TESTING DISINFECTANTS AND ANTISEPTICS. 447 



characteristic reactions of the salt after having been 

 immersed in distilled water, which had been repeatedly 

 renewed, for five weeks. 



S He remarks that a similar firm combination between 

 sublimate and cotton will take place after a longer 

 time, but it occurs so slowly that it cannot interfere 

 with disinfection experiments in the same way as he 

 believes the employment of silk to act. 



The most successful attempt at removing all traces 

 of sublimate from the threads or from the prbteid sub- 

 stances in which are located the bacteria whose vitality 

 are to be tested, is that made by Geppert, who subjected 

 them to the action of ammonium sulphide in solution. 

 By this procedure the mercury is converted into in- 

 soluble sulphide and does not now have an inhibiting 

 effect upon the growth of those bacteria that may not 

 have succumbed to its action when in the form of 

 sublimate. 



In the second method of testing disinfectants, men- 

 tioned above — that is, when cultures of bacteria and solu- 

 tions of the disinfectant are mixed, and after a time 

 a drop of the mixture is removed and added to sterile 

 nutrient media, the inhibiting amount of disinfectant 

 can readily be gotten rid of by dilution, that is to say, 

 instead of transporting the drop directly to the fresh 

 medium, add it to 10 or 12 c.c. of sterilized salt solu- 

 tion (0.6-0.7 per cent, of NaCl in distilled water), or 

 distilled water, and after thoroughly shaking add a 

 drop of this to the medium in which the power of 

 development of the bacteria is to be determined 



Another important point to be borne in mind in 

 testing disinfectants is the necessity of so arranging the 

 conditions that each individual organism will be ex- 



