1038 
Bacillus Cloace. 
We will now consider the resistant organisms. Pro- 
bably the most interesting member of this class is bacillus 
cloace. This organism is one which shows a very great 
variation in its numbers in the feces of man and animals at 
different times of the year; it may constitute as much as 15 
to 20 per cent. of all organisms present at one time, or it may 
be as low as I or 2 per cent., or be entirely absent at 
another. It would appear from our work that bacillus 
cloace is commoner in feces in Madras than it is in Bengal, 
but this requires further investigation. The period of preva- 
lence in feces is usually about May, June and July, in the 
height of the hot weather. Not only is the organism ex- 
tremely prevalent in feces, but at this period of the year it is 
extremely common in lakes and, to a less extent, in rivers in 
Madras. In Bengal we have no lakes worthy of the name, 
and therefore it is impossible to say whether it is so common 
in this part of the country, but it has been shown to be fairly 
prevalent at the bottom of tanks, and less so in rivers. The 
figures given in Chapter IX demonstrate the periodical increase 
in the number of cloace in water-supplies contemporaneous 
with the dry and hot weather. Indeed the figures themselves 
do not really indicate how extraordinarily prevalent this 
organism is at certain times of the year. Lakes, many rivers, 
and even well waters contain practically nothing else when 
they are getting very low. The work carried out on the 
Red Hills Lake, described in Chapter VIII, shows that even 
when large volumes of highly pojluted water pass into the 
lake, the bacillus cloace settles to the bottom and is by far the 
commonest organism in this position. Probably they slowly 
multiply ; and as the water gradually falls this organism appears 
to be the only one of all the fecal organisms present. The 
sunlight experiments show that it is amongst the most re- 
sistant of lactose fermenters. It usually appears late in the 
experiment, and in quite a fair number, it is the last organism 
to survive. The bacillus is also extremely common in damp 
river. sand; in the work carried out on polluted earth 
derived from “trenching grounds,’’ in practically every case 

