262 
TYPHOID FEVER IN DISTRICT OF COLUMBIA. 
amount of gas, gave the best promise of containing B. coli. The 
lactose-litmus-agar plates so made were grown at 40° C. over night, 
and if red colonies appeared a number of them were used to inoculate 
agar slants. These slants were grown at 37° C. for twenty-four hours 
and the culture was invariably subjected to further tests, as observa- 
tion of morphology and motility and reaction on litmus-milk, gelatin , 
lactose broth, peptone solution, and nitrate solution. 
Only those organisms which answered all the tests given in the 
standard methods of the committee of the American Public Health 
Association were finally recorded as B. coli. In a few instances organ- 
isms answering all the tests except the production of indol are con- 
sidered B. coli. Such exceptions are noted in each case. 
Although three gelatin plates were made containing, respective^, 
1 cc., 0.1 cc., and 0.01 cc. of the water to be examined, it was found 
that the most reliable results were obtained from the plates planted 
with 1 cc. of the water, and wherever possible this plate was taken as 
representative of the specimen ; but if the plate containing 1 cc. of the 
water, on account of liquefaction, excessive numbers, or other causes, 
could not be relied upon, the other two plates containing the smaller 
amounts were used. 
Fermentation in the lactose broth at 40° G. is indicated in the 
column so headed by a + or — sign. The amount of gas contained 
in the original fermentation tubes is not given, as it was found to be 
without significance, B.’ coli being sometimes found when the tube 
contained only a bubble and not discovered when a t}q)ical one-third 
to two- thirds of gas was present. 
B. coli is reported present in the amounts of water in which it was 
found, but it was undoubted!}^ present in smaller amounts in some of 
the specimens w^here more than one tube contaiued gas, as only the 
one considered most likely to contain the colon bacillus Avas examined 
further for that organism. Accordingly such fermentation may be 
regarded as presumptive evidence of B. coli, but this CAudence is not 
considered in any of the summaries. 
Summary of bacteriological examinations of raw and filtered waters. 
[Ju]y 16 to August 27, 1906.] 
Dalecarlia reservoir. 
George- 
towm res- 
ervoir. 
AVashing- 
ton reser- 
voir. 
Filtered- 
water res- 
ervoir. 
North end. 
South end. 
Number of specimens examined 
15 
15 
15 
24 
21 
Average number of bacteria per cubic 
centimeter 
526 
381 
306 
235 
36 
Number of specimens 
9 
12 
11 
19 
16 
Percentage shovdng the B. coli in 1 cc 
42.8 
40.0 
33.3 
16.6 
4.7 
Percentage showing the B coli in 10 cc 
28.5 
40.0 
40.0 
41.6 
9.5 
Total percentage showing the B.coli. 
71.3 
80.0 
73.3 
58.2 
14.2 
