CHAPTER IV. 

 INFLUENCE OF ELECTRICITY. 



The influence of electricity upon microorganisms is much less than 

 one might perhaps expect, if the electricity as such is considered. A direct 

 electric current passing through a nutrient medium will, of course, cause 

 electrolysis which is usually manifested by the formation of acid on the 

 positive pole and of alkali on the negative pole. The acid and alkali will 

 kill microorganisms, as is discussed in the chapter on chemical influences. 

 In this case, it is not the electricity itself that destroys the bacteria. It is 

 also possible to kill bacterial cultures by passing an alternating current 

 through the medium for some time. No electrolysis takes place in this case, 

 still it is not the direct action of the current that acts upon the organisms, 

 but rather the heat produced by the current passing through a medium of 

 high resistance. If the culture is cooled properly the influence of the cur- 

 rent is insignificant if at all noticeable. Whenever electricity is applied 

 against microorganisms, the effect is considered electrochemical. 



The electrical current is used in a very small way in the purification 

 of sewage. The sewage passes between two iron plates which represent 

 the two poles of a strong current. The electrical sterilization of milk has 

 been patented. Wines are improved by electricity. The sterilization of 

 drinking water by ozone is also an application of electricity, though of 

 course the ozone once formed by the current acts as a chemical com- 

 pound independent of its source. 



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