METHODS OF TESTING DISINFECTANTS 615 



applications for disinfecting purposes, and in this con- 

 nection it has been shown by Shaefer ' that it is impos- 

 sible to rid silk threads of tlie cori-osive sublimate ad- 

 hering to them by simple washing, as the sublimate 

 acts as a mordant and forms a firiu union with the tis- 

 sues of the threads. Braatz ^ found the same to hold 

 good for catgut. For example, he found that catgut which 

 had been immersed in solutions of corrosive sublimate 

 ga\e the characteristic reactions of the salt after having 

 been immersed for five weeks in distilled water which 

 had been repeatedly renewed. Braatz remarks that 

 a similar combination between sublimate and cotton 

 will take place after a long time ; but it occurs so 

 slowly that it cannot interfere with disinfection-experi- 

 ments in the same way that silk does. 



The most successful attempt at removing all traces 

 of sublimate from the threads or from the proteid sub- 

 stances in which are located the bacteria whose vitality 

 is to be tested was made by Geppert, who subjected 

 them to the action of ammonium sulphide in solution. 

 By this procedure the mercury is converted into inert, 

 insoluble sulphide, and has no inhibiting effect upon the 

 ffrowth of those bacteria that did not succumb to its 

 action when in the form of the bichloride. 



In the second method of testing disinfectants men- 

 tioned above — that is, when cultures of bacteria and 

 solutions 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 

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



» Shaefer : Berliner klin. Wochenschrift, 1890, No. 3, p. 50. 

 2 Braatz : CentralW»tt fSr Pi^kteriolgie und ParagiteukUBde, Bd- vi}, 

 JiTo. 1, p. 8, 



