44 
IgIt. Raw Waters. 
ut of 2,635 specimens 
of B, coli isolated from 
741 samples of zaw 
water, the proportion 
between the typical 
and non-typical races 
of B. coli, expressed 
AS percentages, was as 
Type of B, coli. 

Filtered Waters.* 
Out of 3,522 specivens 
of B. coli isolated from 
7,146 samples of f//ered 
water (including Kent 
and Lee Valley un- 
filtered well water), the 
proportion between the 
typical and non-typical 
races of B. coli, ex- 

follows :— pressed as percentages, 
was as foliows :— 
| 
Typical B. coli (+lactose ;— indol) | — 818 | Ba 49°8 
| | 
(+lactose ; +indol)... | 9°3 | | 19°8 | 
Non-typical B. coli- : 18°1| ; 50°2 
| (lactose ;-+ glucose) | 8°8 f 30°4] 

* Filtered waters all have more or less storage and exposure to sun, 
Considering this mass of evidence we may consider that 
the following points are fairly certain :— 
(2) that the acid and gas line in glucose medium is 
higher than in lactose in ordinary natural water ; 
(77) that the relation between the two classes of organ- 
isms varies at different times of the year ; 
(422) that the relation between the two classes of 
organisms seems to be in some way connected 
with the amount of storage, or exposure to the. 
sun, 
Further evidence is necessary before this last point can 
be accepted as true, and we must enquire into the explanation 
of these facts. 
We may commence the enquiry by the question—How do 
these facts tally with the work on fresh feces given previously ? 
In Chapter III we have shown that the particular class of 
organism, v2z., glucose + lactose —, is, as far as one can tell from 
a very extended investigation on fresh feces, extremely rare ; 
they represent only 5% or less of the total coliform organism. 
Yet within a few weeks of the date of addition of feces to water 
the picture is entirely reversed; the lactose + glucose +, 
represent 5°% of all faecal organisms (as shown by Table VI(d)) 
and the glucose + lactose — now account for the remaining 95%. 
How has this change come about, and what is its significance ? 
i ee eee he Be 
