DETERMINATION OF DISINFECTANT PROPERTIES 317 



tissues of the threads. Braatz 1 found the same to hold good 

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

 been immersed in solutions of corrosive sublimate gave the 

 characteristic reactions of the salt after having been im- 

 mersed for five weeks in distilled water which had been 

 repeatedly renewed. Braatz remarks that a similar com- 

 bination between sublimate and cotton will take place after 

 a long time; but it occurs so slowly that it cannot interfere 

 with disinfection-experiments in the same way that silk does. 



The most successful attempt at removing all traces of 

 sublimate from the threads or from the proteid substances 

 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 growth of those bacteria 

 that did not succumb to its action when in the form of the 

 bichloride. 



Another plan that has been successfully used is to dry 

 the bacteria on small particles of sterile glass rod or on 

 sterile glass beads instead of on threads. The advantages 

 of the method are obvious, but the handling, especially the 

 washing, must be done carefully or all the bacteria will be 

 removed from the glass surfaces. 



In the second method of testing disinfectants mentioned 

 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 can readily be got 

 rid of by dilution; that is to say, instead of transferring the 



1 Centralblatt fur Bakteriologie und Parasitenkunde, Bd. vii, No. 1, p. 8. 



