46 



§ 68. A method for staining spores. Make a cover- 

 glass preparation, dry, and flame as already described. Take 

 the preparation by the edge with the fine forceps, cover the 

 film surface with carbol fuchsin and hold the preparation 

 over the gas flame until steam is given off, then remove it 

 for a few seconds and again heat it. Repeat the heating 3. 

 or 4 times. After the stain has acted for from 3 to 5 min- 

 utes rinse the preparation in water and decolorize it by im- 

 mersing it in a watch-glass containing about 3 c.c. of a 1% 

 solution of sulphuric acid or 95% alcohol. After about one- 

 half minute remove the preparation and rinse it thoroughly in 

 water. If it is not decolorized repeat the bleaching process. 

 This removes the coloring matter from the bodies of the 

 bacteria, but leaves it in the spores. After thoroughly 

 washing the preparation, counter stain it with a saturated 

 aqueous solution of methylene-blue for about 30 seconds, 

 rinse in water and examine. The spores should be stained 

 red (with the fuchsin) and the rest of the organism should 

 be colored blue. 



There is a very satisfactory method recommended by 

 Moller. For this and other methods for staining spores, 

 see text-books on bacteriology. 



EXERCISE XVIII. 

 STAINING THE FLAGEIvLA ON MOTILE BACTERIA. 



§ 69. Explanatory note. The motile bacteria are pro- 

 vided with a variable number of long hair-like appendages 

 or flagella. These are invisible in the fresh preparation and 

 they do not stain by the ordinary methods. By special 

 staining processes, however, their presence can be detected. 

 Several methods have been proposed for staining these fila- 

 ments but nearly all of them are based on the use of a 



