58 THE BACTERIA UNDER PHYSICAL AGENCIES 



Micrococcus jm-odigiosus washed by sedimentation in pure water or in water 

 qualified by nutrient gelatin was killed when the liquid (2500.0. in volume) 

 was exposed for twenty-four hours to the influence of a current of 2.5 amperes 

 and 1.25 volts. Other species of bacteria offered greater resistance: as, for 

 example, those occurring in milk, which are gifted with the power of forming 

 endospores capable of retaining their vitality under very adverse conditions. 

 For this reason the above-named observers never succeeded in thoroughly freeing 

 milk from living germs by electrical treatment, 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. KRVGER (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. 



61. Influence of Temperature. 



The ordinary conceptions with regard to the favourable or prejudicial influence 

 of certain temperatures on organic life cannot be applied, without modification, 

 to bacteria, and this is particularly the case with respect to the effects of cold. 



J. FORSTER (I.) was the first to fiud (in 1887) that there are species of bacteria 

 which at a temperature of o C. are not only alive, but actually reproductive. 

 This report is based on a luminous bacterium isolated by him from the surface 

 of a phosphorescent salt-water fish. B. FISCHER (I ) next discovered fourteen 

 other species, some in sea-wator, others in the soil, all of which were very 

 reproductive at o 0. Returning to the subject, J. FORSTER (II.) then examined 

 more narrowly the natural habitat of similiar bacteria, and found that 



Commercial milk contained up to 1000 per i c.c. 

 Dr.iin water contained up to 2000 per I c.c. 

 Garden soil contained up to 140,000 per I gram. 

 Street mud an innumerable quantity per i gram. 



MIQUEL (I)., by keeping a sample of sea-water at o C., found that an initial 

 number of 150 germs per i c.c. increased to 520 in twenty-four hours and to 

 1750 in four days. These facts indicate that glacier water, haiJ, and snow may 

 also contain bacteria. Quantitative researches on this point have been carried 

 out by L. SCHMELCK (I.), O. BUJWID (I.), W. FOUTIN (I.), TH. JANOWSKI (I.), 

 and especially P. MIQUEL (I.). 



