54 CLINICAL BACTEEIOLOGY 



or mixed with emulsion (bacterial), which we wish to 

 standardize, on one end of the slide, conveniently at 

 the left-hand border (Fig. 28), which is firmly held 

 between the thumb and finger of the left hand. The 

 end of the spreader* should now be placed in the blood- 

 drop, and moved backwards and forwards and from side 

 to side until the drop is spread out along the whole length 

 of the spreader's edge. Now draw the spreader steadily 

 along the surface of the slide ; this will give us a more or 

 less perfectly homogeneous film, composed of red blood- 

 corpuscles, a few small white blood-cells, and blood-plasma. 

 Many of the leucocytes, owing to their size, will be drawn 

 from the field by the spreader. 



The film should now be allowed to air dry, fixed with a 

 fixing agent or a fixing stain, and stained. 



* How to make a spreader, see p. 25. 



