92 APPLIED BACTERIOLOGY 



mends the use of a 1 per cent, solution of caustic soda, 

 while for the acidification of the mordant he employs a 

 dilute solution of sulphuric acid of such a strength that a 

 given volume is exactly neutralised by the 1 per cent, soda 

 solution. 



The following is the composition of the mordant : Solu- 

 tion of tannin (20 parts tannin + 80 parts' water) ; to 

 10 c.c. of this tannin solution add 5 c.c. of a cold aqueous 

 solution of ferrous sulphate and 1 c.c. of a concentrated 

 solution, either aqueous or alcoholic, of fuchsine. 



The prepared cover-glasses, dried and fixed in the 

 manner already described, are now treated with the mor- 

 dant. The simple mordant, as above, can be used for 

 some species, but in most cases, as already mentioned, it 

 must be rendered alkaline or acid, to an extent which varies 

 with the various organisms. The following are the addi- 

 tions of acid and alkali respectively made to the mordant as 

 recommended by Dr. Lofiler for particular organisms : 



22 drops =1 c.c. 

 Spirillum cholerce Asiaticce 

 „ ruhrum... 

 „ MetchniTcoffi 

 Bacillus pyocyameus 

 Spijrillu/m concenfricum ... 

 Bacilkis mesentericus vul- } 



gatus ... ... ... ) 



Micrococcus agilis ... 

 Typhoid bacillus ... 

 Bacillus suhtilus ... 

 Bacillus cedematis maligni 

 Bacillus of symptomatic ) 



anthrax ... ... ... ) 



The mordant, with the proper amount of acid or alkali 

 added, is run from a pipette on to the cover-glass, and the 

 latter is gently warmed over a flame with constant move- 

 ment until steam just begins to form. On no account 

 should it be allowed to boil, for if bubbles are once formed 



