128 BACTERIOLOGICAL ANALYSIS LESSON 



It will be found that mercuric iodide is more germi- 

 cidal than mercuric chloride, and that absolute 

 alcohol and Condy's fluid have but little or no 

 effect on the anthrax spores. 



(&) Test the following solutions of carbolic acid : 



in alcohol, 1 : 20 ; 

 in glycerine, 1:20; 

 in water, 1 : 20 ; 



in water, 1:25, with 2 to 4 per cent of hydro- 

 chloric acid. 



Proceed exactly as above, allowing the threads to 

 soak in the solutions for at least four hours. 



It will be found that a solution of carbolic acid in 

 weak hydrochloric acid is very efficacious, while 

 solutions in glycerine and alcohol are of little use. 



(c) Mercuric chloride 



(1) Keep anthrax threads in this solution for two to 

 four hours. 



(2) Now wash some of them in sterile water ; wash the 

 others first in a solution of ammonium sulphide and then 

 in water. 



(3) Fix the threads on an agar-agar plate, and place the 

 latter in an incubator at 38 '5 C. 



Examine the threads from day to day. 



Growth will be observed around the threads washed 

 with ammonium sulphide, while around the others 

 there is either no growth at all or very limited 

 growth 



