WATER 31 



firmly when the sample has been collected. The collected 

 water should not quite fill the bottle. 



It is essential that full particulars as to the source of the 

 water be supplied with the sample. It is impossible to give 

 a satisfactory opinion without such information. 



The following should be recorded : 



1. Date of sampling. 



2. Nature of the water spring, upland surface, etc. 



3. Whence obtained pump, draw-well, river, tap, etc. 



4. Precise particulars of sampling e.g. depth below sur- 

 face, from middle or sides. If from tap or pump, time during 

 which the water was allowed to run to waste. Filtered or 

 unfiltered. 



If from a tap, note if it was directly connected to a main, 

 or if it was connected with a storage cistern, or other form 

 of supply. 



5. Details as to previous rainfall. 



The above particulars should all be supplied to the bac- 

 teriologist conducting the examination, and in addition to the 

 careful topographical investigation which should be made and 

 recorded in the case of all water supplies. 



The general nature of the examination. 



Bacteriological water examinations, as conducted at the 

 present day, usually involve three lines of investigation, although 

 all three are not, of necessity, carried out for every sample. 

 These are : 



(a) The quantitative estimation of the total number of 

 organisms present capable of developing upon the nutrient 

 media used. 



(b) The isolation and numerical enumeration of organisms 

 not necessarily harmful, but which from their origin are espe- 

 cially liable to be associated with harmful contamination. 



(c) The isolation and identification of actual disease- 

 producing organisms such as Bacillus typhosus and Spirillum 

 cholerae. 



