BACTERIOLOGICAL EXAMINATION OF WATER in 



previously sterilised or washed out with pure sulphuric acid. When 

 the latter method is adopted, the bottle should be well rinsed with 

 the water which is to be examined before the sample is taken. In 

 taking the sample the bottle should be held well below the surface 

 before the stopper is removed, in order to obtain a sample of the 

 main body of water and not the surface water only. If it is an 

 ordinar}^ water supply through pipes or from a cistern, the tap 

 should be turned on and the water allowed to run for a few minutes 

 before taking the sample : and the same principle applies to a well 

 not in regular use. Such a well should be pumped for a consider- 

 able time before taking the sample. For obtaining samples from 

 a considerable depth Miquel's special apparatus may be used, or, 

 if that is not available, a weighted bottle. 



After collection the bottle should be at once stoppered, labelled, 

 and packed in ice and sawdust for transport to the laboratorj^ or 

 placed in one of the various ice cases now in use (Delepine's or 

 Pakes'). Below 5° C. organisms do not multiply in water, and 

 therefore it is important to keep samples previous to examination 

 at a low temperature. In all cases where it is possible the water 

 should be examined at once after collection. 



Physical examination. — The temperature and reaction of the 

 water should first be tested, and an examination made of any 

 deposit or suspended matter. Bubbles of gas, if present, should be 

 noted. The colour, character, and amount of particulate matter 

 in suspension or sediment should be observed and noted. A 

 record of the quantity of the sample, its source, and the date and 

 time of its collection is also important 



Bacteriological examination. — This divides itself naturally into 

 two divisions — {a) a. quantitative examination, and (d) a qualitative 

 examination. 



(a) Quantitative Examination 



The sample should be gently mixed and plate cultivations made. 

 Take five tubes of 10-15 c.c. of gelatine and five Petri dishes, and 

 melt the medium of the former in a water bath. The gelatine should 

 be well liquefied but not overheated. The Petri dishes should 

 be of even surface, equal size, and properly sterilised. Take a i 

 C.C. sterilised pipette accurately calibrated, and pass it into the 

 bottle, removing the necessar>' quantities of w^ater. As a rule 

 05 C.C., 0-2 C.C., 0-2 c.c, o-i C.C., and o-i c.c. are suitable quantities 

 for each of the five plates. Add these quantities to the five tubes of 

 liquefied gelatine, and well mix and pour into the Petri dishes. 



