

GRAMS METHOD. 29 



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 brown 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 counterstain either with the dilute carbol fuchsin 

 or with a saturated aqueous solution of Bismarck brown. 



The Gram positive bacteria are stained a deep violet-black. 



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) . 



