460 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Lancashire. The pollution of the cockles on Horse 

 Bank must be a remote one, that is, the distance between 

 the shellfish beds and the place of origin of the sewage 

 is considerable ; the sewage passes a certain time in tanks, 

 filter beds, and in land under sewage irrigation, and the 

 contained intestinal bacteria are subjected to conditions 

 which are very different from those which they experience 

 in their normal habitat in the human intestine. All this 

 means that its nature becomes different from what it 

 originally was. Therefore, although the bacteriological 

 impurity, revealed by the preliminary analyses made in 

 connection with this investigation, is equally gross in the 

 case of the Eibble channel and the Aberdovey mussels, 

 yet the pollution at Aberdovey is far more dangerous; 

 since only a short distance separates the shellfish from 

 the drains contributing the sewage, and only a few 

 hours may elapse between the voiding of human Bacillus 

 coli and its ingestion by the mussel. 



The conditions all over the Eibble estuary are, of 

 course, not uniform in this respect. The cockles on 

 Horse Bank, even only a mile or so from the end of 

 Southport Pier, may be regarded as free from significant 

 pollution. No sewers open into the sea near the South- 

 port shore, except some pipes conveying surface water. 

 The effluent from Southport and Birkdale flows down 

 Crossens Pool and Channel, and high banks separate this 

 for a considerable distance from the cockle beds. Unless, 

 as Dr. Bulstrode points out, cockles gathered here are 

 washed in Crossens channel they are hardly likely to be 

 polluted. In 1907 I made an analysis of cockles taken 

 from a place about a mile east from Southport Pier. 

 The mean number of sewage bacteria .estimated as being 

 present per shellfish was 12, a result which is practically 

 the same as that obtained in the case of cockles taken 



