482 SEDGWICK AND WINSLOW. — BACILLUS OF TYPHOID FEVER. 
ture of —2V C. was fatal. Von Babes'^' succeeded in keeping a series of agar cultures 
of the vibrio alive, though exposed to the cold of a Berlin winter (1884-85) ranging 
as low as —14* C. In the year 1893 no less than eight papers were published dealing 
with the relation of the cholera germ to cold. Schruff ^'°^ found that a broth culture 
made from fresh choleraic faces was not sterilized by eight months' exposure to the 
winter's cold ranging as low as— 12.5° C. Finkelnburg^^*^ noted that cultures of an old 
laboratory race were killed out in ten days, while c\dtures of fresher races were not. 
Karschinski ^"^ stated that a. cholera culture with which he worked was sterilized in 
four days by an average cold of —12.7° C. with a minimum of —17.6° C. Renk ^"^ froze 
the germs in sterilized river water at —5° C. to —T C. and kept the flasks at that tem- 
perature, removing one each day for examination. Growth resulting from the melted 
ice was tested by cover-glass examination and by the Indol reaction. After five 
days' uninterrupted freezing the cholera germs disappeared, but when the period was 
broken by the melting of the contents of a flask for analysis and its re-freezIng, a little 
longer period was necessary. When unsterilized river water was inoculated and frozen, 
tlie bacteria present fell off from 1,483,000 per centimeter to 62,445 in twenty-four 
hours, and to 4480 after three days. The cholera germs in this case could not be de- 
tected after seventy-two hours, and in one case not after thirty-nine hours. Uifelmann ^'*^ 
found that cholera germs died out in five days at -15.5° C. and in three days at -24.8" C. 
Wnukow,^^*^^ on the other hand, stated that gelatine stick cultures of the same micro- 
organism were subjected for forty days to an outdoor temperature between -1° C. and 
32° C. without aterili/nt.inn 
without sterilization. Double thawing and freezing also failed to destroy their 
power of growth. Montefusco ^'«> tested the pathogenicity of chilled cholera cultures for 
guinea pigs, and recorded that a temperature of -10° to -15° C. entirely destroyed their 
virulence in half an hour, while a temperature between 0° and -5° only weakened it. 
Cultivation at 37.5° soon restored the powers of the germs, but in the chilled and 
attenuated condition they produced a state of immunity in the animals injected. 
Abel^) also mentions experiments in which cholera vibrios frozen in bouillon died out 
completely in from three to eight days. Kasansky,'"«) in 1894, found that cholera 
cultures withstood for four months the winter's cold at Kasan, where the temperature 
fell to -31.8° C. One culture gave growth after twenty days of freezing. Some 
were thawed and refrozen as many as twelve times. After longer exposure, for five 
months, the cultures gave no growth. Kasansky demonstrated nearly as great a 
resistance to cold in the case of the vibrios of Finkler-Prior, Miller, Deneke, and 
Metschnikoff. Finally, some light was thrown on the discordant results of previous 
observer, by the work of Weiss,^^ who inoculated tubes of broth and water from 
