THE CELLS TOUCHING THE LINES
O N T H E R I G H T A N D A T T HE
When all the cells in the four fields have
been counted, multiply the count by 50 for
the total white cell count.
Immediately after completing the count,
clean the counting chamber with distilled
water and dry it with lens tissue. Rinse
pipettes first with cold water, then with
acetone. Draw air through the pipette un-
til it is dry. The pellet should move freely
in the bulb if the pipette is dry.
Sources of error. The errors are generally
caused by the same mistakes as described for red
The Uniopette disposable kit for doing a white
blood cell count consists of a shielded capillary
pipette (20 ul capacity) and a plastic reservoir con-
taining a premeasured volume of diluent (1:100
Using the shield on the capillary pipette,
puncture the diaphragm in the neck of the
reservoir with the tip of the capillary shield.
After obtaining free-flowing blood from a
lancet puncture of the finger, remove the
protective plastic shield from the capillary.
Holding the capillary slightly above the
horizontal, touch the tip to the blood
source. Capillary action will fill the tube
until the blood collection
e.g., when the proper
amount (20 ul) has been obtained. Wipe
blood off the outside of the capillary tube,
making sure none is removed from inside
the capillary tube. An alternative source of
blood is a thoroughly mixed fresh venous
blood sample obtained by venipuncture.
Squeezing the reservoir slightly, cover the
upper opening of the capillary overflow
chamber with your index finger and seat
the capillary tube holder in the reservoir
neck. Release pressure on the reservoir and
remove your finger from the overflow
chamber opening. Suction will draw blood
into the diluent in the reservoir.
Squeeze the reservoir gently two or three
times to rinse the capillary tube, forcing
diluent intobut not out ofthe overflow
chamber, releasing pressure each time to
return diluent to the reservoir. Close the
upper opening with your index finger and
invert the unit several times to mix the
blood sample and diluent.
For specimen storage, cover the overflow
chamber of the capillary tube with the
Immediately prior to cell counting, mix
adequately again by gentle inversion, tak-
ing care to cover the hole with your index
Remove the pipette from the reservoir.
Squeeze the reservoir and reseat the pipette
in the reverse position, releasing pressure
to draw any fluid in the capillary tube into
the reservoir. Invert and fill the capillary
tube by gentle pressure on the reservoir.
After discarding the first 3 drops, charge
the counting chamber of the hemacytom-
eter by gently squeezing the reservoir.
Using the high power objective, count the
white blood cells in the nine large squares
of the hemacytometer chamber.
Calculation: Add 10 percent to the number
of cells counted in the nine large squares
and multiply by 100 to obtain the white cell
Example: The number of cells in 9 large
squares was 90.
The cell count = [90 + (0.1 x
90)] x 100
= [ 9 0 + 9 ] x
= 99 x 100=
DIFFERENTIAL WHITE BLOOD CELL
The total white cell count is not necessarily in-
dicative of the severity of a disease, since some
serious ailments may show a low white cell count.
However, the percentage distribution of the dif-
ferent types of leukocytes in the blood often pro-
vides more helpful information in determining the
severity and extent of the infection than any other
single procedure used in the examination of the
blood. The differential count gives these