Smear Preparation of Human Blood 



197 



137 



138 



* 



139 



140 



141 



Figs. 137, 138, 139, 140, and 141. Good and bad blood films by the method described 

 in this example. Fig. 137 shows an excellent smear under low power. Compare with 

 Fig. 138 in which grease has caused the overly thick film ( notice overlapped cor- 

 puscles of 1 ) to coagulate. At 2 there is an imperfectly stained leucocyte partly masked 

 by erythrocytes. Figs. 139, 140, and 141 show details of excellently stained leuco- 

 cytes. Notice the polymorph at 3, the monocyte at 4, the platelets at 5, and the 

 exceptionally well-demonstrated eosinophil at 6. 



should be clear dark blue, the platelets sharply distinguished, and the 

 granules of eosinophils bright red. Inadequately stained nuclei usually 

 indicate too short a period of exposure to undiluted stain. Poorly stained 

 eosinophils are generally the result of adding too much water or buffer. 

 Batches of Wright's stain vary widely in their performance and a few 

 trials are necessary before uniformly successful results can be obtained. 



Smears that appear to contain no leukocytes are the result of using too 

 large a drop of blood. Capillary attraction draws the large white cells to 

 the edges of the pushing slide and they will be found embedded in the 

 thick strips of blood that outline the periphery of smears so made. 



Most blood smears are regarded as temporary mounts made for 

 diagnostic purposes. They may be stored dry for about a year, but the 

 immersion oil must be washed off with benzene each time thev are ex- 



