30 SCIENCE PROGRESS 



other micro-organisms inhabiting the intestinal tracts of warm- 

 blooded animals, it finds an unfavourable habitat in sea water, 

 or in the tissues of cold-blooded marine animals, and it rapidly 

 dies out in such environments. The ordinary bacteriological 

 examination of sea water or marine shellfish is therefore one for 

 the presence of the organism called Bacillus colt. This is a 

 microbe which inhabits the large intestine of man, and which 

 is always present in domestic sewage in very large numbers. 

 Recognition of B. colt in sea water or shellfish is therefore 

 taken as a proof of the contamination of these media by micro- 

 organisms of human intestinal origin, and their presence is 

 regarded as a proof that the shellfish are unwholesome. B. colt 

 itself is not, in general, a pathogenic organism, but its source is 

 such that it may be accompanied by much more significant 

 micro-organisms. It does not necessarily point to actual, but 

 rather to potential danger. 



Thus the ordinary bacteriological examination of sewage- 

 polluted shellfish simply indicates that these may be dangerous. 

 Obviously if the inhabited area drained by a river that dis- 

 charges in the neighbourhood of a shellfish laying contains no 

 enteric fever, nor enteric fever carriers, no amount of pollution 

 of the shellfish by B. coli can be regarded as indicative of 

 dangerous pollution. But in this dependence on the presence 

 of B. coli as an index of possibly dangerous contamination the 

 weakness really lies in the inconclusive nature of the tests 

 usually adopted for the recognition of the organism. In spite 

 of a very large mass of evidence, and of a number of special 

 investigations, the Commissioners did not find a generally 

 applicable and unequivocal method of identifying B. coli in 

 shellfish and sea water, and it must be contended that they left 

 this question in a thoroughly unsatisfactory condition, as it 

 has turned out. At the present time there is no generally 

 practised method of bacteriological examination for the identi- 

 fication of, and the estimation of the abundance of B. coli in 

 shellfish. Each public health laboratory in this country has 

 its own method except in so far that the very inadequate method 

 of Houston has been adopted. The question of the degree of 

 significance to be attached to a bacteriological analysis therefore 

 turns upon whose method was employed, and it must be con- 

 cluded that the results of the various methods cannot be 

 compared, or at least can only be compared with some con- 



