THEORY OF THE GRAM STAIN 83 
These investigators stated that the Gram negative bacteria could be 
broken up by the sudden release of the pressure when the bacteria 
were in an atmosphere of carbon dioxide while the Gram positive 
bacteria resisted such treatment. The latter, although killed, under- 
went no morphological change. 
Procedure for the Gram Stain. Prepare a smear as outlined above. 
1. Flood with aniline gentian violet and heat gently for five minutes. 
2. Wash in water and immerse in Lugol’s iodine solution for five 
minutes. 
3. Wash in water and place in strong alcohol until most of the dye 
is removed. It may be necessary to repeat this procedure from 2 
if any dye remains. 
4, Wash in water and examine or counterstain if desired. 
5. Counterstain with 10 per cent solution of eosin in water. 
There have been several modifications of the Gram method of 
staining all of which give good results in the hands of those who pro- 
posed them. 
Nicolles Modification of the Gram Stain. This is similar to the 
above except that carbol gentian violet is substituted for the aniline 
gentian violet in the regular Gram’s procedure. Decolorization is 
also accomplished with acetone alcohol (1 part acetone and 2 parts of 
alcohol). 
GRAM POSITIVE BACTERIA GRAM NEGATIVE BACTERIA 
Staphylococcus pyogenes aureus Gonococcus 
Staphylococcus pyogenes albus Micrococcus catarrhalis 
Staphylococcus pyogenes Bacillus typhosus 
Pneumococcus Bacillis coli communis 
Micrococcus tetragenus Bacillus dysenterize 
Bacillus Xerosis Micrococcus melitensis 
Bacillus hoffmanti Pseudomonas pysocyaneus 
Oidium albicans Bacillus pneumonie Fried 
Bacillus tetanus Bacillus proteus 
Bacterium diphtherize Bacillus mallei 
Bacillus zerogenes capsulatus Bacillus influenzee 
Bacillus lepre Koch-Weeks bacillus 
Bacillus anthracis 
STAINING OF CAPSULES 
Muir’s Method. 
I. Mordant. ; 
Mercurie chloride (saturated aq. sol.)........ 2 c.c. 
Tannin (20 per cent aq. sol.)........-..---. 26.6. 
Potassium alum (Sat. aq. sol.).....-.-..---- 5 ¢.€. 
