SEA-FISHERIES LABORATORY. 



453 



is so scarce in the shell-fish sampled as to be safely 

 neglected from the point of view of dangerous contamina- 

 tion. If, on the other hand, a quantity of emulsion 

 corresponding to l/50th part of a mussel contains from 

 100 to 1,000 organisms* growing on neutral-red, bile- 

 salt, lactose agar, as red colonies, we may be pretty sure 

 that the bacteriological contamination is too great to be 

 neglected ; for among these 100 organisms there would 

 certainly be from 10 to 20 which we should be able to 

 identify, on detailed examination, as B. coli. Negative 

 results with either of these primary media are of the 

 utmost value; and the investigator will usually be able 

 to find a parallelism between the numbers of " sewage 

 bacteria " isolated and the results of a survey of the 

 natural conditions of the locality from which the shell- 

 fish samples were collected. 



It is, nevertheless, quite certain that the identifica- 

 tion of the organisms isolated in primary culture is of 

 the highest importance. So long as public health 

 bacteriologists rest content with describing a B. coli as 

 an organism fermenting glucose and lactose, forming 

 indole, and fluorescing neutral-red, they must confuse 

 together, not only the various species of intestinal 

 bacteria inhabiting man and the domestic animals, and 

 possibly also sea-birds and fishes, but also perhaps 

 bacteria normally occurring in the soil and in estuarine 

 waters, and perhaps devoid of any significance from the 

 point of view of public health. To class all these forms 

 as " typical " or " atypical " B. coli seems to be a quite 

 unwarrantable proceeding. It always was so, on purely 

 theoretical grounds, and it is now plainly erroneous in 

 view of Clemensha's recent work. 



* The lower limit is represented in some of the analyses of Eiver Lune 

 mussels (p. 478). The upper limit may be represented in exceptional cases, 

 or in mussels purchased from fish-shops. 



