c. Mounting Procedures. Once the decoloring procedure has been done, the
specimen is ready to be mounted. First of all, the center of the slide should be
determined. This is done by laying a blank glass slide on a sheet of paper and drawing
an outline of the slide on the paper. Then the slide is removed and diagonal Iines are
drawn from corner to corner of the slide. Where these Iines cross is the exact center of
the slide. (See figure 4-6 for an example of how to center a glass slide). After these
preliminary procedures are completed (that is, the decoloring procedure and the
determination of the center of the slide), a temporary mounting medium is chosen.
There are three types in general use: Hoyer's medium, Berlese's medium, and
methylcellulose. Of the three, Hoyer's is preferred as it wiII last one to three years. The
arthropod specimen is mounted in the following manner:
Figure 4-6. Finding exact center of a glass slide.
(1)
Place several drops of mounting medium on the center of the slide.
(2)
Position the arthropod on the slide being sure to center it properly.
(3) Add enough media to cover the specimen as well as the area that the
glass slip wiII cover.
(4) Paint one edge of the cover glass with medium. This allows increased
surface cohesion between the medium on the cover glass and the slide.
(5) Gently lower the cover slip on the slide. (If air bubbles occur in the
medium, they may be removed by gently tapping the cover slip or by heating the slide
over a bunsen burner. Be careful not to crush the specimen when tapping the gIass).
(6) Dry the slide in an incubator at 40 C for four days and air dry for an
additional two weeks.
(7) If the media shrinks, add more media around the cover slip edge, and it
wiII be drawn under the glass. The cover glass must be ringed with shellac or fingernaiI
polish to prevent drying and cracking of the medium.
4-11. PERMANENT SLIDE MOUNTS
In making permanent slide mounts, the kiIIing and decoloring procedures
described for temporary mounts may be used. However, unlike temporary media,
permanent mounting is not soluble in water; so, specimens must be dehydrated by
placing them in ascending series of ethyl alcohol concentrations of 70 percent,
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