^6 MANUAL OF BACTERIOLOGY. 



Prepare films of blood as directed in Chapter VII., Part I., 

 and allow to dry. 



(o) Pour the stain over the surface of the preparation till it 

 covers it and allow to remain for one miunte. This serves to fix 

 the film of blood to the glass as well as to stain it, so it is not 

 necessary or desirable' to pass the preparation through the 

 flame. 



(b) Add distilled water, drop by drop, till a reddish tint ap- 

 pears at the edges and a metallic scum forms on the surface.* 

 About six drops are needed for a three-fourths inch cover-glass. 

 The real staining of the preparation now takes place, and re- 

 quires two or three minutes. 



(c) Wash in distilled water till the thin parts of the prep- 

 aration have a yellowish or pinkish tint, which requires one to 

 three minutes. 



(d) Dry with blotting-paper and mount in Canada balsam. 

 Bacteria, malarial parasities, and cell-nuclei are stained blue, 



red blood-corpuscles are orange-pink, while the specific granule 

 of the leukocytes (neutrophilic, etc.) appear in varoius tints 

 from red to dark blue. The chromatin of the malarial parasite 

 takes a lilac to red color. The blood-plates have a bluish or 

 purplish color and must not be confused with malarial parasites. 

 Hastingsf gives directions of which the following are ap- 

 parently the essential details: Dissolve 2 grams of sodium 

 carbonate in 200 c.c. hot distilled water and stir in 2 grams 

 methylene-blue (Ehrlich rectified). Bring to a boil over a fire 

 flame or boil for 15 minutes over water bath. Replace water 

 lost by evaporation and heat again for 10 or 15 minutes. 

 Pour the hot solution off from the sediment and add distilled 

 water up to 200 c.c. if necessary. Partially neutralize by the 

 addition of 12.5 per cent, or 20 per cent, acetic acid; solution 

 must remain alkaline. Add this to 1000 c.c. of a xV per 



♦Leishman. British Med. Jour., 1901, II., 757. 

 fLoc. cit. 



