1909] STONE—ELECTRICITY AND MICROORGANISMS 369 
whereas these plants, if developed normally and placed under these 
conditions, would suddenly collapse. Our experiments do not furnish 
sufficient data to determine which of these views is correct. The 
maximum stimulation would undoubtedly be different for spores than 
for bacteria existing in the vegetative stage, as it is well known that 
those in the vegetative stage succumb more readily to heat than those 
in the spore form. The effects of electricity on spores can best be 
determined by experiments with pure cultures possessing certain 
characteristics, rather than those of heterogeneous types such as 
characterized the flora of the milk with which we experimented. 
In our experiments with milk and water, where galvanic currents 
were employed, the stimulus was constant, whereas when only one 
shock or a series of shocks was given the organism from a static 
machine the charges soon disappeared, although the effects of 
electrical stimuli of brief duration give rise to decided reactions. 
It should be pointed out that an increase of even twenty fold in the 
number of organisms in a given solution at the outset would make a 
vast difference in the number a few days later, even if the same subse- 
quent rate of increase followed in both the normal and treated cultures. 
The amount of available food supply in a solution, however, is limited, 
and in the end there is often little difference in the number of organ- 
isms present in any treated or untreated series. 
Undoubtedly the use of strong electrical currents is capable of 
destroying bacteria and preventing milk from deteriorating, although 
other methods of electrical treatment would probably prove more 
satisfactory than those which we employed. In some tests made of 
electrically. treated milk we found that souring was delayed. It is 
well to note in passing that there appears to be a difference in the 
effects of the positive and negative charges; for example, if a com- 
parison is made of the averages of the last counts in tables VI to x 
inclusive, it will be found that the milk treated with positive charges 
gave a larger count than that treated with negative charges. he 
number of bacteria shown in the positively charged jars was 135,000,- 
000, while that of the negatively charged was 109,918,164. This is 
what might be expected, since the writer has previously demonstrated 
in a large series of epee. on a aes oe sein that positive 
charges stimulated hit tant tl gative charges. 
