:study the relative frequency of these organisms in human and animal fces, their
power of resisting the forces in nature inimical to bacilli, and. to attach to them
their relative significance as indicators of faecal contamination. Thus A might be an
'extraordinarily sensitive organism, that disappeared from contaminal ed water after a very
. few minutes exposure to sunlight. D, on the other hand, might be a very persistent
bacillus, that Was only found to disappear after weeks of storage and exposure to a
-tropical sun. Obviously therefore the significance of D and A would be very different
if found in any given water sample, and, presuming that the separate characteristics of
A and D rests on a sound foundation of experimental proof, it would be advisable to
use the extra fermentation tests necessary for the recognition of A and D on account of
the valuable information that their presence in any sample indicates. But as long as
the method of calling all organisms, that fulfil a few tests, " coil, " and those that du not
fulfil them, or only fulfil them in part, " atypical coli," the possibilities of progress are
very much reduced. Although it may be true that this method has, in skilful hands
in Europe, given satisfactory results, it is obvious that unless each species of bacterium
is isolated and studied separately, both as regards its positition in nature, and as regards
its prevailing characteristics, we shall remain in our present position, talking of " culi"
and " atypical coli " permanently.
In order to demonstrate the unsuitability of the definition of " coli, " and of the
standards made use of in common practice in Europe and America, when applied to the
Madras Presidency, it will be well to observe the result of applying them to the samples
examined in our laboratory. Houston's " true coli " ferments lactose, ferments
glucose, does not ferment saccharose, gives indol reaction, and the other tests already
described. Organisms that fulfil these tests are indicative of fecal contamination and
a r e m o r e o b j e c t i o n a b l e t h a n o r g a n i s m s t h a t f e r m e n t s a c c h a r o s e . B y m a k i n g u s e o f
the additional reactions of, fermentation of dulcit, adonit, inulin. and Voges-Proskauer
test, it is possible to spli.t up this " true coli " of Houston into about 10 different bacilli
( v i d e
t a b l e I I I ) a n d i f w e a d d h i s " n o n - t y p i c a l c o l i " ( t h a t i s t o s a y t h o s e t h a t d o n o t
give the indol reaction) more are added. Now it must be remembered that all
t h e s e o r g a n i s m s a r e l o o k e d u p o n a s i n d i c a t i n g t h e w o r s t f o r m o f c o n t a m i n a t i o n .
A p a r t
.from the objection of classing 10 different organisms under the term " true coli," it
has never been demonstrated that the members of this group are equally objectionable,
•or in other words equally represent recent and serious contamination.
Savage's definition of " true coli " is virtually the same as Houston's, but as
regards the interpretation, he makes this statement " all workers class both groups
(saccharose and non-saccharose fermenters) of equal value as excretal -indicators."
Consequently all lactose fermenters except, such as liquefy gelatine, do not give the
indol reaction, and are non-motile (vide his previous remark on motility, indol, etc.) may
be said to be of equal value as indicators of fcal contamination. Therefore there
.are, according to the table, 10 or 12 organisms that fulfil all these necessary conditions,
if motility and indol are left out, there are more than 20 bacilli, to be regarded as
equally objectionable in a water sample.
To take Houston's definition of true coli first : of the 239 samples, which have
been worked through in our laboratory, derived from 18 different water-supplies, in 3
separate quarters, only 84 would show no " coli." If Savage's wider statement be
accepted, it means that we have practically not a single supply in the Madras Presi-
dency that does not show objectionable fwcal contamination. Is it reasonable to
urge that we in India should have condemned all these different water-supplies ?
There is another point that demands notice. Take the organism bacillus
c l o a c æ a s a n e x a m p l e ; i . t w i l l b e o b s e r v e d t h a t t h i s o r g a n i s m d o e s n o t c o m e w i t h i n H o u s t o n ' s
definition of " true coli " ; because it ferments saccharose, nor within Savage's group
-that indicates fæcal contamination, because it liquefies gelatine, yet it is undoubtedly
in origin. Why should the mere fact that this organism liquefies gelatine mean
that it does not indicate fecal contamination to an equal extent as any non-liquefier?
Su
faecal
rely, considering it originally came from the faces of man or some other animal, the
coincidence that it liquefies gelatine, cannot put it beyond the lange of indicators
of focal contamination. As a matter of fact B. cloace is not an 'indicator of
d a n g e r
( M S
a n d r e c e n t
p o l l u t i o n , b e c a u s e i t i s a r e s i s t a n t o r g a n i s m , w i t h a f o n d n e s s f o r t h e
bottom of lakes, and river sand ; but the liquefaction of gelatine has nothing to do with
t h e s e f a c t s .