93 
(2) The water itself, of course, was not sterile and con- 
tained about one fecal organism, usually of the very resistant 
type per cubic centimetre. In the light of these facts it is 
not reasonable to base any conclusion on these experiments, 
because it is not certain whether the organisms that survive 
were added with the feces or are those that existed in the water 
previously. One experiment, however, is worthy of short notice. 
Owing to the difficulty of obtaining a mixture of sewage 
which contained large numbers of coli communis, we added to 
the mixture of faces 2 litres of a pure culture of bacillus 
Schafferi. The sewage was added about 4 o’clock in the even- 
ing. Samples were taken at 7 in the next morning. In the 
first samples bacillus Schafferi was found present in as small 
a quantity as I c.c. of the water taken from the surface and 
from the bottom of the tank. It was also isolated at 4 o’clock 
the same evening from a sample taken from the surface. The 
second day no bacilli was found on the surface but on the 
3rd day they were also found. From this time forward bacil- 
lus Schafferi could never be isolated from any surface or bottom 
sample. This is rather an important result, because in this case 
the organisms were laboratory cultures grown in broth, and we 
have already stated that, as a general rule, laboratory culture 
show a greater resistance to the action of inimical forces than 
do bacilli under strictly natural conditions, and yet, in spite 
of this fact, the coli communis disappeared more rapidly than. 
many of the other bacilli added with the sewage. 
