32 ESSENTIALS OF BACTERIOLOGY. 



Heat, Warming or boiling the stains during the process of 

 staining increases their intensity. 



Decolorizing Agents. The object is usually over-colored in 

 some part, and then decolorizing agents are employed. Water is 

 sufficient for many cases ; alcohol and strong mineral acids com- 

 bined are necessary in some. 



lodin as used in Gram's Method. Belonging to this group, 

 but used more in the sense of a protective, is tincture of'iodin. 

 It picks out certain bacteria, which it coats; prevents them from 

 being decolorized, but allows all else to be faded. Then by 

 using one of the acid or tissue dyes, a contrast color or double 

 staining is obtained. Many of the more important bacteria are 

 not acted upon by the iodin, and it thus becomes a very useful 

 means of diagnosis. 



Formulas of different Staining Solutions. 



I. Saturated Alcoholic Solution. 



Place about 10 grammes of the powdered dye in a bottle and 

 add 40 grammes of alcohol. Shake well and allow to settle. 

 This can be used as the stock bottle. 



II. Weak Solutions. 



Made best by adding about 1 part of number I. or stock solu- 

 tion to 10 of distilled water. This is the ordinary solution in use. 



III.Anilin Oil Water. 



Aniline oil 5 parts. 



Distilled water . . * . .100 parts. M. 

 Shake well and filter. To be made fresh each time. 



IV.Anilin Water Dyes. 



Sat. alcoh. sol. of the dye . . 11 parts. 



Aniline oil water .... 100 parts. 



Abs. alcohol 10 parts. M, 



Can be kept 10 days. 



