143 
which we know to be particularly resistant, and which, when 
found by itself, is of little significance as an indicator of recent 
pollution. But the organisms Nos. 2, 6 and g and the Oxy- 
tocus perniciosus fall in with neither Savage’s nor Houston’s 
definition of ‘‘coli,’’ yet there is good reason to believe 
that these bacilli are much more specifically an indication of 
recent pollution than true B. coli communis of Escherich 
itself. 
A second example illustrating this important point will 
be found by referring to the analysis of Cocanada water, given 
below. The water at Cocanada is originally taken from an 
irrigation canal; it is run into a storage tank where it 
remains for anything from seven days to a month; it is then 
filtered and pumped into the town. The canal sample con- 
tains fecal bacilli in I c.c.; but having been exposed to the 
sun for a considerable time, as the water flows slowly for many 
miles down a shallow irrigation canal, it has been so thor- 
oughly well sunned and settled, that the only organism present 
is B. Grunthal. After the water has remained in the storage 
tank, this organism has further decreased in number, till it 
is only present in 10 c.c. of the water. Now these two samples 
would be condemned as containing. colt. The water then passes 
through filter beds. As a result of this would-be filtration, 
the fecal bacilli have run up from I in 10 c.c. to I in °3 of ac.c. 
None of these samples after filtration contain any organism 
which can be called ** true coli.’’ It has been shown by inspec- 
tion that the reason for this increase is due to the fact that 
a polluted subsoil water finds its way through the masonry 
floor of the filter beds. Therefore there can be no doubt 
that this admixture is distinctly undesirable, though the 
bacilli added happen to be mainly B. cloace—an organism 
which neither Houston nor Savage include within their defin- 
ition ‘‘ true coli,’’ and which (because it liquefies gelatine) 
would be regarded as of no serious importance as an indicator 
of fecal contamination. We do not suppose that either Dr. 
Houston or Savage would have overlooked the great increase 
in the number of organisms that gave acid and gas in lactose 
broth without some inquiry, but this case demonstrates the fact 
that the generalization concerning the interpretation of 
