DRYING 105 



"5. The continuous current alone, by means of DuBois-Ray- 

 mond's method of non-polarizing electrodes and exclusion of chemi- 

 cal effects by ions in Kruger's sense, is neither bactericidal not anti- 

 septic. The apparent antiseptic effect on suspensions of bacteria 

 is due to electric osmose. The continuous electric current has no 

 bactericidal nor antiseptic properties, but can destroy bacteria 

 only by its physical effects heat or chemical effects the produc- 

 tion of bactericidal substances by electrolysis. 



"6. A magnetic field, either with a helix of wire or between the 

 poles of a powerful electromagnet has no antiseptic or bactericidal 

 effects whatever. 



"7. Alternating currents of a three-inch Ruhmkorff coil passed 

 through bouillon cultures for ten hours favor growth and pigment 

 production. 



"8. High frequency, high potential currents Tesla currents- 

 have neither antiseptic nor bactericidal properties when passed 

 around a bacterial suspension within a solenoid. When exposed to 

 the brush discharges, ozone is produced and kills the bacteria." 



The electric current is used in the purification of sewage, the 

 sterilization of milk, the improvement of wines, and the purification 

 of water. In all of these cases the effect is due to a chemical pro- 

 duced by the electricity. The purification of water is due to the 

 ozone formed, which in turn acts as an oxidizing agent toward the 

 bacteria. Although expensive, it is one of the most effective means 

 of rendering water safe. 



Drying. The results which have been reported on the influence 

 of drying upon bacteria are exceedingly divergent. This is due 

 mainly to the fact that the influence exerted by drying varies with 

 a number of factors, chief among which are : 



1. Light. Bacteria that are killed in a few minutes in direct 

 sunlight may live for weeks in a dark place or even in diffused 

 light. 



2. Oxygen. Pauli and his associates consider death through 

 drying as due to an oxidation process. They found that bacteria 

 die much faster in pure oxygen than in air. Moreover, they found 

 that the number of bacteria dying in unit time under constant con- 

 ditions is proportional to the number surviving, therefore, com- 

 parable with the simplest chemical processes, the monomolecular 

 reactions. 



3. Thickness and Nature of the Medium in Which They Are 

 Dried. In a dried medium bacteria usually die quickly but may 

 survive long in sputum or feces. Moreover, bacteria suspended in 

 the extract from a rich clay loam before being subjected to desicca- 

 tion in sand live longer than if subjected to desiccation after sus- 

 pensions in a physiological salt solution. 



4. The More Complete the Drying the Shorter the Life. Alternate 

 drying and moistening is unfavorable. 



