58 



LOGARITHMIC ORDER OF DEATH 



transfer of large numbers to media containing different 

 amounts of disinfectants. The customary means of trans- 

 fer is a loop which holds about 0.01 cc. of liquid. One 

 loopful of a grown culture of bacteria contains be- 

 tween 1 and 10 million bacteria. Only a few of these 

 can adapt themselves to the disinfectant, and only these 

 cells multiply. This does not mean that they would be 

 the last survivors if stronger concentrations were ap- 

 plied. In this way, Borman (1932) obtained strains of 

 Bacterium cjU resistant to salts of Fe, Cu, and Hg, 

 and Header and Feirer (1926) could greatly increase 

 the resistance of several species of bacteria to silver 

 nitrate, mercurochrome, formaldehyde, acriflavin, hexyl 

 resorcinol and phenol. 



The outstanding cases of acquired drug-fastness are 

 met with in chemotherapy where a large number of path- 

 ogenic micro-organisms are exposed to the drugs. 



Protection of Living h y Dead C ells. 

 Lange (1922) was probably the first investigator to dem- 

 onstrate experimentally that the presence of dead bacte- 

 ria retards the death of others. He found that the death 



TABLE 11 



Protection of living cells by dead cells in broth. (From Lange, 

 1922.) 



