468 
THE TUBERCLE BACILLUS GROUP 
2. Wash thoroughly with water to remove the excess of stain. 
3. Decolorize with 90 per cent alcohol containing 3 per cent hydro- 
chloric acid until the pink color has practically disappeared. 
4. Wash with water. 
5. Counterstain lightly with Loffler's alkaline methylene blue. 
6. Wash, dry, examine. 
Tubercle bacilli are colored red; non-acid-fast bacteria are colored 
blue. It should be remembered that spores of saprophytic bacilli may 
also be stained red by this method, but they are not likely to be con- 
fused with tubercle bacilli because they are round or oval; tubercle 
bacilli are much longer. 
The decolorization and counterstaining may be accomplished by 
one operation, according to the Friinkel-Gabbett method. ^ The 
preparation of the smear and staining with carbol-fuchsin is carried 
out as above (Steps 1 and 2). Decolorization and coimterstaining are 
accomplished by flooding the preparation with the Frankel-Gabbett 
Fig. 67.— Tubercle bacillus showing branching. X 1800. (Wolbach and Ernst.) 
solution (100 cc. water, 25 cc. sulphuric acid, 50 cc. saturated alco- 
holic solution of methylene blue) for three to five minutes, then wash 
with water, dry and examine. Acid-fast bacteria are stained red, 
all other organisms are blue. 
Much Granules. — Certain graruiles are foimd in old caseous foci 
and occasionally in the pus of cold abscesses which do not contain 
tubercle bacilli demonstrable by the acid-fast stain. INIaterial con- 
taining these granules introduced into guinea-pigs causes a rapidly 
fatal tuberculosis. Much^ states that these granules are living frag- 
ments of tubercle bacilli which develop into the typical bacillus when 
environmental conditions are optimum. They are Gram-positive 
Fninkel: Berl. klin. Wchnschr.. 1884, 21, 193, 214. Gabbett: 
Beitr. z. Klinik d. Tuberkulose, 1907, 8, 85, 357; 1908, 11, 67. 
Lancet, 1887, i, 757. 
