200 LABORATORY EXERCISES IN BACTERIOLOGY. 



Used for general staining, but especially for gonococcus and mycobacterium of 

 diphtheria. This solution is permanent ; the alkali serves as mordant. Filter before 

 use. Contact with film from half to several minutes, warm or cold as required in each 

 case. 



(d) Ehr lick's Aniline-water Solution: 



Aniline oil, 5 



Distilled water, 100 



Shake well the above ingredients in mixture at intervals for five or ten minutes to 

 favor solution of the oil. Filter through a moist filter paper. To each ten cubic 

 centimeters of this "aniline water" add freshly one cubic centimeter of saturated 

 alcoholic solution of gentian violet or fuchsin for use. The aniline water does not keep 

 well and should be renewed in the stock bottle every week or ten days. The mixed 

 stain also keeps poorly and should be made fresh every few days, and filtered before 

 use. These solutions are used as general stains or for special differential purposes in 

 Gram's method; they are useful in demonstration of bacteria in sections of tissues. 



In conjunction with these solutions in Gram's method the following decolorizing 

 solution is employed: 



(e) Gram's Differential Solution: 



Iodine, I 



Potassium Iodide, 2 



Water, 300 



Pulverize potassium iodide in a mortar ; dissolve in water and add iodine, frequently 

 shaking to accomplish solution. Filter. The solution keeps well. 

 (/) Carbol-thionine : 



Thionine, I 



2.5 per cent. aq. sol. carbolic acid, 100 



Used as a general stain; valuable as a stain for bacteria in tissues. Add equal 

 proportions of water for staining. Filter before use. Keeps well. Stain three to 

 five minutes. Decolorize with alcohol. 



(g) Unna's Polychrome Blue: 



Methylene-blue, I 



Potassium carbonate, I 



Water, 100 



This is used in staining bacteria in tissues. Should be ripened for months before 

 use. Permanent. Contact five or more minutes. 

 (h) Acid Alcohol: 



Hydrochloric acid, 3 



Seventy per cent, alcohol, 97 



This is stronger than the acid alcohol used in histologic work. Used as a decoloriz- 

 ing agent. 



(i) Nitric Acid Solution: 



Nitric acid, 30 



Water, 7 



Used as a decolorizing agent for 'Mycobacterium tuberculosis, etc. 



