Il6 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



10 drops of Giemsa's stain, which must be bought ready pre- 

 pared. In mixing the two avoid violent agitation; add the 

 stain to the water in a test-tube, stopper the latter with your 

 thumb and invert it slowly once or twice. Do not mix it until 

 you are ready to proceed with the staining. 



Take the slide in a perfectly clean pair of forceps, flood it 

 with the stain, and heat until it just begins to steam; remove 

 it from the flame and in fifteen seconds pour off the solution, 

 replace it quickly with fresh and heat again, again removing 

 it when steam rises and allowing the action to go on for 

 fifteen seconds. Do this four times in all, allowing the action 

 to go on for one minute on the last application. Then wash 

 in tap-water or in distilled water with a drop or two of potas- 

 sium carbonate solution, blot, dry, and mount, 



Another method is to place the slide face downwards in a 

 Petri dish, supported on two slips of glass. The dish is then 

 filled with a mixture prepared as above, and the staining 

 allowed to go on for twelve to twenty hours in the cold, or 

 three to four hours in the incubator, the dish being covered 

 to prevent evaporation. If the slide is inserted face upwards, 

 it will probably be covered by a fine red precipitate. 



The most minute amount of acid is fatal to the process; 

 hence all instruments must be dry and clean, and distilled 

 water (which often contains traces of acids) should be 

 avoided. 



Examine the film with the T V and your highest eye-piece, 

 taking great care to get a good light, white jf possible. 



FONTANA'S METHOD (RECOMMENDED). 

 Requisites. (i) Fixing fluid : 



Acetic acid ... . . -. i c.c. 



Formalin ... 20 c.c. 



Distilled water , ... 100 c.c. 



(2) Mordant : 



Tannic acid ... . *;v /: ... '&& 5 grammes. 

 Carbolic acid solution (i per cent.) ... 100 c.c. 



(3) Silver solution, prepared fresh as follows : Prepare a 

 25 per cent, solution of silver nitrate (this may be done with 

 sufficient accuracy by dissolving a small crystal in half a test- 

 tubeful of distilled water), and add just enough ammonia 



