134 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



was experienced, and Prof. Klein came to the conclusion that 

 a " quarantine " period of about four days duration would 

 usually be sufficient for the cleansing of polluted shellfish. 

 In 1908 I made several such experiments in the open at Conway 

 and obtained similar results. In four days there was a very 

 marked reduction in the numbers of the contained bacteria, 

 amounting usually to well over 90 per cent. About the same 

 time Mr. A. Scott made similar experiments by keeping mussels 

 in the water of the tanks at Piel Hatchery, and obtained much 

 the same results. Since these first experiments others have 

 been made, and at the beginning of 1914, when I was requested 

 by the Chairman to report generally on the subject, some 

 more precise observations were begun. I regret that it has 

 simply been impossible to follow up the many obvious further 

 questions suggested by these observations, and since the 

 opportunity to do so is not likely soon to occur, I wish to 

 record here the results obtained. 



a. Thecleansingofmusselsbysterilesea-water. 



By " sterile sea- water " is to be understood sea- water 

 taken from the flood stream, and containing no micro-organisms 

 in 1 c.c. capable of growing on neutral-red, bile-salt, lactose 

 agar. The object of this experiment was to ascertain the 

 time required to wash out sewage bacteria from the alimentary 

 canal of the mussel. 



Mussels, regarded as objectionably polluted, were taken 

 from the foreshore in Barrow Channel, near the Piel Laboratory. 

 An analysis made showed that the mean number of sewage 

 bacteria contained per shellfish was 7,400. (The individual 

 counts of 6 plates made each from 1 c.c. of an emulsion made 

 from the soft parts of 5 mussels were : 120, 122, 140, 150, 151, 

 172. Each c.c. of this emulsion represented l/50th part of a 

 mussel). The mussels were put into glass aquarium tanks of 

 about 10 litres capacity, and sea- water was run through these 



