147 

| Quarter | Quarter | Quarter 
ending | ending | ending 
30th’ 31st 31st 
| | Séptem- Decem- | March 
\ber 1908.\ber 1908.} 1909. 


(1) Number of samples examined Be ES ke AR 78 
(2) Number of samples that contain ‘‘ Coli’’ 
according to Houston ots hice 57 blebs 
(3) Number of samples that contain true bacil- 
lus coli communis of Escherich (eee) eae II 
(4) Number of samples in which the only organ- 
ism that falls under the definition of 
Houston‘s ‘‘ Coli’’ is bacillus Grunthal a5 a2 22 
(5) Number of samples containing mixtures of | 
Grunthal, acidi lactici, and others of 
Floeuston’s “‘ Coli”’ group .. 25 
22 
(6) Number containing no ‘‘ Coli ’’ of Houston 13 28 33 
} 



} 

It will be observed that an enormous percentage of the supplies 
would be condemned entirely unnecessarily. 
The recognition of truly recent pollution is, we maintain, 
easy by using certain tests; but it is perfectly obvious that 
tlie application of the ‘‘ true. coli **.and (‘atypical coli 7 
method would tell us nothing in these samples. 
The terms “‘ true and atypical coli ’’ are, we maintain, 
purely a laboratory classification, they are not in the slightest 
degree based on a study of the natural characteristics of faecal 
organisms, and in estimating the age of a pollution they are of 
no value ; indeed we consider that just as much information as 
to the quality of the water can be obtained by roughly estim- 
ating the number of lactose fermenting organisms that are 
present in any water, without saying whether they belong 
to the ‘* true or atypical ’’ class of coliform bacilli. 
Finally, as long ago as 1905, MacConkey recommended 
that all fecal bacilli in a water sample should be separated 
and studied, and that by doing so, we should probably greatly 
increase our knowledge of the true significance of the presence 
of these micro-organisms. 
We consider that we have amply proved the truth of 
these contentions, and the utility of his method. 
Laying aside for the time being all the more debatable 
part of our work—such as, the difference in powers of resist- 
