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PRINCIPLES OF BACTERIOLOGY 
Bacterial Classification According to Gram's. Method 
GRAM—POSITIVE 
(Retain the gentian violet) 
Staphylococci 
Streptococci 
Pneumococci 
Bacillus of anthrax 
Bacillus diphtheria 
Bacillus of tetanus 
Bacillus of tuberculosis 
Bacillus aerogenes 
Capsulatus 
(“Gas” bacillus) 
GRAM-NEGATIVE 
(Lose gentian violet, take carbol 
fuchsin and appear red) 
Bacillus typhosus 
Bacillus coli 
Meningococcus 
Gonococcus 
Glanders bacillus 
Bacillus pyocyaneus 
Bacillus of influenza 
Plague bacillus 
Cholera spirillum 
Friedlander *s bacillus 
Paltauf’s Modification ,—This staining fluid retains its 
power for a much longer period, and is prepared as 
follows: 
Four c.c. aniline oil is mixed with 90 c.c. of distilled 
water and 7 c.c. of absolute alcohol. Shake well and 
filter through a moist filter paper until clear, and add 
2 grains of Gruebler’s gentian-violet; allow to stand 24 
hours, filter before use. This will keep at least 6 to 8 
weeks. 
In staining proceed as follows: 
1. Prepare the smear in the usual manner. 
2. Pour the stain and allow to stand three minutes. 
3. Gram’s iodine solution, two minutes. 
4. Absolute alcohol thirty seconds. 
5. Counterstain with carbol fuchsin (ten seconds) 
without washing. 
Many workers have lately recommended the use of 
acetone instead of the absolute alcohol. It is well worth 
trying. 
