248° BACTERIOLOGY. 
incubator at 37° C. for twenty-four hours. From 
this plate cultures are made. In our experience this 
and other methods have not enabled us to detect the 
typhoid bacillus where we have failed to find it by 
making direct plate cultures. As a matter of fact, the 
typhoid bacillus is found in sucha small number of the 
specimens where we actually know that it is or has 
been present in the water from which they were ob- 
tained, because of cases of typhoid fever which have 
developed from drinking the water, that we must con- 
sider our lack of finding the bacillus in any given 
case as absolutely no reason for considering the water 
to be free from danger. Another serious drawback 
to the value of the examinations is that they are fre- 
quently made at a time when the water is really free 
from contamination, though both earlier and later the 
bacillus was present; it is hardly worth while, there- 
fore, except in careful experimental researches, to ex-— 
amine the water for the typhoid bacillus, but rather 
study the location of the surrounding privies and sources 
of contamination. The colon bacilli are far more easy 
to detect, because they are apt to be more abundant, 
and, also, because they grow more readily in artificial 
culture media. A method suggested by Theobald 
Smith is of value in both finding and excluding the 
presence of bacilli of the colon group. He adds a few 
drops of the suspected water to glucose nutrient bouillon 
in fermentation tubes, and keeps it at 37° C. for from 
thirty-six to forty-eight hours. If no fermentation 
occurs no colon bacilli are present. If it does occur 
plates are made and the bacteria isolated and tested. 
In the bouillon the colon bacilli when present usually 
increase in numbers and are then readily detected. The 
