SEA-FISHERIES LABORATORY. 445 



out in actual practice as follows : All the micro- 

 organisms isolated from shell-fish in the usual methods 

 of analysis (the use of MacConkey's bile-salt broth) 

 ferment glucose, and most of them ferment lactose, while 

 a large proportion form indole, and clot milk, and 

 fluoresce neutral-red. Suppose that the colony we 

 isolate from the primary culture is of value 100, then all 

 the bacilli found were B. coli. Suppose it has the value 

 90 per cent., then 90 per cent, were B. coli, and so on. 

 By using this method we are always sure of getting some 

 B. coli as the result of the 'primary cultures. 



" Bacteriologists," says Dr. Houston in a passage 

 of great literary merit, " ever pressing forward to the 

 unattainable goal of absolute knowledge, are apt to 

 leave in their wake a track of nebulous knowledge which 

 to the uninstructed observer may suggest superficial, 

 and not, as ought to be the case, merely incomplete 

 knowledge." This is really an excess of humility when 

 we remember that it is just this incomplete or superficial 

 knowledge (for both categories of knowledge are 

 identical) that is applied by those who have to do with 

 the public health and the livelihood of fishermen and 

 others. 



Methods of Analysis. 

 The method almost universally applied now is that 

 devised by Dr. Houston. Ten oysters (or mussels) are 

 taken from their shells and cut up into small pieces, 

 and put into a vessel of water containing 1,000 cubic 

 centimetres. Various volumes of this liquid are then 

 taken: 100 c.c. is equal to 1 oyster, 10 c.c. to l/10th 

 oyster, and 1 c.c. to 1/ 100th oyster. We then take 

 10 c.c. of the liquid and mix it with 90 c.c. of sterile 

 water, 1 c.c. of this diluted liquid now contains 1/ 1000th 



