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Transcription
a letter or number by which the two may be identified.
The symbol may be scratched on the capsule with
a pin, or written with India ink.
8. Slides. These come by the dozen or half gross.
The price per slide falls as the quantity rises.
9. Cover glasses, available in several sizes, and in
two shapes, round and rectangular. They are sold by
the ounce. Half an ounce will be plenty to begin with.
10. Some supports to hold up the cover glasses and
prevent the specimens from being squashed as the
balsam dries and shrinks. Supply houses offer, for
this purpose, cover-glass size plastic rings of various
thicknesses called "cells." These are tidy to use, and
look well, but they retard the drying of the balsam by
excluding the air. It is just as practical, and cheaper,
to support your covers with fragments of broken
cover glasses as shown in Fig. 9. If the steel snaps
when bent, grasp the bow of the pin with pliers and
heat the ends red hot over a gas flame. Allow the pin
to cool slowly, without quenching. This will remove
the temper, so that you can bend the metal easily.
14. Gummed paper labels a little less than an inch
square, fine pen, and India ink, for marking the slides.
15. Slide boxes in which to store the finished
product. One of these is shown in Fig. 10.
16. A jig or pattern by which to center the speci-
mens on the slides. Although not strictly necessary
Fig. 9. Newly assembled microscope slide. Note label, cover-
glass stilts, and bobby pin clamp.
cover-glass, if the specimens are thin, and with bits of
transparent plastic sheeting of appropriate thickness,
if they are bulky. These stilts will scarcely show in
the finished slide, and since they do not entirely sur-
round the balsam, they permit it to dry more rapidly.
11. Tools for handling the specimens, including
fine forceps, mounted needles and medicine dropper.
12. Absorbent paper, such as blotters, towelling,
or facial tissues.
13. Bobby-pins, bent into clamps for holding
Fig. 11. A jig for centering specimens on microscope slides.
this is a useful gadget which will save you more time
than its construction will require. Fig. 11 is a picture
of a jig. To make it, you need two rectangular pieces
of cardboard, about four inches by two. Lay a glass
slide on the lower right-hand corner of one of the
pieces, matching the edges, and draw a line around it.
Cut out the corner of the cardboard, following the
outline carefully. Glue the two pieces of card to-
gether, matching the three remaining corners, and put
them to press under a heavy book until dry. You will
now have a thin block of cardboard with a slide-size
depression in one corner. With a ruler, locate the
mid point of this depression. Mark it. With this
point as center, draw a circle or rectangle the size of
a cover glass. This locates the area which the cover-
glass will occupy on the finished slide.
A biological specimen imbedded for scientific
study must be not only covered but completely filled
with resin to make it clearly visible. A trace of water
in the specimen will fog the balsam. An air bubble
inside the animal deflects the light and obscures the
image. To replace the natural liquids and gasses of
the body with a transparent, and ultimately solid,
substance is the purpose of slide preparation pro-
cesses.
The body fluids of animals are largely water.
Balsam is soluble only in oils. The incompatibility of
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