26 LABORATORY BACTERIOLOGY 



Formula for Gram's solution (Lugol's) : — 



Iodine i gram. 



Potassium iodide 2 grams. 



Distilled water . 300 c.c. 



Certain bacteria stain deeply and retain the coloring matter 

 when treated by this method, while others are decolorized by 

 the alcohol. On this account some investigators consider it an 

 important aid in the differentiation of certain bacteria. 



