186 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY 



out of so many oysters or mussels examined during the 

 year a certain number contained " coli " and a certain 

 number " enteritidis," is useless for all practical pur- 

 poses, and cannot lead to any result. As I have shown 

 above, the significance of " coli " infection lies not in the 

 mere presence but in the relative abundance of the 

 organism. Eecords of the bacteriology of samples of 

 shell-fish are futile unless one knows in detail where the 

 shell-fish came from, the conditions under which they 

 were collected, their history since the time of collecting 

 and the relative number of each kind of organism present. 

 The presence of such an organism as B. coli in relatively 

 small quantity, and possibly of remote origin, may be of 

 no importance in connection with the public health, and 

 at most it merely indicates the possibility that the shell- 

 fish in question may under certain circumstances con- 

 tain pathogenic organisms. When the number of 

 organisms present is relatively great, and when there is 

 topographical evidence of comparatively recent con- 

 tamination, then the risk of pathogenic organisms 

 being present — whether actually isolated or not — is 

 much greater, and condemnation of the shell-fish becomes 

 justifiable. But unless the relative amount of infection 

 is determined, and the various factors in the environment 

 affecting the problem are known in detail, the laboratory 

 bacteriologist or public health official runs some risk of 

 being deceived by the samples examined and of arriving 

 at erroneous conclusions, from routine analyses, as to the 

 real condition and history of the suspected shell-fish in 

 relation to sewage contamination. 



In sea-fisheries investigation and administration we 

 must be careful that bacteriology remains our useful 

 servant and does not become a tyrannical master. 



