SEDGWICK AND WINSLOW. — BACILLUS OF TYPIIOID FEVER. js; 
III. EXPERIMENTS BY THE AUTHORS ON THE EFFECT OF C('l.I) 
UPON THE BACILLI OF TYPHOID FEVER. 
A. EXrERIMENTS ON THE PERCEXTAGE REDUCTION OF TYrilOII) FHVKK 
BACILLI EFFECTED BY FREEZING FOR DIFFERENT rERIODS OF TIME. 
Methods Employed. 
The following investigation was undertaken in. order to so extend and amplify 
the work of Prudden as to obtain some idea of the average fatality occurring auiuiig 
typhoid bacilli in ice, and of the special conditions which affect such fatality. Pure 
cultures alone were used, as it is obvious that figures, to ho of much value, must be 
determined separately for each specific germ. Great pains were taken to prc.<orvo, 
as far as possible, the vigor of the culture used, and new cultures from recent 
post-mortem examinations were obtained at intervals during the work. Finally, a 
large number of determinations were made for each set of conditions, in order tn 
obtain average results free from the errors which may beset any individual cas**. 
Our experiments on the percentage reduction effected by freezing were carried 
on by freezing small tubes of infected water, as only in this way can the con- 
ditions of the experiment be rigidly controlled. Ordinary testrtubes, containing about 
10 cubic centimeters of sterilized tap water, were inoculated from a two or three 
day bouillon culture, and duplicate samples were at once planted. The ten tubes 
of the set under experiment were then placed in a double-walled tin vessel in 
which they were to be frozen. The inner vessel was a cylinder about 8 inches 
deep, nearly filled with a mixture of equal parts of glycerine and 95 }>cr cent 
alcohol; in this solution the tubes were immersed, being supported by a di.sc per- 
forated with holes to receive them. The solution served to make the lowermg of 
temperature equal and gradual, and also acted as an antiseptic when the t"^^^« ^''^J;^^ 
which sometimes happened when they contained too much water, or 
temperature went down too rapidly. In the outer vessel, which was jacketc^^ w.t^i 
felt, was placed cracked ice which reduced the temperature of the glyccrme-a - - 
mixture to about 10-15° C. in from an hour to an hour and a half lUe ice 
was then replaced by a mixture of ice and salt which completed the freezmg 
yrlion the 
If-^oliol 
