178 BACTERIOLOGY. 



merse for a few seconds in the " sensitizing bath," viz., 

 a 0.25-0.5 per cent, solution of silver nitrate. Without 

 washing, bring the slip into a watch-crystalful of the 

 " reducing and reinforcing bath," viz. : 



Gallic acid . 5 grammes. 



Tannin . 3 "' 



Fused potassium acetate 10 " 



Distilled water . . . 350 



After a few seconds pass the slip back into a watch- 

 crystal containing the dilute silver bath (0.25-0.5 per 

 cent, solution of silver nitrate in water) and keep it 

 in constant motion until the solution begins to take on 

 a brown or blackish color. Wash in water ihorov,ghly ; 

 dry with blotting-paper, and mount in balsam. 



Bowhill's Method. — From a fresh culture on agar- 

 agar make a suspension in sterilized distilled water in a 

 test-tube ; allow this to stand for five minutes ; from the 

 supernatant fluid, prepare cover-slips, care being taken 

 that the slips are clean and that too much heat is not 

 applied in fixing; float the cover-slip, bacteria down, 

 upon some of the following mixture in a watch-glass : 



Saturated alcoholic solution of orcein (about 10 days old) . 15 c.c. 

 20 per cent, solution of tannic acid in water (acid dis- 

 solved by heating) . . .10 c.c. 

 Distilled water . . 30 c.c. 



Gently warm the fluid and allow the preparation to 

 remain in it for 10-15 minutes; then rinse in water, 

 and finally mount and examine in water or dry and 

 mount in xylol balsam.^ 



Method op Lowit. — Prepare cover-slips by one of 

 the foregoing methods that insures isolation of single 



' Bowhill : Hygienische Rundschau, 1898, No. 3, p. 105. 



