STAINING OF BLOOD 179 



It is unnecessary in such a count to have an assistant; of course, in making a 

 complete differential count it is preferable to have some one tabulate or labor- 

 iously to do this one's self. 



The red cells are practically diaphanous and not disintegrated as when acetic 

 acid is used as a diluent, consequently it is easy to make out the particular red cell 

 as to size, etc., containing a malarial parasite. 



The best results are obtained with a i/6-in objective. Higher powers are of 

 course impracticable by reason of the thickness of the cover-glass of the haemocy- 

 tometer. 



The following are the appearances of the various leukocytes. 



Eosinophiles. In these the bilobed nucleus stains rather faintly and the color 

 is greenish blue. The eosinophile granules show easily as coarse, brickdust-colored 

 particles. 



Polymorphonuclears. The nucleus stains a deep, rich, pure violet but less in- 

 tense than that of the small lymphocyte. The shape of the nucleus is typically 

 three or four lobed but even when of the horseshoe shape of a transitional nucleus 

 is easily recognizable by the intensity of the violet staining. That which makes the 

 polymorphonuclears very easy of differentiation is the distinctness of the cell out- 

 lines produced by the fine yellowish granulations in the cytoplasm. 



Small Lymphocytes. The nucleus is perfectly round and stains a deep violet. 

 It is almost impossible to make out any cytoplasmic fringe. 



Large Lymphocytes. The nucleus here is round and of a lighter violet than that 

 of the small lymphocyte. The cytoplasm is blue, nongranular, and sharply defined 

 from the nucleus. 



Large Mononuclears. These show a washed-out, slate-colored nucleus which 

 blends with the gray slate-blue staining of the cytoplasm so that there is an in- 

 definiteness of outline in the more or less irregularly contoured nucleus. 



Transitionals. These show the same characteristics as the large mononuclears, 

 but with a more faintly stained and more indented nucleus. The large mono- 

 nuclears and transitionals stand out as slate-colored cells. When very much degen- 

 erated these cells have a greenish hue. 



Mast Cells. The granulations show as a rich maroon or reddish-violet color. 



The young ring forms of malaria show as violet-blue areas in the red cells. When 

 half-grown or approaching the merocyte stage, the containing red cell takes on a 

 faint pink coloration, thereby differentiating it from the noninfected red cells. At 

 the same time the parasite is extruded and has the appearance of a violet-blue body 

 projecting from the margin of the red cell. It is as if a blue body were budding 

 from a pink one. 



It is an easy matter with this method to count the number of trypanosomes or 

 malarial crescents in a cubic millimeter of blood. 



PREPARATION AND STAINING OF DRIED FILMS. 



When preparations are desired for a differential count, Ehrlich's 

 method of making films is to be preferred, as the different types of leuko- 

 cytes are more evenly distributed. In making smears by spreading, 



