BACTERIA AND RURAL WATER SUPPLIES 13 



bile salts, and bacteriophage furnished evidence that cultures of both the colon 

 and aerogenes bacilli are stable, and that environment will not change their 

 characteristics easily if at all. Therefore, each would have its meaning in eval- 

 uating the sanitary quality of a raw water supply. 



Finally, intangible values were derived from the studies that may not easily 

 be set down on paper. After doing practical work and experimenting in any 

 field, one acquires experience and a capacity for judgment that cannot be speci- 

 fically explained, but that are of substantial value in the doing of his work. 



ABSTRACTS 



In the abstracts which follow, the numbers in parentheses refer to articles in 

 the literature reference list which terminates this bulletin. Some of these refer- 

 ences are to work done in this laboratory and others are to sources of methods 

 and other data published elsewhere. 



A. Studies of Rural Water Supplies 



The first study (1) was concerned with 172 water samples examined bac- 

 teriologically in the laboratory and condemned as unfit for drinking purposes. 

 Each sample represented an individual source of supply. From these samples 

 223 cultures of coliform bacteria were isolated and studied. For comparison, 

 178 cultures of coliform bacteria were isolated from human feces and studied 

 in the same way. For the most part, the cultures from human sources represented 

 different individuals. 



All of the cultures were studied for their "Imvic" reactions, and the uric acid 

 test was added because of the interest that attached to it at that time (1933). 

 Media were prepared and used as directed in the "Standard Methods" (2). The 

 only deviation from these procedures was the use of Werkman's method (3) for 

 the Voges-Proskauer test. The indol test was not included in the edition of 

 "Standard Methods" then in use. The medium and procedure employed were 

 the same as those incorporated in a later edition of "Standard Methods" (21). 

 Gore's plug test (4) was employed for the detection of indol. 



A summary of the differentiation of the cultures on the basis of their Imvic 

 reactions is shown in table 1.^ In this table the organisms are separated into ten 

 groups on the basis of their reactions. 



Table 1. — Coliform Cultures Isolated From Raw water Samples and 



From Feces Grouped on Percentage Basis According 



to Differential Tests. 



