650 A MANUAL OF BACTERIOLOGY 



Drop from the pipette bottle just enough of the diluted G-iemsa's 

 solution to cover the film. Allow it to act for about ten to 

 twenty seconds [if longer, especially in a hot climate, the alcohol 

 evaporates and precipitates the stain]. 



Then drop on as much distilled water as the slide will hold 

 that is, about eight times as much water as stain allow the 

 stain and distilled water to mix, and stain for the requisite time. 



It is better, however, in order to prevent the precipitation of the 

 stain, to pour off the diluted stain and water from the film on to 

 the surface of a piece of slightly curved plate-glass, and imme- 

 diately place the slide, film side downward, on this. The duration 

 of staining varies according to the temperature of the room and 

 the nature of the film generally speaking, ten to twenty minutes 

 give excellent results ; but a good plan is to remove the film, 

 flood off the stain with distilled water, and examine under low 

 power. If the nuclei of the leucocytes are of a ruby-red colour 

 the staining is successful. If they are blue, the film is insuffi- 

 ciently stained, and it should be replaced on the staining fluid ; 

 if they are blackish red, it is too deeply stained for most purposes, 

 and all that is required is to pour distilled water on the surface, 

 watching the effect (easily seen by holding the slide over a piece 

 of white paper), and as soon as the whole film is faintly pink the 

 staining will be good. This method of staining, generally known 

 as Giemsa's new method, closely resembles Leishman's, but very 

 much more distilled water is added. 



The exact tint or colour of the objects stained in this way will 

 depend largely on the reaction of the distilled water used to dilute 

 the stain. If the water is acid (as most distilled water is) the 

 red blood-corpuscles are stained reddish, if alkaline they are 

 often bluish in colour. 



When the film has been sufficiently stained, do not pour off 

 the stain and then wash, but flood off the stain with distilled 

 water and so avoid any deposition of precipitate. 



When the film has been quickly washed, it is essential to dry it 

 as quickly as possible, otherwise decolorisation proceeds. The 

 films should not be dried with filter or blotting-paper ; it tends to 

 leave fluff. They are best dried by blowing on the surface with 

 air from a Politzer's bag. 



Films of blood which have been kept for some time, especially 

 in the tropics, will never stain well. Films should therefore be 



