2 
THOMPSON YATES LABORATORIES REPORT 
undoubtedly to be found very widespread in nature. These ' coli-like ' organisms have 
been described at length by various observers, most recently by Lunt, in the paper 
already referred to, and by Gordon.* Theobald Smith! is of the opinion that many 
statements of the widespread distribution of B. coli are without experimental 
foundation. He considers that, when found, its presence may be regarded as due to 
direct contamination. But actual experiments on this subject are rarely met with, and 
it therefore seemed worth while to make systematic experiments with polluted and 
unpolluted material, to see what significance might be attributed to the presence of 
B. coli commune. I have taken care to identify the bacillus whenever met with, and I 
have not found that ' coli-like ' bacilli are at all general ; among a very great number of 
examples of B. coli isolated, there were only three that were not typical. In the Tables 
the presence of B. coli commune always refers to the typical bacillus ; and, I think, 
these investigations also tend to show that its presence is a good index of pollution. 
Samples ot rain, snow, hail, air, dust, grains and many foods were found to 
be free from B. coli commune — virgin moorland soil, similarly. Streams and rivulets, 
not obviously polluted, showed an absence of the bacillus in most cases in the 
quantities analyzed ; while, in the cases in which it was present, it was there in very 
small quantity. Water from pipes draining the land was also generally free from it. 
Sewage and sewage effluents, on the other hand, contain B. coli commune in great 
numbers, and its presence is also easily demonstrated in rivers polluted by sewage. 
These experiments have also shown the efficiency of sand and earth as filtering 
material for removing the bacillus, and have added a few more facts to what is already 
known J as to the vitality of B. coli commune under unfavourable circumstances. 
These confirm the conclusions of other observers, that, owing to its low vitality, the 
B. coli undergoes little multiplication in nature outside its normal habitat, viz., in 
water, dust, etc. This being so, the presence of the bacillus may be taken as evidence 
not only of pollution but also of recent pollution. 
I wish to take this opportunity of expressing my indebtedness to Professor 
Bovce for his invaluable help and kind advice during the course of this investigation. 
I. METHOD 
The first method tried, which proved to be unsatisfactory, was the well-known 
one which consists in incubating sewage, etc., properly diluted, with a peptone-salt 
broth, to which enough phenol has been added to make its concentration in the 
mixture equal to i in 1,000. In the case both of sewage and of sewage effluents the 
growth obtained consisted largely of liquefying organisms, which outgrew the B. coli 
commune, although it must undoubtedly have been present. Often, after passage 
X Frankland and Marshall Ward, Proc. Roy. Soc, 189^ 
p. 315. Walliezek, Central/)/. /. Bakt. xv, p. 949. Von 
Freudeureich Centralbl.f. Bah. xx, p. 522. 
