30 THE AMERICAN MONTHLY [Jan. 



MICROSCOPICAL MANIPULATION. 



A New Method of Staining Flagella. — Loeffler's method 

 of stainiag flagella is probably the one most commonly and gen- 

 erally employed. This consists in treating the bacteria to be 

 stained with a mordant made up of tannic acid and ferrous sul- 

 phate, and then staining the bacteria with a solution of an ani- 

 lin color in water. 



I have devised a method which is simple, and in my hands, 

 much more reliable and easier of execution. It is as simple as 

 the staining of bacteria with ordinary carbol-fuchsin, and I 

 have stained over fi^ty preparations of flagellated micro-organ- 

 isms, each time demonstrating the flagella most satisfactorily. 



The method consists in the use of but a single solution, which 

 is at once mordant and stain. The solution should be made in 

 two parts, which are filtered and mixed. 



A. 

 Saturated aqueous solution of alum . . . 10 c.cm. 



Saturated alcoholic solution _of gentian-violet , . 1 c.cna. 



B. 



Tannic acid ..... 1 gm. 



Distilled water ..... 10 c.cm. 



The solution should be made with cold water, and immedi- 

 ately after mixing the stain is ready for use. 



The cover-slip is to be carefully cleaned, the grease being 

 burned off in a flame, and after it has cooled the bacteria are 

 spread upon it, well diluted in water, care being taken to ex- 

 clude culture medium. After the preparation has been 

 throughly dried in the air it should be held over the flame with 

 the fingers, as Loeffler has directed. Afterward the stain is grad- 

 ually poured on the slip and heated gently, bringing the fluid 

 almost to a boil ; the slip covered with the hot stain should 

 then be laid aside for one minute, then washed in water and 

 mounted. 



Upon examination, the bacteria, both isolated and in clumps, 

 will, if motile, be found to have the flagella clearly atid deli- 

 cately defined. In the middle of the cover-slip, as well as 

 around the edges, the bacteria will be found equally well 



