BACTERIA. 257 



6. Staining the Spores of Bacteria. 



475. A well-differentiated staining of the spores of Bac- 

 teria may be obtained, according to the method proposed by 

 H. Moeller (II), by plunging cover-glass preparations fixed 

 by heat or by alcohol in 5$ chromic acid * for from five 

 seconds to ten minutes, then thoroughly rinsing in water, 

 adding carbol-fuchsin in drops, and warming the whole in 

 the flame for 60 seconds, allowing it to boil up once. The 

 carbol-fuchsin is then poured off, the cover-glass is plunged 

 in 5$ sulphuric acid until it is decolorized, and again thor- 

 oughly washed with water. An aqueous solution of methyl- 

 ene blue or malachite green is then allowed to act for 30 

 seconds, and is rinsed off with water. The preparation is 

 allowed to dry and mounted in balsam. In good prepara- 

 tions, the spores are to be seen as bright red spots within 

 the blue or green bodies of the Bacteria. 



Zinc chloride or chloroi'odide may be used as a mordant, 

 instead of chromic acid, but these commonly require a longer 

 time of action than the latter. 



7. Staining the Cilia of Bacteria. 



476. For staining the cilia of Bacteria, Trenkmann (I) and 

 Loeffler (I) have proposed different methods. According to 

 Loeffler's latest publication, the following method is best 

 adapted for the purpose. The Bacteria are first spread 

 upon the carefully cleaned cover-glass ( 459, note), and 

 fixed by being passed three times through the flame, too 

 strong heating being carefully avoided. The mordant is 

 then placed on the warm cover-glass. This is best prepared 



* In general, the action of chromic acid for about 30 seconds is sufficient ; 

 but different species of Bacteria show great differences in this respect. Ac- 

 cording to Moeller, the most favorable duration of its action is : for the 

 brown potato- acil/us, 30 sec.; for the yellow one, 2 min.; for the white 

 one, lomin.; for Bacillus cyanogenus, 30 sec.; for the anthrax Bacillus, 2 

 min. ; for the tetanus Bacilhis, 2 min. I obtained beautiful staining of the 

 spores of Bacillus subtilis on allowing the chromic acid to act 30 sec. on 

 cover preparations fixed by heat, 



