34 STAINING METHODS 



The following stock solutions of Weigert are recommended: 



No. i. No. 2. 



Gentian violet, 2 grams. Gentian violet, 2 grams. 



Aniline oil, 9 c.c. Distilled water, 100 c.c. 



Alcohol (95%), 33 c.c. 



These stock solutions keep indefinitely. Mix i c.c. of No. i with 9 c.c. of No. 2. 

 Filter. This keeps about two weeks and is the solution to pour on the preparation. 

 It may be kept on from two to five minutes. Some hasten the staining by steaming 

 as for tubercle bacilli. Next wash the preparation with water and flood the cover- 

 glass with Gram's iodine solution. Some bacteriologists simply pour off excess of 

 aniline gentian violet and immediately drop on the iodine solution. It is well to 

 repeat the application of the iodine solution a second time. The iodine solution is left 

 on one minute or until the preparation has a coffee-grounds color. 



Gram's Iodine Solution. 

 Iodine, i gram. 



Potassium iodide, 2 grams. 



Distilled water, 300 c.c. 



After washing off the excess of iodine solution at the tap, drop on 95% alcohol 

 and decolorize until no more violet color streams out. Now wash again and counter- 

 stain either with the dilute Carbol fuchsin or with a saturated aqueous solution of 

 Bismark brown. 



The Gram-positive bacteria are stained a deep violet. 



In staining smears of pus for gonococci or other Gram-negative bacteria it is 

 best to first stain with the gentian-violet solution for two to five minutes. Then 

 wash and examine the preparation mounted in water. The organisms stand out 

 prominently. After noting the presence of the cocci treat the smear with the 

 Gram solution and proceed as in the usual Gram staining technic. 



Stained by Gram's Method. Not Stained by Gram's Method. 



S. pyogenes aureus. Meningococcus. 



S. pyogenes albus. M. catarrhalis. 



S. pyogenes. M. melitensis. 



M. tetragenus. B. typhosus. 



Pneumococcus. B. coli communis. 



Anthrax bacillus. B. dysenteriae (Shiga). 



Tubercle bacillus. Sp. cholerae asiaticae. 



Lepra bacillus. B. pyocyaneus. 



Tetanus bacillus. B. mallei. 



Diphtheria bacillus. B. pneumoniae (Friedlander). 



B. aerogenes capsulatus. B. proteus. 



Oidium albicans. B. of influenza. 



Mycelium of actinomyces. B. of bubonic plague. 



Saccharomyces. B. of chancroid. 



Hofman's bacillus. B. of Koch- Weeks. 



B. xerosis. Gonococcus. 



