108 CLINICAL BACTERIOLOGY. 



Staining of Capsules. Some bacteria are character- 

 ized by the formation of capsules in the blood and in 

 other animal substances (anthrax-bacilli, pneumococci, ba- 

 cillus of Friedlander, etc.). Occasionally, the capsules 

 appear also in cultures, and their demonstration can be 

 made in the following method of Johne : The preparations 

 are stained in a warmed two per cent, solution of gentian- 

 violet, are rinsed in water, decolorized for from ten to 

 twenty seconds in two per cent, acetic acid, and are washed 

 and mounted in water (not Canada balsam, as this causes 

 the capsules to shrink). 



Staining of Spores. Spores are stained with extraor- 

 dinary difficulty, because of the dense and impenetrable 

 membrane by which they are surrounded. The usual 

 methods of staining are not sufficient for the staining of 

 spores. This may be effected by exposure of cover-glass 

 specimens prepared in the usual way with spore-containing 

 bacteria for an hour in hot carbol-fuchsin solution or aniline- 

 water fuchsin-solution, which is from time to time brought 

 to the boiling-point. By addition of solution undue con- 

 centration is avoided. The specimen is taken directly from 

 the stain, and is placed in ten per cent, hydrochloric acid 

 or in three per cent, hydrochloric-acid alcohol, in which it 

 is washed for about a minute. By this means everything 

 is decolorized with the exception of the spores, which re- 

 tain their stain. It is here, also, useful to make a contrast- 

 stain, by exposing the specimen briefly to the action of a 

 watery solution of methylene-blue or of malachite -green. 

 The bacilli then appear blue or green respectively, and the 

 spores, on the contrary, a bright red. 



If it be desired to stain the spores without reference to 

 the bodies of the bacteria, the specimens may, according to 

 a suggestion of Buchner, be placed for half a minute in 

 concentrated sulphuric acid. By this means the vegetative 

 forms lose their power of staining, whereas the spores, 

 after thorough rinsing in water, are readily susceptible to the 

 action of the carbolfuchsin. 



Good results are obtained with the aid of the apparently 

 complicated, but quite reliable, method of staining spores 

 proposed by Moller. The cover-glass, dried in air, is placed 

 for two or three minutes in absolute alcohol, is then rinsed 

 in water, and kept for two minutes in chloroform. After 

 again rinsing in water it is exposed for one or two minutes 



