184 BACTERIOLOGY. 



Alcohol (80 per cent.) 98 c.c. 



Nitric acid 9 



until all visible blue color has disappeared. It is then 

 rinsed in water and dipped for from 3 to 5 seconds in 



Saturated alcoholic solution of eosin 10 c.c. 



Water 90 c.c. 



after which it is again rinsed in water and finally 

 mounted for examination. If the decolorization in 

 the acid alcohol be not carried too far, the preparation 

 will show the spores stained blue and the bodies of the 

 cells to have taken on the rose color characteristic of eosin. 

 By another process the cover-slip is floated, bacteria 

 down, upon the surface of freshly prepared Koch- 

 Ehrlich solution of fuchsin contained in a watch-crys- 

 tal. This is then held by its edge with forceps about 

 2 cm. above a very small flame of a Bunsen burner, 

 care being taken that the flame touches only the centre 

 of the bottom of the crystal. After a few seconds the 

 crystal is gradually elevated until it is about 6 to 8 cm. 

 above the flame ; then it is slowly moved down to the 

 flame again, and this up-and-down movement is con- 

 tinued until the staining-fluid begins to boil. As soon 

 as a few bubbles have been given off it is held aside 

 for a minute or two, when the heating is repeated. 

 When the boiling begins the crystal is again held aside 

 for a minute or two. The crystal is heated in this way 

 five or six times. When the fluid has stood for about five 

 minutes after the last boiling the preparation is trans- 

 ferred, without washing in water, to a second watch- 

 crystal containing the following decolorizing solution : 



Absolute alcohol 100 c.c. 



Hydrochloric acid 3 c.c. 



