28 
TYPHOID FEVEP. IX DISTRICT OF COLUMBIA. 
SEPTEMBER. 
Average number of bacteria per cubic centimeter, 41 specimens 83. 4 
Average number of bacteria per cubic centimeter, excluding the 3 specimens 
containing over 100 organisms per cubic centimeter 40. 5 
Percentage in which B. coli was found 12. 2 
Percentage in which P. coli was found in 10 cc 9. 7 
Percentage in which B. coli was found in 1 cc 2.4 
(Note. — Specimen No. 326 is not included in these figures.) 
OCTOBER 1-16, IXCLTTSIVE. 
Average number of bacteria per cubic centimeter, 30 specimens, none over 100 . 21. 0 
Percentage in which B . coli was found 0.0 
Our findings, based upon a limited number of examinations, show 
93.1 per cent bacterial improvement resulting from storage and 
filtration. 
Of the 15 samples of raw water examined bv us 66.6 per cent con- 
tained the colon bacillus. 
Of the 21 samples from the filtered water reservoir 14.2 per cent 
showed the colon bacillus. 
Of the 131 samples of tap water examined 17.5 per cent showed 
the colon bacillus. 
The following are the results obtained at the laboratory of the 
filtration plant for the same period (August and September), based 
upon examinations made daily (except Sunday) : 
Period. 
Dalecarlia. 
Geoi^e- 
town 
reservoir. 
W ash- 1 
ington 
City res- 
ervoir. 
■ Filtered 
water 
reservoir. 
Inlet. 
Outlet. 
August (number of bacteria per cc.) 
September (number of bacteria per cc.) 
8,658 1 
422 
1,077 
245 
1,231 
136 
188 
133 
14 
14 
The percentage reduction, according to these figures, is 99.9 per 
cent. For the period from February to October, 1906, the reduction 
was 99.4 per cent. 
