METHODS OF STUDYING BACTERIA 49 



Anilin-oil Water. Anilin-oil is shaken up with water and 

 then filtered; the anilin water so obtained is mixed with the 

 dyes, forming the " anilin-water gentian- violet " or anilin- 

 water fuchsin, etc. 



Carbolfuchsin. Carbolic acid or phenol can be used 

 instead of anilin-oil, and forms one of the main ingredients of 

 ZiehPs or Neelsen's solution, used principally in staining 

 Bacillus tuberculosis. Kiihne has a carbol-methylene-blue 

 made similar to the carbolfuchsin. 



Alkaline Stains. Alkalis have the same object as the 

 above agents, namely, to intensify the picture. Potassium 

 hydroxid, ammonium carbonate, and sodium hydroxid are 

 used. 



LofHer's alkaline blue and Koch's weak alkaline blue are 

 made with potassium. 



Heat. Warming or boiling the stains during the process 

 of staining increases their intensity. 



Decolorizing Agents. The object after staining is usu- 

 ally overcolored in some part, and then decolorizing agents are 

 employed. Water is sufficient in many cases; alcohol and 

 strong mineral acids combined 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; pre- 

 vents them from being decolorized, but fades the rest of the 

 picture. Then, by using one of the acid or tissue dyes, a con- 

 trast 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 grams of the powdered dye in a bottle and 

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

 This can be used as the stock bottle. 



