C.-E. A. WINSLOW 



77 



this substance wholly unsuitable for the disinfection of feces, or in the interference of 

 organic matter in water with the action of chlorin. Under other conditions more sub- 

 tle reactions are involved, as in the results recently reported by Winslow and Brooke 

 (1927). These observers found that several different types of bacteria die out almost 

 immediately when washed free from culture medium and resuspended in distilled 

 water. Salt and sugar solutions will not check the mortality, so we are not deahng 

 merely with a question of osmosis; but the cells can be protected by the presence of 

 peptone or meat extract, serving as "protective colloids" as indicated in Table VII. 



TABLE VII 

 Viability of B. cereus 



A concentration of .005 per cent peptone or of .003 per cent meat extract will 

 protect the cells; but a concentration of .0005 per cent peptone or of .0003 per cent 

 meat extract fails to do so. 



Finally, we must consider the influence of temperature upon the course of the 

 curve of decreasing numbers of bacteria. Since the processes of death, like those of 

 life, are essentially chemical in nature, it is of course obvious that an increase of tem- 

 perature will favor the lethal process when lethal factors are dominant just as it favors 

 the growth process when growth factors are dominant. The classic work of Houston 



TABLE VIII 



Effect of Temperature on Survival or Typhoid 

 Bacilli in Water (Houston) 



(1911) on the survival of typhoid bacilli in water (illustrated in Table VIII), for ex- 

 ample, seems at first sight puzzling, since we find an organism whose optunum for 

 growth lies at 37° C. dying more rapidly at that temperature than in cooler waters. 

 The explanation lies in the fact that typhoid bacilli in water lack the conditions 

 essential for anabolism; only katabolism can go on, and katabolism is increased by 

 a rise in temperature. 



The effect of high temperature in increasing the eflEiciency of chemical disinfect- 

 ants was noted by Koch (1881) in the earliest studies of disinfection, and was first 



