650 LABORATORY HINTS 



It should not contain more fc'ecal organisms than one in i c.c. 

 There should not be any organisms of Class (i) in less than 



29 c.c. 

 The fecal organisms present should consist mainly of mixtures 



of Class (3) and Class (2), and there should be a tendency for 



one organism to preponderate. 

 (3) Bad river waters to be condemned. 



When the total colonies are more than 800 on agar at 37° C. 

 When lactose fermenters are present in number of 10 to 100 



per c.c. 

 When organisms belonging to Class (i) exceed one in 5 c.c. 

 When the faecal organisms isolated (Class (i) being absent) are 



rich in varieties such as occur in an emulsion of faeces. 



For Well and Spring ]]\iters. 



A good water should contain no f^cal bacilli in 20 c.c. 



No Class (i) in 100 c.c. 



Total colonies under i^ft^' per c.c. 



For the details of this excellent ^^'ork one must see "A Study of 

 the Bacteriology of Drinking Water Supplies in Tropical Climates'* 

 (1909), by W. W. Clemesha. 



Sanitarians are recommended to adopt similar methods. 



Unfortunately he has not told us anything of deep wells. 



It seems to be agreed that if experiments are carried out along the 

 lines adopted by Clemesha, in most tropical countries, sufificient data 

 will be available for suggesting some standard for a tropical water 

 supply fit for drinking purposes. 



We venture to give, however, for comparison, the standards as 

 adopted by British sanitarians. 



(a) Enumerate the bacteria capable of growth at room temperature 



(18-22° C). 



(b) Identify and enumerate the bacilli coli present. 



(c) Enumerate bacteria capable of growth at blood heat (36° to 

 38° C). 



(d) Enumerate the streptococci present. 



(e) Detect the typhoid bacillus. 

 (/) Detect the cholera vibrio. 



(a) To enumerate bacteria grown at room temperature. 



Nutrient gelatin is most often the medium used. 



(In countries with a high temperature nutrient agar should be used, 

 but it is not as useful as nutrient gelatin in showing the presence of 

 liquefying organisms (Simpson).) 



Professor Hewlett prefers beef broth. 



The percentage of gelatin should be increased with the temperature. 



