Staining 153 



albuminous and gelatinous materials as possible. The 

 cover-glass must be cleaned most painstakingly; too much 

 heating in fixing must be avoided. After using and washing 

 off the mordant, the preparation should be dried before the 

 application of the anilin-water-fuchsin solution. 



Pitfield's Method. Pitfield * has devised a simple and 

 excellent method of staining flagella, a single solution at 

 once mordant and stain being employed. It is made in 

 two parts, which are filtered and mixed: 



(A)- 



Saturated aqueous solution of alum 10 c.c. 



Saturated alcoholic solution of gentian violet . . 1 **' 



(B)- 



Tannic acid 1 gr. 



Distilled water 10 c.c. 



The solutions should be made with cold water, and im- 

 mediately after mixing the stain is ready for use. The 

 cover-slip is carefully cleaned, the grease being burned off 

 in a flame. After it has cooled, the bacteria are spread 

 upon it, well diluted with water. After drying thoroughly 

 in the air, "the stain is gradually poured on and by gentle 

 heating brought almost to a boil; the slip covered with the 

 hot stain is laid aside for a minute, then washed in water 

 and mounted. 



Van Ermengem's Method. Van Ermengem f has devised 

 a somewhat complicated method of staining flagella, which 

 has given great satisfaction. Three solutions, which he 

 describes as the bain fixateur, bain sensibilisateur, and bain 

 reducteur et reinforfateur, are to be used as follows: 



i. Bain fixateur: 



2 per cent, solution of osmic acid 1 part 



10-25 per cent, solution of tannin 2 parts 



The cover-glasses, which are very thinly spread, dried, 

 and fixed, are placed in this bath for one hour at the room 

 temperature, warmed until steam arises, and then kept hot 

 for five minutes. They are next washed with distilled 



*"Med. News," Sept. 7, 1895. 



f'Travaux du Lab. d'hygiene et des bact. de Gand.," t, I, p. 3. 

 Abstracted in the "Centralbl. f. Bakt. u. Parasitenk.," 1894, Bd. xv, 

 p. 969. 



