Saving Slides With Mountant Issues: I

Obtaining Damaged Slides

Very often the amateur may come upon the opportunity to obtain significant quantities of prepared slides of a type that makes use of methods or materials that are not generally within the scope of ones own activities. Such slides may provide valuable objects for study. Regrettably, one may find that many slides prepared in professional circumstances only find their way onto the market at excessive cost or when damage sustained in one way or another has rendered them unsuitable for study.

Recently a quantity of slides were obtained by the author that consisted of serial sections from Leptonycteris sp. The exceptionally thin and expertly stained sections were mounted in series under rectangular 18x40mm or 24x50mm coverslips. All of the slides showed degradation of the mountant to a greater or lesser degree characteristic of repeated stress from heating and cooling.

Due to the visible damage 75 individual slides were had for the incredible price of ten United States dollars. One would be hard pressed to obtain a similar number of blank slips or coverslips for the same price.

Assessing the Damage

Visibly degraded mountant, black background.

Initial observation showed that the slip was in fine condition without chips or cracks which would greatly complicate the task of rehabilitation. Despite the significant degradation of the mountant the cover slip remained firmly in place, a good sign that the sections beneath would be intact. Running a fingernail over the cover is often all that is required to determine if the coverglass itself is similarly undamaged.

Visual inspection showed the mountant to be significantly degraded on most of the slides. Pronounced yellowing at the edges gave way to white patterns where mechanical damage had caused the mountant to crack to an extent that it was no longer in optical contact with the coverslip. In some instances the mountant had become brittle to the point that the coverslip had come off entirely. The areas occupied by the specimen were invariably damaged even in places where the surrounding mountant remained sound, as may be seen at the extreme right of the image at left.

Under the microscope one could observe the extensive cracking of the mountant shown below. Focusing on the specimen with a 16mm objective was nearly impossible as the depth of focus afforded by the objective ensured that the cracked mountant would intrude into the image plane. At higher levels of magnification one could optically section the image enough that the cracks were not immediately evident, but resolution was impaired to the point of near total occlusion of any detail.

Photomicrograph showing degraded mountant.

Photomicrograph showing degraded mountant.

Slide Catalogs, Indices, and Labels

When building up a collection of slides it’s not uncommon for the collector to simply put them up in a case without a thought to organization or logging. It’s too bad considering the tools available to keeping track of things. Labels are an old tool but still of value. -K

Part One; Labels

I’m old enough to remember with apprehension the advent of digital catalog systems. I remember when looking for “that article about you know, the new study” in a journal whos name wasn’t remembered meant hoping the librarian knew your field at best, and wading through a cross index compiled by some other librarian at some other library and hoping a name seemed familiar at worst. Digital cataloging and inexpensive terminals changed all that. It became possible to dispense with a wall of tiny drawers and an army of clerks pounding away at typewriters loaded with cream colored cards. Keeping records became faster with the digital revolution, at least as far as looking things up went.

Putting records into the system, whatever system, is still time consuming. In place of typewriters there are keyboards and in place of cards there are fields on a database program. Of course keeping records can be faster now but it still requires some time and thought. What has any of this to do with microscopy? Slides of course. The cataloging used in libraries is rather similar to that needed for keeping slides organized so it’s only fitting that the two might be compared. Books however, have a bit of a leg up on the average microscope slide; there are pages within a book dedicated to identifying it. Slides have their labels, ideally, but often they are nearly useless for the sake of brevity.


Oh AmScope what horror is next?

The record keeping associated with the utility of a microscope slide is often overlooked. It’s tragic that the modern supply houses putting out their cookie-cutter slides, however well made and nicely stained, tend to put next to nothing on their labels. The nearest thing to a catalog is usually a printed card with only the name of the specimen and maybe a number corresponding to a slot in the case. One can see an example of this sort of modern prepared collection above. It is simple, mass produced, dubious in quality (notice specimen 2, Coprimus? because of course they can’t expect an underpaid technician to know that Coprinus is a genus and Coprimus is gibberish) but inexpensive and readily available.

When purchasing antique slides the collectors knowledge of the mounter or the uniqueness of the specimen, even the artistry of the preparation makes up for the usual absence of any extra notes. It’s noteworthy though to consider the differences in the labels on a modern slide and one of significant age. Below are two slides, each from a recognizable firm but of significantly different age. The primary market of each company varied as well. The more contemporary company markets almost entirely to young students and their teachers, the older served professionals, and amateur enthusiasts of every age.


One of these things…

On the more modern slide the information provided is rather limited to say the least. It is labeled “Bacteria Types w.m. Ba 020 Carolina Biological Supply Company”. Certainly knowing it is a slide of whole mount (w.m.) bacteria would permit one to look in the right text for identification but there is plenty of space on the label so it wouldn’t have been impossible to put the type of bacteria on the slide itself. Knowing the company and seeing their own catalog reference (Ba 020) would make it a bit easier to track down more information about the specimen but not knowing a date and considering the recent changes at Carolina finding out anything further about the slide will be difficult. As an example of different bacteria types the slide is useful, but as a representative specimen it is quite useless without a good deal of effort.

The older slide is from W. Watson & Sons and also has rather limited information on it’s labels. However, the quality of that information is entirely more useful because the mounter knew the intended use of the slide. The slide is a test slide, made of a known object under rather exacting conditions so that it may be used to test the quality of a particular objective. One can see that the specimen is of Pleurosigma angulatum and that it is mounted in Styrax. Knowing the mountant is necessary for test objects (or any specimen) because without it (or more specifically the refractive index of it) one can not measure the thickness of the specimen accurately. Electron microscopy has largely eliminated the arguments concerning the actually form of a spring-tails scale but an objectives ability to resolve one is a classic measure of quality.


…is not like the other.

Above one can see two more slides, of an entirely different sort than the previous two. On the left is a blood smear from a Hematology laboratory while on the right are two serial sections of primate brain from a research laboratory. One has a pasted on label which has a coating of balsam, while the other is marked in ink on its frosted end. One has only cryptic markings that are seemingly useless without a knowledge of the specimen and the logging practices of the lab, the other is clearly marked, immediately recognizable and identifiable without additional information. Neither has any information about the specimen preparation or treatment, neither has a date, neither informs on the mounter or the mountant.

On the slide to the right one can see that a printed label reading “Clarkson Hospital Laboratory” has had “Chronic Lymphatic Leukemia” typewritten on it. One may find that Clarkson Hospital is likely Bishop Clarkson Memorial Hospital once of 415 South 26th St. Omaha Nebraska which closed it’s doors and merged with University Hospital in 1997. From the appearance of the label and by virtue of digging into the history of Clarkson one could date the slide to the 1950’s without to much trouble. The characteristic color of the smear makes it rather simple to guess the stain employed and a hematology text of appropriate vintage might even provide information on the preparation method, but it would only be a guess. A textbook with color photomicrographs would likely replace the function of this slide in a modern hospital but as an example of the condition it depicts it is still useful.

The slide on the left reads only what looks like “511 GABA 1:1000 C8 Elilè”. Cryptic to say the least, but the specimen is clearly a section of brain. From its size and morphology one might easily guess it is of a small animal, likely a primate. Looking about for a connection between the markings on the label and primates one can find reference to gamma-Aminobutyric acid (GABA) receptors in the field of neurophysiology without too much effort. The first number is no doubt a catalog or subject reference, I can only guess at what the ratio might be in reference to but it’s not much of a leap to hypothesize that “C8” is a reference to order of the sections. Being in possession of a second slide labeled the same but for “C9” makes such a guess a near certainty. If I had a subscription to the Journal of Neurophysiology, and sufficient interest, I might be able to identify what the marking in red actually reads or likely indicates. An interesting slide, but even with a more comprehensive label it would remain little more than an interesting object of little utility outside the laboratory where it was produced.

It’s worth noting that the contents of a label change depending on the intended use of a slide as much as they do depending on the time period during which it was produced. Whatever information is placed upon a label is useful, but the use to which that information is put might vary wildly. When one prepares their own slides the only limit on the information on the label is what one imposes for ones self. In the various texts available all sorts of claims are made as to the necessary information a label must have. One can see from the above that this information has never become standardized, nor is it ever likely to become so. Labels then are almost exclusively in the realm of preference, yet permit a few exceedingly general suggestions:

  • One should provide a slide with a label the contents of which are useful to the mounter and the intended audience.
  • One should provide a slide with a label which will endure the conditions of use and storage.
  • One should put their name on each slide they prepare.
  • One should put the date of mounting on each slide.
  • One should include some method of referencing more extensive information than the space on the label permits.

Be sure to tune in next time for more exceedingly boring walls of text dealing only in a cursory way with microscopy!