----------+------------------------------------------------------- | NATURE OF TEST ORGANISM. +-------+-------+-------+-------+-------+-------+------- Available | | B. | | | | B. | Chlorine | B. |fæcalis| B. |Proteus| B. |lactis | B. p.p.m. |cloacæ.|alkali-|paraty-| mira- |enter- | aero- |choler[oe]- | |genes. |phosus.|bilis. |itidis.| genes |suis. ----------+-------+-------+-------+-------+-------+-------+------- 0.1 | .....| 99.98| .....| 27.3 | .....| .....| ..... 0.2 | 99.69| 99.99| 99.97| 45.5 | 99.83| 99.17| 95.8 0.3 | 99.75| 100.00| 100.00| 63.7 | 99.98| 99.98| 100.0 0.5 | 100.00| .....| .....| 72.7 | 100.00| 100.00| ..... 0.7 | .....| .....| .....| 63.7 | .....| .....| ..... 1.0 | .....| .....| .....| 63.7 | .....| .....| ..... 3.0 | .....| .....| .....| 90.9 | .....| .....| ..... 5.0 | .....| .....| .....| 90.0 | .....| .....| ..... Original }| | | | | | | number of}| | | | | | | organisms}|160,000| 9,500| 3,000| 8,000 |180,000|180,000| 500 per c.cm.}| | | | | | | ----------+-------+-------+-------+-------+-------+-------+------- With the exception of _P. mirabilis_, which forms endospores, all the organisms were killed (less than 1 per c.cm.) by 0.5 p.p.m. of available chlorine in fifteen minutes. All these observers found that _B. coli_, the organism usually employed as an index of contamination, had approximately the same degree of resistance to chlorine as _B. typhosus_, though Wesbrook et al. directed attention to the varying viability of organisms derived from different sources.