440 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



no agreement as to what is to be understood by the 

 organism B. coli. It is a biological species, and therefore 

 all that applies to the identification of species of animals 

 and plants in general also applies to this bacillus — at 

 least we must assume this until the bacteriologists prove 

 otherwise. Now the recognition of an animal, a disease- 

 producing worm for instance, a malarial parasite, 

 anything of that kind in short, is a matter of no difficulty 

 for the expert. He can say at a glance (after experience, 

 of course) whether or not the thing he is looking at is 

 his animal. This is not the case, however, with a 

 bacillus, for mere inspection fails to identify it. It must 

 be cultivated in a number of nutrient substances, and 

 the changes taking place in those substances must be 

 observed before the organism can be identified with 

 certainty. This is a laborious process, and no matter 

 how great the experience of the bacteriologist may be, 

 it must always be carried out in each analysis. 



The point here is that the public health officials in 

 this country have not agreed upon a series of tests which 

 are sufficient to identify " coli-like " microbes. In the 

 case of animals producing disease in cattle or in man 

 there is agreement among biologists. There is also 

 agreement among chemists as to the series of tests 

 defining a poisonous substance, or a food adulterant. 

 But it is quite evident that no such agreement with 

 regard to the characters of " coli-like " bacteria is to be 

 found in public health practice. Let us see what are the 

 common tests employed. In the following table are the 

 tests which have been suggested, and against them are 

 the names of bacteriologists who have worked at shell- 

 fish contamination. The crosses indicate what tests are 

 regarded by each analyst as sufficient to identify the 

 microbes. 



