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118 
TENTH REPORT. 
Fig. 8. — Removing last drops of saline solution. 
into the capillary tube up to the mark. The pipette is then removed from 
the corpuscles, and the column of the corpuscles lying between the end 
and the mark is drawn up the tube a short distance, leaving an empty space 
at the end of the capillary tube. The suspension of bacteria is now drawn 
in up to the mark and remains separated from the blood-corpuscles by the 
distance the corpuscles were withdrawn from the end. In a similar way a por- 
Fig. 9. — Collecting blood for serum. 
tion of theTblood serum is drawn in, and then all are driven out and mixed. 
Beginners sometimes have difficulty in working accurately with an opson- 
izing pipette, but a little practice usually brings confidence and accuracy. 
Pushing the glass tube well up into the rubber nipple and grasping the glass 
tube through the rubber gives one a firmer grasp and a more delicate control 
over the column of liquid. Drawing the corpuscles in first helps, as they do 
not move as freely as the thinner liquids. Those who prefer can manipulate 
the pipette by mechanical means, using either the simple rubber tube and 
screw clamp as shown in Fig. 10 or the more elaborate pipette holder shown 
