114 
(4) The great rareness of: white colonies on_ solid 
medium obtained from a glucose broth. 
(5) The extraordinary difficulty of isolating the 
bacillus P at this period. 
(6) The rarity of lactis erogenes. 
(7) The fact that resistant organisms, such as cloace 
and vesiculosus. are not prevalent in large 
numbers, but may be isolated in smaller numbers 
in a feeces-like mixture. 
(8) The high figures of the total colony count. 
(9) Fecal organisms, both lactose and glucose fer- 
menters, present in ‘oI of a c.c. or less. 
(10) Possibly streptococci may be isolated from 20 c.c. 
of the water. 
These are the various points noticed in a gross recent 
pollution. The first thing that will occur during the process 
of self-purification will be a considerable decrease in the 
total number of fecal organisms within the first 3 days, so 
that . they can.only be isolated in ‘1 or I c.c. Even at 
this period there would be a tendency for the acid and 
gas line in glucose and lactose to separate. Within the second 
week the following changes would have taken place :— 
(1) The number of varieties of organisms isolated in 
10 colonies would have decreased. | 
(2) There would be a marked tendency for lactis 
zrogenes to predominate. 
(3) The sample taken from the bottom of a lake would 
probably show an increased prevalence of bacil- 
lus cloace. | 
(4) The acid and gas line in glucose and lactose would 
have separated, glucose + lactose—would pro- 
bably be present in ‘o5—1 of a c.c. in the water, 
lactose fermenters being present in-I.-c.c. or 
5 c.c. on the surface, possibly in much less. 
(5) Bacillus P would now be very common and easily 
isolated, no other member of the class glucose 
+ lactose—would be found. 
