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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 ec. 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 teo many of the points 
involved which are left in doubt. For example, we cannot 
be certain that all samples yielding 10 BL. 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 im 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 
