EXAMINATION OF WATER 579 



two pieces of muslin, and the bottle should be not quite 

 filled. In taking the specimen the following details should 

 be attended to : 



(1) If taken from a tap, the water should be allowed 

 to flow for at least five minutes before the specimen is 

 collected. 



(2) The water from a cistern is not a representative 

 sample of the water-supply ; to be so the specimen should 

 be taken direct from the mains. 



(3) If taken from a stream or pond, the bottle should be 

 held about a foot below the surface and away from the 

 edge before the stopper is removed. 



(4) If taken from a well the conditions should be noted, 

 e.g. whether the well has been recently disturbed or not, 

 whether the pumps have been in operation, etc., for such 

 may markedly influence the number of bacteria found. 



The specimen should then be examined with as little 

 delay as possible, for if allowed to stand for any time a 

 large increase in the number of bacteria may take place. 

 Frankland, for example, found that in distilled water, 

 even at the ordinary temperature, organisms multiply 

 enormously : 



Number of organisms 

 Hours in 1 c.c. 



1,073 



6 6,028 



24 7,262 



48 48,100 



In water of good quality the organisms are found to 

 multiply much more rapidly during the first few days, 

 after which time they become less and less numerous ; 

 but in impure water multiplication is slower, and the 

 number more persistent, while in very impure water the 

 number may diminish. It is essential, therefore, if reliable 

 results are to be obtained, for the specimen to be examined 



