Old microscope slides

Image of the month
R. Neumeyer 1997

This picture illustrates several specimen holding devices, the most recent having been made in the late Victorian era. Beginning at the far right are two examples of ivory "sliders" (hardwood was also used) dating from around 1800. The first has four holes drilled all the way through. Into to each cavity a mica disc has been inserted (there is a shoulder at one end). The specimen was placed on to the disc and a second disc was secured on top by means of a small brass ring. This slider was used for transmitted light observation.

Needless to say the mica slips are not perfectly clear so even with a modern microscope the final image is of poor quality, especially at high magnification. However, this slider and the one next to it, were in use at a time when microscope optics were greatly inferior to what is now available on a basic student microscope. For this reason mica slips did not present a serious problem. (In addition it was not possible for glass makers of the period to fabricate comparable slips). It was more common for microscopists of the time to view opaque specimens by means of reflected light, which is less effected by optical defects. The second slider is therefore more typical. Rather than holes, the manufacturer has drilled small cavities and the specimens were "glued" to the bottom.

The circular brass device at the top of the picture is an early "compressorium". It consists of a pair of short brass tubes, each with clear glass plate at one end. The subject, in this case an earwig, was placed inside the larger tube, then the slightly narrower tube was inserted and slowly pressed down onto the subject. The pressure between the top and bottom glass plates held the insect, or other live organisms stationary, allowing the microscopist to view it without unnecessary movement. (The squashed earwig in this particular compressorium has been there for almost 200 years)!

The long brass accessory in the centre of the picture is a "fish plate". (Shown in more detail on the right hand image). This one dates from around 1800, shortly after it became widely known that blood corpuscles circulated within vessels. Consequently, it was all the rage to place a small fish, or frog, on this plate with the tail or foot webbing secured by pins so that it stretched over the rectangular opening visible at one end (the holes are for the pins). The device and it's passenger were then mounted on the microscope stage with the rectangular opening over the centre aperture. The microscopists and guests then viewed blood corpuscles coursing through capillaries in the clear skin of the webbing using transmitted light from the substage mirror.

The last mounting device is more typical of present day preparations. However, it illustrates a peculiar habit of the Victorian microscopist (one of many!), namely the covering of mounted slides with paper! This particular example is relatively ornate, but by no means outstanding. Some of the paper covers are works of art in themselves, and are greatly sought after by collectors.

The Micscape and Microscopy UK Editors thank Ron Neumeyer for submitting this month's Image of the Month.

The author, Ron Neumeyer can be contacted by Comments to the author sent via our contacts page quoting page url plus : ('rneumeyer','')">Email.


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