194 STUDY OF INDIVIDUAL BACTERIA-STAINING 



Staining of Capsules. — Rdbiger's Method. — Films of the 

 organism to show capsules should be freshly prepared, dried, 

 but not fixed. The preparation is covered with a freshly 

 prepared saturated solution of gentian violet in formalin and 

 this allowed to stain for from 30 to 90 seconds. Then wash 

 lightly, dry and examine. The organisms appear deeply 

 violet and much larger than with ordinary stains and capsules 

 are well stained and show well. 



Welch's Method. — Prepare films as in the above method. 

 Cover with glacial acetic acid for 10 to 20 seconds. Wash 

 off the acid with carbol-fuchsin. Wash the stain off with 

 physiological normal salt solution (0.85 per cent.) until all 

 surplus stain is removed. Dry and examine. Capsules and 

 bacteria are red. 



Staining of Flagella. — ^The rendering of flagella visible is 

 considered one of the most difficult processes in staining. 

 Experience of a number of years diu-ing which whole classes 

 numbering from one hundred to three hundred students 

 accomplish this result shows that it is no more difficult than 

 many other staining processes. The essentials are: (1) 

 clean slides, (2) young cultures on agar slopes, (3) freshly 

 prepared mordant and stain which are kept free from pre- 

 cipitate, (4) gentle heating. The author's students are fur- 

 nished only stock materials and make their own cultures, 

 mordants and stains. 



The slides are cleaned with pumice in the usual way. An 

 agar slope culture of the organism to be stained from 6 to 

 24 hours old is selected. A bit of the culture is removed and 

 placed in a watch-glass of water. The bacteria are allowed 

 to diffuse of themselves without stirring. After se\'eral min- 

 utes a loop of this water is removed and spread on the slide 

 with a single movement of the needle, dried and carefully 

 fixed. The film is then covered with an abundance of the 

 mordant by filtering through a small filter onto the slide so 

 that the mordant shows transparent on the slide. The 

 preparation is then gently warmed and cooled three times, 

 adding mordant if necessary. After mordanting for about five 

 minutes the excess is washed off under the tap. It is a good 

 plan to hold the slide level and allow the water to run into 

 the center of the mordant and flow it off. Inclining the slide 



