SHELLFISH 8 1 



When cockles were infected with typhoid bacilli, by infecting 

 the sea water in which they were placed with this bacillus, Klein, 

 in a single experiment, found that after ten days the cockles 

 were still heavily infected with typhoid bacilli. In the same 

 way with mussels the cleansing was only relative, in the few 

 experiments carried out. 



Johnstone 1 carried out some experiments on the self-purifica- 

 tion of mussels. Mussels were used taken from an undoubtedly 

 polluted source and containing, on an average, 1900 intestinal 

 bacteria per shellfish. They were then placed in wooden boxes 

 in sea water which while not unpolluted was reasonably clean. 

 After four complete days some of the mussels were examined 

 and the results showed that the intestinal bacteria had been 

 reduced to about 150 per shellfish (93 per cent, reduction). They 

 were left for a further three days but no, or very slight, reduction 

 in the number of bacilli occurred. 



Carnworth 2 also carried out two experiments with mussels. 

 The numbers of B. coli were reduced 100 5<DO-fold after four 

 days' stay in pure sea water and a longer stay still further reduced 

 their numbers. A 99 per cent, reduction was met with within a 

 few days. 



Houston 3 took 250 oysters *from polluted layings and relaid 

 them in a locality free from sewage pollution. The experiment 

 lasted for only 26 days and during this time the oysters showed 

 no material diminution in the number of B. coli organisms. 



Bacteriological examination of sea water and tidal mud. 



In connection with shellfish examinations it is always of value 

 to bacteriologically examine the sea water over the layings and, 

 in particular, to examine the tidal mud of the estuary in which 

 they are contained and from their neighbourhood. 



The writer 4 in 1904 collected and examined a considerable 

 number of samples of mud from a tidal estuary, at the same time 

 making a careful topographical examination of the sources of 



1 Journ. of Hygiene, 1910, vol. IX, p. 412. 



2 Brit. Med. four. 1909, II, p. 695. 



3 Royal Commission on Seivage Disposal, ^th Report, 1904, vol. ill. 



4 Journ. of Hygiene, 1905, vol. V, p. 146. 



S. W. 6 



