INTRODUCTION

After my last article I searched the Web for "double edged razor blades". It was a surprise to me that 10 pages (at least 200 articles) were offered for my search. Many technicians, in several branches of science, do use or want to use these antiquities. There are even collectors that have spent decades collecting blades. The most interesting thing to me is the fact that you can buy the blades….in the southern hemisphere…and that a few producers in the north sell a limited quantity. Apart from Gillette, there are BIC, Schick, and America Safety Razors; all four have production plants in France, the EU and even Mexico. For those that are near a Wal-Mart supermarket there is an article on the Web stating that they sell our precious blades.

 So I have combed Cancún for old two-edged razor blades, and finally I get plenty of Permasharp ones, made in Brazil.

 Of course I immediately indulged  in new adventures with the Neuburg slicer. (I prefer “slicer” to “microtome” because the sections are not really thin enough to warrant the more technical name.)

 After several trials I became convinced that with this instrument the thickness of the sections was unpredictable. The blades are flexible. My fingers always apply different amounts of pressure. And so on.

 As a consequence successes are less than failures.

So I have finished making 3 additions and 1 major modification (with an additional option) to the little instrument.

1)      I prepared cutting surfaces, making 1.5 cm wide and 3 mm thick strips from the expanded polystyrene trays my wife brings home from the supermarket.

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.

5)      For the reasons I explain in the second part of this article I now use, as an alternative, half a razor blade for the job. The thickness of the blades is nearly 100 microns. I put a half broken razor blade along the upper edge of the slicer, without using the tape at all. See the technical tips.

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.

 Now I put the biological material over the cutting strip, press it with my finger, taking it all in my left hand and submerge the whole under the water in the cutting tray.

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.

 Normally there is a beautiful section stuck near the cutting edge of one of the blades. With a fine and soft brush I pass it to a two cm deep capsule with a few milliliters of 50% glycerin .

To cut another section, I rebuild the razor blades sandwich and press it with the clamp.

medium thick section, x 10 objective, 9 unit pictures click to enlarge	thick section, x 4 objective all three pictures in bright field illumination all three sections from Epipremmnum aureum	section made with a blunt slicer, x 10 objective

 In a few minutes one can make several subsequent sections, obtaining consistent results. Used over the polystyrene surface the sharpness of the blade edges are maintained for many hours (even days). You need of course to find the proper position of the clip’s jaws over (or under) the razor slits. More than any other feature this governs the thickness of the section.

 Try putting the jaws just over or not more than 4 mm from the upper edge of the blades' slits. In my experience within these limits a higher setting gives thinner sections. Isn't it amazing?

 The most common sections are transversal ones (cross sections, x-sections) but with this new configuration you can make longitudinal sections. Use a reasonably wide stem ca. 5-6 mm long. Take it between your fingers and slide the slicer carefully between them to reach the surface of the stem. Make the section taking care the blades are vertical. Not all attempts are successful. I normally make 3 to 5 attempts to finally select a thin, transparent and uniform section.

A composite image of a thin vertical section of an Epipremmnum stem. Bright field, x 10 objective. Five individual pictures stitched with Photopaint. Click the picture to enlarge.

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.

 You know your sections are thin enough when the coverslip lays flat over it, neither tilting nor requiring many drops of media.

 Sometimes I work in small batches.

 The capsule with the sections gathered after one working session is put on the turntable of my microwave oven and treated with 12 to 15 seconds of irradiation. I mount them in pure glycerin or in PVA-G, and set them aside for at least 12 hours before bringing them to the microscope.

 Alternatively I collect the sections in water, and pass them to hypochlorite solution (6% free chlorine) if I intend to make a more permanent slide.

 Permanent slides could be made with 60% fructose, GAF, PVA-G or glycerin jelly, without any subsequent treatment but an adequate stepping in the concentrations of the mounting media (or glycerin infiltration, in the glycerin jelly case). I have even mounted directly in PVA-G.  These slides are good for a general view of the histology of the studied organs.

 And with both alternatives you can profit from an assortment of contrast discs** which gives you the benefit of diffraction staining, besides the normal brightfield illumination.

 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.

 The classical treatment requires getting rid of the cytoplasm with hypochlorite and the differential staining of the remaining cell walls with one or more dyes.

 For the construction and use of contrast discs, and the optical equipment used, see Dioni
http://www.microscopy-uk.org.uk/mag/artdec03/wdonion2.html

To learn to make permanent mounts the classical style, see these web references:
http://www2.ac-lyon.fr/enseigne/biologie/ress/biologie_vegetale/cou_veg.html
http://www.ualr.edu/~botany/celltiss_lab.html
http://www.zoo.utoronto.ca/able/volumes/vol-19/09-yeung/09-yeung.htm

A magnificent presentation of plant histology images from sections made with professional methods is presented in

http://www.mhhe.com/biosci/pae/botany/histology/html/ptmodov.htm

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 Magazine.

In a companion article I gather the technical tips for the slicer design and many illustrations of the performance of the slicer.

PROS

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.

2)      Section quality is sufficient for a detailed anatomical study of stems, petioles, ovaries of many flowers, leafs, and so on. Leaves are dealt with easily with the new configuration. They are difficult materials for the traditional hand microtomes, not to speak of the essays discussing how to make free-hand sections of them. The problem is, that for a section laying on its cut side its width must be thinner than the thickness of the foliar lamina. The new configuration ensures this. Of course if you work with such thin sections (both in height and width) you can expect some mis-manipulations leading to a twisted lamina, but you always have enough spare material to study the leaf anatomy in cross section.

x-section of Epipremmnum stem, treated with hypochlorite and stained with gentian violet. x 10 objective. Bright field	x-section of leaf petiole of Syngonium podophyllum mounted in 50% glycerin and viewed through a dark field stop. x 10 objective
x-section of Epipremmnum leaf, bright field, x 4 objective. Background treated in Photopaint.	Moulds over the epidermis of a x-section of Gerbera leaf. Three focus levels combined with CombineZ. x 40 objective. Bright field.

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.

Thick section (to conserve the seeds in it) of a mature ovary (or young fruit) of Hybiscus rosa-sinensis. This picture is a mosaic of ten individual ones stitched with PhotoPaint click the picture to enlarge

CONS

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.

CONCLUSIONS

            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.

 Its simple construction and use, with consistent good section quality, puts in the hands of every teacher the capacity to give his (or her) students a basic appraisal of the vegetable’s anatomy at a more than reasonably low cost.

 It is really a better choice than the potentially dangerous free-hand cutting method, the original Neuberg design, or all the many recommended elementary, home-made, low tech, bolt and nut based “microtomes”

 I present here the stars of my story. You will be introduced to more of their secrets and those of other garden plants in the second half of this article.

Ocinum basilicum - basil	A monocotyledon plant - Syngonium podophyllum
One domesticated garden cultivar of Epipremmnum aureum, a tropical vine.	The flower of Hybiscus rosa-sinensis.  It was its young fruit that was sectioned.

Plant pictures taken at 1280 x 960 pxs with a Samsung Digimax 201 camera and reduced to 320 x 240
to be inserted here. The foliage under the Hybiscus flower is Aptenia cordiflora to be treated later.

**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.