484 SEDGWICK AND WINSLOW. — BACILLUS OF TYPHOID FEVER. 
in the upper part of the ice 16 bacteria; in the lower part, only partially frozen 
2u0; in the upper anJ lower parts of a duplicate unfrozen vessel of water, ICO and 
170, respectively. He obtained similar results with three species of Infusoria, and 
concluded that 90 per cent of the organisms were removed by freezing. His experi- 
ments appear, however, to show crystallization effects principally. The first careful 
work on this subject was done by Fraenkel in Berlin.^^^^ He collected river water, and 
after planting samples, froze them artificially at -8° to -12° C, thawinir after different 
d 
In two days 83 per cent of the water bacteria present were killed 
days 99 per cent; in five days, 90 per cent; in six days, 80 per cent; in six days, 
in another case, 93 per cent; and in nine days, 99 per cent. The different samples 
evidently varied greatly. Fraenkel also analyzed the regular Berlin ice-supply, and 
got results ranging from 21 to 9700 bacteria per cubic centimeter. He concluded 
that the ice was highly polluted and should not be taken into the system. About 
the same time WolfThuegel and Riedel («^) gave an account of some experiments in 
which flasks of tap-water were kept in the ice-chest without freezing, and showed 
the following reductions : after one day, from 148 germs per cubic centimeter to 126 
Mud from 160 to 115; after two days, from 123 to 69 and from 158 to 101 ; after 
three days, from 123 to 29 and from 156 to 33. 
In 1887 Dr. Prudden of New York published the most exhaustive review hitherto 
attempted of the subject of quantitative reduction, and the first in which specific 
pathogenic germs were used.^^^^ His tubes, in the experiments with the latter organisms, 
were moculated from pure cultures and frozen at -10° to -1° C, and his results were 
as follows, the numbers in each case referring to bacteria per cubic centimeter :- 
B. prod.giosus. In water, 6300; in ice after 4 days, 2970; after 37 days, 22; 
after 51 days, 0. 
Proteus vulgaris. In water, 8320 ; in ice after 18 days, 88 ; 51 days, 0. 
oo. roc o ""''"' P^'"'^'''"' '''"''^'- T" ^^^^'^ innumerable; in ice after 18 days, 
224,0.18; 20 days, 46,480; 54 days, 34,320; 66 days, 49,280. 
In, water, innumerable; in ice after 4 days, 571,450; 11 
amed 
O-s, 020,520; 51 day,,, 183,040; 65 days, 10,078; 77 days, 85,008 
Sp 
B- typhi. I 
In water, 800,000 ; in ice after 7 days, 
^t^fii'r, Vo , ■' "'""'"^'■•''l''^ ; in ice after 11 days, 1,019,403; 27 day; 
336^07; 42 Jays, 80,796; 69 day., 24,276; 77 days, 72,930; 103 days, 7348. 
5 !Z\ np"'t''; '"''"'"^ '" ''" "''''■ ^2 »>--' 164,780; after 3 day.,, 236,676 
"'^ys, ^I,11G; 8 days, 76,032. 
Br. Prudden then made 
experiments to determine the effect of 
