Bresser National Geographic Mode D'emploi page 13

being examined, the light from below goes through the specimen, lens and eyepiece to
the eye and is magnified en route (direct light principle, switch position II).
Some small water organisms, plant parts and animal components are transparent by
nature, but many others require pretreatment — that is, you need to make a thinnest
possible slice of the object by hand cutting or using a microtome, and then examine
this sample.
7.2. Creation of thin preparation cuts
Specimens should be sliced as thin as possible. A little wax or paraffin is needed to
achieve the best results. Put the wax into a heat-safe bowl and heat it over a flame
until the wax is melted. You can use a candle flame to melt the wax.
DANGER!
Be exremely carfeful when dealing with hot wax, as there is a danger
of being burned.
Then, dip the specimen several times in the liquid wax. Allow the wax that encases the
specimen to harden. Use a MicroCut (22) or other small knife or scalpel to make very
thin slices of the object in its wax casing.
DANGER!
Be extremely careful when using the MicroCut, knife or scalpel. These
instruments are very sharp and pose a risk of injury.
Place the slices on a glass slide and cover them with another slide before attempting
to view them with the microscope.
7.3. Creation of your own preparation
Put the object to be observed on a glass slide and cover the object with a drop of
distilled water (No. 3) using the pipette (No. 3, 20a).
Set a cover glass (available at a well-stocked hobby shop) perpendicular to the edge of
the water drop, so that the water runs along the edge of the cover glass (No. 4). Now
lower now the cover glass slowly over the water drop.
TIP: The gum medium (23b) supplied is used to make permanent slide
i
cultures. Add it instead of distilled water. The gum medium hardens so
that the specimen is permanently affixed to its slide.
8. Experiments
Now that you're familiar with your microscope's functions and how to prepare slides,
you can complete the following experiments and observe the results under your mi-
croscope.
8.1. Newspaper print
Objects:
1. A small piece of paper from a newspaper with parts of a picture and some
letters
2. A similar piece of paper from an illustrated magazine:
Use your microscope at the lowest magnification and make a slide preparation from
each object. Place the slide with the newspaper on the microscope table and observe
the slide. The letters in the newspaper appear broken because the newspaper is
printed on raw, inferior paper. Now observe the slide with the magazine preparation.
Letters of the magazine appear smoother and more complete. The picture from the
newspaper consists of many small points, which appear somewhat dirty. The pixels
(raster points) of the magazine image appear sharper.
8.2. Textile fibres
Objects and accessories:
1. Threads of different textiles: Cotton, linen, wool, silk, Celanese, nylon and
any others you can find.
2. Two needles: Put each thread on a glass slide and fray each with the help of the two
needles. Put a drop of water over each thread with the pipette and cover each with a
cover glass. Adjust the microscope to a low magnification. Cotton fibres are of plant
origin and look, under the microscope, like a flat, twisted band. The fibres are thicker
and rounder at the edges than in the centre. Cotton fibres consist primarily of long,
collapsed tubes. Linen fibres are also of plant origin; they are round and run in straight
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