78 A MANUAL OF BACTERIOLOGY 



treatment, the sections are placed for three or four 

 minutes in absolute alcohol, transferred to a solution 

 of potassium permanganate (1*5 per cent.) for ten 

 minutes, and decolourised by immersion in con- 

 centrated sulphurous acid. The sections are then 

 dehydrated in absolute alcohol, clarified in oil of 

 cloves and mounted in Canada balsam. (2) The 

 next method is that of Doutrelepont and Schiitz. 

 The sections of syphilitic tissues containing the 

 bacilli are immersed in an aqueous solution of 

 gentian violet (1 per cent.), and are after-stained 

 with an aqueous solution of safranin (1 per cent.). 

 (3) The last method is that of De Giacomi, in which 

 the preparations are immersed in a hot solution of 

 fuchsine containing a drop or two of ferric chloride. 

 They are then decolourised in a concentrated solu- 

 tion of ferric chloride, and after - stained with 

 Bismarck brown or vesuvin. In both the Doutrele- 

 pont- Schiitz and De Giacomi methods, the prepara- 

 tions (after staining) are dehydrated, clarified, and 

 mounted in the usual way. 



Sections of tissues containing the Bacillus leprce 

 are stained by immersion in a solution of fuchsine 

 in aniline-water. They are then decolourised in 

 hydrochloric acid (33 per cent.), and after-stained 

 with methylene blue. Another method is, first to 

 tie a piece of thread around the base of one of the 

 leprosy nodules, so as to cut off the blood supply ; 

 then with a fine-pointed scalpel (see Fig. 5) a small 

 puncture is made, when a clear fluid exudes. From 

 this fluid, cover-glass preparations are made. Cover- 

 glass preparations and sections of leprosy tissues 



