Quantitative Bacteriological Examination. 29 



and qualitative bacteriological examination of water for 

 sanitary purposes. Tfiese reports have had a far-reaching 

 effect in simplifying and unifying the methods of water 

 analysis. Similar results may be expected from the work 

 of the English Committee appointed to consider the 

 Standardization of Methods for the Bacterioscopic Exam- 

 ination of Water which reported in i'904, although this 

 committee unfortimately did not consider the process of 

 media making in great detail. The last report of the 

 American Committee on Standard Methods (1905) will 

 be adhered to in this and succeeding chapters unless 

 otherwise specifically stated; and that portion of its 

 report which deals with methods of making media will 

 be found in full in the Appendix. 



The procedure for the quantitative determination of 

 bacteria in water consists, in brief, in mixing a definite 

 amount of a suitably collected specimen of the water with 

 a sterile solidifiable culture medium and allowing it to 

 develop for a sufi&ciently long time to permit reproduction 

 of the bacteria and the formation of visible colonies which 

 may be coimted. The process is divided naturally 

 into four stages — sampling, plating, incubating, and 

 counting. 



Sampling. — All samples of water for bacteriological 

 examination should be collected in clean, sterile bottles 

 with wide mouths and glass stoppers, preferably of the flat 

 mushroom type. It is desirable that these bottles should 

 have a capacity of at least 100 c.c. 



