QUALITATIVE DETERMINATIONS 95 



cream, butter, buttermilk, sour milk tablets, mineral waters, 

 oysters, clams, flour, oatmeal, cornmeal, cereals, frozen eggs, dried 

 nuts and fruit, etc. B. coli is not normally present in sea water 

 and its occurrence in salt water shellfish is evidence of sewage 

 contamination. The occurrence and general distribution of 

 the colon bacilli is almost in direct proportion to the density of 

 the population. Am'mals of all kinds are disseminators of colon 

 bacilli, particularly the larger animals as the hOrse, cattle, the 

 dog and domestic fowls. Within and about the home, the house-fly 

 and the stable-fly are the chief distributors of colon bacilli. We 

 may repeat that colon bacilli are found on the skin of persons, 

 particularly on the hands and under the finger nails. The under- 

 clothing worn carries these bacilli and is the agent instrumental 

 in distributing them over the exterior of the body, especially in 

 those of uncleanly habits. Water in which the hands have been 

 rinsed will generally yield positive colon bacillus tests. It is 

 also apparent that the colon bacillus does not survive for a great 

 length of time outside of its natural environment; thus sewage- 

 contaminated waters purify themselves of colon bacilli after a 

 time, the period varying with the temperature and the amount 

 of organic matter present. Thus it sometimes happens that a 

 water supply may show a high bacterial count and yet be quite 

 free of colon bacilli. As a rule, however, water supplies and 

 substances brought in contact with such water supplies which 

 show a high general bacterial count, will also show a comparatively 

 high count in colon bacilli. There may be notable exceptions to 

 this rule. A water supply, or other liquid substance, may show 

 a comparatively low bacterial count and yet yield numerous 

 colon bacilli. Such an occurrence would indicate an unusual 

 source of extensive sewage contamination. 



From the foregoing it is evident that the sanitary examination 

 of foods and drugs resolves itself into the making of quantitative 

 bacterial counts, as already fully explained, and the presumptive 

 colon bacillus test, with an occasional test for other specific 



