INFLUENCE OF PHYSICAL AGENTS. 159 



estimating the power of this agent to destroy the vitality of bacteria. 

 The current was passed through a spiral wire which was wrapped 

 around a test tube of glass, containing the microorganism to be tested, 

 suspended in distilled water. In a first experiment Bacillus prodigi- 

 osus, suspended in sterilized distilled water and contained in test 

 tubes having a capacity of two hundred and fifty cubic centimetres, 

 was subjected to a current having an energy of 2.5 amperes X 1.25 

 volts for twenty-four hours. The temperature did not go above 

 30 C. No development occurred when the microorganism tested 

 was subsequently planted in nutrient gelatin. Further experiments 

 gave a similar result. It was found that stronger currents were 

 effective in shorter time ; but in no case was sterilization effected in 

 less than an hour. 



Pressure. D'Arsonval and Charrin (1894) submitted a culture 

 of Bacillus pyocyaneus to a pressure of fifty atmospheres, under car- 

 bon dioxide. At the end of four hours cultures could still be ob- 

 tained, but the bacillus had lost its power of pigment production. A 

 few colonies were developed after six hours' exposure to this pressure ; 

 but after twenty-four hours no development occurred. 



Agitation. Meltzer (1894) has shown that the vitality of bacteria 

 is destroyed by protracted and violent shaking, which causes a molec- 

 ular disintegration of the cells. 



