STEP 6: Adjust the light intensity by using the neutral density filter control. If
more light is desired, open the iris diaphragm on the substage
1-32. SCANNING TECHNIQUES
The oil immersion objective should never be used with wet preparations such as
formalin preparations, MIF slides, and iodine wet preparations. At least fifteen minutes
should be dedicated to the examination of each slide. When in doubt about the identity
of an organism, continue scanning until absolute identification is made.
a. Wet Preparations. DO NOT USE OIL. These preparations contain
specimens in a suspended state. Therefore, oil will ruin the slide. These slides should
be observed with the low and high dry objectives only. Scan the complete slide on low
power for helminthes. In order to find protozoans, the high dry objective should be
used. Identify all organisms with the high dry objective.
b. Tissue Preparations. Observe these slides on low or high power objectives.
Do not use oil immersion on these slides.
c. Permanent Stains. Iron Hematoxylin, Trichrome, and Chlorazol Black E
stains should be scanned and identified under the oil immersion objective.
d. Malaria Smears. Observe the thick portion of the smear first for the
presence of organisms. Identify the parasites on the thin portion of the slide. Scan and
identify malaria organisms under the oil immersion objective.
1-33. THE STEREOSCOPE
This instrument (see fig. 1-2) is utilized for the identification of large larvae,
helminthes, and intermediate hosts that are too large for the binocular microscope.
Follow these suggested steps in using the sterescope:
Adjust the interpupillary distance by grasping the ocular tubes, one
in each hand, and adjust to desired length by gently pushing or
Focus the oculars in the same manner as for the binocular
Select the proper magnification using the zoom magnification knob.
Sharpen the image by using the focusing knob.
Clean and store in a manner similar to that used with the binocular