214 BACTEEIOLOGY 



acid is advisable, in order to increase the solubility of picric 

 acid in water. 



In the process of B. Prankel, and in that of Gabbet, 

 the staining and decolorisation are carried on simul- 

 taneously. The former is done with fuchsine in aniline 

 water, from which the preparation is directly transferred 

 into a filtered mixture of 60 parts alcohol, 30 parts water, 

 20 parts nitric acid, and as much methyl blue as will dis- 

 solve with repeated shaking. If aniline water gentian 

 violet has been used for staining, the preparation is 

 transferred to a vesuvine solution, consisting of a filtered 

 mixture of 70 parts alcohol, 30 parts nitric acid, and as 

 much vesuvine as will dissolve. Staining is finished in a 

 short time — one or two minutes — and the preparation is 

 rinsed in water or alcohol rendered feebly acid with acetic 

 acid, and thoroughly dried. 



In Gabbet's modification, the Ziehl-Neelsen carbolic 

 fuchsine is used instead of the aniline water solution, and as 

 the second stain methyl blue in sulphuric acid, consisting 

 of 1 or 2 parts methyl blue to 100 parts of 25 per cent, 

 sulphuric acid. 



Arens pours three drops of absolute alcohol over a 

 crystal of fuchsine about the size of a millet-seed in a watch- 

 glass, so as to obtain a saturated alcoholic solution, which 

 is mixed with 2 or 3 com. chloroform. This causes a tur- 

 bidity of the solution, which begins to clear with separation of 

 the fuchsine in the form of flakes. Cover-glass preparations 

 treated in the usual way are laid in the solution, when clear, 

 for four to six minutes, and, after allowing the chloroform 

 to evaporate, are decolorised in a watch-glass full of 96 

 per cent, alcohol, to which three drops of hydrochloric acid 

 have been added. They are now rinsed in water and 

 examined in the same medium, or finally double-stained 

 with methyl blue. 



