526 A MANUAL OF BACTERIOLOGY 



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 a 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 

 stained at once, and they will keep indefinitely in a dry place. 

 The method of packing stained or unstained films face to face or 

 wrapped in paper is a barbarous one ; the surfaces soon get scratched 

 and dirty. The best plan is to pack them back to back in a racked 

 box, or if this is not at hand, stick a small piece of gummed paper 

 at the end of the slide on the film side, and when this is thoroughly 

 dry, but not before, they can be packed together. 



It is essential that the films should be absolutely dry before they 

 are mounted, and if they are mounted in Canada balsam or cedar-oil 

 they will sooner or later fade and be perfectly useless. The best plan 

 is to mount them in parolein or liquid paraffin as described by Coles 

 (Lancet, April 1, 1911), which has lately been advocated by Giemsa. 



If the above-named stains are not available staining may also 

 be done in a half-saturated aqueous solution of methylene-blue or 

 in Loffler's blue for half an hour, washing in water, and counter- 

 staining with a very weak eosin solution for a few seconds, washing 

 and drying. Manson recommends treating the films with a very 

 weak acetic acid two or three drops to the ounce of water to 

 dissolve out the haemoglobin, and, after washing, staining in the 

 following solution for half a minute : 



Borax ....... 5 parts 



Methylene-blue ..... 0-5 part 



Water 100 parts 



washing, drying, and mounting in xylol balsam. 



