1. Make one or more Endo’s medium or lactose-litmus-agar plates from the
tube which, after 48 hours’ incubation, shows gas formation from the
smallest amount of water tested. (For example, if the water has been
tested in amounts of 10 cc., 1 cc., and 0.1 cc., and gas is formed in 10
cc., and 1 cc., not in 0.1 cc., the test need be confirmed only in the 1
cc. amount.)