Page 115 - The Veterinary Laboratory and Field Manual 3rd Edition

84 Willy Schauwers

Table 2.3 Basic adjustments of the microscope.

Objective Condenser diaphragm Immersion oil Mirror Optical limit and purpose
10× Lowered Open/closed No Flat 30–500 µm
Search of eggs and larvae
Search of Ciliata
(Entomology)
40× Halfway Open/closed No Flat 5–30 µm
Details of eggs and larvae
Search of certain protozoans
by means of direct wet smear
(Counting of WBC and RBC)
100× At the top Open Yes Concave 0.25–5 µm
Permanently stained smears

The basic adjustments are listed in Table 2.3. with soft toilet-paper. Dried oil will cause the
If the light source is a mirror, it is mentioned microscopic image to be foggy.
which side (flat or concave) should be used.
• If dried oil is sticking to the immersion-
lenses, it can be removed, using a clean
Precautions
tissue, moistened with a mix of ether
• Use the coarse adjustment only with the low and alcohol (1/1 v/v). This way of clean-
power objective. ing should be kept to a minimum and
• Use oil each time the oil immersion lens is should never be used on internal lenses
used. and prisms. For this reason, one should
• Use immersion oil with the oil immersion always carefully check the manual of the
objective only. microscope for suitable solvents. After
• Clean all oculars and objectives with lens cleaning, the lenses should be dried imme-
paper after each use. diately with another clean and dry tissue
• Do not ‘rack down’ on a specimen slide, or soft toilet paper.
always ‘rack up’. 8
• Move or transport the microscope with one • Other lenses should be cleaned with another
hand under the base and the other hand grip- tissue, which is not used for the immer-
ping the arm. For longer distance transport, sion-lenses, as any contact between oil and
it is advisable to place the microscope in its non-immersion-lenses should be avoided.
box (well-immobilized and padded), always Also, plastic lenses exist, which are not resis-
avoid shocks. tant to organic solvents.
• Lubricate the microscope with the correct • Never leave the tube of the microscope open
lubricant and always clean it after use. (that is, without eyepieces) as this can cause
• Store the microscope covered and in a pro- dust and fungal spores to enter the micro-
tected area. scope.
• Remove the immersion oil from the immer- • After every use, the microscope should pref-
sion-lenses on a daily basis by wiping it off erably be covered with a cotton dust-sheet.
with a non-fluffy, soft and clean tissue or Avoid plastic covers, as these will promote

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