268 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



These conclusions are based on the presence of the 

 microbe B. coli in the stomachs of the shellfish examined. 

 This organism is not necessarily to be regarded, in itself, 

 as a dangerous microbe ; but, being derived from the 

 human intestine, it indicates the possibility of the shell- 

 fish in which it is found harbouring, at any time, 

 pathogenic microbes, which may communicate disease. 

 The bulk of expert opinion nowadays is that B. coli is to be 

 regarded as the best indication of sewage pollution in the 

 medium (water on the stomach contents of shellfish) in 

 which it is found. It is frequently suggested in the 

 evidence submitted to the Sewage Disposal Commission, 

 that a different interpretation may be placed on the 

 presence of B. coli in such media ; that it may possibly be 

 derived from the excrements of sea birds or even of sea 

 fish, and that, if this be the case, its presence may not be 

 of serious significance. I am not aware, however, of any 

 observations which tend to support this (purely a priori) 

 view. The shrimps from Blackpool closed ground, or the 

 oysters from the off-shore grounds, which I examined, 

 most probably would have contained B. coli if their con- 

 tamination from such sources had been at all likely. 

 Nevertheless, except in the case of the oysters taken from 

 near the new lightship, in Liverpool Bay, the whole colon- 

 group of organism was absent. 



The question of a permissible standard of impurity 

 has frequently been discussed, and we must conclude that 

 the creation of such is impracticable. In the case of the 

 Egremout mussels, from 250 to over 1,000 microbes 

 belonging to the colon group were present in x^th cc. of 

 the contents of the stomach of a single mussel, and of 

 these at least one-third were the true B. coli. On the 

 other hand, we have the oysters from the N.W. lightship, 

 m six of which only two colon-like organisms were found, 



