128 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



found in sewage polluted shellfish, are not necessarily the 

 same. Only one group — that formed by B. griinthal and its 

 congeners are about equally abundant in both lists. 

 MacConkey's organisms, Nos. 100 and 101, rare organisms 

 in faeces, are fairly abundant in my samples of mussels, and 

 the same is to be said of the lactic acid bacillus. Then it is 

 very notable that B. coli communis, the third most abundant 

 group in faeces in MacConkey's list, is much rarer in mussels. 

 Generally, one sees that a notable change has occurred in the 

 relative proportions of the bacteria present between the 

 time when they leave the human intestine and the time when 

 they may be found in marine shellfish. Some of the organisms 

 are fairly resistant and appear to withstand the change of 

 habitat, while others cease to multiply and die out more 

 or less rapidly. It is also to be noted that organisms, having 

 a general resemblance to " B. coli," and which incomplete 

 analyses might easily identify as " atypical " forms of that 

 bacillus, are to be found abundantly in shellfish, but are 

 either absent or very rare in human faeces. 



(2) The Longevity of Intestinal Bacteria in Sea- Water. 



What we must do, therefore, is to isolate, one by one, 

 the most characteristic faecal organisms, and then study 

 their natural history, that is, their rate of reproduction in 

 fresh water, in sea- water, in sewage, in shellfish, in soil, in 

 diffuse or bright light, and so on. Hardly any of this kind of 

 work has been done, although it appears to be quite essential 

 if bacteriological methods are to be employed in public health 

 work with respect to the recognition of intestinal bacteria 

 in open natural conditions. Not to do this investigation 

 would be much the same as carrying on fishery regulations 

 with only a knowledge of the morphology of fishes as it is 

 taught in the schools, and without knowing anything about 

 the distribution, migrations and habits of fishes in the open. 



