LABORATORY AND TEACHING METHODS 589 



2. Hold it in the bacteriologic forceps which are so constructed that a spring 

 holds the cover-slip firmly, while an enlargement of the wire handle permits the 

 placing of the forceps on the table while the culture ma^terial is obtained. 



3. Place several drops of distilled water on the cover-slip and add a loopful of 

 the organisms secured from the culture media as described in this lesson and from 

 the pure culture in a test-tube as follows: 



4. Remove the cotton plug by the third and fourth fingers of the left hand. 



5. Hold the open test-tube between the thumb and forefinger of the left hand. 



6. By means of a previously flamed platinum needle remove a little of the 

 culture from the surface of the culture media. 



'/. Replace the cotton plug. 



8. Add the culture material to the drop of distilled water on the cover-slip 

 and distribute this material by stirring. 



9. Evaporate the water on the cover-slip to dryness by holding it some distance 

 above the Bunsen flame and slowly enough to prevent convection circles being formed 

 by the material affixed to the cover. 



10. Pass the cover-glass three times rapidly through the Bunsen flame. 



11. Apply the stain, which should remain long enough to stain the objects. 

 The stains to be used are described in detail below. 



12. Wash off the stain with distilled water either from a wash bottle, or from 

 a bottle suspended some distance above the laboratory table. 



13. Dry between filter paper. 



14. Apply a drop of balsam, turn the cover-slip over and drop it into the center 

 of a glass slide previously provided and cleaned for the purpose. 



Stains. — One of the most useful bacteriologic stains is: 

 Ziehl's Carbol Fuchsin, prepared as follows: 



Fuchsin (basic) i 



Absolute alcohol 10 



Carbolic acid (5 per cent, solution in water) 100 



The fuchsin should be dissolved first in the alcohol and then the two fluids 

 mi.xed. 



Loeffler's Alkaline Melhylcne Blue. — ■ 



Alcoholic solution of methj-lene blue (saturated) 3c 



Caustic potash i \ 100 



Distilled water 10,000 / 



This fluid retains its valuable properties for a considerable time and is an 

 excellent stain. 



Ehrlich's AniUn-watcr Gentian Violet. 



Alcoholic solution of gentian violet (saturated) 5 



Anilin water 100 



This should be used as soon as prepared. It does not keep well. 



