DESTR UCTION OF BACTERIA B Y CHEMICALS. 155 



Pieces of sterile thread (one inch) were placed 

 in bouillon cultures of anthrax and typhoid bacilli 

 for ten minutes, then removed to Petri dishes, and 

 dried in the incubator for twenty-four hours. These 

 were then placed in serum and bouillon respectively 

 (2.5 c.c.). From each a control was taken. Then 2.5 

 c.c. HgCl 2 ( 1: 1000) and carbolic solution (5 per cent.) 

 was added to either, as shown in A, B, C, and D. 

 From each one thread was taken at varying periods of 

 time and planted in bouillon tubes. The threads from 

 A and B (HgCl 2 solution) were washed in sterile water, 

 then in a solution of ammonium sulphide (25 per cent.), 

 then in sterile water again, then in the bouillon. The 

 threads from the carbolic solution were washed in sterile 

 water before planting. 



Observations: The serum seems to have an inhibi- 

 tory action with the bichloride solution, allowing a 

 growth up to forty-five minutes, while with bouillon 

 the action is much quicker, preventing a growth after 

 an exposure of one minute or over. With the carbolic 

 acid solution the serum seems to have made little or no 

 difference in the results. 



Many substances which are strong disinfectants be- 

 come altered under the conditions in which they are 

 used, so that they lose a portion or all of their germ- 

 icidal properties; thus, quicklime and milk of lime are 

 disinfecting agents only so long as sufficient calcium 

 hydroxide is present. If this is changed by the carbon 

 dioxide of the air into carbonate of lime it becomes 

 harmless. Bichloride of mercury and many other 

 chemicals form compounds with many organic and 

 inorganic substances, which, though still germicidal, 

 are much less so than the original substances. 



