

 bacteriological examination may at once confirm the field 

 work in such a manner as to leave no doubt as to the 

 purity or pollution of the locality, or it may give useful 

 indications which suggest the necessity for further observa- 

 tion of the local conditions. It may also give a measure 

 of the amount of pollution. The question has been 

 raised as to whether it is possible to fix a standard of 

 pollution which should be regarded as dangerous to health. 

 Can we say that all samples yielding say 10, or say 20 

 B. coli per c. c. must be condemned, but that those 

 showing less than say, 5 per c. c. may be tolerated ? 

 Before answering such a question we must have further 

 investigations. There are still too many of the points 

 involved which are left in doubt. For example, we cannot 

 be certain that all samples yielding 10 B. coli per c. c. are 

 equally dangerous. Even if we assume (as we probably 

 may safely do) that pure oceanic sea-water is free from 

 B. coli and allied organisms, and that these are to be 

 taken as an indication of some sewage contamination, 

 we do not know how remote in time the pollution may 

 have been and how comparatively harmless from a 

 pathogenic point of view it may have become. It is 

 possible, or even probable, that B. coli may be distributed 

 to considerable distances in the excreta of fish and sea- 

 birds, possibly with some modification. Then again the 

 bacteriology of the shrimp's alimentary canal requires 

 examination, and we may add the fishes that feed upon the 

 shrimp. There are also other sewage feeding invertebrates 

 that may conceivably pass on some organisms and not 

 others, and may favour the distribution of B. coli under 



