More Old Slide Rambles
by Richard L. Howey, Wyoming, USA
In previous essays, I have written about the risks of buying vintage and antique slides, but this time I shall try to keep my cynicism in check and emphasize some of the more positive aspects of making such purchases.
Suppose you buy a grouping of 10 slides for $50; that is, you’re paying $5 per slide which is a bargain considering that most modern slide preparations cost more than that and single speciality slides such as serial sections of a 6 week old chick embryo sell for more than $200. Modern well-stained histological sections can be very good. Human pathology slides can, however, be quite a different kettle of flesh. These are no-frill preparations designed to provide information to medical personnel–they are not meant to be “permanent” slides. This fact means that old slides from medical sources are very likely to be in various states of deterioration, often severe, so Caveat emptor.
However, there are a number of types of relatively simple slides which you can make yourself. Strew and smear slides can be quite simple. Take a drop of blood or a scraping from the inside of your cheek, put a bit on a slide, then take another slide or a thin blade and spread this material across the surface of the slide in a thin layer. Diatom, foram, or radiolarian strews are a bit more challenging in that you want to assure that you have a nice distribution that allows you to examine individual specimens. This means that you don’t want clumped masses of shells or tests. However, this is not a major difficulty and merely requires a bit of practice, but if you would rather purchase them such slides are almost always of very good quality.
Some types of specimens require very elaborate, time-consuming and intricate techniques, some of which should be prefaced with a warning note:
DO NOT TRY THIS AT HOME!!!
Sometimes I think it’s amazing that certain groups of microscopists in the 19th and early 20th Centuries lived beyond the age of 30. Imagine boiling diatom samples in nitric acid to clean the frustules or preparing sections for TEM and observing the progress under the microscope as the uranyl acetate attacks your retinas or breathing ground glass particles as you prepare glass sponge samples. There are techniques that have been developed to deal with these dangerous situations, but such means are rarely available to the amateur.
There are all sorts of risks in being a microscopist and as I pointed out in a previous article, if insurance companies really understood the range and gravity of these risks, it would be almost impossible, or at least, financially not feasible for us, to obtain life insurance.
Preparing slides of pathogens or parasites carries with it significant risks if one is dealing with fresh material that is still biologically active. If you were a sufficiently large firm, then you could hire or subcontract people to collect, kill, and preserve the required specimens thus virtually eliminating the risk of your being infected. There is a list of potential risks which is long and disconcerting. Jut a few: venoms, snakes, toxins of spiders, stings of jellyfish, scorpion fish and watch out for the nasty bites of Komodo Dragon Lizards. I said at the beginning of this essay that I would try to restrain my cynicism and I have, because if you are bidding on old slides, someone else has already taken those risks for you, so now you don’t have to–Coward!
I already mentioned the risk of boiling nitric acid, but there are many other chemical risks which slide makers have faced. Imagine vaporizing arsenic (realgar) to achieve a mountant with a very high refractive index for mounting diatoms. Some researchers wanting to remove silica from tissue used hydrofluoric (NOT hydrochloric, but HYDROFLUORIC acid). This is an incredibly dangerous, aggressive reagent which because it eats glass, has to be stored in wax-lined containers or ones made out of substances impervious to the acid. A very small quantity spilled on the skin can prove lethal and, of course, the vapors are unbelievably corrosive, savagely attacking mucous membranes.
Another “brave” action was the use of mercury compounds. (In earlier days, it was deceptively and quite charmingly called “quick silver” (I wonder if there is such a thing as “slow silver”?) What could be so bad about mercury compounds? In the 16th Century, Paracelsus (Phillipus Aureolus Theophrastus Bombastus von Hohnheim), the father of modern medicine, routinely used mercury compounds, especially in the treatment of syphilis and achieved “fair wondrous” results. And, in fact, such compounds were used for just that purpose up into the early 20th Century. Well, then it became clear that these compounds had some rather nasty side effects. You’re all familiar with the Mad Hatter in Alice in Wonderland. His madness derived from his use of mercury compounds in the tanning of the leather to make his hats. Not a good choice between being mad or syphilitic–although even some who received no such treatment were both. I’ve always counted myself lucky to be merely mad. A very good and popular stain is Harris’ Hematoxylin which contains mercuric oxide (or mercuric chloride in some formulas). Now, those chemicals are very difficult to obtain in the U.S. There is a relatively recent modification which replaces the mercury oxide with less dangerous chemicals and is now the standard stain that supply houses provide as Harris Hematoxylin.
An enormous number of micro-techniques involve the use of alcohols. Pure (100%) or “absolute” ethyl alcohol is called for in many recipes in micro-technique. We tend to treat ethyl alcohol rather casually, in fact, many of us drink it in a variety of modifications. Microscopists often use absolute alcohol which is highly regulated in this country. However, one can go to a liquor store and buy a bottle of Everclear which is 95% ethyl alcohol and if that won’t quite do, there is the option of heating some copper sulfate and driving the water off, then adding it to the alcohol until it slops changing color, then filter the solution and–voila! absolute alcohol (or close enough). Absolute alcohol should not be treated casually; it rapidly removes water from tissue and so you should always dilute by half to make your afternoon laboratory martinis. Unfortunately, some college students have used Everclear or other extremely strong alcohols in hazing rituals forcing fraternity pledges to drink undiluted alcohol. This is extremely dangerous and can lead to death. In microscopy, dehydration of tissue is the whole point, so that the material can be mounted in media, usually resins, which will not tolerate even small amounts of water and when present the medium becomes cloudy thus ruining the preparation.
This led to a quest for mountants that were more water tolerant. Some were developed that could tolerate using 90%, 75%, or even 50% alcohol.
Another approach was to find media that were readily miscible with water, such as, glycerine or glycerine jelly, or mixtures using polyvinyl alcohol.
Just think, in buying the Victorian slides, you don’t have to concern yourself with all this fol-de-rol. Except, in the end, you do. The usual mountant was Canada Balsam which was, and still is, whimsical at best, for several reasons. It is an organic resin from a pine tree and the process of collecting and refining it may vary and produce a product which also varies in quality. Secondly, it is a resin which almost never fully dries and so is subject to a number of environment factors. Because, even after decades, it remains a complex fluid and improper storage of slides (i.e., vertically) can cause the resin to “run” toward the bottom edge of the cover glass and may, if prolonged, cause the specimen to migrate to the edge as well where it may very well become useless. Another problem with balsam (and other mountants) is that if the cover glasses are not properly sealed, then due to seepage, air may get under the cover slip and form intricate and sometimes beautiful patterns while ruining the specimen(s). If balsam mounts are exposed to heat, they cause the cover glass to press down on the mount and thus expel the resin around the edges of the cover slips where it crystallizes. This decrease in the mounted in the specimen area produces pressure which may distort or destroy the specimens.
So, this is another thing to be aware of when attempting to evaluate old slides. If it’s a fairly extensive collection (10 or more slides) or a rare and rather expensive singles slide, you may well wish to ask the seller some pointed questions about the condition.
Sometimes we assume that if the slide(s) come from Möller, Watson, or some other reputable dealer’s stock, then the slides will be in fine condition. Here we need to stop and remind ourselves that these were businesses with a number of employees involved in slide-making. They are not going to be equally skilful no matter how regimented the production procedures. I purchased a Watson slide of moth eggs which I was quite excited to get; however, my first glimpse under a stereo microscope told me that I would be sorely disappointed. The eggs were covered with mold which made them essentially useless as observable objects. Mold spores are ubiquitous and it is not surprising that one encounters this problem repeatedly. However, there are certain preventative steps that can be taken. This was a dry mount, so a tiny crystal of paradichlorobenzine (moth ball) or thymol included under the cover glass would likely have prevented the mold growth. So remember this if you are making your own preparations. If, however, you are buying 19th Century eggs, don’t try to make omelettes. Seriously, ask the seller about mold and if it has invaded the specimens, DON’T buy! However, if you find some slides in good condition, by all means buy them; they are fascinating objects.
Another 19th Century specialty was the production of beautiful thin slices of sea urchin spines. The structure is amazingly complex and once you experience the intricacies, you cannot help but be astonished. The entire object is composed of tiny crystals in patterns. These sections are extremely delicate and when not mounted properly, may suffer damage from the cover glass pressure which can readily ruin a specimen. Well preserved specimens are spectacular and many are dazzling under polarized light so, if you find some good examples at a reasonable price, by all means BUY THEM! And save yourself from the experience of being incarcerated in the loony bin. If you try to prepare such sections yourself, you will find your nerve fibers stretched to the breaking point. You can cut, polish, and hand rub and then, in the final stage, find your specimen has betrayed you and broken into tiny crystalline shards. After spending many hours of preparation and now, facing disaster you may well discover a panoply of four letter words that you didn’t even know you knew. So, think of it this way, a bit of an investment, perhaps a bit of an indulgence, to acquire some prepared slides might well save you from very expensive therapy sessions with a psychiatrist. I have this fantasy in which microscopists who make these remarkable sections do so, like monks, except they are confined to padded rooms in “psychiatric institutes.” So, if you find some nice preparations, treat yourself and save yourself a great deal of frustration.
Another kind of extraordinary slide is the diatom and/or butterfly scale arrangements. These can be as simple as 3 or 4 diatoms or hundreds arranged in intricate and stunning patterns.
Also there are beautiful arrangements consisting solely of butterfly scales. It is these sorts of activities that I have argued in previous essays, lead to mental stress and ultimately breakdown leading to commitment. Obviously, I exaggerated, but imagine the psychological effect of trying to create a diatom or butterfly scale arraignment that consists of 250 elements and then as you put the 240th element in place, you sneeze and your thumb smears that slide thus utterly ruining it. Your cry of anguish is loud enough to rouse your neighbors to call emergency services. So, if you have a passion for such arrangements, I recommend you save up your kopeks and buy some good examples rather than trying to make them yourself. Such slides may seem a bit pricey, but again cheaper than therapy.
Botanical thin sections, especially when properly stained can indeed be minor works of art. Here again, the techniques for producing fine sections can be both costly and time-consuming, not to mention demanding. First of all, you need to determine how you are going to produce the thin sections. With much practice and experimentation, a hand microtome can produce quite good sections, but it is limited to a fairly narrow range of specimen types. A rotary or sliding microtome will produce thinner, more consistent sections and allow for a greater range of specimen material. However, such microtomes are expensive and demand patience and persistence in order to master the techniques necessary for producing good sections. Furthermore you will need to learn embedding techniques for infusing the specimens with paraffin or a resin prior to sectioning. So, once again, we find a situation where generally it is better to buy such slides than attempting to produce them. All of these cases, however, depend upon the intensity of your passion for technique, interest in subtlety and detail and your level of creative commitment. If those factors are all strong and of high priority then, by all means, make your own slides. However, for most of us, it may well be wiser to focus our energy and talents on other aspects of exploring the micro-world.
All comments to the author Richard Howey are welcomed.
Editor's note: Visit Richard Howey's new website at http://rhowey.googlepages.com/home where he plans to share aspects of his wide interests.
Published in the February 2019 edition of Micscape Magazine.
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