138 DISINFECTION— STERILIZATION— DISINFECTANTS 



p. 114) is a laboratory procedure to obtain cell constituents. 

 It is not a practical method of disinfection, however. 



6. Electricity. — Electricity, though not in itself injurious 

 to bacteria, is used as an indirect means for destroying bac- 

 teria in a practical way. This is done by electrical produc- 

 tion of some substance which is destructive to bacteria as 

 in ozone water purification (Petrograd, Florence, and else- 



FiG. 100.— Effect of light on bacteria. X 7/10. This plate was treated 

 exactly as the plate in Fig. 99, except that the letter is L, and that it was 

 exposed inside the window and wire screen. The window was plate glass. 

 It is evident that few of the bacteria were killed, since the letter L is barely 

 outlined. The exposure was at the same time as the plate in Fig. 99. (Stu- 

 dent preparation.) 



where), or the use of ultra-violet rays for the same purpose 

 (Marseilles, Paris) and for treatment of certain disease con- 

 ditions. Electricity might be used as a source of heat for 

 disinfecting purposes should its cheapness justify it. It has 

 also been used in the preservation of meats to hasten the 

 penetration of the salt and thus reduce the time of pickling. 

 Electrolyzed sea water has been tried as a means of flushing 



