TUBERCLE 63 



Method.— We will suppose that the film has been prepared by- 

 one of the methods described subsequently, allowed to dry, and 

 fixed by heat. 



1. Place the side 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 half a minute or so. 



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

 Apply a drop of balsam, and cover. 



A nother Method. — Filter into a test-tube sufficient carbol fuchsin 

 to flood the film, boil it over the Bunsen or spirit-lamp, and pour 

 it on to the film whilst still boiling. Let it act until it is cool, 

 when the bacilli will be found to be stained, and the process of 

 decolorization may be proceeded with. 



The times which are given above may be considerably shortened 

 in practice, but I do not advise this until considerable skill is 

 acquired. Bacilli are much more easy to recognize if they are 

 deeply stained ; this is the reason for the prolonged staining, 

 which may appear unnecessary to some. The prolonged de- 

 colorization is an advantage, since it insures that the tubercle 

 bacilli shall be the only things left stained red ; if you leave the 

 preparation in the acid for a short time, you are more likely to get 

 crystals of carbol fuchsin, stain retained in deep scratches of the 

 glass, etc., all of which a beginner may easily mistake for bacilli, 

 with disastrous results. The counterstaining with methylene 

 blue may be shortened or omitted altogether, though this is not 

 advisable, as it is then more difficult to focus the film. 



