Ioo 
it will be observed that during the wet 6 months of the year 
lactis aerogenes is more prevalent than at any other time, and 
cloace are rare. During the dry 6 months of the year the 
reverse obtained, cloace is a very common organism, and 
lactis zrogenes is less frequently found. 
The work that has been carried out in Bengal also bears 
out these statements very considerably. Unfortunately, 
however, there are no lakes or storage reservoirs in Bengal 
from which figures could be obtained. All the water supplies 
are obtained from rivers. Table IX (e) gives the results of the 
samples obtained in the large rivers in Bengal, exclusive of 
the Hughli, during the year 1911. In Table IX (e) the samples 
TABLE IX (e). 
Percentage Prevalence of Organisms in Bengal Rivers, year 

sR ope 
| Dry weather | Wet weather 
Dec.- June. |  July-Nov. 
| 
Bacillus Grunthal-Vesiculosus af Al | 23'0 
ss Coli communis nf oe cae | 1335 
. Lactis zrogenes A | Ps 19°2 
Cloacze ie = ee 10°9 | 4°2 


were divided into dry and wet weather samples. The rivers 
in this part of the country are, as compared with the 
Madras rivers, deeper, and muddier, and the population along 
the banks is usually greater. Consequently, one would not 
expect to find the same variation between the dry weather 
and wet weather conditions. Still in Bengal the following 
points must be noted :— 
(1) In the dry weather samples lactis zrogenes is rarer 
than in the wet weather. 
(2) in the dry weather samples cloace is commoner 
than in the wet weather ; and 
(3) The vesiculosus and Grunthal group are extraordin- 
arily common during the dry weather, as compared with 
the wet. It is not desirable to push this conclusion further 
