A CHEAP AND PRECISE SLICER FOR TEACHING BOTANY(and new adventures in my garden)
Cross section of
basil stem. 10x
objective. Rheinberg filter with opaque
black 10 mm center and peripheral ring with alternate red and blue
I've put pictures of the plants used for this article in the Gallery at the end.
After my last
article I searched
the Web for "double edged razor blades". It was a surprise to me that
(at least 200 articles) were offered for my search. Many technicians,
branches of science, do use or want to use these antiquities. There are
collectors that have spent decades collecting blades. The most
thing to me is
the fact that you can buy the blades….in the southern hemisphere…and
few producers in the north sell a limited quantity. Apart from
BIC, Schick, and America Safety Razors; all four have production
consequence successes are less than failures.
A new design
So I have finished making 3 additions and 1 major modification (with an additional option) to the little instrument.
2) I buy a paper clamp (see fig 1) 32 mm wide (40 mm could be better).
3) I get a tray of 9 x 20 x 2.5 cm (also from the supermarket) to be filled up with water.
4) In my later attempts I have changed to “Scotch” adhesive tape to separate the blades. The tape has a thickness of nearly 50 microns. I put one piece along each of the lateral sides of one of the razor blades.
When I want to make a section I put the blades together and clamp them with the jaws of the clip just over the slits so they are well fastened. Submerge the edges in the water, or put some drops over one blade before closing the slicer. Water goes up by capillarity between the blades.
With the other hand I place the cutting area of the blades in position over the material. Pressing the instrument down and ahead with a diagonal trajectory I cut slowly until both edges indent the cutting surface. This is important because this ensures that the section is completely separated from the cut material. A plastic strip 10 cm long supports dozens of attempts.
Now I remove the clip and, best under water, manually or with the aid of the point of a needle or a scalpel I open the razor blades.
another section, I rebuild the razor blades sandwich and press it with
You can mount your sections temporarily in water, or in 50% glycerol in water. The latter has a very good refractive index and lasts several hours with minimal replenishment. You can even use a little Vaseline on the coverslip borders as is customary for wet mounts.
After the drawing or photographic session comes to an end, the sections can be recovered, washed in distilled water, and submitted to a more classical and permanent mounting technique.
To learn to
make permanent mounts the classical style, see these web
A magnificent presentation of plant histology images from sections made with professional methods is presented in
A very good
techical paper in two parts covering state of the art techniques for
making and mounting botanical sections is presented by Jim Battersby in
the 2004 February and March editions of Micscape
In a companion article I gather the technical tips for the slicer design and many illustrations of the performance of the slicer.
1) Doesn’t need tissues support (Elder pith, polystyrene, carrot, potato, paraffin wax) which is by itself a huge achievement. Think on this because it is an outstanding feature. Most of the amateurs' discussions on the Web are over the support for tissues to be cut with the Ranvier style microtomes.
quality is sufficient for a
anatomical study of
stems, petioles, ovaries of many flowers, leafs, and so on.
Leaves are dealt with easily with the new configuration. They
difficult materials for the traditional hand microtomes, not to speak
essays discussing how to make free-hand sections of them. The problem
is, that for a
laying on its cut side its width must be thinner than the thickness of
foliar lamina. The new configuration ensures this. Of course if you
such thin sections (both in height and width) you can expect some
leading to a twisted lamina, but you always have enough spare material
the leaf anatomy in cross section.
3) Very cheap. Five instruments require two boxes of razor blades (5 razors a box). With a cost (now at Cancún) of 0.28 dollars (0.056 dollars/ slicer).
4) Easy construction by careful experienced amateurs. Not more than 10 minutes needed to make and put to work a new slicer using the half razor blade separator, or more or less 20 minutes for the Scotch tape version.
5) Easy to use. The learning curve is very quick. Any user can start to do a good job in a matter of minutes.
6) Safe enough to be used under adult supervision even by secondary school students.
1) Not safe enough to be built by very young scholars or amateurs, without adult supervision. Of course no one microtome is safe and all professional or even those amateurs' commercial ones are MORE dangerous, and only appropriate for use by technically trained adults.
2) Sections must be made one by one. You need to put together all parts, to make the section very carefully, to split open the instrument, and to pass the sections on to its further destiny. And repeat all of this for any one section….But are you very pressed? Did you need a lot of serial sections in a limited time?
Don’t try to make several subsequent sections without taking out the first one. The thickness of the first section opens the blades and every new section is wider than the previous one.
3) Air bubbles. It is easy to trap air bubbles in the cut exposed cells or vessels, if you cut dry in the air. Cutting under water mostly obviates this. If there's some persistent bubbles, put the sections in a glass capsule (a little Petri dish is best) in more or less 10 ml of 50% glycerin and submit them to the microwave oven. In a 700W domestic one, at 100% (Full) 10 or 12 seconds, get rid of them. (Make proportional estimates for 400, 600, or 1000W ovens). Additionally the microwave generated heat fixes the plant tissues and clarifies the sections.
A word of warning: the Euphorbiacea and many other plants can have lacticiferous channels full of latex that flows out like milk over the cut surface. Cutting under water and removing after some seconds the just made section, generally washes out the latex.
With this new configuration and including the easy to build and cheap contrast discs, and one or two dyes easily found in drugstores, the double razor blade slicer merits incorporation into not only the amateurs' laboratories, but also to the secondary or even more advanced school laboratories.
pictures taken at 1280 x 960 pxs with a Samsung Digimax 201 camera and
reduced to 320 x 240
**I prefer to say “contrast discs” because it is shorter than “stops, diaphragms, and filters”. After all they are discs, or are mounted on discs, to be put in the filter tray under the condenser of the microscope.
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