314 The Phagocytic Power of the Blood 



a flame, the rubber bulb removed and the tube placed in a 

 thermostat, or in case much work of the kind is being done, 

 to an opsonizing incubator (Fig. 99) in which the temperature 

 is not modified by opening and closing the doors. The tube 

 remains in the incubating apparatus at 37 C. for fifteen 

 minutes (some use twenty, some thirty, minutes as their 

 standard), is then removed, whirled about its long axis 

 between the thumbs and fingers a few times to mix the 

 contents from which the corpuscles have sedimented, its 



Fig. 98.- 



-Mixing liquids by repeatedly expelling on to slide and redraw- 

 ing into pipette (Miller). 



end is broken off, and a good-sized drop is allowed to escape 

 upon a perfectly clean glass slide and spread over its surface. 



The spreading is a matter of some importance, as an even 

 distribution of the leukocytes is desirable. The capillary 

 tube from which the drop has escaped will form a good 

 spreader if laid flat upon the glass and drawn along, but 

 the edge of another slide is better, and in distributing the 

 fluid, it is better to push than to pull it with the end of the 

 slide, rather than its side. 



Miller* says that "a good smear should be uniform in 

 consistency and most of the leukocytes should be found 

 along the edges and at the end. For convenience in count- 

 ing, it is well to have the smear terminate abruptly and not 

 be drawn out into threads or irregular forms." 



* "Therapeutic Gazette," March 15, 1907. 



