Pseudo-Microscopes: A Cranky Essay

by Richard L. Howey, Laramie, USA

 

During the past week I have had two encounters that have annoyed me sufficiently to need to vent a bit of spleen. The first incident was a friend relating that his brother-in-law had purchased his son a toy microscope set. Such news inevitably launches me on a rant. I strongly suspect that toy microscopes have been more responsible for the decisive destruction of interest in microscopy for children than any other single factor. Just consider the psychology—a child is promised that new, beautiful, mysterious universes will be opened; that creatures more bizarre than any found in science fiction films will be revealed; that crystals more dazzling than the Crown Jewels will form before his very eyes. All of this is reinforced by dazzling photographs on the box of the microscope kit which one learns belatedly were clearly not taken through the microscope in the kit!

Now, after a build-up like that, who wouldn't be excited. And what's more, that kit even comes with some prepared slides. So, on Christmas morning, Papa (the high-tech expert), didactically explains to Jeremy and Janice, the importance of being organized, keeping all of the apparatus clean, recording one's observations in a notebook along with careful drawing, all the while setting out the various items from the kit in a neat display on the desktop. The lecture is interrupted for a half hour while Papa goes looking for a small, adjustable high-intensity lamp, since the microscope (this being the economy kit) is fitted with a mirror rather than an illuminator.

Finally, everything in readiness, Papa selects the stained pollen grains slide and cuts his finger on a sharp unpolished edge. Jeremy enthusiastically cries; "Oh, good Daddy. Here's a blank slide. Now we can have a blood sample." Papa rather grumpily replies that there is already a prepared slide of human blood. He quickly puts the pollen slide on the stage, looks through the lens with his right eye, squinting his left eye closed and tries to focus. After several tries some flattened spheres, some blue, some red, come into fuzzy view. The field of view curves out around the edges and there are color fringes around the specimens. Papa grabs the booklet that comes with the kit and reads the following sentence: "This fine instrument is fitted with high quality plastic lenses to assure sharp, clear detail." Now, in an ideal world, Papa sues the manufacturers for false advertising, is awarded a settlement of one million dollars and buys Jeremy and Janice a Zeiss stereo-zoom with all the frills for $20,000.

Back to the real world—Papa gives up, leaving the children to cope and two weeks later the kit is put at the back of the closet to be sold the next summer at a yard sale.

Plastic lenses!?! Oh, yes, unfortunately there are such things. Fuzzy images? I have yet to see a children's microscope (what a concept!) which didn't produce fuzzy images. Spherical aberration—nearly universal. Chromatic aberration—you can count on it. Squinting and closing one eye—well, it's hard not to—especially for a child. At one time, when I was using a monocular compound microscope for some water immersion observation, I bought an eye patch for my left eye. With my beard and bulk, I looked like a rather portly pirate. As soon as I could manage, I found a used binocular microscope and switched the lenses to that.

I understand that monocular microscopes are simpler and ordinarily less expensive to manufacture, but I am neither Polyphemus nor Macrocylops, so if I had my way, all microscopes would be trinocular. No matter what you say now. eventually you'll want to try out a still camera or a video camera on your microscope. All right, I'd settle for binocular, but urge trinoculars for the avid amateur.

I think the microscope manufacturers are missing a good bet. Most modern research microscopes are modular. You can buy a standard brightfield instrument and then, as need and money allow, add phase contrast, darkfield, Nomarski differential interference contrast, epi-fluorescence, and polarizing without having to buy a whole new instrument. Of course, these are expensive instruments and the accessories cost more than having gold crowns put on all your teeth.

But what if a group of first-class educators and scientists set some international standards and said to microscope manufacturers: Here's what we need—how much per unit? I have some ideas of my own about what I'd like to see, but I'll put these in an addendum at the end of this little essay. However, let me give you one example—a good, reasonably priced fiber optics illuminator. My ideas may be a bit naive and I admit to being especially naive when it comes to economics—I've been teaching for thirty-five years and will have to teach another thirty-five before I can afford to retire, so don't trust anything I say about economics. Nonetheless (trust me!), it makes sense that if a company produced a really well-designed, efficient, compact fiber optic illumber optic illuminator and sold a million of them to schools, universities and avid amateurs, then they should be able to bring the price down to something quite affordable.

And there's the general argument! Produce a truly quality series of microscopes that are modular and AFFORDABLE and everybody's happy because Jeremy and Janice can actually see the pollen and blood cells and live protozoa, and as they grow up they buy more accessories and then later on buy microscopes for their children and nieces and nephews and the microscope companies make out like bandits by producing quality instruments at lower prices and the children and parents discover new universes. What more could you ask?

But here I am back in that ideal world. Let's take a look at what's going on in the real world of microscope production. An executive of a laboratory supply company recently told me that for the inexpensive to moderately-priced microscopes (both dissecting and compound), the chances are about 90% that they are manufactured in China.

I recently had occasion to examine one of the stereo dissecting microscopes from China. The company that sells these instruments imports them in considerable quantities. They then have their own technicians in this country go through the microscopes and replace all the lubricants. Chinese lubricants are notorious for becoming so stiff within a year as to make the instruments virtually unusable until they are overhauled. This same company goes through the electrical system and checks all the wiring and replaces the bulbs. This, reportedly, is done to circumvent the problem of having the bulbs blow out the first time they are turned on. All of this, of course, adds to the cost.

This instrument sells for $350 to $400. It has a fluorescent bulb as a substage illuminator. Now, this is admittedly truly a matter of taste, and some people are very fond of this type of illumination. I hate it; give me incandescent any day. The incident illuminator was a small halogen bulb in a metal housing that got so hot that I burned my fingers when I tried to adjust it. After a few minutes of observation, one could have parboiled Paramecia. There was also a rather nasty sharp edge along the top of the rack and pinion strip. The rack had been painted with what appeared to be aluminum paint and the entire affair looked cheap and glossy. The companies that sell these guarantee them for five years; I suspect that will change or they will go out of business. There is also the issue of the labor conditions under which these instrument are produced. There have been reports of sweatshop conditions and the use of child labor in the manufacture of some Chinese microscopes. So, for some people, there will be an ethical consideration about buying these instruments in addition to the issue of quality.

Earlier I mentioned getting some educators and scientists to suggest some international standards, but that's not likely to happen for a variety of reasons. However, another thought occurred to me: what if a group of dedicated amateurs, such as those who read MICSCAPE, initiate an in-depth discussion of their wants and needs in good quality relatively affordable microscopes of several types. From such a discussion, one might hope that several workable patterns might emerge and I suspect that some major manufacturers might very well take note. Larger production runs could very well provide quality instruments that have the features we want at a reasonable price. Such instruments will never be inexpensive, but remember, microscopes are better investments than computers. A good microscope doesn't become obsolete in a year and so far Microsoft doesn't manufacture them. A well-built, well-designed microscope will last for many, many years (if properly cared for). The newest microscopes I own are at least twenty years old and they will last me the rest of my lifetime.

While I'm rambling there is another concern about microscopes that I would like to address and that is the issue of magnification. Many cheap microscopes are promoted by advertisements that try to sell the ideas that more magnification is better. Now you can have not just 200x or 400x or 600x, but 1000x or even 1500x and all of this in a toy stand with plastic lenses. We have been sold the idea that bigger is better and now we rarely even critically question that idea.

One of the reasons that I am such a strong advocate for the stereo dissecting microscope is that it allows the beginner to observe an incredible variety of objects at relatively low magnifications and to achieve thereby a sense of the relationships of the magnified portions to the object as a whole.

With a compound microscope, high magnification often presents complex problems of preparation, observation, and interpretation.; it is crucial to first get comfortable examining a slide at 20x or, in some instances, even lower. At 40x, a seemingly tiny 22 millimeter square coverglass becomes the size of a good-sized back yard and every time you increase magnification, that area increases enormously in apparent size. By the time you increase the magnification to 1000x, looking for a particular specimen in a 22 millimeter square is rather like walking the length and breadth of a football field trying to find a penny.

The compound microscope is an excellent illustration of the fact that bigger is not necessarily better. Suppose you have a good preparation of living Paramecia. At 40x you can get a good notion of the general shape, movement, and feeding behavior. Naturally at 100x more detail is visible, but one must already know how or learn to recognize the key structures and it is at this point that resolution and contrast become crucial. With care you can observe the nucleus, the oral cavity, and the contractile vacuoles appearing circular and the canals like tiny tear-drop petals, thus giving the whole the appearance of a miniature flower.

If the organism is still swimming, then observation is much more difficult. If the coverglass is exerting just the right amount of pressure, then the Paramecia will be held down, but not crushed. This situation will last only briefly and one has four options: 1) let the coverglass eventually crush the cells causing them to break open, 2) add a drop of water at the edge of the coverglass from time to time, 3) prepare the slide by making a ring of petroleum jelly and placing the drop of water in that and then press the coverglass down into the petroleum jelly, or 4) make a preparation with methyl cellulose. With option 1, you can make some good observations even as the cell begins to break apart; option 2 requires patience since the additional water may allow the Paramecia to become active again necessitating a wait until the coverglass once again holds them immobile. Options 3 and 4 have several advantages. If properly prepared they will allow observation for considerable periods of time. The methyl cellulose has two disadvantages, however: 1) in some instances the shape of the organism may be severely distorted and the additional thickness of the preparation may enhance the 3-dimensionality of the organism, but increase the difficulty of observing fine detail. 2) Methyl cellulose is birefringent and this can be an annoyance when using polarization or differential interference contrast techniques.

At 400x everything is indeed larger, but it is also more difficult to resolve. It is crucial that one adjust the illumination and make sure that everything is properly aligned to achieve optimum contrast. You need to develop an overall sense of the organism, so that as you increase magnification, you know exactly what you are looking and at and where to look to find other structures that you are interested in. At 1000x a Paramecium is a giant and you will be able to observe only small sections at a time, assuming that the Paramecium is sufficiently immobilized not to go zipping off out of your field of view.

Another distinct advantage of the stereo dissecting microscope is the wide range of types and sizes of objects which can be viewed without special preparation. A piece of rock with interesting crystals,, a butterfly wing, an iridescent beetle, a mushroom, a mollusc shell, a small starfish, a small dish of pond water—any of these can be observed directly and immediately and fully reveal the marvels that the toy microscope promised. Ideally one should have a good quality stereo microscope—the best one can afford—and a good basic binocular compound microscope which is modular thus allowing for the addition of a variety of accessories. If you can afford only one, start with the stereo dissecting microscope. As your interest expands and grows, you will find ways to set aside bits of money to eventually buy a compound microscope.

Naturally there are special cases when a compound microscope is essential. If you are primarily or exclusively interested in observing diatoms or desmids or protozoa or bacteria, then a high quality compound microscope is indispensable.

In selecting a stereo dissecting microscope, there are several things to keep in mind:

1) Make certain that the instrument is full-sized and meets international standards for such things as the tube diameter for oculars. Some of the older instruments have a smaller diameter ocular than the more recent ones. In any case, be certain that good quality (new or used) eyepieces are available at 10x, 15x, and 20x. If you purchase a stereo-zoom system, you will also want to assure yourself of the availability of 0.75x and 1.5x auxiliary lenses. Often a 2x is available as well, but they are rarely worth the expense; the working distance is so small as to make them very inconvenient and the resolution is usually poor, producing empty magnification.

2) It is highly desirable that you select an instrument either with a) more than one objective b) a variable magnification such as the "zoom" system mentioned above, or c) a system with a Galilean drum with multiple sets of prisms which allow for several different magnifications.

3) In general avoid instruments which have the eyepiece tubes coming straight up. They are less expensive, but if you use the instrument much at all, there is a likelihood of severe neck and shoulder muscle strain. A dedicated amateur should obtain an instrument that he or she is truly comfortable with.

4) Acquire an instrument which allows for substage illuminations preferably with an adjustable mirror. Get two stage plates—a transparent glass one for observations with transmitted light and an opaque plate with one side white and the other black for observations with incident light. For incident light observations get a separate illuminator that allows you to direct the light precisely where you want it.

5) Do not buy an instrument unless you can try it out for a few hours at least, preferably for a few days. Make certain that it will fit your needs and that the accessories which you may want to add later will indeed be readily available. No matter how splendid the instrument sounds or looks, no matter what the guarantees are—DON'T BUY IT WITHOUT PERSONALLY CHECKING IT OUT CAREFULLY! An instrument that looks very attractive may turn out to be a mechanical and optical nightmare.

ADDENDUM

I said earlier that at the end of this article, I would make a few suggestions regarding what I would like to see in microscopes as standards, so here goes:

Stereo dissecting microscopes

1) A full-sized stand with a substage fully adjustable mirror with a light source. (Some stands are quite small and suitable for limited use, but in general it is highly desirable to have a large, comfortable stand).

2) Binocular (or trinocular, if you intend to do micrography or videography)

3) Wide-field oculars 10x (with 15x and 20x available)

4) A magnification range of 10x to 80x (This can be readily achieved with either 1x,2x, and 4x objective and 10x and 20x eyepieces or a zoom system)

5) A clear glass stage plate for transmitted illumination and an opaque stage plate (one side white, the other black) for incident light observation.

Accessories

a) A high intensity light source that can be directed onto opaque specimens at different angles, preferably a fiber optic type as mentioned above.
b) Arm rests which can be attached to the sides of the stage. This is especially desirable when one is doing intricate dissections.

Compound microscopes

I decided to save my suggestions here for another essay. I started sketching out some ideas and got into a tirade against some of the major microscope manufacturers based on some experiences that both I and others have had. So, I'll save all of that for another occasion. However, I would hope that readers would send in suggestions for configurations for both a stereo dissecting microscope and a compound microscope. I am sure that many of us will be interested in the results.

Comments to the
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