208 MICROMETRY AND BLOOD PREPARATIONS 



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. Crescents stand out very distinctly. 



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

 malarial crescents in a cubic millimeter of blood. 



PREPARATIONS 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 

 leukocytes are more evenly distributed. In making smears by spread- 

 ing, there is a tendency for the polymorphonuclears to be concentrated 

 at the margin while lymphocytes remain in the central part of the film. 



In Ehrlich's method we have perfectly clean dry cover-slips. Take up a small 

 drop of blood without touching the surface of the ear or finger. Drop this cover- 

 glass immediately on a second one and as soon as the blood runs out in a film, draw 

 the two cover-slips apart in a plane parallel to the cover-glasses. Slide them apart. 

 Ehrlich uses forceps to hold the cover-glasses to avoid moisture from the fingers, 

 but I find I can work more quickly and satisfactorily with the fingers alone. In 

 making malarial smears it is better to wash the finger or ear with soap and water 

 to get rid of all grease and dirt. Then dry thoroughly before puncturing. Alcohol 

 is not so efficient. 



Slides and spreaders should be absolutely clean and grease free. Scrubbing with 

 soap and water, thorough rinsing and drying, then subjecting the slide to the flame 

 to make it grease free is satisfactory. 



Of the various methods of spreading films on slides there is none 

 equal to that described by Daniels. In this the drop of blood is drawn 

 along and not pushed along. The films are even, can be made of any 

 desired thickness by changing the angle of the drawing slide, and there 

 is little liability of crushing pathological cells. Take a small drop of 

 blood on the end of a clean slide. Touch a second slide about % 

 inch from end with the drop and as soon as the blood runs out along 

 the line of the slide end, slide it at an angle of 45 to the other end of the 

 horizontal slide. The blood is pulled or drawn behind the advancing 



