DIFFERENTIAL STAINING OF BLOOD FILMS 89 
real staining of the preparation takes place, and is then washed off 
with water. 
The differential staining of the preparation is accomplished by 
washing the preparation with distilled water. The washing is con- 
tinued until the better spread portions of the film appear yellowish 
or reddish in color. This method of differentiation of decolorization 
may require from one to three minutes according to the intensity of 
the staining and the tint sought in the red blood corpuscles. When 
the desired color is obtained in the red blood corpuscles the preparation 
is quickly dried between filter papers and mounted in balsam. It is 
important to stop the decolorization by drying the preparation as soon 
as the desired tint in the red blood corpuscles is obtained. A little 
experience will show the operator how far to carry the decolorization 
and the time required for to obtain the desired tint in the red blood 
corpuscles. 
SUMMARY FOR THE METHOD OF STAINING 
1. Make films of the blood, spread thinly and allow them to dry 
in the air. 
2. Cover the preparation with alcoholic solution of the dye for one 
minute. 
3. Add to the alcoholic solution of the dye on the preparation suffi- 
cient water, drop by drop, until the mixture becomes semi-translucent 
and a yellowish metallic scum forms on the surface. Allow the mixture 
to remain on the preparation for two or three minutes. 
4, Wash in distilled water until the film has a yellowish or pinkish 
tint in its thinner or better spread portions. 
5. Dry between filter paper and mount in balsam. 
III. Microscopical Appearance in Blood Films Stained by this 
Method. The red cells are orange or pink in color. Polychromeato- 
philia and punctate basophilia (the granular degeneration of Grawitz) 
are well brought out. The nucleated red cells have deep blue nuclei 
and the cytoplasm is usually of a bluish tint. The lymphocytes have a 
dark purplish-blue nucleus and a robin’s egg blue cytoplasm in which a 
few dark blue or purplish granules are sometimes present. The poly- 
nuclear neutrophilic leucocytes have a dark blue or dark lilac-colored 
nucleus and the granules are usually of a reddish color. The eosino- 
philic leucocytes have blue or dark-colored lilac nuclei. The granules 
have the color of eosin, while the cytoplasm in which they are imbedded 
has a blue color. The large mononuclear leucocytes appear in at least 
