SEA-FISHERIES LABORATOEY. 167 



'' lu taking samples of suspected shell-fish I would 

 attach great importance to personal supervision hy a 

 scientific or fisheries expert. The samples should 

 obviously not be taken by the parties interested, and they 

 should not be taken by disinterested, but untrained 

 collectors who may miss seeing some qualifying factor or 

 some important piece of evidence. A knowledge of the 

 local conditions, of the influence of tidal and other 

 currents, and of prevalent winds, may be of great value 

 in judging of the presence and extent of pollution, and of 

 the parts [of the bed] liable to be affected at a particular 

 time of day, or of the month. Consequently a personal 

 examination of the locality by a scientific man is always 

 important. Samples from various parts of the same bed 

 may have to be taken at different states of the tide, and 

 these should be chosen with knowledge and discrimination. 

 "Any additional evidence that can be obtained from an 

 inspection of the physical and biological conditions on the 

 bed is all the more important because of our want of exact 

 knowledge as to the meaning and value of some bacterio- 

 logical 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 observation 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. coll per c.c. must be 

 condemned, but that those showing less than say 5 per 



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