15.0 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



and does not re-infect the animals. It may also actually 

 destroy the micro-organisms present in the bodies of the 

 shellfish, but it does not appear likely that the action of this 

 kind may be of importance. The trace of chlorine present 

 in the water would immediately enter into combination with 

 constituents of the mucus covering the body, and would not 

 really act on ingested micro-organisms. 



(5) Mussels may be very quickly cleansed, to the extent 

 of getting rid of 90 % of their contained sewage organisms, 

 by exposure to running sea-water, or to repeated changes of 

 standing water dosed with chlorine. Laboratory experiments 

 indicate that the cleansing process need not require more than 

 one day. On a commercial scale the time required would 

 depend on the perfection of the water circulation, and it 

 cannot be estimated except by experiment with the actual 

 plant suggested. 



(6) Faeces, sewage, polluted estuarine sea-water, and 

 shellfish all contain a mixture of species of glucose and lactose 

 fermenting bacilli. All these have been called " Bacillus 

 coli," or " coliform " organisms, or " typical," or " atypical " 

 coli. Some of them are of equal significance with the true 

 B. coli communis, in that they are of exclusive intestinal 

 origin, but others may have sources of origin of vastly less 

 significance. This mixture of species differs in faeces and in 

 polluted shellfish. 



These species probably mostly cease to multiply, and 

 finally die out, when they enter estuarine sea-water, or the 

 bodies of marine shellfish. But the rate at which reproduction 

 falls off and the rate of mortality probably differ according 

 to the species. It is, therefore, of practical importance that 

 analyses should indicate the proportions of the various species, 

 or categories of related species, present in a sample of polluted 

 shellfish, since this may indicate whether the pollution was 

 recent, and therefore of possible danger, or remote, and there- 

 fore of little significance. 



