460 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Dr. Houston says that the " provisional bacterio- 

 logical and topographical conclusions" must be 

 " confirmed by epidemiological and administrative 

 considerations." For instance, " whether the con- 

 taminating material is likely to have a high or low- 

 enteric morbific value : past epidemiological experience 

 in circumstances broadly parallel, &c." But, again, 

 Dr. Houston tells us that " neither the chemist, nor even 

 the bacteriologist, can place a ' disease-value ' on any 

 given pollution" (1904, p. 103). The "standards," 

 then, do not help us materially. There remains, there- 

 fore, epidemiological evidence, but it is clear that this 

 kind of evidence is not always convincing, and further, 

 it is clear that outbreaks of disease would not, in some 

 cases at least, have ever been traced to definite mussel 

 layings if it had not been previously known that these 

 layings were bacteriolo gically contaminated. I would 

 refer in this connection to the case of the Conway 

 Estuary. I can find no suggestion of " epidemiological 

 evidence " in relation to these mussels prior to the 

 publication of my report of 1906, when the Estuary was 

 first shown to be seriously polluted by sewage. Analyses 

 in themselves then do not help us greatly in founding 

 a standard, since we are warned to accept the conclusions 

 of the bacteriologist only qua bacteriologist, and not 

 necessarily as anything leading to immediate helpful 

 practical recommendations. It is true that this remark 

 does not apply to the work of the Fishmongers' Com- 

 pany. We find there that all bacteriological results are 

 interpreted into practical administrative ones, that is 

 the mussels are either passed or rejected, as a rule, on 

 the results of the analyses. Nevertheless, little or no 

 information is given as to the precise degree of bacterio- 

 logical impurity on which these conclusions are founded. 



