DIFFERENTIAL BLOOD COUNTS. 235 



The red cells are practically diaphanous and not disintegrated as they 

 are when acetic acid is used as a diluent ; consequently it is easy to dis- 

 tinguish the particulars concerning the size, etc., of a particular red cell 

 containing a malarial parasite. Whether it is possible to determine the 

 species of malarial parasite in such a preparation I am unable to state, 

 as I have had only benign tertian and aBstivo-autumnal blood to work 

 with since using this method. At any rate I always make an ordinary 

 Ehiiich smear at the same time I take the blood for the white count, so 

 that' I have material for further study with a one-twelfth objective should 

 such further study seem to be advantageous. 



My best results have been obtained with a one-sixth objective. Higher 

 powers are. of course impracticable by reason of the thickness of the 

 cover glass of the hasmocytometer. 



The following are the appearances of the various leucocytes. 



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

 is greenish-blue. The eosinophile granules show easily as coarse, brick-dust 

 colored particles. 



Polymorphonuclears. — The nucleus stains a deep rich violet-blue, but of a less 

 intense color than of the small lymphocyte. The shape of the nucleus is 

 typically 3 or 4 lobed, but even when of the horseshoe shape of a transitional 

 nucleus, it is easily recognizable by the intensity of the nuclear staining. The 

 distinctness of the cell outlines produced by the fine yellowish granulations in the 

 cytoplasm makes the polymorphonuclears very easy of differentiation. 



Small lymphocytes. — The nucleus is perfectly round and stains to a deep rich 

 blue. It is almost impossible to make out any cytoplasmic fringe. 



Large lymphocytes. — The nucleus here is round and of a lighter blue than that 

 of the small lymphocyte. The cytoplasm is nongranular and sharply denned 

 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 

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



Transitionals. — These have 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 without any sharp 

 nuclear definition. When very much degenerated these cells have a greenish hue. 



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

 When half grown or approaching the merocytic stage the containing red cell takes 

 on a faint pink color, 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. The malarial crescents are brought out with the 

 greatest distinctness. 



Trypanosoma leicisi in the blood of rats stains quite distinctly. With the 

 comparatively low powers which it is necessary to use, I have been unable to 

 assure myself of chromatic staining. 



