1070 A. F. Vass 
cell sap within the cell, which in turn enables the cell to resist freezin 
at temperatures sufficiently low to freeze the cells containing a weake 
solution. 
SUMMARY 
The increase in the bacteria counts of frozen soils, as determined by 
the agar-plate method, is due to the breaking up of the clumps of bac- 
teria, not to growth and multiplication. 
There seems to be no change in the bacterial flora of the soil due to 
freezing. The bacterial activities are influenced only in so far as the 
physical properties of the soil are affected. 
The concentration of the medium, the length of time of the exposure, 
and the degree of cold, are the three important factors that determine 
the power of resistance of the bacteria to low temperature. 
The protective action due to the concentration of the medium seems 
to be effective only in cases in which the eutectic point of the substances 
in solution is below the temperature of the exposure. When the bac- 
teria were exposed to the temperature of liquid air the concentration of 
the medium had less effect. 
The death of the bacterial cell when exposed to low temperature seems 
to be due to the withdrawal of water from the semi-permeable membrane, 
or outer layer of the cell. 
ACKNOWLEDGMENTS 
The writer takes pleasure in expressing his indebtedness to Dr. J. K. 
Wilson and Dr. Lewis Knudson, of Cornell University, for many help- 
ful suggestions and criticisms in the preparation of this paper. 
