MICROSCOPICAL EXAMINATION. 205 



maceration of the chromic acid. Even under the best 

 conditions it is almost impossible to stain some spores. 



Staining Flagella. For the demonstration of flagella, 

 which are possessed by all motile bacteria, we are in- 

 debted to Loeffler. The special stains devised by him, 

 and also the one devised by Van Ermengem, are those 

 usually employed. 



Bunge's modification of Loeffler 7 s method is carried 

 out as follows: Cover-glasses which have been most 

 carefully cleaned are covered by a very thin smear of 

 an eighteen-hours' old culture of the motile organism 

 to be examined. After drying in the air and passing 

 three times through the flame the smear is treated with 

 a mordant solution, which is prepared as follows: To 

 3 parts of saturated alum solution add 1 part of a solu- 

 tion of liquor ferri sesquichloride, of the strength of 

 1:20 of distilled water. To 10 c.c. of this mixture 

 add 1 c.c. of a concentrated watery solution of fuchsin. 

 This mordant should be allowed to stand for several 

 days before using. After preparing the cover-slip with 

 all precautions necessary to cleanliness the filtered mor- 

 dant is allowed to act cold for five minutes, after which 

 it is slightly warmed and then washed off. After dry- 

 ing the smear is faintly stained with the carbol fuchsin 

 solution and then washed off, dried, and mounted. 



Frequently the flagella appear well stained, but often 

 the process has to be repeated a number of times before 

 success is arrived at. 



The Preservation of Specimens. Dry unstained or 

 stained preparations of bacteria keep indefinitely if 

 mounted in Canada balsam, cedar oil, or dammar lac; 

 they tend to gradually fade, but may be preserved for 

 many months or years. 



