122 ESSENTIALS OF BACTERIOLOGY 



Colonies. On agar or glycerin-agar there appear in two to 

 three days small white glistening drops, which under microscope 

 seem as round granular masses with an even periphery. 



Stroke Cultures. On glycerin-agar and blood-serum small 

 transparent drops of whitish or grayish color, which soon 

 coalesce to form a broad band. 



Potato. An amber-colored, honey-like growth which grad- 

 ually turns red, then brown, and greenish-brown around it. 

 Weakly acid potatoes are a good medium and give the most 

 typical growth. 



Staining. Since the bacillus is very easily decolorized, some 

 special methods have been recommended. 



Loffler's (jor cover-glass preparations): 



1. Alkaline methylene-blue (Loffler's), five minutes. 



2. Acetic acid with a few drops of tropaeolin, one second. 



3. Washed in water. 



For Sections. Instead of tropaeolin acetic acid, the following 

 mixture is used: 



Oxalic acid (5 per cent.) i drop. 



Concentrated sulphuric acid 2 drops. 



Distilled water 2 drams. M. 



The sections are kept in this five seconds. 

 Kuhne's method (cover-glass): 



1. Warm carbol-blue, two minutes. 



2. Decolorized in weak solution of muriatic acid (10 : 500). 



3. Washed in water. 

 Sections of tissue: 



1. Carbol-blue, one-half hour. 



2. Decolorized in J per cent, muriatic acid. 



3. Washed in distilled water. 



4. Dehydrated in alcohol one second. 



5. Anilin-oil with 6 drops of turpentine, five minutes. 



6. Turpentine, xylol, Canada balsam. 



If contrast stain, add 5 drops of safranin (Bismarck-brown) 

 to turpentine, and use it after the xylol. 



