TYPHOID FEVER IN DISTRICT OF COLUMBIA. 
27 
BACTERIOLOGY OF THE POTOMAC RIVER WATER. 
The following is a summary of our bacteriological examinations of 
the raw and filtered waters : 
Summary of bacteriological examinations of raw and filtered waters of the reservoirs. 
[July 30 to September 27, 1906.] 
Dalecarlia. 
George- 
Wash- 
Filtered 
Inlet. 
Outlet. 
town. 
ington. 
water. 
Number of specimens examined 
9 
12 
11 
19 
16 
Average number of bacteria per cubic centi- 
meter 
526 
381 
306 
235 
36 
Number of specimens examined 
15 
15 
15 
24 
21 
Percentage showing the B. coli in 1 cc 
40.0 
40.0 
33.3 
16.6 
4.7 
Percentage showing the B. coli in 10 cc 
26.6 
40.0 
40.0 
41.6 
9.5 
Total percentages showing B. coli 
66.6 
80.0 
73.3 
. 58.2 
14.2 
The following is a summary of our bacteriological examinations of 
tap water : 
Summary of the bacteriological examination of tap water. 
[July 16 to October 16, 1906.] 
Number of specimens examined 131 
Average number of bacteria per cubic centimeter 64. 0 
Average number of bacteria per cubic centimeter, excluding the 9 specimens 
containing over 100 organisms per cubic centimeter 36. 0 
Percentage in which B. coli was found 17.5 
Percentage in which B. coli was found in 10 cc 15.2 
Percentage in which B. coli was found in 1 cc 2. 2 
JULY. 
Average number of bacteria per cubic centimeter, 30 specimens 74. 1 
Average number of bacteria per cubic centimeter, excluding the 3 specimens 
' containing over 100 organisms per cubic centimeter 39. 3 
Percentage in which B. coli was found /. 33. 3 
Percentage in which B. coli was found in 10 cc 30. 0 
Percentage in which B. coli was found in 1 cc 3.3 
AUGUST. 
Average number of bacteria per cubic centimeter, 30 specimens 60. 7 
Average number of bacteria per cubic centimeter, excluding the 3 specimens 
containing over 100 organisms per cubic centimeter 40. 3 
Percentage in which B. coli was found 26. 6 
Percentage in which B. coli was found in 10 cc 23. 3 
Percentage in which B. coli was found in 1 cc 3.3 
