SEDGWICK AND WINSLOW. — BACILLUS OF TYI'HOID FLYER. I>{ 
the Spree with cholera cultures and froze them, thawing, sampling, and nfnH'zin'' 
the tubes daily. In broth the germs persisted for twcnty-onc dnyg, hut iti livor 
water only for five days, the addition of a little broth to tlie water 
1 
no 
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tlie time to eight days. Fresh intestinal contents of a cholera patient showed 
vibrios after two or three freezings 
From this long series of experiments it is evident that Bterllizntion of rich 
cultures of bacteria cannot always be secured by the nction of even v«'iy «\(iriii,« 
cold. Hence the conclusion was draw^n that the freezin<r of wafer conld not be 
o 
trusted at all to remove its bacterial impurities. There are, however, two objeelionfl 
to this line of reasoning. In the first place, the effect of cold on guriiiH Pii>pond«'d 
in water may differ materially from its action on similar organismf* when in n richly 
nutrient medium. In the second place, even if sterilization docs not result from frcM'X- 
ing in cultures containing millions of bacteria, it is conceivable that ^tieh a lar;r«* 
proportion of the microbes may perish as to render very slender the chance of daiij^tT 
from ice formed under natural conditions. Experiments have shown that entity 
detected germs like B. prodigiosus can pass through a sand fdter when aiiplied to 
the surface In large numbers under certain conditions; yet a sand filler, in prac- 
tice, is regarded as an efficient protection. A quantitative determination of the per- 
centage reduction actually effected by freezing is required before drawing conclunojis 
as to the sanitary significance of ice-supply In relation to the public health. 
D. QUANTITATIVE STUDIES UPON THE DESTRUCTION OF BACTERIA BY 
FREEZING AND OTHER LOW TEMPERATURES. 
The quantitative studies of Frankland «^^ on B. anthracis, of Renk '"'' on river- 
water bacteria, and of Christomonas,^-^) on artificial Ice, have already been mentioned. 
Work on the disappearance of bacteria in the freezing of natural water had, however, 
been undertaken at a much earlier period. Pengra,<«'> In 1884, made an actual 
microscopic count of the organisms present, working with bacteria (species not dated), 
and other micro-organisms from decomposing meat juice, infusion of hay, and stajr- 
nant pools. His freezing was done by the winter's cold, and his figureswere 
obtained by counting the contents of ten drops and taking an average. He found 
^ Macfadyen (Lancet, I, 1000, p. 840) has recentl, exposed cult- of I^ilh.jH^.i^ii;^;^-^ 
nis. Bacillus diphthevi.. Spirillu.n choler. asiatic, Bacillus V^o^ensj^^ ^^^^^^ ,, «,, 
st^i]i7'^*ion 
and without impairing the properties of the organisms in any degree. 5 }„ i.^oth o,nuh\om in fine 
Macfadyen and Rowlan.I (Lancet, Vol. T, 1000, p. 1130) treated ^^^/^^f/Jf;'^;"]^^^ growth wa* tioiired 
quill tubes with liquid air for seven days with the same results, except that a sii^ni > j b 
in some instances- 
