490 SEDGWICK AND WINSLOW. — BACILLUS OF TYPHOID FEVER. 
f 
percentactE reduction observed in experiments on the viability of 
TYrilOID BACILLI IN ICE. 
Race A. B. G. D. 
Frozen 15 minutes 59.4 13.8 
'< 30 " G3.7 
" li hours 
« 2 " 73.6 
« 3 " 
" 6 " 77.8 
"12 « 
« 15 " 
"24 '' 
32.2 
ii 
3 days 
7 
a 
4AA 99.5 74.8 
97.0 
38.6 84.4 
98.0 
53.8 82.7 • 99.0 
98.4 99.9 
93.3 99.5 
" 2 weeks 99.8 99.4 99.9 
" 4 ii 
it 8 " 
99.8 
99.8 
99.8 
I 
Conclusions, 
1. Evidentlj we may reaffirm for the bacillus of typhoid fever the first of Prudden's 
■ 
conclusions as to the various pathogenes with which he worked, namely, that many 
bacteria are killed by freezing. After two weeks' exposure to the freezing tempera- 
ture an average of considerably over 99 per cent of the germs perished. Of the 140 
tubes inoculated with Kaces A, B, and C, and frozen for periods of two weeks and over, 
all but nine showed a reduction of over 99 per cent; and of the nine, all but one 
d a reduction of 98 per 
We may safely conclude that less than 1 
per cent of the typhoid germs present in water can survive fourteen days of freezing. 
2. During the first half-hour of freezing a heavy reduction takes place, amount- 
ing, perhaps, to 50 per cent. The tubes exposed for such short times to the un- 
favorable conditions exhibit a remarkable variability among themselves. In the 
same set one tube may show no reduction, while its neighbor is rendered almost 
sterile. Whether these differences are due to the varying physical conditions in 
the individual tubes, or to variations in the biological character of the loopful of 
bacteria used for inoculation, is uncertain. From the general harmony of the 
remits obtained it appears that this factor of variability, whatever it may be, is 
practically eliminated by the averaging of 20 tubes 
tt'"0 
After this brief period of sudden but uncertain reduction, the destruction of the 
germs proceeds pretty regularly as a function of the time. Although the different 
races vary, there is in each race a steadily increased reduction, with slight variations, 
as the t.me of freezing is prolonged. After 14 days, even with the most resistant 
