IAI 
ered, on all occasions, of equal value as an index of recent 
and dangerous pollution, as the susceptible one. Examining 
the ten organisms, which fall under Houston’s definition of 
‘“coli,’’ and whieh represent his worst type of pollu- 
tion, we have shown that the greatest possible variations 
exist in these ten organisms in their power of resistance to 
the action of natural forces. To take two extreme examples, 
one member of the Grunthal-Vesiculosus group is particularly 
resistant to the action of sunlight. It is found in waters 
that have been exposed to the tropical sun for weeks; it is 
nearly always one of the last bacilli to disappear from a well- 
sunned and stored water, and also from a mixture of cowdung 
and water exposed to the sun. On the other hand, true 
B. coli communis of Escherich (the organism that ferments 
‘dulcit and does not ferment saccharose, adonit, inulin, etc.) 
will disappear with great rapidity from a water exposed to 
the action of tropical sun. Is it reasonable to include both 
these bacilli under the same term of ‘‘ true coli,’’ 
and to state that both equally represent objectionable 
pollution ? 
It is possible to elaborate this still further. Take the 
example of Oxytocus perniciosus: we have pointed out that 
this organism is susceptible to natural conditions, such as 
sunlight, etc., for although it is present in cowdung, and in 
human feces, it has only been found in water-supplies after 
heavy floods, and it disappears with extraordinary rapidity. 
Thus, it is probable that this organism represents a very recent, 
and therefore a more objectionable contamination than any 
other organism met with up to now. Yet it will be observed 
that this particular bacillus does not fall within Houston’s 
definition of ** true coli,’’ nor within the category of organisms 
which according to Savage are ‘“ equally of excretal origin.’’ 
In order to demonstrate what is exactly meant by this last 
paragraph, reference should be made to the analysis of the 
water of the District Jail of Tanjore, given here. 
The water contains fecal bacilli in ‘or c.c. It contains 
sporogenes in 20 c.c., and the total colonies in I c.c. at 37°C were 
2,520. The only bacillus that would fulfil the definition of 
‘“coli’’ according to Houston is B. Grunthal, an organism 
