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Related article: 6. Note whether the front lens of the objective is clean before
attempting to use it. If soiled, breathe on the lens and gently wipe
with an old, clean, soft handkerchief or lens paper. If the lens be
soiled with balsam or some other sticky substance, moisten the
handkerchief or lens paper with a drop of xylol, taking care to wipe
it perfectly dry as soon as possible.
7. Do not let the objective remain long near corrosive liquids,
such as strong solutions of iodine, corrosive sublimate, or mineral
acids. Never examine objects lying in such fluids without putting
on a cover glass.
8. Never lift the slide from the stage, but, after raising Amoxil Online the objec-
tive, slide it off the stage without upward movement.
9. Never allow the stand (microscope without lenses) to be wetted
with such substances as alcohol, soap, etc., which dissolve lacquer.
10. Keep the microscope covered when not in use.
FUNDAMENTAL CONSIDERATIONS 15
MAKING OF SECTIONS
Free-hand Sectioning. Free-hand sections are usually satisfactory
for the general examination of roots, stems, leaves, barks and many
fruits and seeds. Material which is fresh may be sectioned at once,
but dry material should be well soaked in warm water before using.
Very hard material like heartwoods, the shells Amoxil Online of nuts and seeds,
may be softened in solution of caustic potash or ammonia water
and then washed free of alkali before sectioning.
The object to be sectioned is held between the thumb and finger
of Amoxil Online the left hand. If tender and flexible, such as a flat leaf, it must
be placed between the two flat surfaces of elder pith before sec-
tioning. A segment of pith about an inch long is halved lengthwise
with a sharp knife and a portion of the leaf is held between the halves
of pith while the section is cut through pith and leaf. The pith
is later separated from the leaf section. Sections through other
delicate parts of plants may be made in the same way, only a groove
should be made in the pith of such size as is necessary to hold the
material firmly enough without crushing it. In certain instances,
when, because of the smallness of the object and its resistance to
cutting, good sections can not readily be made with the aid of pith,
a small sized cork stopper can be used with better results. A hole
just Amoxil Online large enough to prevent the object from slipping is made in the
center of the smaller end and the object inserted preparatory to
sectioning. The upper surface of the razor is wetted with water or
50 per cent, alcohol. The razor, which should be real sharp, is held
in the right hand and is drawn across the object with the edge toward
the student and the blade sliding on the forefinger of the left hand.
The sections should be cut as thin as Amoxil Online Amoxil Online possible. As soon as a number
of sections have been cut, they can be transferred to a vessel of water
with a camel's hair brush.
Sectioning in Paraffine or Celloidin. When it is necessary to study
the microscopic structure of very delicate plant parts, superior results
can generally be obtained by imbedding the material in paraffine
or celloidin, which is subsequently hardened, and sectioned by means
of a sliding Amoxil Online or rotary microtome.
KINDS OF SECTIONS
1. A transverse or cross-section is one made horizontally through Amoxil Online
the object, hence its plane lies at right angles to the long axis.
2. A radial-longitudinal .section is one which is made parallel to
the long axis of the object in such a way
that it lies in plane of the radius.
3. A tangential-longitudinal section is one
made parallel to a plane tangent to the
cylinder. This type of section is therefore
prepared by cutting parallel to the outer
Microtomes are instruments employed to
facilitate the cutting of sections of organic
tissues. The three most commonly used
types are the hand, sliding and rotary
Hand Microtome.- This type is shown in
Fig. 8. If the object is sufficiently hard to
bear the strain, it is placed directly in a
clamp at the upper end of the tube that is
tightened by the screw seen on the side of
the tube, or it may first be inclosed in elder
pith or cork and then clamped in. The
object to be sectioned is raised a little at a
time through the hole in the glass plate at
the top by turning the finely graduated feed
near the base of the tube. The section razor
is then laid flat on the glass plate and pulled
across the object with a long sliding motion.
FIG. 7. Showing the
planes in which sections
are cut, A, transversely;
B. longitudinal radially;
C, longitudinal tangen-
tially. (After Stevens.)
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