338 PHYSIOLOGY OF BACTERIA 



are also rather essential. Siipfle and Miiller (1920) showed that 

 with HgCh, it is possible to remove the last traces by physical 

 adsorption. Bacteria were washed once or twice after treatment 

 with HgClo, and then were mixed with freshly heated blood charcoal. 

 This charcoal adsorbs the bacteria, and removes from them the 

 last traces of soluble mercuric salts. If broth is added to this mixture 

 of charcoal and organisms directly, bacteria will grow if alive. By 

 this method, it could be shown that Micrococci were still alive after 

 two hours' treatment with 0.1 % HgClo, and the spores of B. anthracis 

 survived treatment with 1% HgCl2 for forty days, with 2% HgCl2 

 for forty days, with 3% HgCl2 for thirty-eight days, and with 5% 

 HgCl2 for eleven days. These data were confirmed later by Alfred 

 Miiller (1920) who removed the mercury salt from the washed 

 bacteria by ammonium sulfide. Data on the difference of viability 

 of washed and chemically treated bacteria, by Gegenbauer (1921), 

 are given extensively on p. 359: 



As antidotes in disinfection experiments, the following 

 reagents are commonly used : 



Against HgCl2 Ammonium sulfide 



Against Cu salts Ammonium sulfide 



Against chlorine Na2S03 



Against formaldehyde Ammonia 



Against peroxide Permanganate 



Against permanganate Sulfides 



Against phenol, lysol, etc Washing with dilute 



ammonia (no very 

 efficient antidote is 

 known) 



In the chapter on Death by Heat, experiments by Lange (1922) 

 were mentioned demonstrating that the addition of large numbers 

 of dead bacteria protected the living bacteria against heat. The 

 same is true with disinfectants; addition of large numbers of heat- 

 killed cells decreases the toxic effect of a disinfecting solution. 



