214 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
erowing in neutral-red, bile-salt, lactose agar are taken 
as the indices of the amount of pollution. I have given 
test-reactions in the cases of all the analyses except the 
last one, but in the present state of our knowledge of the 
cultural reactions of the organisms closely allied to 
Bacillus coli communis, and pending some more critical 
examination of the value of the tests usually employed 
than has yet been attempted, it is as well to speak only of 
“colon-hke organisms.’ Probably we may regard all 
those growing on the medium mentioned as belonging to 
this category, without, of course, committing ourselves 
to the view that they are necessarily of human intestinal 
origin. The following table gives the results of these 
be 
counts. The numbers are “ colon-like organisms” per 
cockle. In almost every case the numbers are averages 
deduced from the examination, in duplicate, of 20 shell- 
fish. The results of the enteritidis reactions may be 
neglected in the meantime. It would appear that there 
is no exact correspondence between the distribution of the 
organisms exhibiting this reaction and PD. colz. 
NumBERS oF ‘ COLON-LIKE’’ ORGANISMS CONTAINED IN ONE 
CocKLE FROM THE FOLLOWING LOCALITIES. 
AmisGell 25 A se tiaw sets eee ee ee , 1915 
Rormby 2.20 ice- osteo eees babel Julet aire aie 
ICASOWE: . Greene certs apenas ot oe oes any 60 
Silverdale ..... sacs Ge Shteoeedaeom art seman wees s Gee 28 
Blookburch !)c.200 encase sae eee 17 
SOUTH POL: As caeetdeccenesceas seat eee eae 12 
There can be little doubt, I think, that the cockles 
from Flookburgh and Silverdale are above reproach. 
Indeed, one would come to that conclusion apart 
altogether from bacteriological evidence. The Southport 
shell-fish would appear from the above results to be the 
