CHAPTER XXIV 



BACTERIOLOGICAL EXAMINATION OF WATER, AIR 



AND MILK 

 EXERCISE I. BACTERIOLOGICAL ANALYSIS OF WATER 

 References — 



Horrocks, Bacteriological Examination oj Water. 



Prescott and Winslow, Elements oj Water Bacteriology. 



Fuller and Johnston, Journal oj Experimental Medicine, Vol. 

 IV. 



Committee Report oj the American Public Health Association, 

 Jour, oj Injections Diseases, Suppl. I, May, 1905. 



A bacteriological examination of water is made for 

 the purpose of determining — 



1. Bacterial numbers. 



2. Bacterial species. 



3. Sewage contamination. 



Collection oj samples. — Procure wide-mouthed, glass- 

 stoppered bottles, having a capacity of at least 100 c.c. 

 After careful cleaning and drying, wrap them in lead-foil, 

 and sterilize in the hot-air oven for i hour at 160°; then 

 deposit them in a metal or wooden case. The samples 

 from surface waters should be taken at least one foot 

 below the surface, to avoid contamination with organisms 

 from the air. If possible, samples should be plated on the 

 spot or in the laboratory within an hour at the very latest. 

 But when a greater interval of time must occur, the 

 samples should be taken to the laboratory packed in ice, 

 despite the probability of thus destroying a certain per- 

 centage of the bacterial flora. 



Method oj examination. — A number of pipettes of 

 various sizes (i c.c, 2 c.c, 5 c.c, and 10 c.c.) are plugged 



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