THE DESTRUCTION OF BACTERIA BY CHEMICALS 



109 



The following table gives the results and methods used in an actual 

 experiment to test the effect of blood serum upon the disinfecting action 

 of bichloride of mercury and carbolic acid upon bacteria: 



TEST FOR THE DIFFERENCE OF EFFECT OF BICHLORIDE OF MERCURY AND 

 CARBOLIC ACID SOLUTIONS ON ANTHRAX AND TYPHOID BACILLI IN SERUM 

 AND BOUILLON. 



Indicates total destruction of bacteria with no growth in media. 

 + Indicates lack of destruction of bacteria with growth in media. 



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.) to remove the HgCl 2 , 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 inhibitory action with 

 the bichloride solution, allowing a growth up to forty-five minutes, while 

 with the bouillon the action is much quicker, preventing a growth after 

 an exposure of one minute or over. With the carbolic acid solution the 

 serum made less difference in the results. 



Many substances which are strong disinfectants become altered 

 under the conditions in which they are used, so that they lose a portion 

 or all of their germicidal properties; thus, quicklime and milk of lime 

 act by means of their alkali and 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. 



