TUBERCULOUS TISSUES 397 



In order to demonstrate the tubercle bacillus in fresh tissue 

 smears may be made and stained like sputum, or sections pre- 

 pared and stained in warm carbol-fuchsin for about ten minutes. 

 For frozen sections the stain may be contained in a watch-glass or 

 small glass capsule, and is warmed until it steams, but not boiled, 

 on a piece of asbestos cardboard or a sand-bath. Paraffin sections 

 should be fixed to the slides with glycerin albumin, and may be 

 stained by flooding with the carbol-fuchsin and warming on 

 asbestos cardboard, or a heated penny, for ten minutes. After 

 staining, the sections are washed in water and are then decolorised 

 in 25 per cent, sulphuric acid. This is a longer process than with 

 sputum, and the sections after being in the acid for a few seconds 

 are washed in water and then returned to tihe acid, and this alter- 

 nate rinsing in acid and in water is repeated until they are nearly 

 colourless when placed in water. It is not necessary to remove 

 the colour absolutely ; a faint pink remaining does not matter. 

 After rinsing in fresh water to remove all the acid, the sections 

 are counter-stained in Loffler's methylene blue for two minutes, 

 rinsed in methylated spirit, passed through absolute alcohol 

 somewhat rapidly to avoid removing too much of the blue, 

 cleared in cedar oil or xylol, and mounted in balsam. The 

 sections may also be counter-stained with hsematoxylin or Bis- 

 marck brown. 



Instead of using the strong acid solution for decolorising, an 

 acid alcohol solution may be used with advantage, or 2 per cent, 

 aqueous hydrochloride of anilin may be employed. 



Gram's method may also be used, but is, of course, not distinc- 

 tive for the tubercle bacillus. 



Sections may also be first stained with Ehrlich's or other hsema- 

 toxylin solution, then stained with warm carbol-fuchsin, washed, 

 treated with 2 per cent, aqueous anilin hydrochloride for a few 

 seconds, decolorised with 75 per cent, alcohol until the red colour 

 is 110 longer apparent (fifteen to thirty minutes), and counter - 

 stained with an aqueous solution of orange. 



When a positive diagnosis is important, a small piece of the 

 tissue may be inserted under the skin of the thigh or abdomen of 

 a guinea-pig. If tuberculous, the animal will show signs of 

 tuberculosis in two or three weeks (see below, ''Urine"). 



Films of pure cultivations of the tubercle bacillus may be 

 stained in warm carbol-fuchsin for two to five minutes, rinsed 



