a 
1909] STONE—ELECTRICITY AND MICROORGANISMS 371 
nearly identical as it was possible to make them, the soil being exposed 
to the air continually. The cultures were plated in agar-agar and the 
usual dilution methods were followed. 
TABLE XI 
Showing the results of electrical stimulation (galvanic currents) on the bacteria in 
soil. 
NUMBER OF BACTERIA IN 1g™ 
DATE OF SAMPLING 
Normal Electrical 
: July 13 33,470,000 37,930,000 
Experiment I....... July 29 28,777,000 32,863,000 
August Ir 19,294,000 35,000,000 
. September 14 38,047,000 37,670,000 
Experiment II....... i October 16 18,720,000 26,384,000 
Two experiments are given in this table, the first date of sampling 
corresponding with the beginning of the experiment. No attempt 
was made to disturb or cultivate the soil in the boxes, and the surface 
became more or less compacted by constant watering, which no doubt 
accounts for the general falling-off in the number of bacteria in all 
cases. It will be noted that no increase is shown in the number of 
bacteria in either the treated or untreated soils, although the extent 
of falling-off in both experiments is less in the electrically treated 
boxes. Similar experiments were made with soil in the same boxes 
with static electricity. The boxes in this case were arranged as fol- 
lows: one box was left normal as before, and the other had 12 wires 
extending into the soil leading to a metal bulb which was given 100 
Sparks from a Tépler-Holtz machine once a week. In this case the 
first samples were taken a few days after electrical treatment, other- 
wise similar methods were employed as in the preceding series. 
In this case there did not occur the same falling-off or decrease 
in the number of the organisms in either the treated or untreated cul- 
tures at the time of the subsequent platings, as in the preceding series. 
On the other hand, the treated soil in this experiment showed a con- 
tinual increase in the number of bacteria present at the time of the 
different platings. This was apparently due to the frequent stirring 
or cultivation of the soil. The number of organisms, however, showed 
only a slight increase at the time of the first platings, whereas the 
