Bacteria in Frozen Soil. qalal 
depth of 20 em. by means of a 2.5-inch auger, except during the time 
that the soil was frozen, when it became necessary to substitute a mat- 
tock or grub hoe for the auger. The samples were collected on a sterile 
mixing cloth and then placed in sterile glass jars and taken to the 
laboratory and innoculations performed as quickly as possible. * * #* 
In this work it was deemed inadvisable to permit such a multiplication 
of organisms to occur in the sample as would undoubtedly take place if 
they were allowed to stand long enough to thaw out completely. Con- 
sequently the frozen samples employed here were thoroughly commin- 
uted by means of a sterile spatula, carefully mixed, and then subsam- 
pled for innoculations. The maximum time required to prepare the 
sample in this way was ten minutes. * * * 100 gram quantities of 
the soil prepared * * * were shaken for five minutes with 200 cc. 
portions of sterile distilled water. Lipman and Brown ‘synthetic agar’ 
was used and counts made after three days’ incubation at 22° C. Re- 
sults are averages of two dilutions which agreed closely in every case.” 
The author summarizes the results given in Figure 2 as follows: 
1. “By means of the ‘modified synthetic’ agar plate method, bacteria 
are shown to be present in large numbers in a typical Wisconsin drift 
soil when it is completely frozen and the temperature is below zero 
degrees Centigrade; furthermore, increases and decreases in numbers 
of organisms occur during this period and larger numbers are found 
after the soil has been frozen for a considerable period than before it 
begins to freeze.” 
2. “During the fall season, the number of bacteria present in the 
soil diminishes gradually with the lowering of the temperature.” 
The methods of sampling and the technic employed in getting the 
results reported in the above mentioned publications were so different 
from those adopted in this laboratory, after much testing, that the 
results of data on bacterial counts obtained on different dates from 
samples of a silt loam variously cover cropped are given in Figure 3. 
The technic of sampling, diluting and plating is that previously de- 
scribed.’ 
It is to be noted that the numbers of bacteria found in the soil when 
the temperature was 32° or lower were greater than those found at 
other times during the winter. The soil thermometers were at a depth 
ef nine inches and the samples were drawn to this depth. It had been 
found impracticable to take samples when the ground was solidly frozen, 
and samples were taken (on the dates) starred just as the soil had 
thawed enough so that the samplers* could be used. The question thus 
2 Noyes, H. A., Voigt, Edwin, in Proceedings Indiana Academy of Science, 1916, 
pp. 272-301. 
3 Noyes, H. A., in Journ. Amer. Soe. Agron. Vol. 7, No. 5 (1915). 
