TUBERCLE. 73 



5. Methylene blue. (Saturated watery solution or 

 LofHer's blue). 



6. A metal (iron or copper) plate. The exact dimen- 

 sions do not matter, but 8 x 4 x % in. is a convenient 

 size. It should be mounted upon a tripod. This slab 

 is not absolutely necessary, but it is a very great advan- 

 tage. 



Method. We will suppose that the film has been 

 prepared by one of the methods described subsequently 

 and fixed by heat. 



1. Place it upon the metal plate and heat the latter 

 by the flame. Flood the slide with carbol-fuchsin and 

 let the heat continue until the stain steams, but do not 

 allow it to dry up ; let this go on for from three to five 

 minutes. If the stain shows signs of .drying up add a 

 little more ; if it begins to boil slide it along the plate 

 away from the flame, or remove the latter for a short 

 time. 



If you have no metal plate it is possible to hold the 

 slide with a pair of forceps, but in this case the film is 

 most conveniently made on a cover-glass. 



Remember not to let the stain dry up. 



2. Remove the slide from the plate with the forceps 

 and wash it under the tap or in a bowl of water. 



3. Put it into the bottle containing the dilute acid. 

 After three or four minutes withdraw it and again wash. 

 If much pink colour comes back re-insert it in the acid 

 for a short time and again wash. The process must be 

 repeated until the film only shows a slight pink tinge. 



4. Now apply the methylene blue for a minute or so. 



5. Wash, dry with blotting paper and then by gentle 

 heat. Apply a drop of balsam and cover. 



