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most sediment samples. Five lactose broth tubes were used for 
each dilution in the dye patch experients and two tubes per 
dilution were used for other types of samples. 
Identification of Coliforms 
For conclusive identification of coliforms, typical colonies 
were picked at random from positive confirmed plates and checked 
morphologically and biochemically by Gram-staining and by the 
Imvic tests. Several dozen colonies thus check proved to be 
species of either Escherichia or Aerobacter, 
Enteric Pathogens 
An effort was made on two occasions to isolate enteric 
pathogens from the sediments around the Hyperion outfall. 
About one gram of mud was introduced into tetrathionate broth 
and the cultures incubated at 37°C for 24 hours. These enrich- 
ment cultures were then streaked on S.S. agar plates. Suspicious 
colonies appearing on these plates were transferred to triple 
sugar iron medium. Tests’were not continued beyond this stage 
because all colonies examined proved negative for pathogens. 
Disappearance of Coliforms With Time (Dye Patch Experiments) 
A total of sixteen dye patch experiments were conducted; twelve 
at the Orange County outfall, three at Whites Point, and one at 
Hyperion. Of the sixteen experiments, thirteen showed a marked 
and usually consistent disappearance of coliforms with time. These 
will be discussed as a group. The three "atypical" experiments will 
be dealt. with separately. 
