1909] STONE—ELECTRICITY AND MICROORGANISMS 363 
experiments made by us on the higher plants has shown that this 
current strength is very close to the optimum, and in all probability 
the optimum current strength for bacteria would differ little if any 
from that of the higher plants. We have employed this method of 
electrically stimulating bacteria and have enormously increased the 
number of organisms in cultures containing the legume Pseudomonas, 
which is used in inoculating soils. 
Some experiments were also carried on at the same time relative 
to the influence which electrical stimulation might have upon nitrogen 
fixation, but the results are incomplete and will not be given in this 
paper. 
The influence of electricity on bacteria in milk 
The purpose of our experiments in this series was similar to that 
in the experiments made with water; that is, to determine the effect 
of electrical stimulation on the microorganisms in milk. Our object, 
however, was not only to ascertain the effects of optimum currents, or 
at least those approximating the optimum on the bacteria of milk, 
but to observe the effects of strong electrical charges. 
Milk constitutes an excellent medium for the multiplication of 
bacteria and is well suited in some respects to experiments of this 
Mature. The experiments given in tables IV and V were conducted 
Similarly to the ones shown in the preceding series; that is, the bacteria 
Were stimulated by galvanic currents and the same size culture jars 
were used (jig. 1). About 1.5 pints of unsterilized milk were placed 
in each jar and a milliammeter indicated the strength of current to 
be approximately o.3 milliampere in the electrically treated samples. 
The jars were provided with cotton plugs and were sterilized before 
being filled with milk. The usual dilution methods were followed 
and the standard agar-agar was used for plate cultures. In practically 
all instances the counts are averages of three and four plates. Plat- 
ings were made of the milk at the beginning of the experiment, that 
is, before being electrically stimulated; therefore these counts, which 
are averages, answer for both the treated and untreated cultures. 
The results of electrical stimulation on bacteria in milk are shown 
In the experiments given in tables IV and V, but since milk sours 
and curdles badly in a few days it was necessary to limit the duration 
