Page 272 - ONLINE PROCEEDING BOOK WSAVA 2017
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272
An Urban Experience
Correct use of a microscope
1. Always use a coverslip
· You should always use a cover-slip (or cover glass).
· The only exceptions are tape-strip preparations (the acetate backing of the tape acts as its own cover-slip).
· Microscope lenses are designed to look through a cover-slip and  uid layer, which provides a  at optical surface, puts material in a similar focal  eld, avoids air–  uid interfaces and reduces contrast.
· Curved surfaces (including cell layers, hairs, skin debris, and oil on top of the cover-slip) act as mini- lenses and cause serious distortion.
· Cover-slips can also protect the lenses from scratches and the mounting  uid, and provide a de ned search area for skin scrapes and hair plucks.
· It is important to use enough mounting  uid to seal the cover-slip to the slide without gaps or air bubbles, but not so much that it gets onto the microscope lenses or stage.
· I prefer to use immersion oil as it is more viscous – it adheres the cover slip to the slide better with less leakage. However, if you collect material into liquid paraf n use more liquid paraf n if required before placing the cover-slip. Mixing liquid paraf n and immersion oil results in an opaque emulsion.
2. Scanning slides
· Initially, visually examine the slide to orientate it, and appreciate the depth of material, degree of staining and possible areas of interest.
· It is useful to check the quality of staining visually or under low power before placing a cover-slip, as the slide can be re-stained at this stage if necessary.
· Study the slide at progressively higher magni cation.
· Low-power lenses (x4–x10) are useful to scan large areas; with skin scrapes, hairs plucks etc., start at one corner of the cover slip, proceed down to the opposite edge, across one visual  eld and back up again to methodically search all the collected material.
· Use the high-power lens (x40) to close in on areas of interest.
· Use the oil-immersion lens (x100) last of all to avoid getting oil on the other lenses.
42ND WORLD SMALL ANIMAL VETERINARY ASSOCIATION CONGRESS AND FECAVA 23RD EUROCONGRESS


































































































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