74 THE BACTERIA UNDER PHYSICAL AGENCIES. 



solution) on a pad of glass wool at 37 C., and then dipping the 

 pad into mercury through which a constant galvanic current was 

 being passed. In this case the bacteria were killed; but the 

 method of experimenting is not free from objection, since the 

 dried constituents of the medium were present along with the 

 bacteria, and might retain moisture and form decomposition pro- 

 ducts noxious to the latter. 



These injurious secondary influences can only be perfectly 

 excluded when the electric current is prevented from coming into 

 contact with the nutrient medium, a condition first attained in the 

 experimental method selected by SPILKER (I.) and GOTTSTEIN (I.). 

 The glass flask containing the bacterial culture was enveloped by 

 a coil of the line wire, and an induction current then passed. 

 Micrococcus prodigiosus washed by sedimentation in pure water or 

 in water qualified by nutrient gelatin was killed when the liquid 

 (250 c.c. in volume) was exposed for twenty-four hours to the in- 

 fluence of a current of 2.5 amperes and 1.25 volts. Other species 

 of bacteria offered greater resistance : as, for example, those occur- 

 ring in milk, which are gifted with the power of forming endo- 

 spores capable of retaining their vitality under very adverse condi- 

 tions. For this reason the above-named observers never succeeded 

 in thoroughly freeing milk from living germs by electrical treat- 

 ment, although the number of the germs could be reduced thereby. 



D'ARSONVAL and CHARRIN (I.) studied the influence of the 

 electric current on the blue pigment of the Bacillus pyocyaneus 

 found in the pus discharged by wounds. They placed a culture 

 of this organism in the cavity of a solenoid traversed by a current 

 of 10,000 volts ; an exposure of twenty minutes sufficed to destroy 

 the chromogenic power of the bacilli almost completely. A similar 

 decrease of virulence was observed by S. KRUGER (I.) in the case of 

 a few pathogenic bacteria ; and, finally, reference may be made to 

 a research of this nature performed by H. FRIEDENTHAL (I.). 



At present, owing to the high cost entailed, the utilisation of 

 the anti-bacterial powers of electricity in the food-stuff industries 

 is out of the question. Use has, however, been made of these 

 powers in the fermentation industries, although the primary object 

 of the process is not the destruction of germs, but the chemical 

 changes effected by the electric current. Alcoholic beverages 

 (wine, cognac) are artificially matured, and a slight esterification, 

 and consequent mellowing of flavour, produced by allowing the 

 liquors to flow slowly through an electrical field. A more detailed 

 consideration of this process is, however, beyond the scope of the 

 present work. A review of the methods proposed for this purpose 

 and the experiments made therewith is given by A. SCHROHE (I.). 



D'Arsonval and Dubois have made a few observations on the 

 influence which magnetism (so closely allied to electricity) has 

 on bacteria, but unfortunately these have not been followed up 

 any further. 



